Extra Terminals on the Back of a Scroll Compressor

York Heat Pumps

Re: 2-STAGE SCROLL COMPRESSORS

Many newer units are using a 2-stage scroll compressor.

These compressors have the standard "C-S-R" power terminals on the front, but also have an extra 2-wire plug connection in the back. This additional connection is for a 24 VAC "unloading solenoid" inside the compressor.

HOW IT WORKS:

• With the solenoid un-powered and the contactor energized, the compressor will operate at approximately 60% capacity.
• With the solenoid powered and the contactor energized, the compressor operates at 100% capacity.
• When the solenoid powers you should see the following:
  • Slight change in the noise of the compressor.
  • Increase in compressor amperage.
  • Slight decrease in suction pressure.
  • Slight increase in head pressure.

ADDITIONAL INFORMATION

• A 2-stage scroll compressor should be matched with a variable or multi-speed indoor blower with the ability to change indoor CFM to match the compressor output.
• The internal solenoid actually operates off of 24V dc. The plug is an AC to DC converter.