hot idle compressor on parallel rack system

[friocold2008]

Recently I have noticed that one of the semi-hermetic compressors in a parallel rack system stays hot even after long periods on idle state. Even the stator cover stays really warm. Nevertheless, whenever the compressor is active, shell temperature, pressures and amperes seem about right. This is a 27 HP Copeland Discus compressor. It looks like it has at least six cylinders.
I don´t know much about the Discus valve plate but, is it possible to have a leaky valve plate such that whenever the compressor is idle, hot gas from the discharge manifold seeps into the suction side of the compressor, keeping it hot.
Any comments welcomed.

[Magoo]

Hi friocold,
certainly sounds like something is by-passig hot gas through compressor, could be discus valves leaking at stop and fine when running or oil level control management system, or really efficient sump heater adding to all above. does compressor have discharge stop/ check valve, should have to safe.
martin

[taz24]

Recently I have noticed that one of the semi-hermetic compressors in a parallel rack system stays hot even after long periods on idle state. Even the stator cover stays really warm. Nevertheless, whenever the compressor is active, shell temperature, pressures and amperes seem about right. This is a 27 HP Copeland Discus compressor. It looks like it has at least six cylinders.
I don´t know much about the Discus valve plate but, is it possible to have a leaky valve plate such that whenever the compressor is idle, hot gas from the discharge manifold seeps into the suction side of the compressor, keeping it hot.
Any comments welcomed.


That is a possibility.

Is there a check valve (one way valve) in the discharge line?

With the comp running measure the temp of each cylinder head and any temp difference will show up as the suspect.

taz.

.

[coolhibby1875]

almost certain it is a sticking n,r,v on the discharge this through time will lift the oil from the compressor

[NoNickName]

Or the internal safety valve blown and did not close properly.

[D.D.KORANNE]

Check if it is leaking through oil separator if one is installed ; check oil / gas balancing lines . Any valve which is not holding could lead to such a problem .

[friocold2008]

First of all thank you all for your kind advice. I thought that there was only one reason for this situation to occur ( a damaged valve plate), but now I know there are a few other causes.
I went back to the compressor and can inform you of the following:
1. there is no discharge check/stop valve
2. oil sump heater is of the same wattage of those installed in the other paralleled compressors, and none exhibits the same warming when idling.
3. there is a large oil separator located at the main discharge line going up to the condenser, but it seems to be working fine, as none of the other paralleled compressors shows this behavior.
Sorry, what is a n,r,v ?
Also, where is that internal safety valve located inside the compressor?
I think I`m going to get a new valve plate and gaskets before venturing into taking the heads off.
Best regards

[NoNickName]

NRV = non return valve

The safety valve is placed across high and low side. Where exactly, depends on the actual manufacturer. Ask for exploded views from the compressor supplier.

[KibGaimb73]

will your book show me how to build a eutectic system running off a car aircon compressor??

[oldtimer]

if the discharge is leaking through to suction you will have a increased suction pressure close the suction valve on that compressors and see what reaction it has on the suction

[4 evr learnin]

Thanks old timer its nice to see some reactive logic being used... They must of stopped teaching that at technical colleges these days !

[Fridge in Focus]

Sounds like a reed valve poppd on one of your heads. Would need to be removed and replaced.

Check the temp of each head with a laser temp display, they should be around 90oC. Your problem head will be the hottest... or the old way.. remove each head and inspect the valve plate.. it will show straight up if you have a reed valve blown.