76
meet the latent load. As the refrigerant leaves the compressor, the
modulating valves vary the amount of refrigerant that enters and/
or bypasses the condenser coil. As the bypassed and hot refriger-
ant liquid, gas or two-phase mixture passes through the Humidi-
MiZer coil, it is exposed to the cold supply airflow coming from
the evaporator coil. The refrigerant is subcooled in this coil to a
temperature approaching the evaporator leaving air temperature.
The liquid refrigerant then enters a thermostatic expansion valve
(TXV) where the refrigerant pressure is decreased. The refrigerant
enters the TXV and evaporator coil at a temperature lower than in
standard cooling operation. This lower temperature increases the
latent capacity of the evaporator. The refrigerant passes through
the evaporator and is turned into a superheated vapor. The air
passing over the evaporator coil will become colder than during
normal operation. However, as this same air passes over the Hu-
midi-MiZer reheat coil, it will be warmed to meet the supply air
setpoint temperature requirement. See Fig. 18.
Temperature Compensated Start
This logic is used when the unit is in the unoccupied state. The
control will calculate early Start Bias time based on Space
Temperature deviation from the occupied cooling and heating
setpoints. This will allow the control to start the unit so that the
space is at conditioned levels when the occupied period starts.
This is required for ASHRAE (American Society of Heating,
Refrigerating, and Air-Conditioning Engineers) 90.1 compli-
ance. A space sensor is required for non-linkage applications.
SETTING UP THE SYSTEM
The settings for temperature compensated start can be found in
the local display under
Configuration
UNIT
.
TCST-Cool Factor (TCS.C)
This is the factor for the start time bias equation for cooling.
TCST-Heat Factor (TCS.H)
This is the factor for the start time bias equation for heating.
NOTE: Temperature compensated start is disabled when these
factors are set to 0.
ITEM
EXPANSION
RANGE UNITS CCN POINT
TCS.C
Temp.Cmp.Strt.Cool Factr 0 to 60 min
TCSTCOOL
TCS.H
Temp.Cmp.Strt.Heat Factr 0 to 60 min
TCSTHEAT
Fig. 17 — Humidi-MiZer
®
System Control
Evaporator Discharge Temperature
In Subcool or Reheat Mode, compressor staging
and increased subcooling drives evaporator
discharge temperature down to meet higher latent
loads
Airflow
EVAPORATOR
HUMIDI-MIZER ADAPTIVE
DEHUMIDIFICATION
SYSTEM COIL
Supply Air Temperature Control
Innovative algorithm to control supply air temperature
modulates flow bypass to meet desired supply air setpoint -
no overcooling or overheating of the space.
Subcooling Mode: Meet Cooling Mode Supply Air Setpoint
Reheat Mode: Meet Return Air Offset or Reheat Setpoint (configurable)
CCT
S
AT
D.C.SP COOL
RAT-D.V.RA or
D.V.HT
3
4
EXPANSION
INDOOR AIR
EVAPORATOR
5
5'
EVAPORATOR
REHEAT HX
EXPANSION
DEVICE
4'
3'
CHECK VALVE
3-WAY VALVE
3a'
2'
2a'
BYPASS
MODULATING
VALVE
CONDENSER
OUTDOOR AIR
CONDENSER
MODULATING
VALVE
1'
COMPRESSOR
1
2
CONDENSER
OUTDOOR AIR
COMPRESSOR
CIRCUIT B
CIRCUIT A
Fig. 18 — Humidi-MiZer
®
System Diagram
In all Dehumidification modes the three-way
valve is open to the reheat HX. As the percent
Humidi-MiZer capacity increases the Bypass
valve will fully open first, bypassing gas
around the condenser. Then the Condenser
modulating valve will close. From 0 to 50%
Bypass valve is moving; from 50 to 100% the
Condenser modulating valve is moving.
Summary of Contents for WEATHERMAKER 48A2020
Page 112: ...112 Fig 20 Typical Main Control Box Wiring Schematic 48 50A Units ...
Page 113: ...113 Fig 21 Typical Auxiliary Control Box Wiring Schematic ...
Page 114: ...114 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown ...
Page 115: ...115 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown TO NEXT PAGE ...
Page 116: ...116 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont ...
Page 117: ...117 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown ...
Page 118: ...118 Fig 25 Typical Controls Option Wiring Schematic SW1 SW2 OR DEHUMIDIFY SWITCH ...
Page 119: ...119 Fig 26 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown ...
Page 120: ...120 Fig 27 Typical Power Schematic of Greenspeed Low Ambient Option 48 50A 060 Unit Shown ...
Page 121: ...121 Fig 28 Typical Small Chassis Component Location Size 020 035 Units ...
Page 122: ...122 Fig 29 Typical Large Chassis Component Locations Size 040 060 Units ...
Page 185: ...185 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716 ...