Case of Chocolate biscuits to whoever can help me!!

[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.
Capture6.JPG

Evaporator plate It states 4800 m3 / hour:
Capture7.JPG

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!

[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!

[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:
tunnel view.JPG
This is unit 1 with the evaporator cabinet on the right:
unit 1.JPG
THis is unit 2 with the evaporator cabinet on the left (unit 3 also has the evap on the left):
unit 2.JPG
Unit 1 compressor:
unit 1 comp.jpg
same view on thermal camera:
thermal comp.JPG
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)
drier thermal.JPG
Thermal image of the solenoid valve. Also seems the same on both sides:
solenoid val ve.JPG
This is the side of the evaporator with the panelling removed.
evap 1.jpg
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.
evap thermal + temps.jpg

[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:
Attachment 10667
THis is a thermal view of this evap, with temps as measured by the camera superimposed:
Attachment 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:
evap 2.jpg
thermal image of evap 2:
evap 2 + temps.jpg

[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?

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.

Danfoss TXV.PNG

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.co...0&d=1377353284

& also
http://www.refrigeration-engineer.co...5&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/re...gth-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/TechnicalI....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]

chocolate.jpg

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

[nike123]

Give me a real boost and I'm all on a mission! 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.

Slika zaslona iz 2013-08-26 19:12:50.jpg
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?