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