getting closer to helping my scrolls

[ENERGY KNIGHT]

hi and thanks for all the help in the past. im still working on this mis-matched chiller
the condenser coil was piped wrong, I have re piped it to be a 9 pass 10 fpi
1/2 in tubes 4 row and its 50in tall by 70in wide and 13250 cfm. I ran those numbers through
a condenser program and it handels 300,000 btu at 95 f ambient
with 6psi drop. I re filled it and now psi drop showed up in the 1 3/8 vapor line and 1 1/8
liquid line . this is a 25 ton chiller which runs 42 deg water . so I ran a new vapor line so now I have a 1 5/8
vapor line and 1 3/8 liquid line. I re filled system or should say im am trying to get it filled corectly . it does have a
huge reciever just before the txv. I really want to see a clear sight glass. I am at 8-10 deg superheat right now but sight glass is only clear for a few sec. then flash full of vapor should I keep adding r-22

[mad fridgie]

Is the receiver a horizontal or vertical?
Your sightglass is before the TXV and after the reciever?

[ENERGY KNIGHT]

the receiver looks just like the 25 ton scroll comp. it has a line going in almost at top and a line coming out just below half way down then there is a filter housing then sight glass then txv. Im trying to get the best charge in this thing. right now ive got 8 - 10 deg f superheat about 12in away from comp. but the suction pres. goes up and down alot. im not shure if the comp. will be happy with that.

[aramis]

I supposed you have no problems with the air circulation and you are NOT recirculating hot air at the condenser intake, and your piping is correctly designed and not trapping oil/liquid somewhere.

You are missing two important pieces of information:

- How much subcooling measured at the expansion valve?

- Does the condenser pressure vary following the same pattern as the bubbles in the sight glass?

If the liquid at the expansion valve is subcooled all the time, don’t worry about the bubbly sight glass and read no further.

If the condenser pressure varies in a regular pattern following the bubbles I'm afraid you still have problems with the condenser and the most probable cause is that it is stacking up liquid in some of the circuits, thus increasing condensing pressure until it flashes the liquid out starting a cycle all over.

Using programs for estimating capacity is not enough. You need to know where inside your condenser you will start to have mostly liquid and try to circuit downwards from there on. Otherwise your condenser (and the system) will suffer from these cycles.

Second cause is the receiver:
- It needs a minimum amount of refrigerant to cover the outlet tube.
- In rare occasion I´ve had it installed in the wrong position (example a receiver designed to be hang on a wall vertically installed horizontally on the same base).

[Magoo]

Just a comment, a vertical liquid receiver next to a vertical air cooled condenser can give the symptoms you are describing. Basically the condenser acts as a receiver to overcome the lift up to entry of vertical receiver. R22 is heavy. So your receiver fills then empties, pulse flow through sightglass, irratic suction pressures due to TXV hunting. If discharge pressure can handle added gas, add more refrigerant, but you may loose effective condenser area. But good sub cooled liquid. Or else install a horizontal receiver.
magoo

[ENERGY KNIGHT]

yes the condenser fans speed up and slow down . so the condenser could be backing up liquid ? any way to fix this.
also the reciever is inside away from condenser. the liquid does have to lift straight up about 6 feet with a back check valve in the line. i filled this thing up until the sight glass prety much stayed clear but high side went higher than the other units so I took itt back out. how would a horizontal receiver help im not shure the difference but it does seem like my reciever is not doing its job. but this condenser is messed up it was made with a sub cooling circuit originaly but it is kind of bypassed

[mad fridgie]

The liquid line raise 6 feet from the cond or from the reciever.
Is the receiver inside warmer or colder than the ambient.

[Magoo]

Your liquid receiver should be at or close to the condenser, a 6 foot lift is way too much. DO not charge any more liquid into system please. You will start blowing releif safety valves. You can have condenser were ever but HP receiver should there as well.
There is your major/ the problem. The receiver must be below the condenser so move it

[aramis]

yes the condenser fans speed up and slow down . so the condenser could be backing up liquid ?

Yes.


any way to fix this.

Do exactly what Magoo suggests: Place the receiver under the condenser.

But also check what mad fridgie says, warmer receivers can cause the same symptom.

There is another possibility but requires measuring small pressure drops and knowing the design of the inlet of your receiver and that is to build a syphon that lifts the liquid column against that known pressure drop, so that the condenser does not have to work against that liquid column lift.


also the reciever is inside away from condenser.

If this is a heat pump you need to re-check mad fridgie’s point when you are heating inside.


the liquid does have to lift straight up about 6 feet with a back check valve in the line.

Any pressure drop here only makes things worse!


filled this thing up until the sight glass prety much stayed clear but high side went higher than the other units so I took itt back out.

Proof that charging with a misplaced sight glass is not a good idea! You may find your system is overcharged.


how would a horizontal receiver help im not shure the difference but it does seem like my reciever is not doing its job.

The receiver is doing its job the problem are all the pressure drops the condenser hast to fight against to fill it!


but this condenser is messed up it was made with a sub cooling circuit originaly but it is kind of bypassed

Are you sure it wasn’t the receiver’s position all along?

Anyway I’m as confident as Maggo that the main problem is the lift (or pressure drop) but several causes may produce the same result (including the new circuiting of the condenser) so keep your fingers crossed and don’t curse us if you keep having the same symptoms. It should be much better though.

And for future reference, fans should never cycle up and down if your air in temperature is constant or the capacity control of the system doesn’t kick in. This should have told you immediately you (still) had a condensing problem.

[ENERGY KNIGHT]

ok this system is a climacool chiller with 42 deg f water going through the chiller barrel
everything is inside about 30 feet away from the condenser which is outside
the liquid line comes off bottom of condenser and goes up to ceiling
then piped about 30 feet across ceiling and back down to the top of the reciever
then out of reciever to the filter (about 2 feet) then to sight glass (about 12 inches )
then to txv (about 12inches) this is a "modular" chiller. the compressor is on top the reciever and chiller barrel sit just below . any ideas what I should do?

[aramis]

Sorry I don't know the climacool chiller. A picture could help.

You have several possibilities:

A)

You can dimension a syphon, though it has a height limit. So more information is needed.

