Unloaded situation

[GENERALCOOL]

Hi friends,

Suppose that we have 50HP semi-hermetic compressor that works on air-conditioning system and it is working on unloaded situation and 30% of capacity for long time.
What will happen if compressor works on unload situation for long time ?
If it is possible analyze it and tell which part of compressor will damage during this unloaded situation if it works for long time.

Thanks for sharing your knowledge in advance.

Sincerely yours.


http://www.generalcooltrade.com

[RANGER1]

GENERALCOOL,
As far as I know oil may build up in the unloaded head/s as no gas flow, oil can accumulate from loaded head.
Semi-hermetic there is danger for motor cooling & can overheat, as gas flow over windings keeps cool, as well as cylinders can overheat too in some cases. That might overheat valves, oil, discharge temperature due to recycled gas.
Low load could also cause poor oil return, due to low pipework velocity.

In larger systems common to install high oil & discharge temperature protection.

What problem do you have, if any?

[GENERALCOOL]

Thanks Ranger for your reply,

I understand situation on compressor about hot valves, Cylinder, Oil viscosity losses and ….. .
What about stator (coil) of compressor while there is low mechanical load on it ?
As you know while we have high mechanical load on stator (coil) of compressor we would have damage and burn out, In the other hand if mechanical load be very low, Twice there is not any damage possibility to compressor ?
Suppose we have a compressor working with R22, If we replace refrigerant in system with R134a we decreased mechanical load on stator (coil) of compressor very much and I had this experience that compressor has been burn out.

Sincerely yours.

[RANGER1]

GENERALCOOL,
Each situation would have to be checked to see if conditions okay & all safety protections works.
Motor thermistors should be checked, suction superheat etc.
Most OEM have software to check conditions & recommend things like liquid injection.

Do you have any pressures & temperatures, superheat at compressor readings to offer?

[Josip]

Hi, GENERALCOOL

Hi friends,

Suppose that we have 50HP semi-hermetic compressor that works on air-conditioning system and it is working on unloaded situation and 30% of capacity for long time.
What will happen if compressor works on unload situation for long time ?
If it is possible analyze it and tell which part of compressor will damage during this unloaded situation if it works for long time.

Thanks for sharing your knowledge in advance.

Sincerely yours.

I assume this is installed in Qatar ...
and now is "winter" time there, thus no big request for air-condition ...

for me the biggest problem is air-condition design ...
it will be much better to have two compressor of 25HP
or even three of 20HP which will switch over by timer
and in this time of the year will run only one probably at full capacity.

In case if one is broken you still have another one or two to run
AC plant ... in this case with any problem regarding compressor
you have to stop your plant ...

Maybe is not bad idea to install in parallel one smaller compressor if possible
to run in winter time and the big one in summer time ...

I will not recommend you to change refrigerant,
because you need bigger heat exchanger due to
lower thermal conductivity of R134a than R22 ...


All other problems you can face are described by Ranger1...


Hope some other members will add a word or two to this ...


Best regards, Josip