View Full Version : RSIR start relay

23-01-2017, 11:39 PM
Hi guys, quick question in regards to a comp running an RSIR relay.
I have a CSIR relay and cap. If I fit this will I get better starting or will I just kill the comp?
I have tested the donor comp and the receiver one to find very similar start winding resistance. Donor comp is an 8cc aspera. Receiver comp is a 9cc Chinese.
I assume it will be a small improve but wanna avoid an immediate dead comp.

Glenn Moore
25-01-2017, 12:01 AM
Hi kiwi
The RSIR relay produces virtually no starting torque for the compressor motor, and therefore is used on capillary tube systems, where during the off cycle the pressure will equalise allowing the compressor to start under a no load state .ie LST (Low starting torque)application
The CSIR relay and capacitor does give a reasonable starting torque and therefore can be used with both capillary tube systems and expansion valve systems where pressure equalisation often does not occur due to short off cycle times.HST (High Start Torque) systems
Your problem comes in when the cut in and cut out voltages of the CSIR kit does not match the receiver compressor motor design. If this is the case the relay could potentially keep pulling in the start winding which will burn the start winding out.
There are thousands of these relays and they are designed to match specific motor sizes and designs and fitting the wrong match could have bad results for you.
There are manufacturers of "universal relays " for the after market which make a universal relay/ capacitor kit to fit by HP size of the motor.
There are several manufacturers but from personal experience I have used the kits from a US company called Supco or (Superior Controls Co ) who have a great range of these kits .
Upgrading to a CSIR would give a better starting performance especially if low voltages or short cycling of the system was a problem .Hope that helps