Two-Stage Copeland Scroll Compressors

DESIGN AIR UNIVERSITY External view 1 st stage = 67% 2 nd stage = 100% Used in 17 SEER AC.

DESIGN AIR UNIVERSITY Customer Experience Majority of run 67% Majority of run 67% Delivers steady state cooling. Delivers steady state cooling. Eliminates temperature peaks & valleys from compressor cycling. Eliminates temperature peaks & valleys from compressor cycling. Better humidity control. Better humidity control. Majority of run 67% Majority of run 67% Delivers steady state cooling. Delivers steady state cooling. Eliminates temperature peaks & valleys from compressor cycling. Eliminates temperature peaks & valleys from compressor cycling. Better humidity control. Better humidity control.

DESIGN AIR UNIVERSITY How does it work? Solenoid opens or closes a port on the internal scrolls. Valve is actually a ring that rotates. Ring opens or closes the bypass port. Solenoid opens or closes a port on the internal scrolls. Valve is actually a ring that rotates. Ring opens or closes the bypass port.

DESIGN AIR UNIVERSITY Internal assembly

DESIGN AIR UNIVERSITY 1st Stage Position Solenoid is NOT energized. Port is OPEN. Only 2/3 of scroll compresses refrigerant. The other 1/3 is bypassed thru the open port. Solenoid is NOT energized. Port is OPEN. Only 2/3 of scroll compresses refrigerant. The other 1/3 is bypassed thru the open port.

DESIGN AIR UNIVERSITY Solenoid: “unpowered”

DESIGN AIR UNIVERSITY Port open

DESIGN AIR UNIVERSITY Port open

DESIGN AIR UNIVERSITY 2nd Stage Position Solenoid is energized w 24 volts dc. Ring rotates & closes the port. The entire scroll capacity is delivered. Solenoid is energized w 24 volts dc. Ring rotates & closes the port. The entire scroll capacity is delivered.

DESIGN AIR UNIVERSITY Scroll internals Solenoid operates on DC voltage. Initial inrush is 18 to 28 volts DC. Holding voltage is less. Solenoid operates on DC voltage. Initial inrush is 18 to 28 volts DC. Holding voltage is less.

DESIGN AIR UNIVERSITY Solenoid: “powered”

DESIGN AIR UNIVERSITY Port closed

DESIGN AIR UNIVERSITY Port closed

DESIGN AIR UNIVERSITY Staging Control Wiring Separate wiring to terminal block on compressor shell. Connects integrated compressor control to internal solenoid. Separate wiring to terminal block on compressor shell. Connects integrated compressor control to internal solenoid.

DESIGN AIR UNIVERSITY Checking Solenoid Use your ohmmeter.

DESIGN AIR UNIVERSITY Solenoid Molex Plug

DESIGN AIR UNIVERSITY Molex unplugged

DESIGN AIR UNIVERSITY Placement of probes

DESIGN AIR UNIVERSITY “Good” Ohm reading 32 to 60 ohms.

DESIGN AIR UNIVERSITY Ohm check on Molex plug If resistance is infinite, the solenoid is electrically “open”. Compressor never operates on 2nd stage. The fix? Replace the compressor. If resistance is infinite, the solenoid is electrically “open”. Compressor never operates on 2nd stage. The fix? Replace the compressor.