Case of Chocolate biscuits to whoever can help me!!

[JoeReade]

I have a problem with a cooling tunnel that is baffling our local refrigeration engineer. If anyone here can suggest the solution, I'll happily send them a case of chocolate biscuits (made on said cooling tunnel)
The tunnel has three identical copeland refrigeration sets along its length. Unit 1 works badly - the lowest temperature we can achieve in that section of the tunnel is 13c with the compressor running constantly. Unit 2 works well - in exactly the same circumstances it can get down to 3c. Unit 3 is somewhere between the two. Our concentration has been on unit 1. I have tested all three units in ideal and controlled conditions - ie cool ambient temperature with no passing product and both ends of the tunnel blocked. The problem remained and therefore must be with the units themselves, not the circumstances. Here's what we have checked:
Gas - All full of gas until no bubbles in the sight glass.
Evaporator - fans working in the right direction, not frozen and air not by-passing it. Also checked to see that ice forms evenly by blocking the airflow with cardboard, therefore there are no blockages in an individual pipe.
Defrost heaters - definitely not on, not even partially.
Compressor rotation - correct (three phase units)
Condenser - clean and clear, fan running well and in the correct direction.
Solenoid valve - operating correctly
Orifice - clean and clear. Tried orifices of different sizes too, no change. Currently using the same size orifice as unit 2 that works well.
Gas pressure - there are gauges fitted to the low and high pressure sides. The readings are:
Unit 1 (the faulty one) high pressure 1 Mpa, low pressure 0.1 Mpa
Unit 2 (works well) high 1.4 Mpa, Low 0.02Mpa
Unit 3 (doesn't work briliantly) high 0.8Mpa, low 0.02Mpa

The pressures are therefore different, but not sure if the range of difference is significant. Would these pressure measurements suggest the compressor(s) is not generating enough flow?

The compressors are Copeland ZB21KQE-TFD-558.

If anyone can suggest the solution and get it right, those biscuits will be on their way!

Thanks.

[frank]

What refrigerant are you using on the 3 stages and what temperatures are you trying to achieve on each stage?

[r.bartlett]

I think we have already had discussions on this issue. It would have been better to use the old thread you started back in June.

[JoeReade]

Sorry, the old post related to the same machine but was a slightly different question. Then I was trying to establish what performance we SHOULD expect; now I have thoroughly tested it all three units and have a benchmark from the best performing unit. The question I'm now trying to answer is what on earth is wrong!! Our local fridge man is stumped. Any suggestions? I have just checked that each unit has the same model of evaporator installed - and they do.

[The Viking]

As said above +,

You need someone with their hands on the machines to solve this for you.
A good starting point for whomever that is would be to check subcooling and superheat then take further actions from there.

:cool:

[JoeReade]

Thanks. The refrigerant is R134A. I'd like to achieve 8 - 10c on each of the three units. But currently number 1 will not go lower than 13c in the best circumstances (15-18c if ambient temp is warmer than usual). To compensate I have the second unit set at 6c, which it achieves no problem, with the compressor cycling on and off. Unit 1 runs continuously and gets no lower than 13c.

[frank]

Has the gas charge been checked?
Are you able to post more details, such as
evap air on temp
evap air off temp
condenser air on temp
cond air off temp
High side pressure and pipe temp at time of reading
Low side pressure and pipe temp at time of reading
Pipe temp entering TEV
Pipe temp leaving TEV

[JoeReade]

Thanks. Can you clarify the measurements you need? See below.
Joe


Has the gas charge been checked? Yes. All have been filled until there are no bubbles visible in the sight glass. In the case of unit 1, that's just under 3kg.
Are you able to post more details, such as
evap air on temp Do you mean the temperature of the air entering the evaporator?
evap air off temp Do you mean the temperature of the air exiting the evaporator?
condenser air on temp as above - the temp entering?
cond air off temp - temperature of the air exiting?
High side pressure and pipe temp at time of reading no problem
Low side pressure and pipe temp at time of reading no problem
Pipe temp entering TEV What's the TEV?
Pipe temp leaving TEV

[frank]

Yes and yes
The TEV is the metering device where the orifice fits

[camelCase]

Wow... so your low side of #1 is some 400% higher than the low side of #2 and #3 (0.1Mpa vs 0.02Mpa)? That might have something to do with not being able to pull as much heat out.

[RANGER1]

Thanks. Can you clarify the measurements you need? See below.
Joe

Compressor amps might be helpful as well.

Does no1 have any unloaders on it reducing its capacity.

Carry out compressor valve leak test, maybe broken suction or discharge valves.

[install monkey]

think your problem lies with ur fridge monkey
what biscuits do i win???

Gas pressure - there are gauges fitted to the low and high pressure sides. The readings are:
Unit 1 (the faulty one) high pressure 1 Mpa, low pressure 0.1 Mpa
Unit 2 (works well) high 1.4 Mpa, Low 0.02Mpa
Unit 3 (doesn't work briliantly) high 0.8Mpa, low 0.02Mpa

[passandscore]

Scroll compressors are pretty bullet proof! What type of condensing units do you have? I would suspect a system problem over a compressor problem. Are all 3 TEVs set the same and sized properly? What is your superheat reading? Are the bulbs located at the right position on the suction line, before the equalizer line and properly insulated? Do you have equalizer lines? If not that's a problem!

What is your distance of pipe from the condensing units to the evaporators and what size of pipe are you using?

What is your subcooling reading?

We're going to figure this out!

[JoeReade]

I'll get the measurements and get back to you!

[FreezerGeezer]

Some more questions:
Are all three systems supposed to reach the same temperature?
Are the heat loads the same for all three systems?
Do all three condensers have good air flow & plenty of space around them? Is there any way the condenser air off is recirculating to the air on side, or might the condensers be side discharge & blowing from one to the other?
Have you recovered the refrigerant, triple evacuated the systems & recharged with fresh R134a?
Are there any solenoid valves on the systems? If so, are they working properly? I had an issue recently where the apprentice had put one back together the wrong way around.

[frank]

We're going to figure this out!

Steady on......I'm not going to share the biscuits....I asked first :p

[install monkey]

googled biccy manufactures in scotland- as if it shortbread-u can fix it frank- if its jaffa cakes-im going to site for an induction! haha:o

https://www.google.co.uk/search?q=scottish+biscuit+companies&oq=scottish+biscuit+companies&aqs=chrome.0.69i57j0.11052j0&sourceid=chrome&ie=UTF-8

[frank]

Chocolate Shortbread.....Yuk....

[JoeReade]

OK - I have some measurements that I hope will shed some light. Let me know what you think...

Measurements for unit 1, which is not cooling well:
Pressure just after the compressor 160psi
Pressure just before the compressor 20 psi
Pipe temperature just before compressor 15.5c
Pipe temperature just after compressor 70c (measured with infra-red rather than surface probe for all other measurements, so may be a little inaccurate)
Pipe temperature just before condenser 57c
Pipe temperature just after evaporator 8.6c
Air temperature entering the condenser 36c
Air temperature leaving the condenser 43.3c
Air temperature entering the evaporator 16.9c
Air temperature leaving the evaporator 14.6c

Measurements for unit 2, which cools well:
Pressure just after the compressor 200psi
Pressure just before the compressor 14psi
Pipe temperature just before compressor 6.5c
Pipe temperature just after compressor 76c (measured with infra-red rather than surface probe for all other measurements, so may be a little inaccurate)
Pipe temperature just before condenser 62.7
Pipe temperature just after evaporator 4.4c
Air temperature entering the condenser 27.2c
Air temperature leaving the condenser 39.3c
Air temperature entering the evaporator 11.1c
Air temperature leaving the evaporator 6.9c

Ambient temperature for both units 28c – but locally higher around unit 1 as can be seen from the air temp entering the condenser. This unit definitely working harder but with less effect.
To recap on previously mentioned points:
Both units cooling the same volume of air
Both units have good gas load (sight glass bubble-free)
Both units have same size of orifice fitted
Both units checked for air bypass, fan rotation, compressor rotation, both set to 6c.

That case of biscuits is primed and ready for the right answer.....

[nike123]

You should measure pipe temperature just before TXV (with contact thermometer or with calibrated IC thermometer adjusted for correct emissivity) to get rate of subcooling (if any).


Ambient temperature for both units 28c – but locally higher around unit 1 as can be seen from the air temp entering the condenser. This unit definitely working harder but with less effect.

This should be rectified. Air entering condenser 1 temperature is too high. Why is that way?
It looks like recirculating air from another unit condenser. Any photography of condenser location?

What is distance and what is placed after liquid line sight glass and before TXV on both units. Are the evaporators above or below condensers and what is height difference?


What is oriffice number and TXV model #.

I propose you to put some black insulating tape over sight glasses until we resolve the issues here.

Frank, I will give you biscuits if you give me some of yours Pales.:D

[joe-ice]

Compressor 2 seems to be under serious pressure going by these readings condensing at 55c .With the air entering condenser 1 at 9k warmer than system 2 i would not be suprised if the compressor is worn and not pumping fully which the readings might suggest.I have also come across systems running high heads under pressure like this where the gas had just broken down and lost its efficiency ,but these were 404 systems .by the way a gas change and a filter and a cleaned condenser cured these

[r.bartlett]

Is that not an R404a compressor?

https://opi.emersonclimate.com/was.extension.opi.web/OPIServlet
https://opi.emersonclimate.com/was.extension.opi.web/OPIInterfaceServlet

[r.bartlett]

Compressor 2 seems to be under serious pressure going by these readings condensing at 55c .With the air entering condenser 1 at 9k warmer than system 2 i would not be suprised if the compressor is worn and not pumping fully which the readings might suggest.I have also come across systems running high heads under pressure like this where the gas had just broken down and lost its efficiency ,but these were 404 systems .by the way a gas change and a filter and a cleaned condenser cured these

Can you tell me exactly which readings suggest the compressor isn't pumping?

