Temperature Compensated Start - Carrier WeatherMaker 48A2020 Controls, Start-Up, Operation, Service And Troubleshooting Instructions

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
Airflow
3-WAY VALVE
CHECK VALVE
3'
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.
EVAPORATOR
CCT
Evaporator Discharge Temperature
In Subcool or Reheat Mode, compressor staging
and increased subcooling drives evaporator
discharge temperature down to meet higher latent
loads
D.C.SP COOL
Fig. 17 — Humidi-MiZer
BYPASS
MODULATING
VALVE
2a'
2'
3a'
CONDENSER
OUTDOOR AIR
CIRCUIT B
REHEAT HX
EVAPORATOR
4'
EXPANSION
DEVICE
Fig. 18 — Humidi-MiZer
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
ITEM
TCS.C Temp.Cmp.Strt.Cool Factr 0 to 60 min
TCS.H Temp.Cmp.Strt.Heat Factr 0 to 60 min
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.
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)
® System Control
CONDENSER
MODULATING
VALVE
1'
COMPRESSOR
5'
3
INDOOR AIR
®
System Diagram
76

UNIT.
EXPANSION RANGE UNITS CCN POINT
SAT
RAT-D.V.RA or
D.V.HT
2
CONDENSER
OUTDOOR AIR
CIRCUIT A
EVAPORATOR
4 5
EXPANSION
TCSTCOOL
TCSTHEAT
1
COMPRESSOR