Carrier 48TC 04 Series Service And Maintenance Instructions page 65

valves, remain de- - energized and closed. See Fig. 75 for
illustration of each circuit's operation.
Hot Gas Reheat (Reheat 2) Mode: When the unit is
operating in a part- - load Cooling Mode (space temperature
above the set- - point, and only Y1 calling) and the space
humidity is also above its set- - point, the humidistat will
close and the unit operation will shift to Reheat1
(Subcooling) in Circuit 1 (as described above) and
Reheat2 (Dehumidification) in Circuit 2 (as described
below).
When there is only dehumidification demand (humidistat
is above set- - point but no Y1 call), both circuits will
operate in Reheat2 mode. The supply fan motor and both
compressors will be energized through the Reheat Control
Board logic. All solenoids are energized; Cooling Liquid
valves are closed and Discharge bypass valves open. All
liquid flow and the bypassed discharge gases are directed
into the Humidi- - MiZer coil circuits. See Fig. 76 for
illustration of each circuit's operation in Reheat2.
If the space temperature drops during a Reheat2 Mode
until the Heating Thermostat W1 closes, the W1 signal is
received by the RCB. The RCB logic de- - energizes the
compressors, the Cooling Solenoid valves and the
Discharge Solenoid valves. The compressors and solenoid
valves will remain in these conditions until the Heating
Mode demand ends. If the humidistat is still above the
set- - point after the heating ends, the unit will restart in
Reheat2 Mode.
Unit Size 16 (Type 3 - - Dual Stage Cooling)
Normal Cooling Mode: When there is only a cooling
demand (thermostat Y1 alone or with Y2), one or both
circuits will operate in normal Cooling Mode. Both
solenoid valves in both circuits are de- - energized. The
LDV1 and LDV2 valves are 3- - way valves with a
Normally Open (NO) port and a Normally Closed (NC)
port. In the Cooling Mode, the liquid flows out of the
Normally Open (NO) port and into the TXVs on the
evaporator coil. The RDV1 and RDV2 valves are
Normally Closed (NC) and remain closed during the
Cooling Mode. See Fig. 77.
Subcooling (Reheat 1) Mode: When the unit is operating
in a full- - load Cooling Mode (with the space temperature
above the set- - point, and both Y1 and Y2 calling) and the
space humidity is also above its set- - point, the humidistat
will close and the unit operation will shift to Reheat1
(Subcooling).The LDV1 and LDV2 3- - way valves will
become energized, causing the valves to close their
Normally Open (NO) ports, open their Normally Closed
(NC) ports redirecting all
Humidi- - MiZer coil circuits. The increased subcooling
causes the evaporator coil surface temperature to
decrease, thus increasing the unit's Latent Cooling effect.
The RDV1 and RDV2 valves remain de- - energized and
closed. See Fig. 78.
liquid flow into the
Hot Gas Reheat (Reheat 2) Mode: When the unit is
operating in a part- - load Cooling Mode (with the space
temperature above the set- - point, but only Y1 calling) and
the space humidity is also above its set- - point, the
humidistat will close and the unit operation will shift to
Reheat1 (Subcooling) in
(Dehumidification) in Circuit 2. The LDV1 and LDV2
3- - way valves and the RDV2 valve becomes energized;
valve RDV1 remains de- - energized and closed. Circuit 1
will operate in Reheat1 as described above. Circuit 2 will
operate in Reheat2 as described below. See Fig. 79.
When there is only dehumidification demand (humidistat
is above set- - point but no Y1 call), both circuits will
operate in Reheat2 mode. The supply fan motor and both
compressors will be energized through the Reheat Control
Board logic. All solenoids are energized; valves LDV1
and LDV2 close their Normally Open (NO) ports and
open their Normally Closed (NC) ports and discharge
bypass valves RDV1 and RDV2 open. All liquid flow and
the bypassed discharge gases are directed into the
Humidi- - MiZer coil circuits.
If the space temperature drops during a Reheat2 Mode
until the Heating Thermostat W1 closes, the W1 signal is
received by the RCB. The RCB logic de- - energizes the
compressors, the Liquid Diverting Solenoid valves and the
Reheat discharge Solenoid valves. The compressor and
solenoid valves will remain in these conditions until the
Heating Mode demand ends. If the humidistat is still
above the set- - point after the heating ends, the unit will
restart in Reheat2 Mode.
65
Circuit 1 and Reheat2