View Full Version : EXV and Compressor Variable speed drive

07-10-2010, 03:04 PM

can someone please explain on how EXV and Compressor VSD work together? Will EXV send signals to the compressor VSD to regulate the flow rate?

please advice.


15-10-2010, 03:02 PM
Hi JP,

From my experience, the required cooling load will be worked out by the main control unit for the chiller/refrigeration machine, from the leaving water/air temperature and the time it took to reduce the temperature.
The control unit will then send a signal to both the compressor and EXV to regulate the refrigerant flow and pressure difference to match the required cooling capacity; if possible.

I hope this helps, though it is a bit vague. I have done a lot of work with Turbocor units, and they generally work on this principle.



17-10-2010, 01:30 PM
The vsd needs a signal to change the frequency of vsd . The signal is either from a pressure transducer mounted on the casing of compressor . In other words, the suction pressure change due to fall in load is sensed by pressure transducer & it is converted in a 4 to 20 milliamp signal .the signal changes the frequency & hence the speed .
You can install a temperature transmitter to achieve the frequency change .the exv will respond on the pressure differential across it`s port

17-10-2010, 03:04 PM
EXV and VSD do not necessarily know what they are doing one another. They are on different control loops. EXV is regulated on superheating, VSD on heat load.