Carrier WeatherExpert 48N2 - Dehumidification and Reheat; Setting up the System

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Table 58 — Humidity Configuration
Table 59 — Related Humidity Points
Dehumidification and Reheat — The Dehumidifi-
cation function will override comfort condition set points based
on dry bulb temperature and deliver cooler air to the space in
order to satisfy a humidity set point at the space or return air
humidity sensor. The Reheat function will energize a suitable
heating system concurrent with dehumidification sequence
should the dehumidification operation result in excessive cool-
ing of the space condition.
The dehumidification sequence requires the installation of a
space or return air humidity sensor or a discrete switch input. A
CEM (option or accessory) is required to accommodate an RH
(relative humidity) sensor connection. Reheat is also possible
using a heat reclaim coil (field-supplied and installed) or a hot
gas reheat coil (special order, factory-installed). Reheat is not
possible with electric heat or gas heat.
Dehumidification and reheat control are allowed during
Cooling and Vent modes in the occupied period.
On constant volume units using thermostat inputs (C.TYP =
3), the discrete switch input must be used as the dehumidifica-
tion control input. The commercial Thermidistat device is the
recommended accessory device.
SETTING UP THE SYSTEM — The settings for dehumidi-
fication can be found at the local display at Configura-
tion
 IAQ  DEHU.
Dehumidification Configuration (
D.SEL) — The dehumidi-
fication configuration can be set for the following settings:
• D.SEL = 0 — No dehumidification and reheat.
• D.SEL = 1 — The control will perform both dehumidifi-
cation and reheat with modulating valve (hydronic).
• D.SEL = 2 — The control will perform dehumidification
and reheat with staged gas only.
• D.SEL = 3 — The control will perform both dehumidifi-
cation and reheat with third party heat via an alarm relay.
In the case of D.SEL=3, during dehumidification, the
alarm relay will close to convey the need for reheat. A
typical application might be to energize a 3-way valve to
perform hot gas reheat.
• D.SEL = 4 — The control will use the Humidi-MiZer
®
adaptive dehumidification system.
• D.SEL = 5 — The control will perform both dehumidifi-
cation and reheat with third party heat reclaim via the
heat reclaim output. The heat reclaim output (H.SEL)
must be configured before D.SEL.
Dehumidification Sensor (
D.SEN) — The sensor can be con-
figured 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.
Economizer Disable in Dehum Mode (
D.EC.D) — This
configuration determines economizer operation during Dehu-
midification mode.
• D.EC.D = YES — Economizer disabled during dehu-
midification (default).
• D.EC.D = NO — Economizer not disabled during dehu-
midification.
Vent Reheat Set Point Select (
D.V.CF) — This configuration
determines how the vent reheat set point 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) — Set point offset used
only during the vent mode. The air will be reheated to return-
air temperature less this offset.
Vent Reheat Set Point
(D.V.HT) — Set point used only dur-
ing the vent mode. The air will be reheated to this set point.
Dehumidify Cool Set Point (
D.C.SP) — This is the dehu-
midification cooling set point.
Dehumidity RH Set Point (
D.RH.S) — This is the dehumidi-
fication relative humidity trip point.
Heat Reclaim Configuration (
H.SEL) — This is the heat re-
claim configuration.
• H.SEL = 0 (NONE) — Heat reclaim is not performed.
• H.SEL = 1 (RELAY) — The control will perform both
dehumidification and reheat with third party heat via a
heat reclaim relay on the SCB board. In the case of
D.SEL=5, during dehumidification, the heat reclaim
relay will close to convey the need for "re-heat" need. A
typical application might be to energize a 3-way valve to
perform hot gas reheat.
• H.SEL = 2 (MODULATING) — The control will per-
form both dehumidification and reheat with modulating
valve (hydronic).
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
HUMD HUMIDITY CONFIGURATION
HM.CF Humidifier Control Cfg. 0 - 4 HUMD_CFG 0
HM.SP Humidifier Setpoint 0 - 100 % HUSP 40
H.PID HUMIDIFIER PID CONFIGS
HM.TM Humidifier PID Run Rate 10 - 120 sec HUMDRATE 30
HM.P Humidifier Prop. Gain 0 - 5 HUMID_PG 1
HM.I Humidifier Integral Gain 0 - 5 HUMID_IG 0.3
HM.D Humidifier Deriv. Gain 0 - 5 HUMID_DG 0.3
ACT.C HUMIDIFIER ACTUATOR CFGS
SN.1 Humd Serial Number 1 0 - 9999 HUMD_SN1 0
SN.2 Humd Serial Number 2 0 - 6 HUMD_SN2 0
SN.3 Humd Serial Number 3 0 - 9999 HUMD_SN3 0
SN.4 Humd Serial Number 4 0 - 254 HUMD_SN4 0
C.A.LM Humd Ctrl Angle Lo Limit 0-90 HUMDCALM 85
ITEM EXPANSION UNITS CCN POINT WRITE STATUS
ConfigUNITSENSSRH.S Space Air RH Sensor SPRHSENS
ConfigUNITSENSRRH.S Return Air RH Sensor RARHSENS
ConfigUNITSENSMRH.S Mixed Air RH Sensor MARHSENS
InputsREL.HRA.RH Return Air Rel. Humidity % RARH forcible
InputsREL.HSP.RH Space Relative Humidity % SPRH forcible
InputsREL.HMA.RH Mixed Air Relative Humidity % MARH forcible
OutputsACTUHMD.P Humidifier Act.Curr.Pos. % HUMDRPOS
OutputsACTUHMD.C Humidifier Command Pos. % HUMDCPOS
OutputsGEN.OHUM.R Humidifier Relay HUMIDRLY