high discharge pressure

[abet_meneses]

we have a problem on low temprature rack.four compressor handle the coldrooms,glass door and multideck freezer while a compressor serve the island freezers.before we have no problem on system pressure but after one comp bogged down a very high pressure occurs.
we already done air purging ,already ruled out driers and filters,but still high discharge exist.i"m confused :confused:
help is greatly appreciated.

[GXMPLX]

Measure pressure drop between discharge of compressors and condenser inlet, if this difference is about the same magnitude as the diferential in todays-before discharge pressure the compressor you probably have debris somwhere in the line. If not the problem is at the condenser where it could be uncondensables, debris, capacity problem now that all compressors work ok, or an unrelated problem.

[abet_meneses]

GXMPLS,
pessure on the outlet of condenser is sligthly higher than condenser inlet.although the system still can handle the required load i'm very worried on high discharge pressure.like what i said before system pressure shot up when one of the comp fail.

thanks,

[nike123]

GXMPLS,
pessure on the outlet of condenser is sligthly higher than condenser inlet.although the system still can handle the required load i'm very worried on high discharge pressure.like what i said before system pressure shot up when one of the comp fail.

thanks,

How much slightly in bars, PSi, etc..

Do you have elevated suction pressure? Compressor is like amplifier. It amplifies what's in his suction.
Make full audit of system and send here findings.
Pressures, temperatures like here:

http://farm4.static.flickr.com/3277/2576650727_7e365de88a_o_d.jpg

http://farm4.static.flickr.com/3120/2577482452_3110d67a9c_o_d.jpg

Also, air in and out temperatures at condenser and evaporator. Setings of evaporator pressure regulators etc...

[The Viking]

OK, let's recap....
-System works fine without excessive high pressure
-A compressor goes down
-Compressor is replaced/repaired
-System is re-commissioned but now we got a very high discharge pressure

My first suspect would be non-condensable gases in the system.
Did you evacuate it properly, no chances of air or OFN trapped anywhere?

[1torr]

could it be that the non return valve is not opening fully on that one compressor?

[abet_meneses]

Nike 123,

discharge pressure is max 350 psi.yes suction line is elevated,but with p trap.pressure regulator is ok and already purge air.

The Viking,

I think there's no condensable gas in the system ,cause we close all isolation valve before removing the failed compressor.

1 thorr,

Forgive me cannot understand your post.

abet

[Pooh]

Could it be that the new compressor is the wrong one and not suitable for low temp applications.
Check model numbers?

Ian

[abet_meneses]

Ian,

thanks,but the comp is copelamatic discus comp R22 designed to operate on low temp applications.

[nike123]

Nike 123,

discharge pressure is max 350 psi.yes suction line is elevated,but with p trap.pressure regulator is ok and already purge air.



What refrigerant?

I did not meant how much high is condensing pressure, I meant how much is difference in between condenser inlet and outlet pressure expressed in numbers.

Second, I meant at pressure on suction side is elevated above some normal point, and i did not meant by that at your particular pipe layout.

Also, I meant that you provide us with actual settings of yours pressure rergulators and not if they are OK or not ( albeit, it is good to know that they are OK).

[abet_meneses]

What refrigerant?

I did not meant how much high is condensing pressure, I meant how much is difference in between condenser inlet and outlet pressure expressed in numbers.

Second, I meant at pressure on suction side is elevated above some normal point, and i did not meant by that at your particular pipe layout.

Also, I meant that you provide us with actual settings of yours pressure rergulators and not if they are OK or not ( albeit, it is good to know that they are OK).

1.refrigerant is R22
2.condenser pressure difference
cond in 340psi
cond out 35
3.suction press 16psi
4.press regulator in 18 to 20 psi
press regulator out 16 to 18 psi.:cool:.

[nike123]

2.condenser pressure difference
cond in 340psi
cond out 35

Did I read correctly that your pressure difference between condenser inlet and outlet is 35 psi?
What is condenser air in and out temperature. What is suobcoling?
Did you made any measurments I asked before?



Make full audit of system and send here findings.
Pressures, temperatures like here:

http://farm4.static.flickr.com/3277/2576650727_7e365de88a_o_d.jpg

http://farm4.static.flickr.com/3120/2577482452_3110d67a9c_o_d.jpg

Also, air in and out temperatures at condenser and evaporator. Setings of evaporator pressure regulators etc...

[1torr]

Has each compressor got a nrv fitted in discharge line? If so could it be partially restricted, causing high head pressure on that compressor?

[abet_meneses]

1torr,

no return valve on each compresor.only a check valve on hot gas line.

[abet_meneses]

nike123,
sorry for the mistake cond otgoing should read 350psi.
will get measurement in the field.

many thanks for the reply.

[GXMPLX]

I don't want to add noise, but having slightly higher outlet pressure than inlet pressure in the condenser tells me you either need to give a more thorough description of the high side of the system including all high pressure control equipment or there is something wrong with your measurements. Can you describe all you have connected in high side? and tell EXACTLY WHERE are you measuring the pressure? Sorry if this sounds too basic but if you are using different instruments you should make sure they are calibrated and your measurements should be as simultaneous as possible. If you are using the same instrument make sure conditions in the system don't change while you measure i.e. close branches that may open while you are measuring.