Carrier Weathermaster 48P2030-100 Controls, Start-Up, Operation, Service, And Troubleshooting page 91

Dehumidification Configuration (D.SEL)
The dehumidification configuration for Humidi-MiZer is
D.SEL = 4 (DH – HUMDZR).
Dehumidification Sensor (D.SEN)
The sensor can be configured for the following settings:
• D.SEN = 1 — Initiated by return air relative humidity sensor.
• D.SEN = 2— Initiated by space relative humidity sensor.
• D.SEN = 3 — Initiated by discrete input.
The default sensor is the return-air relative humidity sensor
(D.SEN = 1). Units ordered with the Humidi-MiZer option will
have factory-installed return air relative humidity sensors.
Economizer Disable in Humidi-MiZer Mode (D.EC.D)
When D.SEL = 4 (DH – HUMDZR), this configuration is au-
tomatically set to D.EC.D = YES (Economizer disabled during
dehumidification).
Vent Reheat Set Point Select (D.V.CF)
This configuration determines how the vent reheat set point is
selected. This set point becomes the supply air set point when
the Humidi-MiZer function is initiated and the unit enters a Re-
heat Mode (relative humidity above set point with no cooling
demand).
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)
Set point offset is used only when the Humidi-MiZer function
is initiated and the unit enters a Reheat Mode. This occurs
when the relative humidity is above set point with no cooling
demand. The air will be reheated to return-air temperature less
this offset.
Vent Reheat Set Point (D.V.HT)
Set point used only when the Humidi-MiZer function is initiat-
ed and the unit enters a Reheat Mode. This occurs when the
relative humidity is above set point with no cooling demand.
When D.V.CF = 0, the supply air will be reheated to D.V.HT
minus D.V.RA. When D.V.CF = 1, the supply air will be re-
heated to D.V.HT.
Dehumidify Cool Set Point (D.C.SP)
This is the Humidi-MiZer cooling set point used to determine
the temperature the air will be cooled to prior to it being reheat-
ed to the desired supply air temperature. This set point is used
during the Humidi-MiZer dehumidification and reheat modes
of operation.
Dehumidify RH Set Point (D.RH.S)
This is the Humidi-MiZer 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.
HumidiMiZer Adjust Rate (HZ.RT)
This is the rate (seconds) at which corrections are made in the
position of the modulating valves (C.EXV and B.EXV) to
maintain supply air set point.
HumidiMiZer Proportional Gain (HZ.PG)
This is the proportional gain used in calculating the required
valve position change for supply air temperature control. It is
essentially the percentage of total reheat capacity adjustment
that will be made per degree Fahrenheit of supply air tempera-
ture error.
OPERATION
Mode Qualifications
An HVAC: Off, Vent, Cool, or Heat mode must be in effect to
launch a Humidi-MiZer mode.
Sensor Failure
If an associated sensor responsible for controlling Humidi-MiZer
fails, dehumidification will not be attempted (SPRH, RARH).
Initiating a Humidi-MiZer Reheat (Venting Dehumidifica-
tion or Heating Dehumidification) or Dehumidification
(Cooling Dehumidification) Mode
To call out a Reheat (Venting Dehumidification) mode in the
"Vent" or the "Off" HVAC mode, Heating Dehumidification in
the "Heat" HVAC mode, or Dehumidification (Cooling Dehu-
midification) mode in a "Cool" HVAC mode, one of the fol-
lowing 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.
Ending a Humidi-MiZer Reheat or Dehumidification Mode
When either the humidity sensor falls 5% below the set point

(Configuration DEHU
"LOW", the Humidi-MiZer mode will end.
Relevant Outputs
The Humidi-MiZer 3-way valve (reheat valve) commanded
output can be found in Outputs
The Humidi-MiZer Condenser Modulating Valve (Condenser
EXV) position output can be found in Outputs
C.EXV. The condenser position will be provided as percent open.
The Humidi-MiZer Bypass Modulating Valve (Bypass EXV)
position output can be found in Outputs
The bypass position will be provided as percent open.
HUMIDI-MIZER MODES
Cooling Dehumidification Mode (Subcooling)
This mode will be engaged to satisfy part load type conditions
when there is a space call for cooling and dehumidification. Al-
though the temperature may have dropped and decreased the sen-
sible load in the space, the outdoor and/or space humidity levels
may have risen. A typical scenario might be when the outside air
is 85°F and 70 to 80% relative humidity (RH). Desired SHR for
equipment in this scenario is typically from 0.4 to 0.7. The Humi-
di-MiZer unit will initiate Dehumidification mode when the space
temperature and humidity are both above the temperature and hu-
midity set points, and attempt to meet both set point requirements.
Once the humidity requirement is met, the unit can continue to op-
erate in normal cooling mode to meet any remaining sensible ca-
pacity load. Alternatively, if the sensible load is met and humidity
levels remain high, the unit can switch to Hot Gas Reheat mode to
provide neutral, dehumidified air.
Reheat (Venting Dehumidification) Mode
This mode is used when dehumidification is required without a
need for cooling, such as when the outside air is at a neutral
temperature but high humidity exists. This situation requires
the equipment to operate at a low SHR of 0.0 to 0.2. With no
cooling requirement and a call for dehumidification, the P Se-
ries Humidi-MiZer adaptive dehumidification system will cy-
cle on enough compressors to meet the latent load requirement,
while simultaneously adjusting refrigerant flow to the Humidi-
MiZer coil to reheat the air to the desired neutral air set point.
The P Series Humid-MiZer system controls allow for the dis-
charge air to be reheated to either the return-air temperature
minus a configurable offset or to a configurable Reheat set
point (default 70°F). The hot gas reheat mode will be initiated
when only the humidity is above the humidity set point, with-
out a demand for cooling.
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
D.RH.S) or the discrete input reads
 
COOL RHV.


COOL

COOL

B.EXV.