You may measure the actual pressure drop from the condenser to the ceiling (but at maximum load) or estimate using:

1) Pressure drop to at least the ceiling and you'll have to go with the tube well above the level the pipe is now. Can you do this?

2) Measure the subcooling you are getting from the condenser and probably insulate the pipe if ambient temperature is above refrigerant temperature (year round). This is because the syphon must not get vapor or the liquid column will collapse.

3) The pipe's inner diameter number and type of curves fittings valves, anyting that is between the condenser and the ceiling.

4) A drawing showing disposition lengths as accurate as you can showing all horizontal, inclined and vertical lines.

5) Mass flow from the compressor information as accurate as you can, this means you must get the selection program and measure all variables it has to calculate it.

Keep your fingers crossed while you do all this to get accurate answers!

B)
Or you can try with a syphon but if you reach a pressure in it below the saturation pressure of the R22 it won't work!

C) Get a bigger condenser that works OK despite this problem.

D) Leave all as it is but try to feed the TXV from enough height for it to have subcooling all the time, also using a balanced port or EXV are less affected by condensing pressure variations.

I'm sure someone with more imagination will come with more answers! ... Like Magoo, please help!

[Magoo]

The problem is with the vertical lift from bottom of condenser to ceiling height. Is it possible /practical to lift condenser to ceiling height, or moving receiver to condenser location.
A the moment the condenser is acting as receiver and condenser. Liquid would be returning to receiver existing location in shots, as the pressure diff from riser is overcome

[mad fridgie]

Lets start with the simple things first.
Your cond fan(s) are cycling, this will cause big a fluctuation in pressure and you will see bubbles in your sight glass. Do you know if there is a baffle between the fans in the cond. If not install! Without the air can short the cond when a fan is off, this speeds up the cycling time and the system can not react quickly enough.
For example lets say 2 fans both running 100% airflow passing through coil, without a baffle one fan turns off, logic would say that air flow through the coil has dropped by 50%, but flow has dropped by much more, say down to 25%. This massive change causes great swings in liquid pressure, almost to point where flow is going backwards from the receiver. This then would cause the evap to be starved for a short period, we then have a very erratic system.
It would seem that the original cond design (dedicated sub cooler section) was designed for a system without a receiver of the conventional type.
You have converted back to a more standard design, a free draining cond, but it is not as the line has to rise. Best place the receiver directly under the cond drop leg.

[ENERGY KNIGHT]

the fans all run together on variable speed. also it would not be practical to lift condensers up. but I could move reciever out to the condenser if that would help. If I knew that would fix my system I will move the reciever out there right now

[Magoo]

Moving the receiver to condenser would solve your problems. Free draining from condenser to receiver with a small balance line between discharge hot gas and top of receiver if possible.

[mad fridgie]

Moving the receiver, would balance that side of the system.
Does the liquid line run through a area which is warm or colder than the ambient. (this becomes a separate issue)

[ENERGY KNIGHT]

the liquid line runs inside which is not air conditioned so in the summer its probly about the same or a little warmer than outside but I could get it a little cooler if I need to. also what do you mean about the small line from discharge vapor to top of reciever. that would be easy to do if that would help the system. onother thought is do I even need the reciever the system is shut down when it gets cool out. like 50 deg f
thanks

[mad fridgie]

I would keep the receiver.
Personally I would not but the balancing line if the receiver is very close and below the cond. (But will leave to Magoo for his opinion on this)
The liquid line running through a warmer area can cause flash gas (a similar issue might be seen), a liquid/suction heat exchanger would recondense the bubbles.
Go for it, please give us the results good/bad or indifferent. (more numbers the better we can assist)

[Gary]

In order to push the liquid from the condenser to the receiver, the condenser must be at a higher pressure than the receiver. If the receiver is warmer than the condenser, the receiver could be at a higher pressure than the condenser, slowing or even stopping the flow.

In addition, it takes even more of a pressure difference to lift the liquid up to the receiver.

Putting the receiver outdoors and below the condenser would solve both of these problems.

[ENERGY KNIGHT]

ok Im sucking the refrigerant out right now. I will cut out the receiver and re pipe the indoor chiller.
At that point could I fill the system and try it with no receiver or would that be dumb?

[mad fridgie]

Leave the receiver in.

[Magoo]

Hello MF.
the balance line to receiver is for extended liquid lines and cold starts and cold ambients. Prevents short cycling due to lack of liquid at chiller. Basically fires hot gas on top of liqiud and gets things perculating, I think sporlan have a diff vav for that purpose ORD or some name like that.

ps MF this comes from experience at a site in Pahiatua, Wairarapa. Large multiplex chiller and freezer system and nut cracking cold outside and large compressor sets short cycling in the winter. Also common practice with large industrial system.

[ENERGY KNIGHT]

I have been reading and read that the only way to prevent flash in a liquid line that has vertical lift is to have subcooling.
ok I can see that. now with a receiver doest the subcooling become zero unless totaly full of liquid?
that is why I would like to try this with no receiver. but I really respect you guys knoledge. and it looks like
I should cut the receiver in outside just after condenser outlet . so I probly will (I might still try it without first cant hurt right ) would like to know why I would be better off with keeping it . sorry for all the questions but I think i could be learning some giid stuff. thanks

[Gary]

now with a receiver doest the subcooling become zero unless totaly full of liquid?


No, it doesn't.

[ENERGY KNIGHT]

ok will my chiller work ok without the receiver or will it work better with the reciever just curious why. because I dont run when under 50 deg f outside. and the chiller does not pump down when it shuts off. maby it should

[mad fridgie]

I have been reading and read that the only way to prevent flash in a liquid line that has vertical lift is to have subcooling.
ok I can see that. now with a receiver doest the subcooling become zero unless totaly full of liquid?
that is why I would like to try this with no receiver. but I really respect you guys knoledge. and it looks like
I should cut the receiver in outside just after condenser outlet . so I probly will (I might still try it without first cant hurt right ) would like to know why I would be better off with keeping it . sorry for all the questions but I think i could be learning some giid stuff. thanks

The first issue is allowing the condenser to free drain into the receiver, which will ensure that you have at the very least a solid stream of liquid leaving that area.
The amount of sub cooling in a receiver (many of use have different opinions to what level actually occurs) so will leave this alone for now.
You can if want sub cool the liquid after it leaves the receiver and before it rises.
just run a length or so of pipe in the inlet air steam of the condenser or you could sub cool down by the indoor unit.
You are after a liquid seal at the TXV.