[install monkey]

run 1 system at a time to get it working correctly
see if ur figures are any different
check gauzes on ur orifices
check u havent got biccy crumbs in ur evap fins- compressed air is good for that

[hookster]

SEVERE OUTDOOR LOW AIR FLOW = High superheat, suction pressure, head pressure & current draw. Low indoor TD & subcooling. . nike123

http://www.refrigeration-engineer.com/forums/showthread.php?17214-9-superheat-amp-subcooling-scenarios

It does look like the condenser air on temp should be investigated.

[joe-ice]

Can you tell me exactly which readings suggest the compressor isn't pumping?
He said in one post its 134a ,200 psi is pretty high for this, The unit working ok has high head 200 and low back pressure 14 .The unit not working ok has higher air temp going to it (9k more) but has a lower head pressure and is not able to pull down the back pressure which would suggest to me its not pumping fully or as ive come across with 404 the high head it would have been operating has broken down the gas (in correct running order it should have been running higher head than current good unit due to hotter air on)

[Peter_1]

Air in compressor 2?

[r.bartlett]

He said in one post its 134a ,200 psi is pretty high for this, The unit working ok has high head 200 and low back pressure 14 .The unit not working ok has higher air temp going to it (9k more) but has a lower head pressure and is not able to pull down the back pressure which would suggest to me its not pumping fully


Indeed, this is the one which worries me the most:


Pipe temperature just before compressor 15.5c

[joe-ice]

[QUOTE=r.bartlett;28384nndeed, this is the one which worries me the most:[/QUOTE]

How is that ?

[nike123]

@joe-ice
Signatures in our posts does not have anything with actual posts. It represent our global attitude. I am sure that Peter_1 as teacher (and moderator here ;)), has some good reasoning for showing that statement as his signature.


To the subect:

Circuit 1

Te=-5,6°C (air in 16,9°C air out 14,6°C)
Tc=46,5°C (air in 36°C air oit 43,3°C)
Tsh=14,2K
Evaporator:
TD=22,5K
dt=2,3K (not much heat collected)
Approach=20,2K (starving)

Condenser:
TD=10,5K
dt=7,3K
Approach=3,2K (not much heat to reject)

Circuit 2

Te=-10,5°C (air in 11,1°C air out 6,9°C)
Tc=54,8°C (air in 27,2°C air out 39,3°C)
Tsh=14,9K
Evaporator:
TD=21,5K
dt=4,2K
Approach=17,3K

Condenser:
TD=27,6K
dt=12,1K
Approach=15,5 K

Approach of condenser in circuit 2 is too high (15,5K) and approach of evaporator is also to high (17,3K).

Something is probably wrong with that refrigerant inside that unit, or vacuum is not sufficient (or not done at all) prior to refrigerant charging and possible noncondensables are occupying condenser volume or unit is heavily overcharged (my bet is here) with filter dryer dirty or some other obstruction in liquid line region.


Superheat in both circuits is similar (around 15K), but without knowing for real subcooling before TXV, I cannot make any further judgment.

Condenser issues in both circuits should be examined before further evaluation.

Based on given numbers, to me, circuit 1 is working with better numbers but with starving evaporator and recirculating condenser air than circuit 2 with less starving evaporator but with condenser which cannot reject heat efficiently.

Also, as compressor is R404A model, possibly is that TXV is also R404A model and somebody has decided just to switch refrigerant without changing TXV. We need to clarify that also.

Is this new equipment just installed or used one from some other project and someone has decided to use it with R134a instead of R404A?

We need more background of these units since:

The average heat transfer coefficient of R404A is estimated to be 26 to 30% higher than that of R134a for the same saturation temperature.

http://www.tandfonline.com/doi/abs/10.1080/08916152.2011.623820#.Ug81iIKHqxQ

If equipment is designed to work with R404A, than with use of R134A instead of it, you have 30% less capacity then designed, just by using wrong refrigerant. Therefore, you should provide here all equipment specifications and data to troubleshoot that.

[install monkey]

but joe have u seen some of the posts on here! haha
thats why newbies always start off- hello im new please be gentle-!!!!!:p

apart from the pricks floggin mobiles/ipads!
go to your settings and u can create a signature-


How is that ? On a sidenote peter 1 you posted a very short wording so i ended up reading the crap you wrote after it instead . Why do you feel the need to have a funny statement after your name .?. If i was first time posting on this site i would find it most offensive .

[JoeReade]

Here are answers to various questions! -

The tunnel is brand new, and designed to run on R134a, with correct expansion valves, which are Danfoss TN2 (internally equalised) units with orifice number 02 on units 2 and 3. Number 1 unit has been fitted with a Danfoss TEN2 (externally equalised) but with no discernible improvement over the TN2s (fitted recently to unit 1 to try to improve performance)
There's no unloader on any of the three units, the TXV bulb is in the correct place.
Length of pipe between condensor and evaporator max 2 metres.
There is nothing between the sight glass and the TXV.
Condenser and evaporator are on the same level, with 3/8 inch liquid line and 3/4 inch suction line.
There are solenoid valves and they appear to open and close correctly (suction pressure decreases if we lift the coil off)
A new orifice has been fitted to unit 1, with a new strainer.
Unit 1 was vacuumed and fresh 134A used to re-fill it.
A new compressor was fitted to number 1 some months ago, because we suspected it wasn't pumping properly. It was pressure tested back at the supplier and they found it be working fine.

We've removed all panelling from around the compressors / condensor to maximise airflow, with no improvement seen in the cooling effect, but it is certainly now cooler around the condenser. We've blasted all 3 condensers with compressed just to be absolutely sure they are good and clean. Very slight improvement in head pressure as a result.
Condenser fans run in parallel with the compressor, not thermostatically controlled.

We haven't been able to measure the current.

Number 2 works well in the sense that it cools well - though it has been pointed out that the pressure is suspiciously high. Units 2 and 3 have not been touched, and have the original gas load in them. It's possible that number 2 has got too much in it, but it's number 1 that concerns us because it's just not cooling.

[nike123]

This should be rectified. Air entering condenser 1 temperature is too high. Why is that way?
It looks like recirculating air from another unit condenser. Any photography of condenser location?

...................

Any liquid receiver there?
Any picture of TXV bulb placement?

[frank]

Do you know what air volumes you have on both the condensers and evaporators?

[JoeReade]

Thanks for the quick reply, much appreciated.
Here's a picture of the compressor / condenser unit so you can get the general idea. It's close to the ground, and did have perforated panels to the front and rear. I took them off today to make sure there was good airflow. The temp of air entering the condenser definitely went down a good deal, but there was no discernible improvement in the cooling effect in the tunnel. The neighbouring unit 2 is a mirror image of this unit with the same space around it, but it cools much more effectively.
10650

Here's a pic of the txv on unit 1, with the bulb clamped to the suction line leaving the evaporator. Are you asking if there is a liquid receiver at the txv? There is one just after the condenser; then a drier; then a solenoid valve (open whenever the compressor is running) then a sight glass then back to the TXV.

10651

Some other pics of the compressor for good measure (not running):
10652
10653
10654

Is it possible that we have some kind of obstruction in the high pressure line? The drier? The solenoid valve not fully opening?

Cheers

Joe

[chemi-cool]

Pictures makes sense,

Its all Chinese s****, it will work properly.

Had to dump 4 new condensing units very similar to your pictures and get real condensing units.

[JoeReade]

Hi Frank

No - I don't know what the air volumes are... I could get details off the units. But I can tell you that the fans on all three identical units are working well, without doubt. Units 2 and 3 have exactly the same spec as unit 1, but cool much more effectively (10c cooler). Shall I get the air volume numbers, or is it sufficient to know that the other identical units are working fine with the same fans?

[JoeReade]

Pictures makes sense,

Its all Chinese s****, it will work properly.

Had to dump 4 new condensing units very similar to your pictures and get real condensing units.

What could be wrong with the condensers? they're clean, and the fans are running well. Surely after that there's not much that can go wrong??

[nike123]

Give us make and model# of condenser!
Does air on condenser fan flow from condenser to compressor or from compresor to condenser?

[nike123]

This should be rectified. Air entering condenser 1 temperature is too high. Why is that way?
It looks like recirculating air from another unit condenser.

Still no answer! From what I see at pictures, these condensing units are placed inside of production room near the obstacles which can prevent proper air circulation and can make part of discharged air to recirculate.

Bad placement.

In order too cool, unit need to reject heat properly.

[nike123]

Circuit 1
Measure again all, but now include liquid pipe temperature just before TXV (15-20 cm) but after solenoid valve and drier. Also, using same thermometer, preferable contact type, measure pipe temperatures just before and after drier (looking in direction of refrigerant flow). Check for correct orientation of drier and solenoid valve regarding refrigerant flow.

[chemi-cool]

What could be wrong with the condensers? they're clean, and the fans are running well. Surely after that there's not much that can go wrong??

These are very old design condensers, I dont believe they were checked for flow, pressure controlls set can not be changed,

to be honest with you, it is impossible to find a fault from here, you are not familiar with the physics of refrigeration.
My 5 pennies worth advice, get the design papers, a good fridgy and sort your problem once and for all.

And don't forget to give him the cookies box.......

