Carrier 48HC D17 Series Service And Maintenance Instructions page 13

Humidi- - MiZer System Components
The Humidi- - MiZer uses the standard unit compressor(s),
evaporator coil and Round Tube- - Plate Fin (RTPF)
condenser coil. Additional refrigeration system hardware
includes a subcooler/reheat coil and solenoid valves. On
50HC models, the evaporator coil includes a TXV as a
standard feature. Units with Humidi- - MiZer FIOP also
include a factory- - installed head pressure control system
(Motormaster I) to provide proper liquid pressure during
reheat modes. Unique controls include a Reheat Relay
Board (RHB), evaporator coil freezestat, secondary low
pressure switch and a low outdoor temperature lockout
switch (LTLO). Units with two refrigeration circuits
include a solenoid valve, TXV, freezestat and low pressure
switch for each circuit. See Fig. 15.
RH2.A RH2.B
Fig. 15 - - Humidi- - MiZer Valve Locations
Subcooler/Reheat Coil
The Subcooler/Reheat Coil is mounted across the leaving
face of the unit's evaporator coil. The coil is a one- - row
design with two separate circuits.
3- - Way Solenoid Valve
Hot Gas Bypass Solenoid Valve
Relay Reheat Board (RHB)
Evaporator Freeze Protection Thermostat
Low Outdoor Temperature Lockout Switch
Secondary Low Pressure Switch
Head Pressure Control
Operating Sequences
The Humidi- - MiZer system provides three sub- - modes of
operation: Normal Cooling (see Fig. 16), Subcooling
Reheat1 (see Fig. 17) and Hot Gas Reheat2 (see Fig. 18).
The Reheat1 and Reheat2 modes are available when the
unit is not in a heating mode and when the Low Ambient
RH1.B
Lockout Switch is closed.
When there is only a single cooling demand (thermostat
Y1 alone or with thermostat Y2), one or both circuits will
operate in Reheat2 mode. Both solenoids are energized in
both circuits. See Fig. 18, Hot Gas Reheat Schematic for
system refrigerant flow.
RH1.A
When there is both cooling demand (thermostat Y1
demand) and dehumidification demand, circuit 1 will
operate in Reheat1 mode (Subcooling, Fig. 17) and circuit
will operated in Reheat2 mode (Reheat, Fig. 18). In
Reheat1 mode, the 3- - way solenoid valve is energized,
opening the reheat coil to the refrigeration flow path
providing sub- - cooling to the liquid before it enters the
TXV.
C08057
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