Humidi- - Mizer Adaptive Dehumidification; System - Carrier 48TC 04 Series Service And Maintenance Instructions

HUMIDI- -MIZER ADAPTIVE
DEHUMIDIFICATION SYSTEM
Units equipped with the factory installed Humidi- - MiZer
option are capable of providing multiple modes of
improved dehumidification as variations of the normal
cooling cycle. The Humidi- - MiZer option includes
additional valves in the liquid line and discharge line of
each refrigerant stage, a single- - row reheat condenser coil
mounted to the evaporator coil and a Motormaster
variable- - speed control of some or all outdoor fans.
Operation of the revised refrigerant stage for each mode is
described below.
The Humidi- - MiZer system provides three sub- - modes of
operation: Cooling, Reheat1 and Reheat2.
Normal Cooling Mode - - provides a normal ratio of
Sensible and Latent Cooling effect from the evaporator
coil.
SubCooling Mode (Reheat1) - - provides increased Latent
Cooling while slightly reducing the Sensible Cooling
effect.
Hot Gas Reheat Mode (Reheat2) - - provides normal
Latent Cooling but with no or minimum Sensible Cooling
effect delivered to the space.
The Reheat1 and Reheat2 modes are available when the
unit is not in a Heating mode and when the Low Ambient
Lockout switch is closed.
Unit Sizes 04 - - 07 (Type 1 - - Single Stage
Cooling)
Normal Cooling Mode: When there is only a single
cooling demand with thermostat Y1 calling, the single
circuit will operate in Normal Cooling Mode. The Cooling
Liquid Valve (CSV) is Normally Open (NO) and
energized. The Reheat Discharge Valve, DSV, is Normally
Closed (NC) and remains closed during the Cooling
Mode. See Fig. 74.
Subcooling (Reheat 1) Mode: When the unit is operating
in the Cooling Mode (the space temperature is above the
set- - point, with Y1 calling) and the space humidity also
above its set- - point, the Humidistat will close and the unit
operation will shift to Reheat1 (Subcooling) Mode.
The CSV is energized and closed, blocking the liquid flow
around the Humidi- - MiZer coil. The liquid flow then
passes through the Humidi- - MiZer, a Metering Device
(TXV) and a Acutrol metering device before entering
the Evaporator Coil. The increased subcooling causes the
Evaporator Coil surface temperature to decrease, while
increasing the unit's Latent Cooling effect. The DSV
valve remains de- - energized and closed. See Fig. 75.
Hot Gas Reheat (Reheat 2) Mode: When there is only a
dehumidification demand (the Humidistat is above its
set- - point but no thermostat Y1 call), the unit will operate
in Reheat2 mode. The Supply Fan Motor and the
Compressor will be energized through the Reheat Control
Board (RCB) logic. See Fig. 73. The CSV is energized
and closed blocking liquid flow around the Humidi- - MiZer
Coil. The DSV valve is also energized and opened
allowing bypassed discharge gas to mix with liquid while
entering the Humidi- - MiZer coil. The additional heat from
the bypassed discharge gas offsets the Sensible Cooling
effect from the evaporator coil during the Reheat2 Mode.
See Fig. 76.
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 CLV valve and the DLV valve. 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.
Fig. 73 - - Reheat Control Board (RCB)
Unit Sizes 08 - - 14 (Type 1 - - Dual Stage
Cooling)
NOTE:
Unit sizes 08- - 12 and size 14 use different
designations in the wiring and piping schematics for
Cooling Solenoid and Discharge Solenoid valves.
VALVE TYPE SIZES 08---12
Cooling Solenoid CSV1,2
Discharge Solenoid DSV1,2
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. The CSV1
and CSV2 (on size 14, CLV1 and CLV2)valves are
de- - energized and open allowing liquid to flow around the
Humidi- - MiZer coil and directly to the unit's TXVs and
Evaporator Coil. The Reheat Discharge Valves, DSV1 and
DSV2, (on size 14, RDV1 and RDV2) are de- - energized
and remain closed during the Cooling Mode. See Fig. 74
for illustration of each circuit's operation.
Subcooling (Reheat 1) Mode: When the unit is operating
in a full- - load Cooling Mode (space temperature above
set- - point and both thermostats Y1 and Y2 calling) and the
space humidity is above its set- - point, the humidistat will
close and the unit operation will shift to Reheat1
(Subcooling). The CSV1 and CSV2 (or CLV1 and CLV2)
valves, become energized and closed, redirecting the
liquid flow into the Humidi- - MiZer coil. The increased
subcooling causes the evaporator coil surface temperature
to decrease, while increasing the unit's Latent Cooling
effect. The DSV1 and DSV2 (or RDV1 and RDV2)
64
C12714
SIZE 14
CLV1,2
RDV1,2