[frank]

Are the condenser fans 3 phase or single phase?

[frank]

Hi Frank

No - I don't know what the air volumes are... I could get details off the units. But I can tell you that the fans on all three identical units are working well, without doubt. Units 2 and 3 have exactly the same spec as unit 1, but cool much more effectively (10c cooler). Shall I get the air volume numbers, or is it sufficient to know that the other identical units are working fine with the same fans?

Joe

It would be helpful if you could measure the airflow but if that's not possible, can you give the make and model numbers of the condensing units/evaporators?

[install monkey]

insulate ur tev bulbs

[frank]

OK - I have some measurements that I hope will shed some light. Let me know what you think...

Measurements for unit 1, which is not cooling well:
Pressure just after the compressor 160psi
Pressure just before the compressor 20 psi
Pipe temperature just before compressor 15.5c
Pipe temperature just after compressor 70c
Pipe temperature just before condenser 57c
Pipe temperature just after evaporator 8.6c
Air temperature entering the condenser 36c
Air temperature leaving the condenser 43.3c
Air temperature entering the evaporator 16.9c
Air temperature leaving the evaporator 14.6c

Ambient temperature for both units 28c – but locally higher around unit 1 as can be seen from the air temp entering the condenser.
The saturated condition of the discharge gas at 160psig is 46.5C and with a measured temp of 70C you have a superheat of 23.5K...a little high

The saturated condition of the suction gas at 20psig is -5.6C and with a measured pipe temp of 8.6C you have a superheat of 14.2K, but then your suction temp just before the compressor is 15.5C so your superheat at this point is 21.1K. You are picking up too much heat in the suction line. Is it insulated?

If the gas charge is correct?(are you saying the charge is correct because the sight glass is full) I would say that you have a restriction, as your evaporator is starved. Has the TEV been adjusted to try to bring the superheat under control?

If the ambient temperature is 28C, where is the additional 8K of heat coming from onto the condenser?

[mad fridgie]

Incorrect circuiting of the evap and overcharged.

[Magoo]

Hi JoeReade.
Your problem is that there are three cooling systems in one cooling tunnel, each one is fighting the other.
I have done a few in the past for Cad Sch and all were single blower systems with counter air flow to product flow full length tunnel with high suction heat factor evaporators.

[JoeReade]

Are the condenser fans 3 phase or single phase?

Three phase, but they're running the correct way (ie drawing through the condenser and toward the compressor)

[JoeReade]

Hi JoeReade.
Your problem is that there are three cooling systems in one cooling tunnel, each one is fighting the other.
I have done a few in the past for Cad Sch and all were single blower systems with counter air flow to product flow full length tunnel with high suction heat factor evaporators.

Definitely not the problem.

[JoeReade]

insulate ur tev bulbs

They are insulated - I removed the insulation for the photo above.

[r.bartlett]

can you confirm the compressors are rated for R134a- there should be a sticker on the compressor.

[mad fridgie]

can you confirm the compressors are rated for R134a- there should be a sticker on the compressor.
Yes it is, and would not matter if it were not

[mad fridgie]

Large comp on small evap (to achieve low temps with with high entering air temp_ , low suction pressure, yet no frost on TEV outlet indicating very high pressure drop across evap coil, to raise the suction pressure, the system has been loaded with refrigerant, hence the high head pressure.
Looks like the evap is only a single circuit, as shown by original TEV being internal equalized, "no distributor"
the evap is the problem.
Quick fix, 2 evaps on one cond unit.
Hope it is a bloody big box of bickies?

[JoeReade]

The saturated condition of the discharge gas at 160psig is 46.5C and with a measured temp of 70C you have a superheat of 23.5K...a little high

The saturated condition of the suction gas at 20psig is -5.6C and with a measured pipe temp of 8.6C you have a superheat of 14.2K, but then your suction temp just before the compressor is 15.5C so your superheat at this point is 21.1K. You are picking up too much heat in the suction line. Is it insulated?

If the gas charge is correct?(are you saying the charge is correct because the sight glass is full) I would say that you have a restriction, as your evaporator is starved. Has the TEV been adjusted to try to bring the superheat under control?

If the ambient temperature is 28C, where is the additional 8K of heat coming from onto the condenser?

OK - Here are a new set of measurements and info. These have been taken after removing panelling from around the compressor and improving the airflow. There is a modest improvement in the cooled temperature of the tunnel, but perhaps just by 1c. (12c now, was 13c). The other two units are maintaining 6c. When product istops passing through the tunnel, the tunnel tempterature on unit 1 drops by a further degree to 11c. Unit 1 is at the infeed end of the tunnel, but this does not explain its warmer temperatures - we have tested several times with the tunnel blocked at either end to verify this.

Ok - on to the measurements

Pressure before Compressor 17psi (-10c approx as read from the same dial)
Pressure after Compressor 130psi (36c approx as read from the same dial)
Pipe Temp before compressor 11.3c
Pipe temp after compressor 65.2c
Pipe temp as entering condenser 66.3c
Pipe temp at exit from condenser 35.6c
Pipe temp before drier 37.0
Pipe temp after drier 37.0
Pipe temp after solenoid (very shortly after the drier) 37.3c
Pipe temp 20cm before txv (inside evaporator compartment on intake side, therefore cooled by air flow) 30.5c
pipe temp after txv -2.5c
Pipe temp at txv bulb, on return from evap fluctuates between 2.5c and 9.6. Seems to fluctuate very rapidly.
Air temp before condenser 27.7c
Air temp after condenser 36.3
Air temp before evaporator 16.5
Air temp after evaporator 11.3c

And now pictures :
condenser fan name plate. states 3620 m3 / hour.
10655

Evaporator plate It states 4800 m3 / hour:
10656

Other answers -
Yes, the suction line is insulated.
Orientation of drier - yes, arrow is in line with gas flow.
Orientation of solenoid valve - no indication on body of valve.

Make and model of the condenser - don't know! It has a label on it saying 'Diya Refrigeration' and a web address of www.shdiya.com. That seems to be a company that makes tazers however! So no idea.

What do you think??!

[chemi-cool]

Diya refrigeration is an Indian company according to google.
looks like they buy their units from China.

I still think you need someone to check the unit and come with solid conclusions.

[JoeReade]

can you confirm the compressors are rated for R134a- there should be a sticker on the compressor.

Yes. Although the spec on the Copeland website says 404 for these units, they have the correct expansion valves for R134A.

[JoeReade]

Large comp on small evap (to achieve low temps with with high entering air temp_ , low suction pressure, yet no frost on TEV outlet indicating very high pressure drop across evap coil, to raise the suction pressure, the system has been loaded with refrigerant, hence the high head pressure.
Looks like the evap is only a single circuit, as shown by original TEV being internal equalized, "no distributor"
the evap is the problem.
Quick fix, 2 evaps on one cond unit.
Hope it is a bloody big box of bickies?

There is frost on the TEV - see the temperature measurements below. The picture showing no frost was taken without the system running. We have three units on this tunnel, all identical. THe other two are working fine, therefore it is not a design issue (which I think is what you're suggesting here?). Have been careful to only put enough gas in to result in bubble-free sight glass, so definitely not overloaded with gas.

[JoeReade]

Diya refrigeration is an Indian company according to google.
looks like they buy their units from China.

I still think you need someone to check the unit and come with solid conclusions.

The tunnel was built in China, all the major components appear to be Chinese.
We have a very good fridge man here (Isle of Mull), but he is baffled by this one. Hence we are hoping that the collective intellect of the internet may be able to help! All the obvious things have been checked and re-checked, so what we're hoping for is a diagnosis from you guys based on the measurements we have taken. Or at least a list of suspects that we can try to eliminate from our enquiries.
I have more than one case of biscuits by the way.....

[frank]

It appears that your tev is hunting. Move the phial up around the pipe towards the top of the pipe to about 2 o'clock position and as Monkey says, make sure it is insulated.

Do you see any difference in the pipe temperature if you adjust the TEV half a turn at a time?(wait for it to settle after each turn)

Can you take some temperature readings on the return bends at the end of the evaporator from bottom to top

[chemi-cool]

The tunnel was built in China, all the major components appear to be Chinese.
We have a very good fridge man here (Isle of Mull), but he is baffled by this one. Hence we are hoping that the collective intellect of the internet may be able to help! All the obvious things have been checked and re-checked, so what we're hoping for is a diagnosis from you guys based on the measurements we have taken. Or at least a list of suspects that we can try to eliminate from our enquiries.
I have more than one case of biscuits by the way.....

As I wrote before, there is a limit to how much we can help from a distance, me for example, have to feel the tubes, compressor, other components on the system, use many times thermal camera to see the internal function af varius parts, you see, refrigeration is about temperature and temperature difference.
one or more parts of your system are wrongly manufactured or do not function right, and the out come is wrong tempetatures, find the spot and your'e done.
Old Chinese man said once: "The Bitterness of Poor Quality remains Long after the Sweetness of Low Price is Forgotten."

[Peter_1]

Haven't read all the posts yet: do you have the possibility to check the temperature all the bends on the evaporator and figure out how the circuits are going through the coil? Or with a thermal imaging camera, you can see through the tubes if every circuit is correct feeding.
Is one of the capillaries of the distributor not blocked? Air baffles inside correct installed? eck every bend on the suspected evaporator

[nike123]

Pressure before Compressor 17psi (-10c approx as read from the same dial)
Is this TXV with MOP at -10°C (068Z3370)?
Tell us his part number!
It should be 068Z3349!

