Reheat Modes - Carrier WeatherExpert 48LC 04 Series Installation Instructions Manual

REHEAT MODES

Dehumidification (reheat) is a cooling mode function. Refer to
Cooling Operation for cooling mode control. With Humidi-
MiZer units, there are three additional HVAC Mode (HVAC)
expanded texts available for the user: Reheat1, Reheat2, and
Reheat1/Reheat2. Selection of the reheat mode for each refrig-
erant circuit is determined by the dehumidification demand and
the cooling demand. Table 7 shows the corresponding circuit
mode and output status for the different demand combinations.
Units with multiple circuits can operate with a combination of
Reheat1 and Reheat2 circuits, as determined by the amount of
space cooling demand.
NOTE: Compressor staging control for Humidi-MiZer units re-
quires that circuit A always operates when circuit B is on. This ap-
plies to normal operation, service test, and for control alarm re-
sponses. This operation difference is required due to the fact that
the Motormaster outdoor fan control senses circuit A only. Opera-
tion of the revised refrigerant circuit for each mode is described
below.
Normal Cooling
For 48LC04-6 units, refrigerant flows from the outdoor con-
denser through the normally open Cooling Liquid Valve (CLV)
COMPRESSOR
COMPRESSOR
RDV
VALVE
CONDENSER COIL
OUTDOOR AIR
= CLOSED VALVE
= OPEN VALVE
Fig. 49 — Normal Cooling Mode — Humidi-MiZer System
RDV
VALVE
CONDENSER COIL
OUTDOOR AIR
= CLOSED VALVE
= OPEN VALVE
Fig. 50 — Subcooling Mode (Reheat 1) — Humidi-MiZer System
to the expansion device. Reheat Liquid Valve (RLV) and Re-
heat Discharge Valve (RDV) are closed. (See Fig. 49.)
Reheat 1 (Subcooling Mode)
This mode increases latent cooling and decreases sensible
cooling compared to normal cooling.
For 48LC04-6 units, refrigerant flows from the outdoor con-
denser, through the normally open Reheat Liquid Valve (RLV),
and through the reheat condenser coil to the expansion device.
Cooling Liquid Valve (CLV) and Reheat Discharge Valve
(RDV) are closed. (See Fig. 50.)
Reheat 2 (Hot Gas ReheatMode)
This mode provides maximum latent cooling with little to no
sensible capacity. This mode can operate to provide dehumidi-
fication when there is no cooling demand. Similar to Reheat 1
mode, refrigerant flows from the outdoor condenser, through
the normally open Reheat Liquid Valve (RLV1), or through the
energized 3-way Liquid Diverter Valve (LDV), and through the
reheat condenser coil to the expansion device. Reheat Dis-
charge Valve (RDV) is open, which provides some compressor
discharge gas to the reheat condenser to further increase the re-
heat of the evaporator air stream (See Fig. 51).
INDOOR SUPPLY
RLV
VALVE
HUMIDI-MIZER COIL
CLV
VALVE
EVAPORATOR COIL
INDOOR RETURN
INDOOR SUPPLY
HUMIDI-MIZER COIL
RLV
VALVE
CLV
VALVE
EVAPORATOR COIL
INDOOR RETURN
29
AIR
EXPANSION
VALVE
(TXV)
AIR
AIR
EXPANSION
VALVE
(TXV)
AIR