90
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 sen-
sor (
D.SEN=3
) must remain OFF before the dehumidification
mode is disabled.
OPERATION
Dehumidification can occur on all P series units. However, de-
humidification 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, Hydronic heat, Third Party Heat or Humidi-MiZer. Dehu-
midification without reheat (
D.SEL=5
) will only operate in
Venting Dehum or Cooling Dehum. See Humidi-MiZer Adap-
tive Dehumidification System section on page 90 for details on
the operation of the Humidi-MiZer system for dehumidifica-
tion and reheat. If the machine’s control type is a TSTAT type
(
Configuration
UNIT
C.TYP
=3) and the discrete input se-
lection 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 pro-
vide cooling, a dehumidification mode may be called out, but
the control 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
(
C
onfiguration
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,
dehumidification 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.
• 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. In addition, for multi-stage
cooling units the cooling control point will be set to
Config-
uration
DEHU
D.C.SP
(no SASP reset is applied).
• Reheat — Reheat control occurs when dehumidification
demand is present. On units with Hydronic, Modulating, or
Staged gas, third party or Humidi-MiZer heat types, the
control can perform reheat during dehumidification.
During dehumidification, the air through the unit is cooled
in order to remove moisture. This cooler air temperature
can result in overcooling of the space. To alleviate this, re-
heat is added to raise the leaving air temperature to a Vent,
Cool or Heat set point. The reheat will control the leaving
air to a Vent, Cool to Heat supply air temperature. See
Table 72 for heating control point when dehumidification
with reheat is active.
• Cooling Dehum (23) – During cooling dehumidification,
the heating control point will be whatever the actual cool-
ing set point would have been plus any reset.
• Venting Dehum (24) – During venting dehumidification,
the heating control point will depend on the configuration
of the Vent Reheat Set Point Select (
D.V.CF
).
• D.V.CF = 0 – The heating control point will be an offset
(D.V.RA) subtracted from the return air temperature.
• D.V.CF = 1 – The heating control point will be the Dehu-
midification heat set point (
D.V.HT
)
• Heating Dehum (29) – During heating dehumidification,
the heating control point will be the heating supply air set
point (SASPHEAT)
Ending Dehumidification and Reheat Control
When either the humidity sensor fall 5% below the set point
(
Configuration
DEHU
D.RH.S
)
or the discrete input reads
“LOW”, the Dehumidification mode will end.
Humidi-MiZer
®
Adaptive Dehumidification
System
Units with the factory-equipped Humidi-MiZer option are ca-
pable of providing multiple modes of improved dehumidifica-
tion as a variation of the normal cooling cycle. The design of
the Humidi-MiZer system allows for two humidity control
modes of operation of the rooftop unit, utilizing a common
subcooling/reheat dehumidification coil located downstream of
the standard evaporator coil. This allows the rooftop unit to op-
erate in both a Dehumidification (Subcooling) mode and a hot
gas Reheat Mode for maximum system flexibility. In reheat
mode, the supply air temperature can be raised to either a vent-
ing (neutral) air temperature or a heating air temperature. The
Humidi-MiZer package is factory installed and will operate
whenever there is a dehumidification requirement present. The
Humidi-MiZer system is initiated based on input from a facto-
ry-installed return air humidity sensor to the large rooftop unit
controller. Additionally, the unit controller may receive an in-
put from a space humidity sensor, a discrete input from a me-
chanical humidistat, or third-party controller. Dehumidification
and reheat control are allowed during Cooling and Vent modes
in the occupied period.
SET UP THE SYSTEM
The settings for Humidi-MiZer system can be found at the lo-
cal display at
Configuration
DEHU
. See Table 70.
Table 72 — Heating Control Point Settings
Heating Control Point (HEATCPNT) setting
CTRL MODE=VAVRAT or CTRLMODE=VAVSPT
MODEHVAC (#)
DHVHTCFG
DHVHTCFG=0
DHVHTCFG=1
Venting
Dehumidification (24)
RAT-DHVRAOFF
DHVHT_SP
Heating
Dehumidification (29)
SASPHEAT
Cooling
Dehumidification (23)
SASP + SASPRSET
Heating Control Point (HEATCPNT) setting
CTRL MODE=SPT_MULTI or CTRLMODE=STAT_MULTI
Cooling
Dehumidification (23)
HVACMODE
LO_COOL
HI_COOL
SASP_LO
SASP_HI
Содержание Weathermaster 48P2030-100
Страница 130: ...130 Fig 19 Typical Power Schematic Sizes 040 075 Shown ...
Страница 131: ...131 Fig 20 Main Base Board Input Output Connections ...
Страница 132: ...132 Fig 21 RXB EXB CEM SCB Input Output Connections ...
Страница 133: ...133 Fig 22 Typical Gas Heat Unit Control Wiring 48P030 100 Units Shown ...
Страница 134: ...134 Fig 23 Typical Electric Heat Wiring 50P030 100 Units Shown ...
Страница 135: ...135 Fig 24 Typical Power Wiring 115 V ...
Страница 136: ...136 Fig 25 Typical Gas Heat Section Size 030 050 Units Shown ...
Страница 138: ...138 Fig 27 Component Arrangement Size 030 035 Units ...
Страница 139: ...139 Fig 28 Component Arrangement Size 040 075 Units ...
Страница 140: ...140 Fig 29 Component Arrangement Size 090 100 Units ...