Also, that compressor have volume flow of 8,5m3/h which translates to about 4.8kW of cooling capacity at 0°C/45°C temperatures with used R134A refrigerant.

If numbers are correct, evaporator capacity is 3.6 kW and TXV capacity with oriffice No 02 is 2,5 kW.
As we can see numbers don't match here regardless of what you are saying that other units work fine. They don't!


Orifice should be at least No 03. Evaporator is probably to small, or compressor is too big for that setup, and superheat is high because of too small orifice.

Any background on who has made design, and what are design parameters there.

P.S. Now I see mad fridgie has already found the problem and proposed the solution (two evaporators on one compressor). No biscuits for me this time.:(

[mad fridgie]

There is frost on the TEV - see the temperature measurements below. The picture showing no frost was taken without the system running. We have three units on this tunnel, all identical. THe other two are working fine, therefore it is not a design issue (which I think is what you're suggesting here?). Have been careful to only put enough gas in to result in bubble-free sight glass, so definitely not overloaded with gas.
Given that your earlier numbers, I would say non are right.
also the evap name plate does not match up with any of the data, design is for 3-4K td
The duty would marry up to the comp at -5C SST and 50SCT on R134a.
So all being equal air on to the evap should just be below 0C, which it aint.
Can you take a pick of the face of the evap and some measurements, and a pic of the end of the evap, where the pipes go in.

[JoeReade]

THanks for all the suggestions chaps. Although we have tested the evap previously by blocking the airflow and seeing if ice formed evenly, I'm arranging to borrow a thermal camera to make closer inspection. I'll let you know how I get on.
Our fridge engineer has long suspected that the orifices were too small, and has tried a number 3 to little effect. Currently back on number 2s. But perhaps something we should re-visit once we have this problem sorted - there is definitely something else wrong in addition, since all three units have number 2s and only 1 of them is misbehaving.
Re the suggestion of a hunting TEV - it seems to be cycling between 12 - 2c every 30 seconds. I've compared this with the 'good' unit 2 and it has a similar frequency and range. That's with the insulation removed for testing. Should there be any fluctuation like this?

Cheers

Joe

[JoeReade]

Is this TXV with MOP at -10°C (068Z3370)?
Tell us his part number!
It should be 068Z3349!

Also, that compressor have volume flow of 8,5m3/h which translates to about 4.8kW of cooling capacity at 0°C/45°C temperatures with used R134A refrigerant.

If numbers are correct, evaporator capacity is 3.6 kW and TXV capacity with oriffice No 02 is 2,5 kW.
As we can see numbers don't match here regardless of what you are saying that other units work fine. They don't!


Orifice should be at least No 03. Evaporator is probably to small, or compressor is too big for that setup, and superheat is high because of too small orifice.

Any background on who has made design, and what are design parameters there.

P.S. Now I see mad fridgie has already found the problem and proposed the solution (two evaporators on one compressor). No biscuits for me this time.:(

Evaporator size and orifice size could well be issues, but there is something additional that is wrong with unit 1 - since all three units are identical, and it's only number 1 that is causing problems for us. We have to find the problem with number 1 first.
The TXV part numbers - one recently fitted to unit 1 is a TEN2, part number 068Z3348
The original TXV (still fitted on units 2 and 3) is TN2, part number 068Z3346

[install monkey]

swap orifices to see if the operating parameters change- hope these biccys are choccy ones!:p

[nike123]

That valve model is OK for application. Valve hunting for many reasons and one of them could be moisture in system. Also, if distribution of refrigerant is poor at distributor or air is partially obstructed at portion of evaporator, you can have hunting. Picture revealing distributor will be of help. Oversized orifice is not problem here.
For TXV, remove phial from pipe and hold it in hand, and check if superheat drops. If orifice is of good size than liquid will flood back to compressor and you will hear that. If it is to small, you will have some superheat at pipe. If you have liquid floodback with oriffice of that size, you have problem with air quantity and distribution in evaporator.

Personaly, i dont like how TXV is positioned there with 2 elbows (visible).

Regarding refrigerant you using. Is it from reputable manufacturer in original cylinder?

[r.bartlett]

can you not pump down two condensing units and swap them over to see if the problem goes with it or stays on the faulty unit?

[marc5180]

Do you have the compressor running amps for each of the compressors at the same time as the running pressures.
Also as Nike123 has suggested, is the bulb on a flat piece of the copper and making good contact.

[install monkey]

1st thing to clarify- can u define "a case of biscuits"- ie dimensions,weight, ratio of air/biccy- as we've all opened a bag of crisps for the scented air that escapes leavin a few crisps in an oversized bag!
also a data sheet,nutritional values only state per 100grm- in this case im guessing over 2kg- typical weight of them red boxes of biccys everyone gets at christmas and doesnt eat!

ps im allergic to every biccy except jaffa cakes,choc chip,hazelnut cookies,jammy dodgers! :o

[desA]

Let's start at the beginning.

Send us clear pictures of your cooling tunnel & how the individual evaporators are positioned in the tunnel itself - or relative to the tunnel. Send as much as you can.

Did this setup ever work properly - or, are you in the commissioning stages?

[JoeReade]

can you not pump down two condensing units and swap them over to see if the problem goes with it or stays on the faulty unit?

I'm hoping I can get some firmer possibilities before going down that route. If the evap is the prime suspect, I can get a new one from the manufacturer rather than spend the time swapping.

[JoeReade]

Let's start at the beginning.

Send us clear pictures of your cooling tunnel & how the individual evaporators are positioned in the tunnel itself - or relative to the tunnel. Send as much as you can.

Did this setup ever work properly - or, are you in the commissioning stages?

See below for pictures of the tunnel, and above for pictures of the compressor. There are three units along the tunnel, unit 1 is the problematic one, unit 2 seems to work well (although as suggested by others we may have air in the gas on that one as the pressure is high; but it is cooling well) and unit 3 seems to be fine (though doesn't cool quite as well as 2). Units 2 and 3 can hold 6c no problem, unit 1 can't get down below about 12c at best. Lots of people have suggested design problems (eg incorrectly matched compressor / TXV / Evaporator) but since all three units are identical and we only have serious problems with 1, we have to put that to one side for the moment and find the fault on number 1.
The tunnel was new a year ago, but we've really only noticed the problems with unit 1 when the warm weather hit this summer. I am pretty sure it has never worked properly, but we'd just not noticed until the system was stressed by the heat.

[JoeReade]

Here are some pictures.... firstly of the tunnel as requested desA -
The tunnel from the inlet end, with the three units down its 16m length:
10657
This is unit 1 with the evaporator cabinet on the right:
10658
THis is unit 2 with the evaporator cabinet on the left (unit 3 also has the evap on the left):
10659
Unit 1 compressor:
10660
same view on thermal camera:
10661
I'm not allowed to post more than five pics at a time.... so see the next post.

[JoeReade]

Thermal image of the drier - seems the same temp on both sides (as also recorded in the measurements above)
10662
Thermal image of the solenoid valve. Also seems the same on both sides:
10663
This is the side of the evaporator with the panelling removed.
10664
This is the same view of the evaporator, but seem through the thermal camera. I've also superimposed the temperatures of each of the five coils on the flow and return, as measured by the camera.
10665

[JoeReade]

THis is the evaporator on unit 2, to compare with unit 1 above. Unfortunately I could not expose the distributor end, since on this unit it is next to the compressor and would have involved a lot of dissasembly:
10667
THis is a thermal view of this evap, with temps as measured by the camera superimposed:
10668


So.... does any of this suggest a solution??? Certainly all the circuits on evap 1 are working; It's not possible to identify one or more that are completely blocked for example. But there is variation in their temperatures. COuld this just be due to normal differential airflow from top to bottom? Or is it a symptom of another problem?

The hunting of the expansion valves has ceased - it was observed previously whilst the insulation was off the bulbs. It's now on and the suction temp just after the evap is steady. at about 14c

Re the question about the bulb positions - both are horizontal, mounted just after the five circuits combine back into one pipe on the return pipe, are well clamped to the pipe and insulated.

One thing I have not been able to yet measure is the current on each compressor. Hope to get that soon.

Could we have a restriction of some sort in the liquid line? Temperatures either side of the drier, solenoid valve and sight glass are equal. Should I expect a temperature drop across one of them if there was a restriction? Or could there still be a restriction without showing a temperature difference?

What should we do next??!!

Thanks for all the help and suggestions chaps. I think more than one of you will be getting biscuits.... a 'case' by the way is 12 x 150g...... enough to feed a refigeration engineer for a day or too.

Thanks!

Joe

[JoeReade]

lets try those images again. evap on unit 2:
10669
thermal image of evap 2:
10670

[JoeReade]

I now have current measurements -
Unit 1 is drawing 4.3A, 4.2A and 4.0A on each of the three phases.
Unit 2 is drawing 4.7A, 4.8A and 4.5A
Unit 3 is drawing 3.9A, 3.7A and 4.0A.

To recap - unit 1 is the one that's not chilling well. at the time of taking these readings, high pressure was 110psi, and low 20psi.
Unit 2 is the one that's chilling well, but may either be over-loaded with gas or have some air in the system (pressure readings are always higher). It's pressures were 210psi and 23psi
Unit 3 runs pretty well, but doesn't seem to chill as quickly as unit 2. We're not too concerned about this one. It's pressures were 110psi and 13psi.

The current readings were taken at the contactors, and include the condensor fans and solenoid valves.

Does this enable us to remove any components from our enquiries???

CHeers

Joe

[frank]

From all the data so far I would be inclined to replace the TEV on unit 1.

