Hot Gas Reheat - Lennox LGH480 Installation Instructions Manual

Optional Hot Gas Reheat
General
Hot gas reheat units provide a dehumidifying mode of
operation. These units contain a reheat coil adjacent to
and downstream of the evaporator coil. Reheat coil
solenoid valves, L14 and L30, route hot discharge gas
from the compressor to the reheat coil. Return air pulled
across the evaporator coil is cooled and dehumidified; the
reheat coil adds heat to supply air.
See 49 for reheat refrigerant routing.
L14 and L30 Reheat Coil Solenoid Valves
When Unit Controller indicates room conditions require
dehumidification, L14 and L30 reheat valves are energized
and refrigerant is routed to the reheat coil.
Reheat Setpoint
Reheat is factory-set to energize when indoor relative
humidity rises above 60% (default). The reheat setpoint can
be adjusted by changing parameter 106 (SETUP MENU). A
setting of 100% will operate reheat from an energy
management system digital output. The reheat setpoint can
also be adjusted using an optional Network Control Panel
(NCP).
Evaporator Coils
(Row Split)
4
NOTE:
Circuit 1 and Circuit 2 are similar
Circuit 3 and Circuit 4 are similar
507232-04 7/2017
REHEAT MODE REFRIGERANT ROUTING
3
1
Reheat Coils
1
2
2
FIGURE 49
Page 53
Reheat will terminate when the indoor relative humidity falls
3% (57% default) or the digital output de-energizes. The
reheat deadband can be adjusted 1-10% RH by changing
parameter 107.
A91 Humidity Sensor
Relative humidity should correspond to the sensor (A91)
output voltage listed in table 23. For example: if indoor air
relative humidity is 80% + 3%, the humidity sensor output
should read 8.00VDC.
Check the sensor output annually for accuracy. Keep the air
intake openings on the sensor clean and free of
obstructions and debris.
Relative Humidity (%RH + 3%)
20
30
40
50
60
70
80
90
Condenser
Coils
4
3
2
S
TABLE 23
Sensor Output (VDC)
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
1 REFRIGERANT CIRCUIT 1
2 REFRIGERANT CIRCUIT 2
REFRIGERANT
3 REFRIGERANT CIRCUIT 3
REFRIGERANT
4 REFRIGERANT CIRCUIT 4
REFRIGERANT
REHEAT
S
VALVE
CHECK VALVE
THERMAL
EXPANSION
VALVE
Outdoor
1
Air
Compressors
3
2
1
4