[mad fridgie]

Hello MF.
the balance line to receiver is for extended liquid lines and cold starts and cold ambients. Prevents short cycling due to lack of liquid at chiller. Basically fires hot gas on top of liqiud and gets things perculating, I think sporlan have a diff vav for that purpose ORD or some name like that.

ps MF this comes from experience at a site in Pahiatua, Wairarapa. Large multiplex chiller and freezer system and nut cracking cold outside and large compressor sets short cycling in the winter. Also common practice with large industrial system.

Hi magoo,

Have used them many times, but nothing as simple and as close to this. and at such high ambient.

[mad fridgie]

ok will my chiller work ok without the receiver or will it work better with the reciever just curious why. because I dont run when under 50 deg f outside. and the chiller does not pump down when it shuts off. maby it should
Just bang the receiver in.

[ENERGY KNIGHT]

ok Im starting to get it my condenser is kind of built for this come out of first liquid header then into receiver then out of receiver back through a few passes (subcooling circuit) in very bottom of condenser
then out pure liquid?

[mad fridgie]

ok im starting to get it my condenser is kind of built for this come out of first liquid header then into receiver then out of receiver back through a few passes (subcooling circuit) in very bottom of condenser
then out pure liquid?

yes................

[ENERGY KNIGHT]

cool if this works I owe you guys bigtime!

[mikeref]

ok will my chiller work ok without the receiver or will it work better with the reciever just curious why. because I dont run when under 50 deg f outside. and the chiller does not pump down when it shuts off. maby it should The receiver is necessary because your expansion valve is constantly opening and closing with the various heat loads in the room. Receiver levels will rise and fall so the receiver is there to ensure the expansion valve has a constant supply of liquid refrigerant.
Receiver is also sized to accommodate refrigerant when system is pumped down.
(Sort of.. explains "Mads" bang the receiver in)

[ENERGY KNIGHT]

well I hope no one gets pissed at me but I eliminated the receiver friday and did not have enough time to relocate it to the condenser yet but if I have to I will. but so I coukd run the chiller for the weekend I re filled the unit . I just kept adding r22 until the sight glass cleared. it finally did and stayed clear but Im concerned i may be too full? the low side was 38deg on my gauge and 48 deg on the pipe 12 in from comp. so I have 10 deg superheat right? I turned fans on full speed and high side was 220psi. it was 70 deg outside. is all that ok no more hunting just worried high side may be too high when it gets hot outside? any thaughts

[mad fridgie]

If the fans are running at full speed, then head does seem to high.
I would say you have loaded the cond partially full of liquid.
At least you know that the system can be stable, so half way there!
Finish the job off and looks like all will be good.
keep us posted!

[ENERGY KNIGHT]

I got the receiver out and am going to put it out by the condenser. the inlet of my receiver will be lower than the liquid header on condenser coil. then out of my receiver the pipe will go straight up about 2 feet back into the condenser subcooling header. then out of condenser subcooler up about 6 feet and across room then back down to filter into sight glass into txv. my question is the 2 feet vertical lift out of receiver is that ok .

[install monkey]

morning energy knight- the 2 ft lift after the condenser into the reciever will be ok- you only need oil traps every 3-4mtr depending on the manufacturers requirements-
-
I got the receiver out and am going to put it out by the condenser. the inlet of my receiver will be lower than the liquid header on condenser coil. then out of my receiver the pipe will go straight up about 2 feet back into the condenser subcooling header. then out of condenser subcooler up about 6 feet and across room then back down to filter into sight glass into txv. my question is the 2 feet vertical lift out of receiver is that ok .

[ENERGY KNIGHT]

thanks did you mean out of receiver up 2 feet to condenser subcooler is ok to lift at that point also im not too shure about oil traps im new to this big stuff.

[mad fridgie]

She will be OK

[install monkey]

* Liquid receivers are to be mounted after
the condenser.
* For optimal operation, special attention
should be paid to the receivers’ level:
RLHCY receivers should be perfectly
horizontal and RLVCY should be perfectly
vertical.
* If sizing of the receivers is performed
on the basis of the total refrigerant load,
it is imperative to select receivers with
an internal volume 20 % bigger, so that
the gas reserve is always above
the liquid level

after reading breifly all the comments on this- am i right in guessing your worried about the fluctuating suction pressure destroying your compressors- is this not just the tev modulating to maintain superheat,i take it youve changed the filter drier to ensure theres no pressure drop/restrictions- do they do crankcase pressure regulators for 1 5/8?

thanks did you mean out of receiver up 2 feet to condenser subcooler is ok to lift at that point also im not too shure about oil traps im new to this big stuff.

[install monkey]

danfoss dont do them- only upto 1 3/8
Crankcase pressure regulator, type KVL
Limits the maximum crankcase pressure. KVL controls the suction pressure during start and at high load conditions and thereby protects the compressor motor against overload. Using a KVL prevents the suction pressure from becoming too high and overloading the compressor motor, with subsequent cut-out by the motor protection device. Connections and sizes: KVL - Flare or solder ODF connections 12 → 35 mm (1/2 → 1 3/8 in.)

[ENERGY KNIGHT]

i just got done moving and re piping . It took a lot of r22 . it is 85 deg f outside and I get 265 psi at comp outlet. and 60 psi suction pres. about 15 deg superheat at 12 in away from comp.
I just filled until sighht glass cleared. 44 deg water through chiller barrel. fan are on full speed. when I look into oil sight glass on comp. the oil is full of foam on top of oil level, but all the other ones are that way but I dont like when the oil twirls when txv is hunting. I think that is liquid geting in there. not shure why its hunting again .

[install monkey]

raise your chilled water setpoint as 44degf is 6.6deg increasing the setpoint to 10deg say will increase the duty thus preventing liq flood back

i just got done moving and re piping . It took a lot of r22 . it is 85 deg f outside and I get 265 psi at comp outlet. and 60 psi suction pres. about 15 deg superheat at 12 in away from comp.
I just filled until sighht glass cleared. 44 deg water through chiller barrel. fan are on full speed. when I look into oil sight glass on comp. the oil is full of foam on top of oil level, but all the other ones are that way but I dont like when the oil twirls when txv is hunting. I think that is liquid geting in there. not shure why its hunting again .