[JoeReade]

That valve model is OK for application. Valve hunting for many reasons and one of them could be moisture in system. Also, if distribution of refrigerant is poor at distributor or air is partially obstructed at portion of evaporator, you can have hunting. Picture revealing distributor will be of help. Oversized orifice is not problem here.
For TXV, remove phial from pipe and hold it in hand, and check if superheat drops. If orifice is of good size than liquid will flood back to compressor and you will hear that. If it is to small, you will have some superheat at pipe. If you have liquid floodback with oriffice of that size, you have problem with air quantity and distribution in evaporator.

Personaly, i dont like how TXV is positioned there with 2 elbows (visible).

Regarding refrigerant you using. Is it from reputable manufacturer in original cylinder?

The hunting seems ot have been caused by having the insulation removed whilst taking the readings. With insulation on, the return temperature is steady.

Refrigerant is good, recently re-filled with fresh gas.
The expansion valve is new, so we don't think the problem lies there. We put on an externally equalised valve to replace the internally equalised one, to try to solve he problem. It made no improvement. We agree that the orifice should be a #3 rather than #2, but that is a separate issue I think. All three units have #2's in them, but only unit 1 is not cooling properly.
See above for pictures of the evap distributor - all five sections seem to be receiving gas flow.

[JoeReade]

From all the data so far I would be inclined to replace the TEV on unit 1.

We put a new one on there a week or two ago, an externally equalised one replacing an internally equalised one. It made no difference. Pretty sure the TEV is fine.
Could we have an obstruction somewhere? Could it be that we're just not getting the necessary volume of gas around the system? Does anything so far suggest an obstruction, or rule it out?
Cheers

Joe

[chemi-cool]

Condensing pressure in unit 1 is too low, check the compressor for faulty valves.

Liquid distributer should be mounted downwards to get even flow of refrigerant.

i did not see or have missed your answer to the qwestion, Did it ever worked ok? or these problems are from day 1?

[al]

Are the condensing units under the tunnel?? Is there any chance heat is being drawn in from the condensing units.

alec

[install monkey]

do you normally have condensers in a food prep area?:D

Are the condensing units under the tunnel?? Is there any chance heat is being drawn in from the condensing units.

alec

[al]

Them's pretty big condensers to be sitting integral:) i'd have them outside, where it's like, i dunno, cooler;)

alec

[mad fridgie]

Good pics.

Uneven distribution.

All need externally equalized valves.

Move Expansion valve directly on to distributor.

I do not know the pressure drop of the distributor, so I would install a larger orifice (which size ???, experiment.)

This is on all units if the same.

[nike123]

On unit 1 we see uneven distribution and underfeeding.
TXV and distributor should be as close as possible but slightly above 7 OD of line feeding distributor. I would make one elbow or none. TXV could be in any position to allow that distributor work properly. Distributor should feed downwards. Orifice should be of size 3 or even 4 to let TXV to feed enough refrigerant and to start to control superheat.

10671

Suction line right after evaporator and bulb should have equalization line connection, and then it should go in oil trap to allow to drain oil from evaporator. All details are on this picture and BTW that picture is on box which TXV is shipped in.

[desA]

I'm concerned about the airflow distribution coming into the evaporators.

This is shown up in the following link picture, quite nicely.
http://www.refrigeration-engineer.com/forums/attachment.php?attachmentid=10670&d=1377353284

& also
http://www.refrigeration-engineer.com/forums/attachment.php?attachmentid=10665&d=1377346610

I'm concerned about how the circulating tunnel air is directed into the evaporators. It must be even. Your first task is going to have to be to take a good look at the way the air is collected from the tunnel & directed to the evaporator entrance. Take an air anemometer & read air velocity onto the evaporator, over as much of the coil, as possible. Your end goal is to have as little variation across the face, as possible.

I suspect that your evaporator manufacturer, or tunnel manufacturer, may have skimped a little on the finer design details. I'd like to see evaps with more rows - as it gives the air more of a fighting chance - to even itself out as it moves through the core.

Please show pics of the ductwork & fan details moving the airflow from tunnel, through evap, & return to tunnel.

I'd say that, once the airflow is reasonably even in all three evaps, that you'll then be in a position to begin moving further with your investigation. The refrigerant distribution would then be next in line.

[nike123]

Evaporator size and orifice size could well be issues, but there is something additional that is wrong with unit 1 - since all three units are identical, and it's only number 1 that is causing problems for us. We have to find the problem with number 1 first.
The TXV part numbers - one recently fitted to unit 1 is a TEN2, part number 068Z3348
The original TXV (still fitted on units 2 and 3) is TN2, part number 068Z3346

Difference is TXV. It is not off same type. It is with external equalization, as oppose to other two circuit. TXV on other units underfeed somewhat less than this on circuit 1. They all underfeed refrigerant because all 3 have too small orifice.
And, as desA has pointed out, you could probably have also problem with uniform air distribution over evaporator, which should be measured with anemometer.

There is lot of small details which should be addressed here and all of them should be rectified to get unit to work properly. Since this one is misbehaving worst, start with all necessary corrections and actions needed to make it work, and than, proceed to other ones when that is sorted.

[JoeReade]

Thanks again everyone!
SO - on unit 1 -
a) check airflow and try to get it as even as possible. Seems sensible - but the ducting arrangement is the same on all three units, and only have trouble on number 1. But certainly worth looking at.
b) Move TXV closer to distributor (8 x O.D?), and make minimum number of elbows between the two.
c) Invert the distributor so that small pipes exit downwards, not up as currently.

Moving the txv closer to the distributor seems like an interesting suggestion, because this is one thing that is different on unit 1 compared to the other two units. The pipe routing is different, resulting in an extra elbow after the txv.

On all three units -
a) check for even airflow
b) perhaps invert distributors on all three evaps?
c) move condensers / compressors outside
d) bigger orifices
e) externally equalised txvs

Can anyone tell me whether a restriction in the pipe is still a possibility from the numbers provided, or can we discount that?

Thanks

[JoeReade]

Are the condensing units under the tunnel?? Is there any chance heat is being drawn in from the condensing units.

alec

No, definitely not.

[JoeReade]

Difference is TXV. It is not off same type. It is with external equalization, as oppose to other two circuit. TXV on other units underfeed somewhat less than this on circuit 1. They all underfeed refrigerant because all 3 have too small orifice.
And, as desA has pointed out, you could probably have also problem with uniform air distribution over evaporator, which should be measured with anemometer.

There is lot of small details which should be addressed here and all of them should be rectified to get unit to work properly. Since this one is misbehaving worst, start with all necessary corrections and actions needed to make it work, and than, proceed to other ones when that is sorted.

unit 1 used to have an internal txv, but we changed it in an attempt to improve performance. It made no difference.

[nike123]

Obstruction can be in pipe from TXV to distributor, and in distributor to pipe connection. Maybe because of different length and more elbows. 25" is maximum lenght of pipe between TXV and distributor, but we prefer to make it as short as possible but longer than 7 OD of pipe (after elbow).

Also, every bend has its equivalent length of straight pipe. For example long radius elbow of 1/2" pipe has equivalent length of 2,2 feet. Therefore 1 such elbows means equivalent length of 26" which is greater than maximum allowed length of that pipe. You have at least 2 there. That could be too much restriction and possible cause of difference in behavior of that unit in comparison with other units.

http://www.engineeringtoolbox.com/resistance-equivalent-length-d_192.html

Therefore, make that correction first to eliminate as possible cause of problem, but since you will be opening system for that correction, than other details should be corrected as well, to make everything by the book.

[nike123]

Thanks again everyone!
SO - on unit 1 -
a) check airflow and try to get it as even as possible. Seems sensible - but the ducting arrangement is the same on all three units, and only have trouble on number 1. But certainly worth looking at.
b) Move TXV closer to distributor (8 x O.D?), and make minimum number of elbows between the two.
c) Invert the distributor so that small pipes exit downwards, not up as currently.

Moving the txv closer to the distributor seems like an interesting suggestion, because this is one thing that is different on unit 1 compared to the other two units. The pipe routing is different, resulting in an extra elbow after the txv.

On all three units -
a) check for even airflow
b) perhaps invert distributors on all three evaps?
c) move condensers / compressors outside
d) bigger orifices
e) externally equalised txvs
f)oil trap at exit of evaporator before vertical rising
g) equalization line connection just before oil trap and right after TXV bulb
h) connection for pressure measurement, at suction line after evaporator, for correct evaporator superheat measurement.
i) inverted trap at top of vertical riser
j) maybe one size smaller diameter vertical riser pipe




Can anyone tell me whether a restriction in the pipe is still a possibility from the numbers provided, or can we discount that?

Thanks

Without measuring pressure drop at portion of pipe from TXV to distributor we cannot tell if there is obstruction or not because refrigerant here is in saturated condition and there is no temperature difference there.

[nike123]

b) Move TXV closer to distributor (8 x O.D?)
7 OD or more is necessary only after elbow. If you don't have elbow, it is not necessary to make 7 OD (or more) minimal length. That is for ensuring uniform feeding of distributor which is disturbed at shorter length of that, if elbow is used.

http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/01/DKRCC.PI.A00.A4.AA.pdf

[nike123]

unit 1 used to have an internal txv, but we changed it in an attempt to improve performance. It made no difference.
All units MUST HAVE external equalization, because distributor is used. There is no visible difference because other things on that circuit are masking performance improvement by that change.

[nike123]

http://www.keychoc.com/cooling-tunnels.php
http://www.heronfms.com/index/classdetail.asp?id=76
Is this what you bought?

