38Audc With Svr Relays; All Units - Carrier Gemini 38AU 07 Series Installation, Start-Up And Service Instructions Manual

WATCH
YOUR
SUCTION
RISERS
LIQ INJ BULB
TO SUCTION LINE
SOLENOID
VALVE
Fig. 31 — Location of Hot Gas Bypass in 38AUDC12
SUCTION LINE
HOT GAS
DE-SUPERHEAT
CHAMBER
HOT GAS BULB
TO SUCTION LINE
AND INSULATE
SCHRADER VALVE
AT BOTTOM
COMPRESSOR
Fig. 30 — Hot Gas Bypass Option
HOT GAS BYPASS
FACTORY INSTALLED
OPTION
30
EVAPORATOR
COIL
HOT GAS LINE

38AUDC with SVR Relays

With no thermostat demand, there will be no voltage at LVTB-A1;
HGBP SOLENOID is de-energized and solenoid valve remains
closed, preventing bypass vapor from the desuperheating tank to
enter the suction line at the compressor.
On a thermostat call for first-stage cooling, LVTB terminal Y1 is
powered; when CADM1 is satisfied, compressor contactor C1 and
Solenoid Valve Relay SVR1 are energized. SVR1 contacts close,
providing 24-v to LVTB terminal A1, then through HGBP RE-
LAY NC contacts to HGBP SOLENOID. HGBP solenoid valve
opens, allowing bypass vapor from the desuperheating tank to en-
ter the compressor suction port.
If thermostat calls for second stage cooling, LVTB terminal Y2 is
powered; when CADM2 is satisfied, compressor contactor C2,
Solenoid Valve Relay SVR2 and HGBP RELAY are energized.
HGBP RELAY NC contacts open, de-energizing the HGBP SO-
LENOID; solenoid valve closes, blocking bypass vapor from the
desuperheating tank and unit runs at full cooling capacity.
The model 38AUDC also includes the 32LT Motormaster low
ambient control as a standard feature. Refer to Appendix C for in-
formation on the Motormaster control.

All Units

If either the Low Pressure Switch or High Pressure Switch opens
while thermostat output Y1 or Y2 remain energized, the compres-
sor contactor is de-energized, the compressor stops and liquid line
solenoid is de-energized (valve closes). CADM initiates a TRIP
event (cooling demand sensed at CADM terminal Y but no cur-
rent is measured at T1, T2, T3 motor sensors); CADM relay opens
and RED LED is illuminated. TRIP condition maintains lockout
CONDENSER
COIL