92
The N Series Humidi-MiZer system controls allow for the dis
-
charge air to be reheated to either the return air temperature mi
-
nus a configurable offset or to a configurable Reheat set point
(default 70°F). The hot gas reheat mode will be initiated when
only the humidity is above the humidity set point, without a de
-
mand for cooling.
System Control
The essential difference between the De-humidification mode and
the Reheat mode is in the supply air set point. In Dehumidification
mode, the supply air set point is the temperature required to pro
-
vide cooling to the space. This temperature is whatever the cool
-
ing control point would have been in a normal cooling mode. In
Reheat mode, the supply air set point will be either an offset sub
-
tracted from return air temperature (
D.V.RA
) or the Vent Reheat
Set Point (
D.V.HT
). Both values are configurable. For both Dehu
-
midification mode and Reheat mode, the unit compressor staging
will decrease the evaporator discharge temperature to the Dehu
-
midify Cool Set Point (
D.C.SP COOL
) in order to meet the latent
load and reheat the air to the required cooling or reheat set point.
There is a thermistor array called
Temperatures
AIR.T
CCT
connected to the RCB. This thermistor array serves as the evapo
-
rator discharge temperature (EDT). See Fig. 14.
The N-Series Humidi-MiZer
®
system uses refrigerant flow mod
-
ulation valves that provide accurate control of the leaving-air
temperature as the evaporator discharge temperature is de
-
creased to meet the latent load. As the refrigerant leaves the
compressor, the modulating valves vary the amount of refriger
-
ant that enters and/or bypasses the condenser coil. As the by
-
passed and hot refrigerant liquid, gas, or 2-phase mixture passes
through the Humidi-MiZer coil, it is exposed to the cold supply
airflow coming from the evaporator coil. The refrigerant is sub
-
cooled in this coil to a temperature approaching the evaporator
leaving air temperature. The liquid refrigerant then enters an
electronic expansion valve (EXV) where the refrigerant pressure
is decreased. The refrigerant enters the EXV 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 Humidi-MiZer reheat coil, it will be
warmed to meet the supply air set point temperature require
-
ment. See Fig. 15.
During dehumidification with Humidi-MiZer (
Configuration
DEHU
D.SEL
=4), If dehum results in over-cooling (If Humi
-
dimizer capacity is not sufficient to heat it up enough), there will
be a transition from dehum to heat mode for
Configura
-
tion
HEAT
HT.CF
=1 or 2 or 5 (2-stage electric heat or 2-
stage gas heat or SCR electric heat) and all compressors will turn
OFF. This requirement on heating after cooling is that compres
-
sors must shut down and cannot be powered when electric heat
powers up. This large power draw can result in blown fuses and a
fire hazard.
During Heating Dehum mode with Humidi-MiZer (
Configura
-
tion
DEHU
D.SEL
=4), control enables Staged Gas or Hy
-
dronic heat sources (
Configuration
HEAT
HT.CF
=3 or 4)
as Reheat sources along with Humidi-MiZer reheat. This is called
supplemental reheat.
Fig. 14 —
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
SAT
D.C.SP COOL
RAT-D.V.RA or
D.V.HT
Summary of Contents for WeatherExpert 48N2
Page 135: ...135 Fig 18 48 50N Typical Power Schematic Nominal 075 Ton Unit Shown ...
Page 136: ...136 Fig 19 48 50N Typical Power Schematic Nominal Ton 90 150 Units Shown ...
Page 137: ...137 Fig 20 48 50N Main Base Board Input Output Connections ...
Page 138: ...138 Fig 21 48 50N RXB EXB CEM Input Output Connections a48 9307 ...
Page 139: ...139 Fig 22 48 50N EXV SCB Input Output Connections a48 9308 ...
Page 140: ...140 Fig 23 48N Typical Modulating Gas Heat Unit Control Wiring ...
Page 141: ...141 Fig 24 50N Typical Electric Heat Unit Control Wiring ...
Page 144: ...144 Fig 27 48N Typical Gas Heat Section Wiring Nominal Ton 120 to 150 Units ...
Page 145: ...145 Fig 28 48 50N Typical Power Component Control Wiring 460 v ...
Page 146: ...146 Fig 29 48 50N Component Control Wiring 575 v Nominal Ton 075 to 150 Units ...
Page 147: ...147 Fig 30 48 50N Component Arrangement Power Box ...
Page 148: ...148 Fig 31 48 50N Component Arrangement Control Box ...
Page 240: ...240 APPENDIX D VFD INFORMATION CONT Fig G VFD Bypass Wiring Diagram WHEN USED ...