[desA]

10676

Nike's well on his way to the choccies... ;)

[nike123]

Give me a real boost and I'm all on a mission!:D I wouldn't mind trade that for Frank's beers, but vitamin D is also here!

BTW, question to more qualified members!
As I can see from pictures, evaporator is mounted vertically, but individual pipes of each branch in evaporator makes down-up-down pattern. Is that of any concern regarding oil transport and oil logging in evaporator (not sure if velocity here is sufficient) since we have portion of evaporator with oil trap? I was thinking that all pipes should gradually go down (serpentine, and in case this evaporator was mounted horizontally that would be exactly the case here) and only oil trap should be at exit of evaporator, and, if top of evaporator is above suction line, than we should have vertical riser with inverted trap at level above top of evaporator.

10677
It looks to me that this evaporator is originally constructed for horizontal installation.

Other thing, I have some colleagues who telling me that, if we have elbow after TXV and before distributor, than length before elbow should be 5 OD and after elbow 7 OD (5/7 ratio). Any document or explanation which support that?

[desA]

nike123 - when you say evaporator mounted vertically, do you mean:

http://www.refrigeration-engineer.com/forums/attachment.php?attachmentid=10665&d=1377346610

or :

http://www.refrigeration-engineer.com/forums/attachment.php?attachmentid=10664&d=1377345835

Sorry pics so large - does anyone know how to reduce their size?

[nike123]

I mean both picture, and I suppose one (second in your post) is wrongly oriented. I concluded that from other pictures.

I mean thermal camera picture shows natural orientation of evaporator.

[desA]

Mmmhh... I see what you mean. If it is the thermal camera picture, I'd have expected to see the distributor facing in the opposite direction - with thin, off-take tubes at the lower end of the evap. Higher velocity after split carrying the oil.

Would like to hear what other folks think.

Can the OP please clarify the operating orientation for the evaporators?

[JoeReade]

Thanks for the help Nike!
I've done one further test, which was to eliminate any effects of the ducting on the airflow over the evaporator. I removed the panelling behind and in front of the evaporator, so that there was no restriction on the airflow whatsoever. Below are the temperature results I got.
10678
What do you think of the results? To me it seems that there is too much variation, and the gas cannot be circulating evenly. (Please bear in mind that the right-hand temperature measurements may not be very meaningful, since they were taken very close to the return manifold, and will be affected by the temperature of gas returning from the other circuits).
Would you conclude from this picture that the gas distribution was not even?
We think that if this is the case, the next course of action will be to optimise the TXV position and pipe routing immediately before the evaporator (invert the distributor, minimise elbows, follow your guide for the minimum straight distance after an elbow etc).

The pipe between the TXV and the distributor is 720mm long, and has three elbows in it. This is well in excess of the limits you suggest. However, I think the pipe arrangement is the same on the other two units, and they work much better.

Also - do you think there remains the possibility of a restriction somewhere else in the system, perhaps between the compressor and the TXV? Or can we discount that, based on the temperature readings we made along the pipe? This is one point I am unclear on.

Thanks again.

Joe

[frank]

Joe

I mentioned a few posts ago that the evaporator was starved leading to poor performance and Mad Fridgie said that your evaporator was configured incorrectly.

Nike also has identified that the problem lies with the evaporator. 700mm from TEV to distributor? you could have mentioned this before.

Your thermal pictures show an unusual amount of superheat and now you are telling us that there is ducting on the evap....come on mate..tell us the whole story.

I can't understand why this is baffling your local fridge engineer..

A question I asked a few posts ago...have you adjusted the TEV to reduce the superheat?

[nike123]

J
I can't understand why this is baffling your local fridge engineer..



Probably because he is not real fridge engineer, or, he is not competent for the job!

Also, i expect that someone who buy that equipment, should at least have commissioning done by competent and authorised engineer by equipment supplier.

In 10 min., competent fridge engineer will discover all defects we discussing here, at least one week already now.

[nike123]

@Joe Reade

If that thermal camera reading is any good, than, if pipe is covered in ice in any portion (like on evaporator picture before), it should read 0°C. I don't see any reading of 0°C, and therefore, that camera reading is not relevant to me, if pipe was anywhere covered with ice during that measuring.
All IR thermal measurements should have compensation for emissivity from different surfaces. Therefore, if emissivity is not adjusted for every spot, measurement is faulty.

As I said earlier, your "fridge engineer" should rectify obvious, scool things, first, and then, if necessary, proceed further.

We (you) cannot solve this problem if we (you) disregarding obvious errors, no matter what other units, as you say, "work satisfactory".

We established that before TXV you have enough subcooling, we also established that evaporator is starved. And, we established that you have excess distance (in both case, with or without equivalent length off elbows) between TXV and distributor. All other is influenced with that. Remove that influence (and all other obvious errors while rectifying that, since system will be opened) and we can proceed further with troubleshooting.

This is exact science with very little space for wandering!

[chemi-cool]

Well guys, look at my first post here, cheap, shiny chinese stuff.
In a way, i feel sorry for businesses whom spend money on such units,

Its not the biscuits but the challenge to help a friend, there are some of the best fridgys here in the world.
But even though, bad product are imposible to fix and I hope someone will prove me wrong.

[nike123]

To some extent, it could be fixed. If it is bad construction and bad execution, we can fix bad execution. I am not putting expenses to that equation for now.;)

[JoeReade]

Joe

700mm from TEV to distributor? you could have mentioned this before.



Well that's kind of why I am after the kind assistance of the posters here! If I knew exactly which things were relevant and which weren't, I might be able to fix it myself.....



Joe

Your thermal pictures show an unusual amount of superheat and now you are telling us that there is ducting on the evap....come on mate..tell us the whole story.



DesA suggested that I make sure that there is even airflow over the evaporator. The purpose of that test was to remove all possible impediments to the free flow of air, and to see if it resulted in a more even temperature distribution across the evaporator. It did not seem to, therefore I conclude that air circulation is not a significant factor. I was looking for some confirmation that my conclusion was correct.


Joe

I can't understand why this is baffling your local fridge engineer..



Well it is.... which is why I am here. He has tried all of the easier answers and can find no fault. He's also tried many of the solutions that have been proposed here. Obviously what we have is a fault of manufacture or design rather than damage or failure of a component. That seems a bit harder to diagnose. I should explain that we are on a relatively remote Scottish island, and we are lucky to have any fridge engineer at all resident here; and as is common in a small community he has to wear many different hats in order to make a living. He does not benefit from the breadth of experience that you have. Which is why I am very grateful for the help you all are offering.


Joe

A question I asked a few posts ago...have you adjusted the TEV to reduce the superheat?

Sorry if I missed that one. Yes. He fitted a new one because the original was internally equalised, and adjusted it correctly.

[mad fridgie]

Some things are predictable and other things are less so.
Because you have issues with the expansion valves, position, type and size, then your results are somewhat less predictable. (applies to all 3), this is why you are see difference in performance.
So fix what you know is wrong, change all expansion valves, move all expansion valves. Have some different orifices in stock. (pressure drop across distributor is not known).
a new equalibrium will be reached. Only when this is done, can we move onto the next stage. (if there is a next stage)

[JoeReade]

Mmmhh... I see what you mean. If it is the thermal camera picture, I'd have expected to see the distributor facing in the opposite direction - with thin, off-take tubes at the lower end of the evap. Higher velocity after split carrying the oil.

Would like to hear what other folks think.

Can the OP please clarify the operating orientation for the evaporators?

I think my orientation of the thermal camera has confused things - sorry! Below is a picture showing the evaporator mounted in its cabinet. I've also added some arrows showing the airflow to and from the tunnel compartment above. You can see the TEV on the right too - the total length of the pipe from it to the distributor is 700mm. The last straight section is 120mm, which is 7.5 times the OD of the pipe (16mm). But from what you all are saying, we have to move the TEV right up to the distributor and turn the distributor 180 degrees.

I wondered whether the evaporator had been mounted upside down - but it appears not to be, judging by the labelling and the position of the condensate drain.

10681

[nike123]

Sorry if I missed that one. Yes. He fitted a new one because the original was internally equalised, and adjusted it correctly.

It cannot be adjusted with that size of oriffice. In fact, it should not be adjusted at all, before all other things are sorted. That is last adjustment which should be done.
Tell him to make it back to factory adjustment, and forget to further adjustments, at least for now!

[JoeReade]

@Joe Reade

If that thermal camera reading is any good, than, if pipe is covered in ice in any portion (like on evaporator picture before), it should read 0°C. I don't see any reading of 0°C, and therefore, that camera reading is not relevant to me, if pipe was anywhere covered with ice during that measuring.
All IR thermal measurements should have compensation for emissivity from different surfaces. Therefore, if emissivity is not adjusted for every spot, measurement is faulty.

As I said earlier, your "fridge engineer" should rectify obvious, scool things, first, and then, if necessary, proceed further.

We (you) cannot solve this problem if we (you) disregarding obvious errors, no matter what other units, as you say, "work satisfactory".

We established that before TXV you have enough subcooling, we also established that evaporator is starved. And, we established that you have excess distance (in both case, with or without equivalent length off elbows) between TXV and distributor. All other is influenced with that. Remove that influence (and all other obvious errors while rectifying that, since system will be opened) and we can proceed further with troubleshooting.

This is exact science with very little space for wandering!

Thanks Nike. Quite possibly the thermal readings are not accurate. Those measurements above were actually taken using an IR thermometer, I just used the thermal image for context. The IR thermometer is reasonably accurate, and at the time of measuring there was no frosting. In that test I was trying to remove uneven airflow as a significant factor, but removing much of panelling that directs the air to and from the tunnel compartment above.

