12
When there is only a single cooling demand (thermostat Y1 alone
or with thermostat Y2), one or both circuits will operate in Re
-
heat2 mode. Both solenoids are energized in both circuits. See
Fig. 20, Hot Gas Reheat Schematic for system refrigerant flow.
When there is both cooling demand (thermostat Y1 demand) and
dehumidification demand, circuit 1 will operate in Reheat1 mode
(Subcooling, Fig. 19) and circuit will operated in Reheat2 mode
(Reheat, Fig. 20). 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. See
Table 3 for further details on Humid-MiZer system operating
modes. See Table 4 for details on troubleshooting the Humidi-
MiZer system.
Humidi-MiZer Modes
NORMAL COOLING
During the Normal Cooling mode, the liquid refrigerant flows
from the outdoor condenser through the normally open (NO)
Cooling System Valve (CSV) to the expansion device. Both the
Reheat1 (RH1.x) and Reheat2 (RH2) valves are closed during the
normal cooling mode.
During the Normal Cooling mode, the refrigerant flows from the
outdoor compressor through the condenser coil. The Reheat2
(RH2.x) is closed, preventing the refrigerant from bypassing the
condenser coil. The refrigerant then flows through the open Re
-
heat2 (RH1.x) 3-way valve to the TXV Metering Device, bypass
-
ing the Humidi-MiZer coil, and finally passing through the evapo
-
rator coil before returning to the outdoor compressor. See Fig 18.
REHEAT1 (SUBCOOLING MODE)
The Reheat1 or Subcooling mode will be engaged to satisfy part-
load-type conditions when there is a space call for cooling and de
-
humidification. Although the temperature could have dropped and
decreased the sensible load in the space, the outdoor and/or space
humidity levels could have risen. A typical scenario could be
when the outside air is 85°F (29°C) with 70% to 80% relative hu
-
midity (RH). Desired Sensible Heat Ratio (SHR) for equipment in
this scenario is typically from 0.4 to 0.7. The Humidi-MiZer unit
will initiate the Dehumidification mode when both the space
temperature and humidity are above the temperature and humidity
setpoints while attempting to meet both setpoint requirements.
Once the humidity requirement is met, the unit can continue to op
-
erate in normal cooling mode to meet any remaining sensible ca
-
pacity load. Alternatively, if the sensible load is met and humidity
levels remain high, the unit can switch to Hot Gas Reheat mode or
Reheat2 mode to provide neutral, dehumidified air.
During the Reheat1 or Subcooling mode, the liquid refrigerant
flows from the outdoor compressor through the condenser coil to
the Reheat1 (RH1.x) 3-way valve and on to the Humid-Mizer coil.
The Reheat2 (RH2.x) valve is closed. The liquid refrigerant then
passes through the Humid-Mizer coil and then a metering device
or Thermostatic Expansion Valve (TXV). From the TXV, the liq
-
uid refrigerant passes through the evaporator coil and back to the
outdoor comprssor. See Fig 19.
REHEAT2 (HOT GAS REHEAT MODE)
This Reheat2 or Hot Gas Reheat mode is used when dehumidifi
-
cation is required without a need for cooling, such as when the
outside air is at a neutral temperature, but high humidity exists.
This situation requires the equipment to operate at a low SHR of
0.0 to 0.2. With no cooling requirement calling for dehumidifica
-
tion, the Humidi-MiZer adaptive dehumidification system will en
-
ergize both compressors, opening the two hot gas bypass valves,
allowing refrigerant flow to the Humidi-MiZer coil to reheat the
unit’s supply air to a neutral temperature.
The hot bypassed refrigerant liquid (gas or two-phase mixture) ex
-
its the outdoor compressor and passes through the open Reheat1
(RH1.x) at the same time it passes through the condenser coil to
the open Reheat2 (Rh2.x) to the Humidi-MiZer coil. After the re
-
frigerant passes through the Humidi-MiZer coil, it enters a TXV
metering device, decreasing the air pressure, and on to the evapo
-
rator coil. The refrigerant is subcooled in this coil to a temperature
approaching the evaporator leaving air temperature. The liquid re
-
frigerant then returns to the outdoor compressor. See Fig. 20.
The refrigerant enters the TXV and evaporator coil at a tempera
-
ture lower than the temperature in the standard cooling operation.
This lower temperature increases the latent capacity of the evapo
-
rator. The refrigerant passes through the evaporator turning it into
a superheated vapor. The air passing over the evaporator coil be
-
comes colder than it would during normal operation. As this same
air passes over the Humidi-MiZer Reheat Coil, it will be warmed
to the neutral supply air temperature.
Fig. 18 — Normal Cooling Mode – Humidi-MiZer
System
CONDENSER COIL
HUMIDI-MIZER COIL
EVAPORATOR COIL
COMPRESSOR
OUTDOOR AIR
INDOOR AIR
RH2.x
VALVE
RH1.x
VALVE
TXV
VALVE
= CLOSED VALVE
= OPEN VALVE
= 3-WAY VALVE
Summary of Contents for WeatherMaker 50TC 17-30 Series
Page 34: ...34 Fig 48 RTU Open Overlay for Economizer Wiring ...
Page 35: ...35 Fig 49 VFD Overlay for W2770 Controller Wiring ...
Page 80: ...80 Fig C 50TC 17 28 Control Wiring Diagram APPENDIX D WIRING DIAGRAMS ...
Page 81: ...81 Fig D 50TC 30 Control Wiring Diagram 208 230 3 60 Units APPENDIX D WIRING DIAGRAMS ...
Page 82: ...82 Fig E 50TC 30 Control Wiring Diagram 460 3 60 575 3 60 Units APPENDIX D WIRING DIAGRAMS ...
Page 83: ...83 Fig F 50TC 17 30 Power Wiring Diagram 208 230 3 60 Units APPENDIX D WIRING DIAGRAMS ...
Page 84: ...84 Fig G 50TC 17 30 Power Wiring Diagram 460 3 60 575 3 60 Units APPENDIX D WIRING DIAGRAMS ...
Page 89: ...89 Fig L 50TC PremierLink System Wiring Diagram APPENDIX D WIRING DIAGRAMS ...
Page 90: ...90 Fig M 50TC RTU Open Wiring Diagram APPENDIX D WIRING DIAGRAMS ...
Page 91: ...91 Fig N 50TC SAV VFD System Wiring Diagram APPENDIX D WIRING DIAGRAMS ...
Page 93: ......