[mad fridgie]

What is the temp leaving the cond (entering the receiver)
what pressure/temp leaving the receiver.
What temp leaving the sub cooler.
What temp prior to the expansion valve (liquid pressure would be nice as well)
If you got 15f superheat i do not think you got liquid coming back

[ENERGY KNIGHT]

I will check . and install monkey I need 42 deg f chilled water when it gets hot out to keep building cool.
mabey I didnt pipe it right ?

[Magoo]

The 85'F / 29'C ambient is part of problem, 265pisg discharge./ 18 bar condensing at +50'C is the next problem.
44'F water/6.6'C, 60 psig/ 4.1 bar and +2'C evaporating at compressor. Something doesn't stack up.
Oil is foaming because it is way too hot.
Potentially overcharged. Recheck the TXV super heat.

[ENERGY KNIGHT]

I think it took way too much r22 to get a clear sight glass . I dont know what to do.
I liked the pres better with the sub cooling bypassed wich eliminated most of the pres drop
should I repipe it like a normal condenser coil just one in and one out very little pres drop. no receiver
and charge it just enough to get 10 deg superheat at comp? I would not have a clear sight glass but if I can keep high pres down and make cold water and not hurt my comp. please help

[Gary]

265 psi = 123F - 85F = 38F over ambient. Under heavy load, I would expect no more than 35F over ambient. At 38F over ambient it is just slightly high.

What are your chilled water in and water out temps?

[ENERGY KNIGHT]

hi Gary. my chilled water in is 54 deg f and water out is 44 deg f. I re piped the condenser header
again today to get rid of most of my pres drop. now my readings are 80 deg f outside air. 245 psi
leaving comp. 74 psi suction . I have it set at 8 deg f superheat about 12 inches away from comp.
and I have a clear sight glass !! I wonder if what I'm seeing in the comp. sight glass is oil coming in and not liquid refrigerant? I see a flat line of oil about half way up on glass and on top of oil is full to top of glass with very tiny bubles. then once in a while the smooth line of oil gets wavy and twirls around. do you think that is oil coming back once in a while or do you think its liquid refrigerant ? and what do you think about these new presures? thanks

[Gary]

Your superheat is set too low. It should be at least 15-20F near the compressor inlet.

[Magoo]

Totally agree with Gary. Check and reset the TXV superheat as suggested previously. Your water split at 10 'F is fairly standard

[ENERGY KNIGHT]

ok I will set between 15 and 20 but in the other units with superheat that high the discharge gets hot . but with the diferent piping mabey this one will be better. that will also bring down my suction right? what do you think is hapening with the oil . and what should it look like in the oil sight glass? and do you think the high side at 240 at 80 f outside is ok or will that change with higher superheat? thanks

[ENERGY KNIGHT]

I now have 85 f outside 235 psi discharge at 170 f 12 in away from comp. 225psi at filter 215 - 220psi after filter at txv. at 105 f ...suction is 60 psi at 50 f how does this look?

[Gary]

I now have 85 f outside
235 psi discharge
at 170 f 12 in away from comp.
225psi at filter
215 - 220psi after filter
at txv. at 105 f
suction is 60 psi
at 50 f
how does this look?

What does "at 170 f 12 in away from comp" mean?

What does "at 50 f " mean?

[ENERGY KNIGHT]

discharge pres. is 235 psi and the discharge pipe is 170 deg f about 12 in away from compresor outlet.
the suction pres is 60 psi and the suction pipe is 50 deg f about 12 in away from compresor.
it was 85 deg f outside. I adjusted the txv way open and took out a lot of r22 until my superheat was around 15 - 20 deg f
the oil in the sight glass on the compresor is "foamy" looking is that normal or what should it look like in there also are my pressures looking any better or close.

[aramis]

Gary its 170 degrees fahrenheit measured 12 inches away from the compressor.

235 psi is about 113 °F so your condenser is working at a 113-84 Dt = 28°C which is right at the edge between “normal” and “high” condensation.

If your maximum ambient can go 4°F higher for long periods of time then you will have condensation problems.

The same situation for suction saturation temperature is about 34°F which is at the edge of being low suction.

About the 50°F 12 inches away from the compressor: Did you insulate your sensor or thermometer when taking that measure. If not you will have to repeat it with insulation.

With a 50°F – 34°F saturation your superheat is at the edge of OK, Copeland would require 2°F higher suction temperature.

If you have small suction lines with high velocity then some level of foaming is expected anyway but it also depends on the “foam” if bubbles change size and behave violent then you should really re-check your suction temperature and pressure measurements this time with insulation at least 10 inches to either side of the sensor, including the sensor.

Measure the temperature of the air near the condenser intake and far away from the condenser if this difference is significant you may be recirculating hot air. Try to avoid this installing any air barrier at the sides and up and down of the condenser, with cardboard for example. If this improves condensation then you will have to install a definitive barrier.

If you have no problems with the air intake the system maybe still slightly overcharged.

When you compare system you have to take into account their working conditions too. Causes of high discharge are:

High condensing temperature

High superheat

Low suction pressure

... or any combination of the above. So you can’t only compare the superheat.

For example if all three above are the same but the amps drawn are different, one motor is causing more internal superheat because it is working at a higher (internal) temperature and this causes higher discharge temperatures on that system.

You may think the systems are equivalent but when you MEASURE you will discover they are NOT!

[ENERGY KNIGHT]

my compresor sit directly above my chiller barrel (evaporator) less tha 2 feet of pipe not shure what size but its very big and its factory right from climacool. this morning I started it up and my super heat was up to arround 25 deg f its 75 deg f outside now. I think I took out a little too much r22? do I have too much pres drop in my filter dryer. its a c489gt sporlan 402152 I cant find anywhere to tell me if that is the right one for 25 tons. is 10psi drop ok through filter ?and my oil looks violent once in a while when presures high and low hit the right pres at the right time ( meaning things are still fluctuating) the oil looks nice but then boom violent again I must still be missing something

[aramis]

Superheat also depends on thermal load, with higher load you should expect higher superheat.

