back pressure valve in chiller

[vinod]

Hi,
can any body answer me about the back pressure valve of the carrier aircooled chiller (30gxn screw chiller). what is the function of this valve.

regards
vinod

[WangFu]

While Im not familiar with the model indicated, The purpose of a suction pressure regulator valve or back pressure valve is to ensure that the evaporator pressure (chiller pressure in this case) does not fall below a certain point. Keeping the pressure above that limit keeps the saturation temp above that limit which prevents the temperature in the chiller from faliing into the frozen range. In the case of a chiller one of the worst possible things that can happen is you freeze the chiller. The only chiller installation I have seen used a temp sensor to protect the chiller. Hope that answers your question.

[malik55]

Hello Vinod,
I had seen one on HX series carrier screw and as I remember that was on oil separator out let line if you means for that then and as reference from carrier manual it is for to ensure sufficient pressure difference at least 15psig between compressor and oil separator to allow for oil to be driven back to the compressor, the small line which connected to the valve and economizer activates a piston if pressure reduces, for more info see your chillers manual piping drawings.