Page 48
LGH/LCH420, 480, 540, 600
Optional Hot Gas Bypass (HGB)
Hot gas bypass is a factory-installed option only. The HGB
valve routes refrigerant from the discharge line to the
suction line to keep the evaporator coil from icing when
supply air volume is low. The HGB valve will start to open
when the suction pressure drops below 105 psig (R410A).
The de-superheating TXV routes cooler gas from the liquid
line to the suction line. This prevents high refrigerant
temperatures in the compressor. See figure 49 for
components and figure 50 for refrigerant routing.
FIGURE 49
HOT GAS BYPASS (HGB) PIPING - REFRIGERANT CIRCUIT 1 ONLY
DE-SUPERHEATING TXV
HOT GAS
BYPASS
(HGB) VALVE
SERVICE
VALVE
SUCTION
LINE
FROM
DISCHARGE
LINE
FROM
LIQUID
LINE
HGB valve starts to open
when suction pressure drops
below 105psig or (34°F evap
orator temperature.
FIGURE 50
REFRIGERANT CIRCUIT 1
Compressor 1
Manual
Shut-Off
Valve
Condenser
Circuit 1
Evaporator
Circuit 1
CAV Units
HGB Valve
De-Super
heating TXV
Equalizer
Lines
Suction - Gas
Suction - Gas
Discharge - Hot Gas
Liquid
Liquid
Hot Gas
Tempered
Hot Gas
Evaporator
Circuit 1
VAV Units
