30
Fig. 30 — Hot Gas Bypass Option
Fig. 31 — Location of Hot Gas Bypass in 38AUDC12
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
of compressor operation until CADM is manually reset. Reset
CADM by cycling unit main power.
Complete system shutdown may be caused by loss of main pow-
er, open compressor internal overload, open low-pressure or
S
UCTION LINE
LIQUID LINE
WATCH
YOUR
S
UCTION
RI
S
ER
S
HOT GA
S
LINE
COMPRE
SS
OR
CONDEN
S
ER
COIL
EVAPORATOR
COIL
S
OLENOID
VALVE
HOT GA
S
BULB
TO
S
UCTION LINE
AND IN
S
ULATE
S
CHRADER VALVE
AT BOTTOM
LIQ INJ BULB
TO
S
UCTION LINE
HOT GA
S
DE-
S
UPERHEAT
CHAMBER
HOT GAS BYPASS
FACTORY INSTALLED
OPTION