I think it's clear what we need to do now, as you say, to remove the obvious errors. We'd better get on and do the work. Fingers crossed!

[JoeReade]

Some things are predictable and other things are less so.
Because you have issues with the expansion valves, position, type and size, then your results are somewhat less predictable. (applies to all 3), this is why you are see difference in performance.
So fix what you know is wrong, change all expansion valves, move all expansion valves. Have some different orifices in stock. (pressure drop across distributor is not known).
a new equalibrium will be reached. Only when this is done, can we move onto the next stage. (if there is a next stage)

Thanks Mr Mad Fridge. I'm already looking at postage costs for New Zealand and all the other far flung places you guys are posting from....

[JoeReade]

But even though, bad product are impossible to fix and I hope someone will prove me wrong.

"All things are possible until they are proved impossible - and even the
impossible may only be so, as of now."
Absolutely!

[desA]

http://www.refrigeration-engineer.com/forums/attachment.php?attachmentid=10681&d=1377637751&thumb=1

This picture is worrying me! I'd like to hear others' opinions on the evaporator orientation.

I would expect to see the following:
1. TXV high up & close to distributor;
2. Distributor facing in opposite orientation to that at present.

With the current orientation, I'd expect issues, as follows:
a. Oil logging in the pipe between TXV & distributor. Oil could slug intermittently.
b. Three 90 degree elbows prior to distributor will have liquid/gas separation occurring.
c. (c) basically means that it will be very difficult to see an even refrigerant (two-phase) feed into the distributor. Liquid will prefer one route, vapour another.
d. I have to wonder if there is operational vibration in the line between TXV & evap.

If your refrigeration lad is brave, he'll probably have to rotate the evap through 180 degrees until the distributor is correctly oriented - then move TXV to its correct position - close to distributor. In other words, to the other side of the cabinet. Sporlan has some useful literature on the best set-ups between TXV & distributor.

You'll probably be better off getting all evaps correctly oriented, followed by TXV re-location. After that, at least you have a part-way decent configuration, to begin adjusting. What a job you have on your hands.

At the temps you're working at, the outlet manifold looks remarkably free from moisture. I'd be expecting puddles of water below the manifold. What am I missing?

[desA]

Also, looking at air the flow space before entry to the evaporator, I'd expect a fair amount of air flow maldistribution across the face of the evaporator.

If you are able to locate an air anemometer, this would tell you a great deal - in terms of air-flow.

[Magoo]

Hi JoeReade. your last photo is worth a thousand words, the TXV and distributor should be only sweating, either the TXV is starving evap or lack of load from evaporator is closing TXV. Interesting the red arrows for air flow. Can you sketch the air pattern over product, if air dwell over product is too short the cold return air to evap will force TXV closed and starve coil, the conditions indicated in photo

[mad fridgie]

The distributor, we could have a separate thread about this, but as long as the TEV is close coupled, and the distributor is vertical (up or down) then this should not be a major problem.
The coil well maybe up side down, but if you look at the circuits, the flow is up/down and side wards, so little difference would be made by changing it.
The airflow, OK the name plate seems to indicate a high volume, higher than I would expect, but it is just a name plate. It is induced so air flow will be relatively even (The fan would be better further away, to even out) But this is not the major issue at the moment. There is also a bit of air by-pass, not to worry at this stage.
The air temps are not to cold to shut down the TEV, SST is low and SH is high.

[JoeReade]

The distributor, we could have a separate thread about this, but as long as the TEV is close coupled, and the distributor is vertical (up or down) then this should not be a major problem.

You say it does not matter which way up the distributor is, so long as its vertical? This is supported by the Danfoss literature. It shows the distributor with the small pipes downward, but does not say it 'MUST' be this way. It certainly shows the distributor on its side with a cross through it - that is the only position that is explicitly ruled out.
Inverting the distributor is the larger part of the work we think we need to do - are you sure it's OK the way it is? So we could just move the TEV much closer and leave the distributor as it is? This would be a lot easier.

[r.bartlett]

The picture looks more like a freezer evap... but I am interested in the moving the tev closer thing as my gut instinct is that it will make eff all difference, so I want him to move it so I can learn.



Have you tried a larger orifice as suggested as to flood the evap and see what happens...?

[install monkey]

distrubutor tubes should be all the same length for even distribution!- do i get to choose what flavour biccys???;)

I think my orientation of the thermal camera has confused things - sorry! Below is a picture showing the evaporator mounted in its cabinet. I've also added some arrows showing the airflow to and from the tunnel compartment above. You can see the TEV on the right too - the total length of the pipe from it to the distributor is 700mm. The last straight section is 120mm, which is 7.5 times the OD of the pipe (16mm). But from what you all are saying, we have to move the TEV right up to the distributor and turn the distributor 180 degrees.

I wondered whether the evaporator had been mounted upside down - but it appears not to be, judging by the labelling and the position of the condensate drain.

10681

[JoeReade]

The picture looks more like a freezer evap... but I am interested in the moving the tev closer thing as my gut instinct is that it will make eff all difference, so I want him to move it so I can learn.



Have you tried a larger orifice as suggested as to flood the evap and see what happens...?

Currently #2, and we've tried #3, which seemed to make no difference. But general concensus is that we should have bigger orifices.

[JoeReade]

distrubutor tubes should be all the same length for even distribution!- do i get to choose what flavour biccys???;)

If only it were that simple....

[r.bartlett]

Currently #2, and we've tried #3, which seemed to make no difference. But general concensus is that we should have bigger orifices.
take the nut off the adjusting screw (one with not any pipe coming out of it) and open it up fully anti clockwise to see if the pressure rises and frost clears.

[mad fridgie]

Just move the TEV directly onto the distributor, no need to re pipe evap.
The pipe and bends, acts as separator, so the distributor does not get an even mix of liquid and vapour.
At this stage DO NOT adjust the expansion valves.
The orifice size, is yet to be known we do not the pressure drop of the distributor. It maybe a 4.
The coil does look like low temp with the defrost heaters.
Until we can get a fully wetted evap do not worry about other issues.

[JoeReade]

Just move the TEV directly onto the distributor, no need to re pipe evap.
The pipe and bends, acts as separator, so the distributor does not get an even mix of liquid and vapour.
At this stage DO NOT adjust the expansion valves.
The orifice size, is yet to be known we do not the pressure drop of the distributor. It maybe a 4.
The coil does look like low temp with the defrost heaters.
Until we can get a fully wetted evap do not worry about other issues.

OK - going to get that done. Will let you know how we get on......

[install monkey]

are all 3 tev's the same distance from the distributor?

[r.bartlett]

Just move the TEV directly onto the distributor, no need to re pipe evap.
The pipe and bends, acts as separator, so the distributor does not get an even mix of liquid and vapour.
At this stage DO NOT adjust the expansion valves.
The orifice size, is yet to be known we do not the pressure drop of the distributor. It maybe a 4.
The coil does look like low temp with the defrost heaters.
Until we can get a fully wetted evap do not worry about other issues.

I greatly look forward to seeing the measured difference. As I say my gut suggests little or no measurable difference in this case. However I am more than willing to take this lesson on board should it prove to be otherwise

I would be interested if you could walk me through this particular case on the pictures and show where the uneven distribution actually occurs. Is there laminar flow along the pipe section or is it turbulent for instance. ?
If it is laminar then the 'gas' should stay on the top which means as it bends round vertical it will be on the right side of the pipe, then what?
Does it speed up to the distributor because it's less dense than the liquid or does it travel at the same speed?

If turbulent who cares as the gas will be evenly distributed in any case?
(why are all splits two phasing for up to 50m in some cases and don't suffer from this issue?)

Why not just insulate that section to reduce the flash gas?
Are you expecting to see a wetted evap just by moving the tev?
if not, or are you then going to say, "now change the orifice to a no/4?"
If you do end up suggesting he changes the orifice (which has been mentioned many times already and remains a possibility) why not try it first to see the difference as we seem to be off on a flight of theoretical ideals at someone else’s expense

TIA :-)

[mad fridgie]

In short, you are getting move vapour through the distributor, which cases a bigger pressure drop and leaves the coil short of liquid, the liquid and vapour separate in the line. The distributor is part of the expansion process, that why when sizing an expansion valve we need know the the pressure drop across the distributor, liquid pressure - pressure drop across valve - pressure drop across the distributor - evaporating pressure.
The flash gas is to reduction in pressure mainly, not absorbed energy (not to say there is not some)
On a split the evap line "the pipe between the expansion device and the evaporator" (or liquid line to you), is small keeping the mixture in a homogeneous state.

[r.bartlett]

In short, you are getting move vapour through the distributor, which cases a bigger pressure drop and leaves the coil short of liquid, the liquid and vapour separate in the line. The distributor is part of the expansion process, that why when sizing an expansion valve we need know the the pressure drop across the distributor, liquid pressure - pressure drop across valve - pressure drop across the distributor - evaporating pressure.
The flash gas is to reduction in pressure mainly, not absorbed energy (not to say there is not some)
On a split the evap line "the pipe between the expansion device and the evaporator" (or liquid line to you), is small keeping the mixture in a homogeneous state.

Thanks this poses more questions than it answers but:

I would be even happier if you went down my questions one by one as that way I can learn as you seemed to have skipped most of the points.. Especially highlighting on the pictures what and where this has occured.

