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Modulating Hot Gas Reheat Start-Up And
Operation
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 valve, L14, routes 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 figure 28 for
reheat refrigerant routing and figure 29 for standard
refrigerant routing.
L14 Reheat Coil Solenoid Valve
When Unit Controller input (Unit Controller J298-5 or
J299-8) indicates room conditions require
dehumidification, L14 reheat valve is energized (Unit
Controller J394-1) 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 mobile
service app Settings - Control 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). Reheat will
terminate when the indoor relative humidity falls 3% (57%
default) or the digital output de-energizes. The reheat
deadband can be adjusted at Settings - Control menu.
Check-Out
Test hot gas reheat operation using the following
procedure.
1- Make sure reheat is wired as shown in wiring section.
2- Make sure unit is in local thermostat mode.
3- Select:
RTU MENU > SERVICE > COMPONENT TEST >
DEHUMIDIFICATION
The blower and compressor 1 (reheat) should be
operating.
DEHUMIDIFIER 1 ON
will appear.
4- Press STOP to discontinue the testing mode.
Compressor 1 (reheat) and blower should de-energize.
FIGURE 28
REHEAT MODE REFRIGERANT ROUTING
