Two-Stage Copeland Scroll Compressors

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External view• 1st stage = 67%• 2nd stage = 100%• Used in 17 SEER

AC.

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Customer Experience• Majority of run hours @ 67%• Delivers steady state cooling.• Eliminates temperature peaks

& valleys from compressor cycling.

• Better humidity control.

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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.

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Internal assembly

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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.

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Solenoid: “unpowered”

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Port open

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Port open

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2nd Stage Position• Solenoid is energized w 24 volts dc.

• Ring rotates & closes the port.

• The entire scroll capacity is delivered.

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

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Solenoid: “powered”

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Port closed

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Port closed

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Staging Control Wiring• Separate wiring to terminal

block on compressor shell.

• Connects integrated compressor control to internal solenoid.

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Checking Solenoid

Use your ohmmeter.

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Solenoid Molex Plug

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Molex unplugged

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Placement of probes

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“Good” Ohm reading

32 to 60 ohms.

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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.