Page 26
6. Dehumidification Operation
Dehumidification mode is a combination of cooling to dehumidify and heating to maintain space temperature. Supermarket
reheat uses gas heat and Humiditrol
®
units route hot discharge gas to a reheat coil downstream of the evaporator. A gas
heat unit is required for Supermarket Reheat and a Humiditrol
®
unit is required for Humiditrol
®
Reheat. Economizer
operation is disabled during dehumidification operation except when dehumid mode operation - Parameter 105, Option 1 is
selected.
6.1. Supermarket Reheat Operation Settings
Go to SETTINGS > RTU OPTIONS > EDIT PARAMETER=105 (DEHUMID MODE)
Parameter 105 (Option 0) - No Reheat
Parameter 105 (Option 1) - Supermarket Reheat using de-humidistat (wired thermostat mode only)
IMPORTANT
Supermarket Reheat is allowed on gas/electric units only; not electric/electric or heat pump units. A de-humidistat will
bring on first-stage cooling to dehumidify and a room thermostat will energize heating to maintain indoor temperature.
To disable free cooling in this mode, select economizer global mode (figure 5) but do not connect the global input (P297-9).
An optional de-humidistat is required. Refer to figure 5.
K55
B
A
K55-1
7
5
2
S86
P297
J297A
1
2
B
3
4
5
6
7
8
C
9
10
R
OCP
C
G
W1
W2
Y1
Y2
24 VAC POWER
A55
TO R
TO G
TO Y1
TO M3 THERMOSTAT INPUTS
ALL OTHER THERMOSTAT
SIGNALS REMAIN CONNECTED
AS SHOWN ON THE RIGHT.
TO PROVIDE DEHUMID SCHEME, USE S86
DEHUMIDISTAT AND K55 RELAY
R
OCP
C
G
W1
W2
Y1
Y2
Figure 5. Dehumidification Diagram (Parameter 105, Option 1)
Parameter 105 (Option 2) — Supermarket Reheat using Relative Humidity Sensor Control
A relative humidity sensor will bring on first-stage cooling based on the set point set with Parameter 106 or from the
L Connection network. First-stage cooling will de-energize when relative humidity drops to Parameter 106 minus
Parameter 107. A wired thermostat or room sensor will energize heating to maintain indoor temperature.
An optional relative humidity sensor is required. Refer to figure 6.
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 106 (DEHUMID SETPOINT) and 107 (DEHUMID
DEADBAND) (see paragraph 6.3. for further details concerning dehumid set point)
6.2. Humiditrol Dehumidification Operation — (Humiditrol
®
Reheat)
Go to SETTINGS > RTU OPTIONS > EDIT PARAMETER = 105 (DEHUMID MODE)
A relative humidity sensor reading above set point will energize first-stage compressor(s) and hot gas will be routed
to the reheat coil based on the set point set with Parameter 106 or from the L Connection network. The following options
show additional conditions which must be met before reheat will be energized:
Humiditrol dehumid will de-energize when the relative humidity drops to Parameter 106 minus Parameter 107.
An optional relative humidity sensor is required. See figure 6.
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