Sump Pressure > Suction Pressure

[schquenz]

Do anyone can advice me for this mcquay centrifugal compressor, Sump pressure higher than Suction Pressure, normal?

I have observe alot unit, suct pres > sump pres about 3psi.

But got one unit found sump pres>suct pres about 5-7psi. it is depend on %RLA. higher %RLA, sump pres > suct pres is increasing.

help!!

[james10]

With that small difference i would check the calibration of transducers

[Brian_UK]

What is the resistance between where the two pressure are measured?

Should they be the same ?

[ptsac]

Are you losing oil?
oil pump sump is vented to impellor wheel eye pressure, which is alot lower at low load as the vanes are shut. As the machine loads vanes open and wheel eye pressure is closer to suction pressure.
If you are not losing oil level then there is no problem.
Also, If you are reading pressures from the microtech, confirm that the pressures read are correct with reliable gauges.

[bipin]

Hello,

I think that there is some problem with compression. Also check the Discharge pressure

[schquenz]

James10 & ptsac,
Pressure checked by calibrated pressure gauge.

Brain_UK,
No idea how to check when unit is running.pls advice me how to do.

ptsac,
No very sure there is losing oil. but this unit has been stop becasue of this issue. I will run the unit and monitor the oil level. If there is oil losing, what should i to do?

bipin,
I cant get what you mean?

Some information would to check with yours, if impeller seal no good, could it be such problem?

thanks for the support.

[MQFS OZ]

schquenz,
Sump press > than suction is quite normal when the chiller is at or near full load. Do not shut the chiller down because of this, you can't diagnose a fault if its not on line.
Firstly- is it loosing oil? if not you don't have a problem.
If its loosing oil you need to an oil loss analysis to check the various seals and o-rings in the compressor, if your not familar with this process then you should contact McQuay Service in Singapore.
What's the Model No?
Does it have liquid injection?
A faulty wheel eye or high speed seal can cause high sump pressure and oil loss / hang up.

[schquenz]

schquenz,
Sump press > than suction is quite normal when the chiller is at or near full load. Do not shut the chiller down because of this, you can't diagnose a fault if its not on line.
Firstly- is it loosing oil? if not you don't have a problem.
If its loosing oil you need to an oil loss analysis to check the various seals and o-rings in the compressor, if your not familar with this process then you should contact McQuay Service in Singapore.
What's the Model No?
Does it have liquid injection?
A faulty wheel eye or high speed seal can cause high sump pressure and oil loss / hang up.

thanks.
unit running,so far so good, no oil loss occur, unit under monitoring.
this unit is WSC,have liquid injection, hot gas bypass.
any relationship of have or do not have liquid injection to sump press > suct pressur?