Hot Gas Bypass - Lennox LGH480 Installation Instructions Manual

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
Evaporator
Circuit 1
Evaporator
Circuit 1
Suction - Gas
507232-04 7/2017
HOT GAS BYPASS (HGB) PIPING - REFRIGERANT CIRCUIT 1 ONLY
FROM
LIQUID
LINE
SERVICE
VALVE
FROM
DISCHARGE
LINE
REFRIGERANT CIRCUIT 1
Liquid
Tempered
Hot Gas
Manual
Shut-Off
Valve
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 51 for
components and figure 52 for refrigerant routing.
DE-SUPERHEATING TXV
HGB valve starts to open
when suction pressure drops
below 105psig or (34°F evap­
orator temperature.
FIGURE 51
Liquid
De-Super­
heating TXV
HGB Valve
Hot Gas
Equalizer
Lines
FIGURE 52
Page 57
HOT GAS
BYPASS
(HGB) VALVE
SUCTION
LINE
Condenser
Circuit 1
Discharge - Hot Gas
Suction - Gas
Compressor 1