Out of interest a 3/8 pipe running 50m has far more opertunity to change state % end to end than 500mm of 1/2 inch would you not agree.
Does change of state % only occur in larger pipes or can it exist in smaller pipes ?

If by homogeneous you mean there is no difference from condenser to evaparator (50m) then what is keeping it that way? Insulation? 3/8 v 1/2 pipe??



tia

[mad fridgie]

Thanks this poses more questions than it answers but:

I would be even happier if you went down my questions one by one as that way I can learn as you seemed to have skipped most of the points.. Especially highlighting on the pictures what and where this has occured.

Out of interest a 3/8 pipe running 50m has far more opertunity to change state % end to end than 500mm of 1/2 inch would you not agree.
Does change of state % only occur in larger pipes or can it exist in smaller pipes ?

If by homogeneous you mean there is no difference from condenser to evaparator (50m) then what is keeping it that way? Insulation? 3/8 v 1/2 pipe??



tia

It has already changed state, but as the pressure drops further flash will be produced. The fllash gas is being produced because of reduction of pressure and not infiltration. "vapour fraction"

Homogeneous, I mean that the liquid and vapour say evenly mixed.

By moving the TXV yes expect to see wetted evap (I am talking about the internal of the walls having liquid refrigerant on them, no flooded but wet)

I can not say what size the orfice is because I DO NOT know the pressure drop through the distributor.
Nike has already sized using basic rules and has said present size is reasonable, not going to question Nike on this.

As far as tubeulent and laminar, bends also cause eddies. so not as predicable as one thinks.

Moving the TEV to the right place is only a small job, 10-15 mins, not that long to make right a Known error.

Look at the frost on each circuit, you can see an imbalance, but the main problem is lack of liquid entering the evap.

[mad fridgie]

Is no news, good news?
My cup of char needs some dunking material!

[chemi-cool]

10711

Untill you get the Scotish ones......

[frank]

Patience chaps....I think that the local fridgie is half way through the alterations as we speak (post)...;)

Hope they are dark chocolate...mmmmm

[desA]

The joys of buying Chinese quality products. :D

[hookster]

Do Chinese chocolate biscuits taste different to Scottish ones??? :D
and if I dunk one in a glass of Talisker would I notice the difference? ;)

[chemi-cool]

if I dunk one in a glass of Talisker would I notice the difference?

I think they will float......

[If you can afford a bottle of Talisker]

[desA]

Lol... :D

[nike123]

15 days passed without update on what is current development on this case! These cakes, what are they made off?
Chocolate cannot be that much precious to avoid given promises. :eek:

[mad fridgie]

???????????????????????????????????????

[nike123]

I have seen this many times! Problem solved, nobody cares cares to inform us about development. Since there is no problem anymore, there is no need to responce to this thread.

[r.bartlett]

send Joe an email and tell him what you thing of him joe(remove this bit)@islandbakery.co.uk (joe@islandbakery.co.uk)

[marc5180]

I've emailed him and asked him if he wouldn't mind replying which I suspect he will be doing shortly.

[JoeReade]

Hello!
Sorry for the silence. For various reasons we have only just been able to move the expansion valve. We've run it for a day since then, and we definitely have significant improvement. The TEV is now mounted directly below the distributor. Whereas before that section if the tunnel would go no lower than about 11c, it now reaches 8c.
It's still not running as well as unit 2 however...it will cycle on and off at 6c no problem, and will reach 1c if running constantly.
The gas pressure on the faulty unit is about 110psi. On unit 2 it's 160psi.
On the assumption that this could be caused by some kind of restriction, as a next step we're going to put in a new drier and remove the solenoid valve altogether. (It's not doing anything anyway; it's just wired in with the compressor and opens when the compressor runs.
Anyone got any better suggestions?

[JoeReade]

Me again. I think it's probably time for a round of biscuit deliveries. Nike123 and mad fridgie are the first recipients. Can you both please pm me your addresses ? Cheers.

[marc5180]

Hello!
Sorry for the silence. For various reasons we have only just been able to move the expansion valve. We've run it for a day since then, and we definitely have significant improvement. The TEV is now mounted directly below the distributor. Whereas before that section if the tunnel would go no lower than about 11c, it now reaches 8c.
It's still not running as well as unit 2 however...it will cycle on and off at 6c no problem, and will reach 1c if running constantly.
The gas pressure on the faulty unit is about 110psi. On unit 2 it's 160psi.
On the assumption that this could be caused by some kind of restriction, as a next step we're going to put in a new drier and remove the solenoid valve altogether. (It's not doing anything anyway; it's just wired in with the compressor and opens when the compressor runs.
Anyone got any better suggestions?

So it's made a considerable difference, the works that you have done so far.
Did you use the same TEV with the same size orifice? If so would it be possible to post a new set of measurements including the superheat across the Evaporator.

Do the compressors have crankcase heaters? If not then the solonoid valve has probably been fitted to stop liquid migration to the compressor in the off cycle.
You should have something in place to stop this.

[install monkey]

if theres no temperature diff accross the drier then theres no point in changing it, as mark mentions check ur orifice size as undersized orifice will affect operating pressures and maybe use the solonoid as your control to pump down when at setpoint

[mad fridgie]

Focus on the evap, do we have even frost/cooling all over coil.
Suction pressure and superheat please

[hookster]

http://www.islandbakery.co.uk/about/news.htm

This must be the most beautiful setting in the world for a bakery that I have ever witnessed.
Awesome use of the forum and feed back Joe, I am sure a lot of the people active on this post found it interesting and stimulating the old grey cells with your problem.

Your product looks good too (no melting chocolate):D

[mad fridgie]

Hello!
Sorry for the silence. For various reasons we have only just been able to move the expansion valve. We've run it for a day since then, and we definitely have significant improvement. The TEV is now mounted directly below the distributor. Whereas before that section if the tunnel would go no lower than about 11c, it now reaches 8c.
It's still not running as well as unit 2 however...it will cycle on and off at 6c no problem, and will reach 1c if running constantly.
The gas pressure on the faulty unit is about 110psi. On unit 2 it's 160psi.
On the assumption that this could be caused by some kind of restriction, as a next step we're going to put in a new drier and remove the solenoid valve altogether. (It's not doing anything anyway; it's just wired in with the compressor and opens when the compressor runs.
Anyone got any better suggestions?
From what you have described,Gut feeling is that the modified unit is working far better than the other 2,
There maybe some other issues, but lets no worry yet. A simple test, turn off unit 2 and 3.
What is the result?

[r.bartlett]

From what you have described,Gut feeling is that the modified unit is working far better than the other 2,
There maybe some other issues, but lets no worry yet. A simple test, turn off unit 2 and 3.
What is the result?
You appear to be picking up the dialect?

[chemi-cool]

Hello!
and remove the solenoid valve altogether. (It's not doing anything anyway; it's just wired in with the compressor and opens when the compressor runs. .
Anyone got any better suggestions?

Yes, i got one suggestion, dont remove the SV, it cuts the liquid out when compressor stops to prevent from liquid runs into compressor sump.
Your compressors are under the evaporator , check also the compressor sump heater, it should run when compressor at rest.

[JoeReade]

if theres no temperature diff accross the drier then theres no point in changing it, as mark mentions check ur orifice size as undersized orifice will affect operating pressures and maybe use the solonoid as your control to pump down when at setpoint

OK - thanks guys. I'll get a new set of readings before we go any further. I'll check re crank case heaters too.
From the temperatures we measured previously, there did not seem to be a temperature drop across either the drier or the solenoid. Even so, we just thought that restriction could still be a possibility, and swapping the drier is not a big task.

If there is no temperature drop across the drier or solenoid, does that CATEGORICALLY mean there is no restriction there?

We have also changed the orifice from #2 to #3. We did try this previously before we moved the expansion valve, and the performance change seemed to be negligible. So the improvement we have achieved now is definitely due to the shorter distance between expansion valve and distributor.

I'll get a new set of readings posted soon. Hopefully later today.

Thanks again

Joe

[JoeReade]

http://www.islandbakery.co.uk/about/news.htm

This must be the most beautiful setting in the world for a bakery that I have ever witnessed.


It's not bad! But doesn't make a great deal of difference when you're inside baking....

[mad fridgie]

You appear to be picking up the dialect?
Och I
It coming back, spent a couple week on the isle of Mull (35years ago), climbed some hill, nipped across to Iona.
Loved the golf course! Stopped in the castle grounds.
Even though i was young, I did sneak a dram or 2

[marc5180]

If there is no temperature drop across the drier or solenoid, does that CATEGORICALLY mean there is no restriction there?




Ideally you should check for pressure drop across the drier or solenoid but more often that not, it isn't possible and so another way is to check for a temp difference across the part.
If it's 2C (2K) or more then the drier is blocked and needs replacing. If there's no temp difference then leave it as it is.

[nike123]

We have also changed the orifice from #2 to #3. We did try this previously before we moved the expansion valve, and the performance change seemed to be negligible. So the improvement we have achieved now is definitely due to the shorter distance between expansion valve and distributor.


In order to see if orifice change has influence we need some numbers.
First, TXV should be adjusted to factory position. Than orifice changed to No 3 and, when tunnel is near set temperature (1-2K), subcooling and superheat measuring should be done. Only after that we can go further with conclusions.
Maybe orifice need to be one size bigger, if superheat now is still to high.

[JoeReade]

Sorry for the delay... I think we have a minor gas leak, and so I want to make sure that is fixed before I take readings again. The engineer is on holiday right now...

[nike123]

Since you will be opening system for fixing a leak, then I suggest to change orifice to No 4 to see if with that orifice you will have floodback or not.