pressure control settings

[jcool808]

In pump down refrigeration systems what cut-in/cut-out settings on the pressure control are ideal or correct? I'm asking for both medium and low temp applications. Thanks.

[SteinarN]

Cut out:
Low enough that the compressor don't stop under normal operating conditions. Lets say SST -20*C on a system operating normally at -10*C. -40*C on a system operating at -30*C.

Cut in:
Slightly lower than the normal room temperature. Lets say SST -25*C on a -20*C freezer and -5*C on a coold room system.

Spesific conditions on each system may make it necessarry to deviate from these values, but as a starting point they should be ok.

[taz24]

When pumping down or if the thing lost its gas you do not want it to go into a vacum so set the cutout at just above zero about 0.2b or 2-3psi in old money.

For cut in you want as wide a differential as possible without the temp being affected and that will depend on the refrigerant and the opperating temp.


Cheers taz.

[jcool808]

[quote=SteinarN;104024]Cut out:
Low enough that the compressor don't stop under normal operating conditions. Lets say SST -20*C on a system operating normally at -10*C. -40*C on a system operating at -30*C.

Cut in:
Slightly lower than the normal room temperature. Lets say SST -25*C on a -20*C freezer and -5*C on a coold room system.

Spesific conditions on each system may make it necessarry to deviate from these values, but as a starting point they should be ok.[/quote]


So by room temperature, you mean box/space temperature? Does the same go for multiple evap/cooler applications? In this case is it possible to set cut in pressure slightly above evap coil freezing temp (converted to pressure) to allow defrost without affecting temp too much in any box connected to this system. Thus the elimination of any mechanical defrost timers?

[SteinarN]

So by room temperature, you mean box/space temperature?

Yes, box temperature.

Does the same go for multiple evap/cooler applications?

Yes, set the cut in slightly lower than the SST for the lowest temp room or case. But be aware of short cycling protection if it is not sufficient capasity regulation on the compressor(s).

In this case is it possible to set cut in pressure slightly above evap coil freezing temp (converted to pressure) to allow defrost without affecting temp too much in any box connected to this system. Thus the elimination of any mechanical defrost timers?

This solution is new to me. It seems to be a rudimentary defrost system. I will not advice it.

[MrGeneralLee]

Ok I am in the USA we are in Farenhight and PSIG not kilo pascals, CAn any help with correct temp/pressure chart for r414b hotshot and is it close for off cycle air cooled defrost? as is R 12

Please no slamming to us here in CAlifornia From the saddle Bill

[mojica2369]

In pump down refrigeration systems what cut-in/cut-out settings on the pressure control are ideal or correct? I'm asking for both medium and low temp applications. Thanks.

i need to set my control settings

[nike123]

i need to set my control settings

What is usage and what refrigerant?

[acdc]

im knew to all this stuff just completed my second fridge year and wondered about stuff like how would u know what to set pressure switches at like low and high side there must be some sort of rule of thumb?

[Brian_UK]

im knew to all this stuff just completed my second fridge year and wondered about stuff like how would u know what to set pressure switches at like low and high side there must be some sort of rule of thumb?

High side would be the safety setting that you require for your particular system. You are protecting the compressor and the weakest part of the system.

Low side it all depends what you are using the LP switch for, safety, temperature, control, pump down.

[modvalve]

on the high side the hp switch must stop the compressor before the relief valve blows