This is something you should check with low thermal load when you get the lowest superheat it should not drop below 18°F measured at the compressor (or follow manufacturer's recomendation) and not less than 9°F at the TXV exit (unless it is an EXV).

Anyway 25°F sounds OK.

I only know the C-489-G and 10 psi is way too high it should be less than 1 psi.

[stufus]

Can you post photos of the piping arrangement from condenser to receiver something on the liquid line is a miss
Cheers
Stu

[kleen]

Hi guys dont want to hihgjack this thread but why 10 f is to low for Suction superHeat . On a Wgz unit Scroll compressers with a brazed plated evaporator water cooled or airCooled the recommand Superheat his 8 to 12 TxV or ExV .

[aramis]

Really 0.01°F should be enough but in the field you have to take precautions mainly due to measurement errors and you have to get rid of droplets travelling in the gas flow that don’t touch the tubes in straight runs.

In mechanical TXV the minimum static superheat is 7.2°F and you have to operate them a little higher.

If you read different manufacturer’s literature you’ll notice slight changes and that’s only because they use different safety factors.

[ENERGY KNIGHT]

I tink the climacool rep said 10 deg f superheat with one compresor runing and as low as 5 deg, f superheat with both compresors runing, ( two compresors share one brazed plate heat exchanger)
that might be right after heat exchanger or (chiller barrel) but the is so little pipe between barrel and compresor that it wont make mugh diference. would lowering the superheat to 8 - 10 deg f help with the high side . it looks like I have two problems the high discharge pres. and the foaming oil. again the chiller and condenser are from two different companies and something is not right. I can try and get some pictures on here. I was looking in a book on filters and the one that had 1 1/8 lines that could handle 25 tons used two filters in it and the one that had 1 1/8 line and only one filter in it could only handle like 15 tons or something like that . but I put in the numbers in the internet and didnt find tonage for my housing. I just know last time I checked It had 10 psi drop through it

[Gary]

I adjusted the txv way open and took out a lot of r22 until my superheat was around 15 - 20 deg f

The superheat is raised by closing the TXV, not opening it... and removing refrigerant is NOT the way to increase superheat on a TXV system.

Is the sight glass clear?

[Gary]

I now have 85 f outside
235 psi discharge
at 170 f 12 in away from comp.
225psi at filter
215 - 220psi after filter
at txv. at 105 f
suction is 60 psi at 50 f

235 psi = 113F - 85F = 28F TD

28F over ambient is normal.
170F discharge temperature is normal
More than a few psi drop through the filter is not normal.

[r.bartlett]

235 psi = 113F - 85F = 28F TD

28F over ambient is normal.
170F discharge temperature is normal
More than a few psi drop through the filter is not normal.

Are you trying to tease Aramis ?

[aramis]

Nah r.bartlett is just trying to stir the nest Gary. :)

[Gary]

Are you trying to tease Aramis ?

Nahhh... if I were trying to tease Aramis, I would point out that a temperature comparison of two flow streams is a TD, not a dT... and that a temperature change in a single flow stream is a dT. :)

[Magoo]

EK.
what is the TXV super heat, light load what ever load, can you indicate please.
The evaporator barrel is now a PHE, I must have missed something in earlier posts.
magoo.
ps.., cool comment Gary

[ENERGY KNIGHT]

Im sorry guys I may not have all the best info from my side , I will do my best please dont give up on me .
I do not have a reciever in the system at all right now. I dont know what the txv super heat is .I am just measuring temp on pipe about 12 inches away from comp. and the brazed plate heat exchanger is only 2 feet away . just below the compressor so the temp in the pipe can not be that much different? the sight glass is not clear right now since I have taken a lot of r22 out. Im thinking about puting just enough r22 in to get 10 deg super heat so my comp stays cool and see what my high side and oil look like . I dont know what else to do I would like to hire an engineer to come out here and tell me what I need to do but thats not up to me I hope I can get the right infp o you guys and fix it .. what do you guys need to know to make this system happy.

[MikeHolm]

What you need is Gary to come out, engineers on this side of the pond will muck it up.....LOL

[aramis]

Im sorry guys I may not have all the best info from my side , I will do my best please dont give up on me .
I do not have a reciever in the system at all right now. I dont know what the txv super heat is .I am just measuring temp on pipe about 12 inches away from comp. and the brazed plate heat exchanger is only 2 feet away . just below the compressor so the temp in the pipe can not be that much different? the sight glass is not clear right now since I have taken a lot of r22 out. Im thinking about puting just enough r22 in to get 10 deg super heat so my comp stays cool and see what my high side and oil look like . I dont know what else to do I would like to hire an engineer to come out here and tell me what I need to do but thats not up to me I hope I can get the right infp o you guys and fix it .. what do you guys need to know to make this system happy.

I learned that getting the correct information in the forum is as hard as milking a dry cow! ... and even then you can’t be sure it is correct.

Thanks to the off topic chat I didn’t notice the BPHE reference sooner!

BPHE rely on turbulent flow and enough to cover all the plates if the mass flow of your compressor(s) is not enough to satisfy both conditions the performance of the coil drops to the floor and you´ll NEVER get the capacity you want. And just for the record this applies to the water side also. This means you should respect minimum pressure drops on both sides.

You should try to get the BPHE manufacturer’s software and check what happens with smaller flow.

Without compressor and BPHE models (provided they are known here) we can’t help you with this.

:off topic:

Nahhh... if I were trying to tease Aramis, I would point out that a temperature comparison of two flow streams is a TD, not a dT... and that a temperature change in a single flow stream is a dT. :)

That’s just because here we don’t use hyperbaton that much. We pronounce it Dt. But I’ll keep it in mind thanks! (I imagine r.bartlett grinning with delight!)


Totally agree with Gary. Check and reset the TXV superheat as suggested previously. Your water split at 10 'F is fairly standard

I thought You, Gary and Energy Knight were on the same side of the pond, but maybe this is another miss pronunciation.

[Gary]

That’s just because here we don’t use hyperbaton that much. We pronounce it Dt. But I’ll keep it in mind thanks! (I imagine r.bartlett grinning with delight!)

