66
Diff. Air Quality Hi Limit (
Configuration
→
IAQ
→
AQ.SP
→
DAQ.H) — This is the differential CO
2
level at which IAQ
control of the dampers will be at maximum and the dampers
will be at the Configuration
→
IAQ
→
DCV.C
→
EC.MN.
DAQ ppm Fan On Set Point (
Configuration
→
IAQ
→
AQ.SP
→
D.F.ON) — This is the CO
2
level at which
the indoor fan will be turned on.
DAQ ppm Fan Off Set Point (
Configuration
→
IAQ
→
AQ.SP
→
D.F.OF) — This is the CO
2
level at which the
indoor fan will be turned off.
IAQ Low Reference (
Configuration
→
IAQ
→
AQ.S.R
→
IQ.R.L) — This is the reference that will be used with a
non-Carrier IAQ sensor that may have a different characteristic
curve. It represents the CO
2
level at 4 mA.
IAQ High Reference (
Configuration
→
IAQ
→
AQ.SR
→
IQ.R.H) — This is the reference that will be used with a
non-Carrier IAQ sensor that may have a different characteristic
curve. It represents the CO
2
level at 20 mA.
OAQ Low Reference (
Configuration
→
IAQ
→
AQ.S.R
→
OQ.R.L) — This is the reference that will be used with a
non-Carrier OAQ sensor that may have a different characteris-
tic curve. It represents the CO
2
level at 4 mA.
OAQ High Reference (
Configuration
→
IAQ
→
AQ.S.R
→
OQ.R.H) — This is the reference that will be used with a non-
Carrier OAQ sensor that may have a different characteristic
curve. It represents the CO
2
level at 20 mA.
Diff. IAQ Responsiveness (
Configuration
→
IAQ
→
AQ.SP
→
IAQ.R) — This is the configuration that is used to select the
IAQ response curves as shown in Fig. 11.
PRE-OCCUPANCY PURGE — The control has the option
for a pre-occupancy purge to refresh the air in the space prior to
occupancy.
This feature is enabled by setting Configuration
→
IAQ
→
IAQ.P
→
IQ.PG to Yes.
The IAQ Purge will operate under the following conditions:
• IQ.PG is enabled
• the unit is in the unoccupied state
• Current Time is valid
• Next Occupied Time is valid
• time is within two hours of the next occupied period
• time is within the purge duration (Configuration
→
IAQ
→
IAQ.P
→
IQ.P.T)
If all of the above conditions are met, the following logic is
used:
If OAT ≥ IQ.L.O and OAT ≤ OCSP and economizer is
available then purge will be enabled and the economizer will
be commanded to 100%.
Else, if OAT < IQ.L.O then the economizer will be posi-
tioned to the IAQ Purge LO Temp Min Pos (Configuration
→
IAQ
→
IAQ.P
→
IQ.P.L)
If neither of the above are true then the dampers will be
positioned to the IAQ Purge HI Temp Min Pos (Configuration
→
IAQ
→
IAQ.P
→
IQ.P.H)
If this mode is enabled the indoor fan and heat interlock
relay (VAV) will be energized.
IAQ Purge (
Configuration
→
IAQ
→
IAQ.P
→
IQ.PG) — This
is used to enable IAQ pre-occupancy purge.
IAQ Purge Duration (
Configuration
→
IAQ
→
IAQ.P
→
IQ.P.T) — This is the maximum amount of time that a purge
can occur.
IAQ Purge Lo Temp Min Pos (
Configuration
→
IAQ
→
IAQ.P
→
IQ.P.L) — This is used to configure a low limit for
damper position to be used during the purge mode.
IAQ Purge Hi Temp Min Pos (
Configuration
→
IAQ
→
IAQ.P
→
IQ.P.H) — This is used to configure a maximum po-
sition for the dampers to be used during the purge cycle.
IAQ Purge OAT Lockout Temp (
Configuration
→
IAQ
→
IAQ.P
→
IQ.L.O) — Nighttime lockout temperature below
which the purge cycle will be disabled.
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 cooling 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 possible when
multiple-step staged gas control option or hydronic heat (op-
tion or field-installed coil) is installed. Reheat is also possible
using a heat reclaim coil (field-supplied and installed) or a hot
gas reheat coil (special order, factory-installed).
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 or 4), the discrete switch input must be used as the dehumidi-
fication 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 Configuration
→
DEHU. See Table 79.
Table 79 — Dehumidification Configuration
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
DEHU DEHUMIDIFICATION CONFIG.
D.SEL Dehumidification Config 0-2 DHSELECT 0
D.SEN Dehumidification Sensor 1-2 DHSENSOR 1
D.EC.D Econ disable in DH mode? Yes/No DHECDISA Yes
D.V.CF Vent Reheat Setpt Select 0-1 DHVHTCFG 0
D.V.RA Vent Reheat RAT offset 0-8 deltaF DHVRAOFF 0
D.V.HT Vent Reheat Setpoint 55-95 dF DHVHT_SP 70
D.C.SP Dehumidify Cool Setpoint 40-55 dF DHCOOLSP 45
D.RH.S Dehumidify RH Setpoint 10-90 % DHRELHSP 55
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