93
Table 72 — Dehumidification Configuration
Vent Reheat RAT Offset (D.V.RA)
Set point offset used only during the vent mode. The air will be re-
heated to return-air temperature less this offset.
Vent Reheat Set Point (D.V.HT)
Set point used only during the vent mode. The air will be reheated
to this set point.
Dehumidify Cool Set Point (D.C.SP)
This is the dehumidification cooling set point.
Dehumidity RH Set Point (D.RH.S)
This is the dehumidification relative humidity trip point.
Dehumidify RH Deadband (DH.DB)
This is the control deadband for the RH control.
Dehumidify Discrete Timeguard (DH.TG)
This is the amount of time that the discrete input humidity sensor
(D.SEN=3) must remain OFF before the dehumidification mode
is disabled.
OPERATION
Dehumidification can occur on all P series units. However, dehu-
midification with reheat (Venting Dehum, Cooling Dehum or
Heating Dehum) can only occur if the unit is equipped with one of
the following types of heat: Multi-Staged or Modulating Gas, Hy-
dronic heat, third-party Heat or Humidi-MiZer. Dehumidification
without reheat (D.SEL=5) will only operate in Venting Dehum or
Cooling Dehum. See Humidi-MiZer Adaptive Dehumidification
System section on page 94 for details on the operation of the Hu-
midi-MiZer system for dehumidification and reheat. If the ma-
chine’s control type is a TSTAT type (Configuration
UNIT
C.TYP=3) and the discrete input selection for the sensor is not
configured (D.SEN not equal to 3), dehumidification will be
disabled.
If the machine’s control type is a TSTAT type (Configura-
tion
UNIT
C.TYP=3) and the economizer is able to provide
cooling, a dehumidification mode may be called out, but the con-
trol will not request mechanical cooling.
NOTE: Configuring Configuration
DEHU
D.SEN to 1, 2 or
3 will enable the CEM board along with the sensor selected for
control.
NOTE: If Configuration
DEHU
D.SEL = 1 or 2, then either
staged gas or hot water valve control will be automatically enabled
(Configuration
HEAT
HT.CF will be set to either 3 or 4).
If a tempering, unoccupied, or “mechanical cooling locked out”
HVAC mode is present, dehumidification will be disabled. An
HVAC: Off, Vent or Cool mode must be in effect to launch either a
Heat or Dehumidification mode.
If an associated sensor responsible for dehumidification fails, de-
humidification will not be attempted (SPRH, RARH).
Initiating a Dehumidification Mode
To call out a Dehumidification mode in the Off, Vent, Cool, or
Heat HVAC mode, one of the following conditions must be true:
• The space is occupied and the humidity is greater than the
relative humidity trip point (D.RH.S).
• The space is occupied and the discrete humidity input is
closed.
Dehumidification and Reheat Control
If a dehumidification mode is initiated, the rooftop will attempt to
lower humidity as follows:
• Economizer Cooling — The economizer, if allowed to per-
form free cooling, will have its control point (Run Sta-
tus
VIEW
EC.C.P) set to Configuration
DEHU
D.C.SP. If Configuration
DEHU
D.EC.D is disabled, the
economizer will always be disabled during dehumidification.
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
DEHU DEHUMIDIFICATION CONFIG.
D.SEL Dehumidification Config 0 to 4 DHSELECT 0
D.SEN Dehumidification Sensor 1 to 3 DHSENSOR 1
D.EC.D Econ disable in DH mode? Yes/No DHECDISA Yes
D.V.CF Vent Reheat Setpt Select 0 to 1 DHVHTCFG 0
D.V.RA Vent Reheat RAT offset 0 to 8 deltaF DHVRAOFF 0
D.V.HT Vent Reheat Setpoint 55 to 95 dF DHVHT_SP 70
D.C.SP Dehumidify Cool Setpoint 40 to 55 dF DHCOOLSP 45
D.RH.S Dehumidify RH Setpoint 10 to 90 % DHRELHSP 55
HZ.RT Humidi-MiZer Adjust Rate 5 to 120 sec HMZRRATE 30
HZ.PG Humidi-MiZer Prop. Gain 0 to 10 HMZR_PG 0.8
DH.DB Dehumidify RH Deadband 1 to 30 % DHSENSDB 5
DH.TG Dehumidification Discrete Timeguard 10 to 90 seconds DHDISCTG 30
Table 73 — Dehumidification Heat Source Dependency upon Heating Stages
HT.CF (HEATTYPE)
Heating provided by the system
HT.ST
HTSTGTYP
D.SEL (DHSELECT)
Selected Heat for Dehum
DEHUM
ALLOWED
REHEAT
ALLOWED
0–5 any N/A 0 None No No
0–5 any N/A 4 Humidi-MiZer Yes Yes
0–5 any N/A 5 Dehum without reheat Yes No
0 No heat N/A 3 3rd party heat Yes Yes
1 2-stage electric heat N/A 5 Dehum without reheat Yes No
2 2-stage gas heat 0 5 Dehum without reheat Yes No
3 Staged or mod gas heat 0–5 2 Stage or mod gas Yes Yes
4 Hydronic N/A 1 Hydronic Yes Yes
5 SCR electric 6, 7, 8 5 Dehum without reheat Yes No
LEGEND
DHSELECT — Dehumidification Heat Source
HEATTYPE — Heating Type
HTSTGTYP — Heating Stage Type
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