Carrier 48FC Series Controls, Start-Up, Operation And Troubleshooting page 18

When using an SPRH sensor, the demand is based on the Space
Humidity Sensor (INPUTSANALOG INPUTSLEVEL) value
compared to the Space RH Setpoint (SETTINGSSPACE
SETPOINTSOCC SPRH SETPOINT or UNOCC SPRH SP). If
the Space Humidity Sensor (SPRH) value is above the Space RH
Setpoint, then dehumidification is needed. If the Space Humidity
Sensor (SPRH) value is below the Space RH Setpoint minus the
Space RH Deadband
DEADBAND), then dehumidification is no longer needed.
NOTE: When there is a dehumidification demand, the economizer
damper position is limited to its minimum damper position.
Humidi- - MiZer R System Modes
With Humidi- -MiZer system units there are two additional HVAC
modes available for the user: Dehumidification and Dehum/Mech
Cooling. Selection of the Dehum/Mech Cooling mode is
determined by the dehumidification demand and the cooling
demand. Table 11 shows the corresponding circuit mode and
output status for the different demand combinations.
Normal Cooling
This mode is the standard rated cooling system performance, and
occurs when there is cooling demand without dehumidification
demand.
For 48/50FC 04- -06 units, refrigerant flows through the outdoor
condenser and is diverted away from the reheat coil with the open
Cooling Liquid Valve (CLV) into the expansion device. Figure 10
shows the complete refrigerant flow.
For 48/50GC 04- -06 and 48/50FC 07 units, refrigerant flows
through the outdoor condenser and is diverted away from the
reheat coil with the closed Reheat Liquid Valve (RLV) and open
Cooling Liquid Valve (CLV) into the expansion device. Figure 11
shows the complete refrigerant flow.
Dehum/Mech Cooling (Subcooling) Mode
This mode increases the latent heat removal and decreases sensible
cooling compared to normal cooling. This occurs when there is a
cooling and dehumidification demands.
For 48/50FC 04- -06 units, refrigerant flows through the outdoor
condenser and is diverted through the reheat coil with the closed
DEMAND AND MODE
Dehumidification
Cooling Demand
Demand
No Power No Power
No No
No Yes
Yes Yes
Yse No
(SETTINGSCOOLINGSPRH
Table 11 – Humidi- -MiZer System Control Modes - - Sizes 04- -07
Mode
No power
Off
COOL
DEHUM/MECH
COOL
DEHUM
Cooling Liquid Valve (CLV) into the expansion device. Figure 12
shows the complete refrigerant flow.
For 48/50GC 04- -06 and 48/50FC 07 units, refrigerant flows
through the outdoor condenser and is diverted through the reheat
coil with the open Reheat Liquid Valve (RLV) and closed Cooling
Liquid Valve (CLV) into the expansion device. Figure 13 shows
the complete refrigerant flow.
Dehumidification (Hot Gas Reheat) Mode
This mode provides maximum latent cooling with little to no
sensible capacity. This occurs when there is a dehumidification
demand and no cooling demand.
For 48/50FC 04- -06 units, refrigerant flows through the outdoor
condenser and mixes with hot gas bypassing the condenser, then
diverted through the reheat coil with the closed Cooling Liquid
Valve (CLV) into the expansion device. Figure 14 shows the
complete refrigerant flow.
For 48/50GC 04- -06 and 48/50FC 07 units, refrigerant flows
through the outdoor condenser and mixes with hot gas bypassing
the condenser, then diverted through the reheat coil with the open
Reheat Liquid Valve (RLV) and closed Cooling Liquid Valve
(CLV) into the expansion device. Figure 15 shows the complete
refrigerant flow.
Reheat Control
When there is only a cooling demand, the unit will operate in
normal cooling mode. When there is only dehumidification
demand, the unit will operate in Dehumidification mode (Hot Gas
Reheat). When there is both cooling demand and dehumidification
demand, the unit will operate in Dehum/Mech Cooling mode
(Subcooling). During Dehumidification and Dehum/Mech cooling
mode, the unit will run all cooling stages. The unit can be restricted
from reheat operation by the outside temperature HUMZ
LOCKOUT OAT (SETTINGSUNIT CONFIGURATIONS
COOLINGDEHUMIDIFICATIONREHEAT OAT LIMIT)
sets the lowest outside temperature the unit is allowed to run reheat
control (Default = 40_F).
Compressor RDV
De ---energized
Off
(no flow)
De ---energized
Off
(no flow)
De ---energized
On
(no flow)
De ---energized
On
(no flow)
Energized
On
(flow)
18
OUTPUTS
CLV (48/50FC 07 and
48/50GC 04--- 06 only)
De ---energized De ---energized
(flow)
De ---energized Energized
(flow)
De ---energized Energized
(flow)
Energized De ---energized
(no flow)
Energized De ---energized
(no flow)
RLV
(flow)
(no flow)
(no flow)
(flow)
(flow)