Temperature Compensated Start; Setting Up The System - United Technologies Carrier Weathermaker 48A2 Controls, Start-Up, Operation, Service, And Troubleshooting

evaporator leaving air temperature. The liquid refrigerant then
enters a thermostatic expansion valve (TXV) where the refrig-
erant 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 opera-
tion. However, as this same air passes over the Humidi-MiZer
reheat coil, it will be warmed to meet the supply air setpoint
temperature requirement. See Fig. 18.
Temperature Compensated Start —
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,
EVAPORATOR
Airflow
BYPASS
MODULATING
VALVE
2a'
2'
3a'
CONDENSER
CIRCUIT B
3-WAY VALVE
CHECK VALVE
4'
3'
EXPANSION
DEVICE
This logic is
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
CONDENSER
MODULATING
VALVE
1'
OUTDOOR AIR
COMPRESSOR
REHEAT HX
EVAPORATOR
5'
INDOOR AIR
Fig. 18 — Humidi-MiZer
72
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 tempera-
ture compensated start can be found in the local display under

Configuration UNIT.
ITEM EXPANSION
TCS.C Temp.Cmp.Strt.Cool Factr 0 - 60
TCS.H Temp.Cmp.Strt.Heat Factr 0 - 60
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
SAT
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)
RAT-D.V.RA or
D.V.HT
®
System Control
2
CONDENSER
CIRCUIT A
4
3
EXPANSION
®
System Diagram
RANGE UNITS CCN POINT
min TCSTCOOL
min TCSTHEAT
1
OUTDOOR AIR
COMPRESSOR
EVAPORATOR
5