74
Vent Reheat Setpoint Select (D.V.CF)
This configuration determines how the vent reheat setpoint is
selected.
• D.V.CF = 0 — Reheat follows an offset subtracted from
return air temperature (D.V.RA).
• D.V.CF = 1 — Reheat follows a dehumidification heat set-
point (D.V.HT).
Vent Reheat RAT Offset (D.V.RA)
Setpoint offset used only during the vent mode. The air will be
reheated to return-air temperature less this offset. This configu-
ration will have a range of 0 to 8°F with default of 0°F.
Vent Reheat Setpoint (D.V.HT)
Setpoint used only during the vent mode. The air will be re-
heated to this setpoint. This configuration will have a range of
55 to 95°F with default of 70°F.
Dehumidify Cool Setpoint (D.C.SP)
This is the dehumidification cooling setpoint. This configura-
tion will have a range of 40 to 55°F with default of 45°F.
Dehumidify RH Setpoint (D.RH.S)
This is the dehumidification relative humidity trip point. This con-
figuration will have a range of 10 to 90°F with default of 55°F.
Enable Hmzr St Oil Ret (HZ.OR)
[ENHORTST] This configuration can enable or disable the
Humidi-MiZer oil return during service test. It is recommended
leaving this configuration enabled. This configuration will
have a range of DSLB/ENBL with default of ENBL.
OPERATION
Dehumidification and reheat can only occur if the unit is
equipped with staged gas, or hydronic heat, or Humidimizer, or
an external heat source via the alarm relay. Dehumidification
without reheat can be done on any unit but Configuration
DEHU
D.SEL must be set to 0 or 2.
If the machine’s control type is a TSTAT type (Configuration
UNIT
C.TYP=3 or 4) and the economizer is able to provide
cooling, a dehumidification mode may be called out, but the con-
trol will not request mechanical cooling and D.EC.D=NO.
NOTE:
• Configuring Configuration
DEHU
D.SEN to 1
(RARH or SPRH SENSOR) will enable the ECB1 board
along with the sensor selected for control.
• Configuring Configuration
DEHU
D.SEN to 2
(DISCR.INPUT) will enable the CEM board along with
the switch input for control.
• Configuring Configuration
DEHU
D.SEL to 3
(DH-HMZR) will enable the EXB2/RXB board with the
CCT input and three-way valve in addition to the EXV
board with the modulating valves.
If an associated RARH sensor responsible for dehumidification
fails, dehumidification will not be attempted; see Alert T078
Return Air Relative Humidity Sensor Fail.
Initiating a Dehumidification Mode
To call out a Dehumidification mode in any 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 Including 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 Status
VIEW
EC.C.P) set to Configuration
DEHU
D.C.SP.
If Configuration
DEHU
D.EC.D is disabled, the econ-
omizer will always be disabled during dehumidification.
• Cooling — For all cooling control types: A High Cool
HVAC mode will be requested internally to the control to
maintain diagnostics, although the end user will see a Dehu-
midification mode at the display (Cooling Dehum). In addi-
tion, for multi-stage cooling units the cooling control point
will be set to Configuration
DEHU
D.C.SP (no
SASP reset is applied).
• Reheat When Cooling Demand is Present — For reheat con-
trol during dehumidification: If reheat follows an offset sub-
tracted from return-air temperature (Configuration
DEHU
D.SEL = 2), then no heating will be initiated and
the alarm relay will be energized. If Configuration
DEHU
D.SEL = 1 and Configuration
HEAT
HT.CF =
staged gas or hot water valve, then the selected heating con-
trol type will operate in the low heat/modulating mode.
• The heating control point will be whatever the actual cool-
ing setpoint would have been (without any supply air reset
applied).
• Reheat During Vent Mode — If configured (Configura-
tion
DEHU
D.V.CF = 0), the heating control point
will be equal to RAT – D.V.RA. If configured (Configura-
tion
DEHU
D.V.CF=1), the heating control point
will be equal to the D.V.HT setpoint. (VENTING DE-
HUM) will be displayed for the MODE.
• Dehumidification and Reheat in a Heat Mode — If there is a
Dehum demand and the temperature demand requires heat,
the Heating Dehum will be displayed and in LO-Heat condi-
tions the reheat setpoint will be equal to the Heat Control
point HT.SP. In a High heat condition the Heat will stage up
fully or go to 100%.
Ending Dehumidification and Reheat Control
When either the humidity sensor fall 5% below the setpoint
(Configuration
DEHU
D.RH.S) or the discrete input
reads “LOW”, the Dehumidification mode will end.
Table 69 — Dehumidification Configuration
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
DEHU DEHUMIDIFICATION CONFIG.
D.SEL Dehumidification Config 0 to 3 DHSELECT 0
D.SEN Dehumidification Sensor 1 to 2 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 ^F 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
DH.DB Dehumidify RH Deadband 1 to 30 % DHSENSDB
DH.TG Dehum Discrete Timeguard 10 to 90 s DHDISCTG
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
HZ.OR Enable HMZR St Oil Ret Dsbl/Enbl ENHORTST Enbl
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