It's not hyperbaton. TD and dT have precise meanings.

The temperature difference between the air on and the saturation temperature for any coil is the coil's temperature difference or TD.

The temperature difference between the air on and the air off for any coil is the coil's delta temperature or delta-T or dT.

[Gary]

What you need is Gary to come out, engineers on this side of the pond will muck it up.....LOL

Retired... that's ***R*E*T*I*R*E*D*** Best job I ever had... :D

[aramis]

:off topic:


It's not hyperbaton. ...


Well it is and from my point of view you use a lot of it. The correct order is adjective before noun like in Latin. This was preserved in French and Spanish, not in English.

If the meaning is clear in the context then we save a lot of explanation and we don’t have to pay attention to every little detail when we post.

For example saying “170 f 12 in away...” is clear enough in context.

Now r.bartlett must be holding his beer belly lol! :D

[ENERGY KNIGHT]

so any ideas on what I should do . I guess I will just add a little r22 back in until I get 8 - 10 deg f superheat at comp. then see what my presures look like. and I will keep looking to see if the filter is the correct size .
in case I didnt mention this is a(clima cool) factory built modular chiller with two 25 ton scroll compresors and one brazed
plate heat exchanger. the condenser has to be the problem because it is the only thing not factory hooked up to the chiller. and maby the piping because Im shure there other climacool modular chillers out there working.

[aramis]

Yes! Wake me up after you measure subcooling at the TXV inlet! If possible at a high and low condensing cycle.

It would be a good idea to turn off the fan control and keep the running (depending on ambient).

I would like to get compressor and BPHE model but I think this is asking too much.

Maybe you can measure the face area of the BPHE and the number of plates?

[Gary]

It needs a receiver.

[Magoo]

EK.
an example of checking TXV superheat. Not necessarily yours but,
water in 52'F water out 42'F, evaporating pressure at compressor 32'F.
System TD is water in, versus evaporating temp.
52'F - 32'F = 20'F Super heat should be in region of 60 > 70% of system TD, so 20'F x 0.65 = 13'F.
Temp at tXV thermo bulb should be 32'F + 13'F = 45'F. That is for close coupled as you have any suction strainers will change things and add pressure drop to reading taken at compressor.
Checks are done with suction gauge and contact thermometer. Opening TXV will lower the superheat closing will increase. Any adjustments wait for 15 minutes for TXV to stabalize. Idealy a schrader connection at the thermo bulb would be perfect, or on the external equalizer line of TXV.

[ENERGY KNIGHT]

I will get the subcooling at the txv and the compressor moldel number Ill try to get bphe #
also the other units have receivers and they get up to 380 psi when it gets hot . they are making cold water but we have lost 4 of the 8 compressors in 4 years. this last year we didnt loose any but I have water runing down condensers when high side gets to 300 psi. climacool says they want nothing to do with it unless we change out the condenser to the one they would have used . then they will work with us. thats fine and dandy but the new condensers are like 20g each x 8 . I think with you guys help we can get these scroll's to run

[aramis]

If they are installed close together you could have an important problem of hot air recirculation.

Supposing your condenser is correctly sized, one important difference with more expensive ones is the air throw. With good designs you can minimize hot air recirculation, cheaper models don't have these designs and you should check whether recirculation occurs.

[Gary]

We can't see it from here, but this is what I suspect is happening:

The condenser has a subcooling loop, which serves as a receiver.

The chiller has a receiver.

You can have one or the other, but not both. They are interfering with each other.

Please correct me if I'm wrong about any of this.

If the above is true, then on one of the other systems, simply bypass the receiver and you should see a big difference.

[ENERGY KNIGHT]

85 - 90 deg f entering condenser coil. 225 - 250 psi discharge . now at the txv temp is 103 - 116 deg f and 105 - 119 psi. suction was 63 psi and 52 deg f. this is all with fans full speed , and sight glass never clears.
so I added some r22 and it looks like the sight glass is clear only when I have between 8 and 9 deg f subcooling at txv. anything less and it instantly flashes off.

[ENERGY KNIGHT]

8963 this is my condenser before I re piped it . it is nine 1/2 in tubes four row
10 fins per inch. then there is four more 1/2 in tubes that come out of the liquid header and back to that
small header which the liquid line comes off of. I have tryed to re pipe it a bit.

[Gary]

It would be clearer for me if you could report temps/pressures in this format:


Evap air in temp:
Evap air out temp:
Low side pressure:
Suction line temp at TXV bulb:

Cond air in temp:
Cond air out temp:
High side pressure:
Liquid line temp at TXV:

[ENERGY KNIGHT]

bphe in temp: 54 deg f
bphe out temp: 44 deg f
low side pressure: 63 psi
suction line temp : 52 deg f


cond air in temp: 85 - 90 deg f
cond air out temp: not shure
high side pressure: 225 - 250 psi
liquid line temp at txv: 103 - 116 deg f
liquid line pressure at txv: 205 - 219 psi

[Gary]

bphe in temp: 54 deg f
bphe out temp: 44 deg f
low side pressure: 63 psi
suction line temp : 52 deg f


cond air in temp: 85 - 90 deg f
cond air out temp: not shure
high side pressure: 225 - 250 psi
liquid line temp at txv: 103 - 116 deg f
liquid line pressure at txv: 205 - 219 psi

54 - 44 = 10F evap dT. That's good.
63 psi = 36F SST. 52 - 36 = 16F SH. That's good.

Averaging:

87.5 - ? = ? cond dT
237.5 psi = 114F SCT. 114 - 110 = 4F average SC. Too low. Your subcooling needs to be 10-15F... or a clear sight glass, whichever comes first.
114 - 87.5 = 26.5 TD. That's good.

You need to add more refrigerant to bring the subcooling up to 10-15F... and you need a receiver OR a subcooling circuit.

The liquid pressure at the TXV is going to be severely affected by modulations in the valve, which makes this reading useless.

Ideal would be pressure and temperature readings at the sight glass.

