Carrier WeatherExpert 48N2 Controls, Start-Up, Operation, Service, And Troubleshooting page 91

ITEM
DEHU DEHUMIDIFICATION CONFIG.
D.SEL Dehumidification Config
D.SEN Dehumidification Sensor
D.EC.D Econ disable in DH mode?
D.V.CF Vent Reheat Setpt Select
D.V.RA
Vent Reheat RAT offset
D.V.HT Vent Reheat Setpoint
D.C.SP Dehumidify Cool Setpoint
D.RH.S Dehumidify RH Setpoint
DH.DB Dehumidify RH Deadband
DH.TG Dehum Discrete Timeguard
HZ.RT
Humidi-MiZer Adjust Rate
HZ.PG Humidi-MiZer Prop. Gain
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 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 de-
mand. 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 reheated
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 dehumidification relative humidity sensor's deadband.
Dehum Discrete Timeguard (DH.TG)
This is the dehumidification discrete switch's timeguard.
Humidi-MiZer 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.
Humidi-MiZer 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 or Cool 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).
Table 60 — Dehumidification Configuration
EXPANSION RANGE UNITS
0-5 DHSELECT
1-3 DHSENSOR
No/Yes DHECDISA
0-1 DHVHTCFG
0-8 ^F DHVRAOFF
55-75 dF DHVHT_SP
40-55 dF DHCOOLSP
10-90 % DHRELHSP
1-30 % DHSENSDB
10-90 sec DHDISCTG
5-120 HMZRRATE
0-10 HMZR_PG
Initiating a Humidi-MiZer Reheat or Dehumidification Mode
To call out a Reheat mode in the "Vent" or "Off" HVAC mode,
or to call out a Dehumidification mode in a Cool HVAC mode,
one of the following 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 below relative humidity
sensor's dead band % (Configuration  DEHU  DH.DB) or
below the set point (Configuration  DEHU  D.RH.S), or the
discrete input reads "LOW", and discrete switch time guard ex-
pires (Configuration  DEHU  DH.TG), the Humidi-MiZer
mode will end.
Relevant Outputs
The Humidi-MiZer 3-way valve (reheat valve) commanded
output can be found in Outputs  COOL  RHV.
The Humidi-MiZer Condenser Modulating Valve (Condenser
EXV) position output
 COOL  C.EXV. The condenser position will be provided as
percent open.
HUMIDI-MIZER MODES
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 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 N 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.
91
CCN POINT DEFAULT
0
1
Yes
0
0
70
45
55
5
30
30
0.8
can be found in Outputs