[Magoo]

EK.
your initial post indicated a vertical air cooled condenser, "x " wide and " ÿ "inches high, the pic/sketch of your of condenser with full face sub cooling will complicate things I beleive, with additional internal pressure drop/ loses in condenser.Generating a high pressure differential across condenser. Generally a sub cooling circuit is at the bottom on a vertical arrangement air cooled condenser.
magoo

[ENERGY KNIGHT]

not shure what you mean . the coil is 50 in tall and 70 in wide . the air flows horizontal through the coil. and the subcooler is at the bopttom.
I was trying to measure the air temp going into my coil I noticed the temp was a lot higher than outside
air. I think the air blowing out the top is coming back down and through again . is that heard of ?

[Magoo]

OK.
the condenser coil is mounted vertically, and air flow is horizontal. Hot off coil air re-generation is a constant problem with induced air patons as most of air flow is off the fan blade tips so goes side ways and can be re-introduced back into air on air flow. Baffling may be necessary to direct air away from re-generation.
Seems that all your problems relate to location and positioning of remote air cooled condenser and receiver vessel.

[ENERGY KNIGHT]

with a clear sight glass my discharge temp - outside air is 30 deg f
what should I set my super heat at when measuring 6 in from comp. 8 - 12 or 15 - 20 deg f ?
what should suction pres be with 54 deg f water in and 44 deg f out of bphe ?

[Gary]

what should I set my super heat at when measuring 6 in from comp. 8 - 12 or 15 - 20 deg f ?

At 10F superheat, all of the liquid droplets have boiled off. Some compressor manufacturers call for a minimum of 15F SH at the compressor inlet, while others call for 20F SH at the compressor inlet.

It's a trade-off. We want to completely utilize the coil, without flooding the compressor.

[mad fridgie]

not shure what you mean . the coil is 50 in tall and 70 in wide . the air flows horizontal through the coil. and the subcooler is at the bopttom.
I was trying to measure the air temp going into my coil I noticed the temp was a lot higher than outside
air. I think the air blowing out the top is coming back down and through again . is that heard of ?
Now this making a lot of sense.
Yes air re-circ is a common problem.
Stop this first, before you make your next move!

[ENERGY KNIGHT]

ok I now have the condenser re-piped and the receiver out next to the condenser
I also have a baffle built to keep the hot air from coming arround
I have a clear sight glass
10 deg superheat
30 deg difference between discharge and ambient
new larger contactor and timer
should I install an oil seperator on discharge line so oil does not go through system?
I believe that would help my foamy oil let me know what you guys think on this thanks.

[Gary]

Evap air in temp:
Evap air out temp:
Low side pressure:
Suction line temp at TXV bulb:

Cond air in temp:
Cond air out temp:
High side pressure:
Liquid line temp:

[ENERGY KNIGHT]

sorry Gary its really cool here 55 deg f . it was hot. in need te get those readings with fans full speed .
what would you say min. high side pres. should be ? its suposed to be mid 60's f tommarow could I run fans full speed and get you those readings?

[ENERGY KNIGHT]

would an oil seperator be helpfull

[Gary]

I've seen no indication of oil problems.

[ENERGY KNIGHT]

I would like to post the new readings but I'm not shure about my superheat where should I be most concerned about the temp of the pipe. my compressor is very cold and most of the comperssor is very wet. I have about 10 deg f superheat at compressor inlet. some say at comp i should have at least 15 deg. f . but there is only about 3 foot of insulated pipe between bphe and compressor so the temp is the same . what do you think I should do?

[ENERGY KNIGHT]

o and when I change the filter just before the txv I get about a coffee cup of oil out of filter housing.

[Gary]

The compressor inlet superheat needs to be at least 15-20F... and the compressor crankcase should be warm. The cold crankcase indicates flooding, which washes oil out of the compressor. Adjust the TXV superheat.

[ENERGY KNIGHT]

ok Gary I will adjust the txv in a little thanks a lot for helping me. after I get around 15F I will try and get all those other readings and post them .

[Magoo]

Hello Ek
I totally agree with Gary's comments, but any adjustments should be small then wait for TXV to stabalize. For a better understanding go back to my ealier post on setting TXVs

[Gary]

Hello Ek
I totally agree with Gary's comments, but any adjustments should be small then wait for TXV to stabalize. For a better understanding go back to my ealier post on setting TXVs

Exactly so. It takes at least 15 minutes for the TXV to stabilize between adjustments.

Make an adjustment... wait at least 15 minutes... then check the results... repeat as needed.

[ENERGY KNIGHT]

I adjusted the compressor superheat. it stays between 15 and 20 F. it does not stay exactly the same . still a little hunting. is that normal or ok. I have a clear sight glass and very steady fan control now. my water stays same but mabey I should check to see how much my water pump is changing?

[Gary]

Evap air/water in temp:
Evap air/water out temp:
Low side pressure:
Suction line temp at TXV bulb:

Cond air/water in temp:
Cond air/water out temp:
High side pressure:
Liquid line temp:

[Gary]

I adjusted the compressor superheat. it stays between 15 and 20 F. it does not stay exactly the same . still a little hunting. is that normal or ok. I have a clear sight glass and very steady fan control now. my water stays same but mabey I should check to see how much my water pump is changing?

A little hunting won't hurt anything as long as it is not flooding the compressor.

Why would your water pump change?

[ENERGY KNIGHT]

the water pump is variable speed. because when a chiller is off no water flows through it. there has been a lot of talk about how to control pump speed. clima cool wants 2.4 gal per min per ton. the pump was controlled by differential pressure. but that does not work because when the building demand changed so did the DP but it changed opposite than when the chiller demand changed. long story but I am now controlling pump speed by DT and that seems to be the best. I could play with the pid loop maby but I think its ok. now Im just waiting on my oil seperator to see if the oil will settle down some.
then I will post all of those readings to see if we made a healthy system. thanks everyone coments ?

[ENERGY KNIGHT]

Hi all and thanks for all the help I hope I will be able to help someone in the future.
I built a three foot tall wall on condenser but I think it should have been taller still getting some hot air recirculating. it was 100 deg f yesterday. if the wind gust blew just right I had 105 deg f air entering condenser. which gave me 320psi
so my condenser is working at 30 deg f above saturation witch is at design. good
my receiver is out by condenser and I get 10 deg subcooling at txv inside. good
witch means clear sight glass all the time. good
txv adjusted so I get 15 - 20 deg superheat. and compressor discharge stays bellow 200. good
Now I have two more concerns.
1. the oil sight glass on compressor Oil is very foamy Im worried about proper lubrication in there.

2. and could anyone help me with the low side pres. I would like to understand about the freeze up
of evaporator and low load or low temp.
what should the low pres be on r-22 with 52deg f entering and 42 degf leaving a bphe?

[Gary]

Think of pressure as a means to an end. You are looking at the pressure in order to determine the saturation temperature of the refrigerant. On the low side, we are looking for the saturated suction temperature (SST).

The difference between the leaving water temp and the SST is the "approach temperature".

Given normal heat load (normal dT) and full coil utilization (normal superheat), the approach tells us something about the heat transfer between the water and the refrigerant. The closer these temperatures are to each other (lower approach), the better the heat transfer between them... and vice versa.

The approach temp can vary considerably, depending on such things as relative evap size and type... so the question is what is the normal approach for your particular system? As a rule of thumb, anything over 20F approach for a chilled water evap indicates a heat transfer problem. However, on a high efficiency BPHE coil I would expect a much tighter (lower) approach.

From previous readings, I would say the normal evap approach for this system is about 8-10F... but the SH was low in those readings. New readings with normal SH may (or may not) tell a different story.

Given water leaving temp of 42F, with normal dT and SH, I would expect the SST to be roughly 8-10F lower... 32-34F SST... which for R22 translates to 57-60 psi. But then, there are a lot of ifs in there.

With all else normal, higher than normal approach indicates an insulative coating on the heat transfer surface slowing the heat transfer between water and refrigerant. This could be a mineral build-up on the water side or an oil coating on the refrigerant side (oil logging). Oil logging is generally intermittant, while mineral build-up is steady. Both are relatively rare in chilled water evaporators. Mineral build-up is far more common in water cooled condensers.

On air cooled condensers the approach would be the difference between leaving air temp and saturated condensing temp (SCT) and high approach usually indicates carbon build-up from car exhaust in heavy traffic areas... requiring chemical cleaning.

[MikeHolm]

I have watched this thread with a lot of interest and must admit, I have learned a lot. EK, you have a great teacher in Gary.

gary, you should put your 8 measurements on your tag line. It is repeated far too often.:D

[ENERGY KNIGHT]

now remeber I have only changed the piping and moved reciever on one out of eight.
so seven of the compressors still have reciever inside and about a 40 psi pressure drop in the condenser line and no clear sight glass.

all eight seem to run good at high outside temps or high discharge pres. above 270psi or so.
but last night the outside air temp droped to arround 60 deg. f and three compressors kicked out on low pres. (about 50 psi setpoint)

I guess Im asking you guys what I should do.
re-pipe condenser to rid the pres. drop and move recievers on the rest of the units or just set my controls to raise my water setpoint when oat. drops or do I do both.

also why do they trip on low pres when high side is under 260psi. is it the huge pres. drop and no clear sight glass
I just need to be clear because my boss will want to know why I need to re- pipe everything when the all worked by just adding the wall on top of condenser.
It looks like moving the reciever and re-piping is more for lower oat than higher oat?

[install monkey]

lower ur lp cut out to prevent nusance tripping- in lower ambients u should have condenser fan speed controllers or pressure switch to cycle the fans.
the lp could be lowered to 1 bar -15psi

[Gary]

Since the condensers have subcooling circuits, I would try removing/bypassing a receiver on one of the units. If the sight glass can be cleared without driving up the high side pressure, possibly the receiver can be eliminated.

Receiver or condenser subcooling circuit. One or the other, but not both.

[Magoo]

With eight systems and the problems you have, there has got be some re-course back onto supplier installer to supply stable operational systems, with what ever local ambient conditions.

[ENERGY KNIGHT]

yes I have condenser fan speed control. when the factory guys were
here trying to figure this thing out they wanted me to set the fans to maintain 275 psi on the high side.
I think that is too high and is just a bandaid.
I think we are very close to getting this .
I originaly had two problems (but didnt know it)
1. high head pressure.....finally came down to hot discharge air recuirculating back through condenser.
that part is pretty much fixed although I could use a little taller wall like 6 feet instead of 3 feet.
2. low suction pressure.....I think there is two ways to fix this. simply remove reciever and charge to a clear sight glass.
or re-pipe condenser to get rid of subcooler and pres drop and move reciever out to condenser.
I would like to see everyones opinions on which way would make a better system thanks everyone!

[ENERGY KNIGHT]

Gary I removed reciever and cleared sight glass, but like you said the high side might climb too high . it did. the high side is 40 deg above saturation and it should be 30 deg f.

my next step is re-piping condenser and using the subcooling circuit at bottom of condenser as a surge reciever.

does that make sense to anyone?

and you guys help has been better than any school.(and cheaper too) I do need to go back for spelling though

[Gary]

Gary I removed reciever and cleared sight glass, but like you said the high side might climb too high . it did. the high side is 40 deg above saturation and it should be 30 deg f.


That pretty much answers your previous question, then.

I would still like to see a full set of measurements for the modified system. Once perfected, this system sets the pattern for the other seven systems.

[ENERGY KNIGHT]

evap water in temp: 54 f
evap water out temp: 45 f
low side pressure: 60 psi
suction line temp at compressor: 50 f

cond air in temp: 90 f
cond air out temp: 110 f
high side pressure at compressor: 235 psi
high side temp at compressor: 170 f
high side pressure at txv: 225 psi
liquid line temp at txv:100 f

[install monkey]

looks good!

[Gary]

Those numbers are near perfect. You have made your compressor very happy. :D

[engineerhvacr]

In my opinion the air cooled condenser seems to be of problem, for a 25 ton air cooled unit the heat rejection capacity will be around 32 TR and the coil should have cfm around 25000 to 30000 and coil face area with 4 rows around 64 sft. your condenser size 50 x 70 = 24.5 sft seems to be on undersize.

[engineerhvacr]

25 Tr x 2 nos compressors, can u post all the major component details such as
compressor model / make / quantity
phe model / make / quantity :
air cooled condenser data - no of fans, total face area,no of rows, total cfm, ambient temp
expansion valve data..: model / make / quantity
will help to evaluate from design point of view...