Reheat Operation; General; Supermarket Reheat Operation - Lennox Prodigy M2 Application Manual

6. Reheat Operation

6.1. Reheat Operation
Reheat is a combination of cooling to dehumidify and heating to maintain space temperature. Supermarket reheat uses gas
®
heat and Humiditrol units route hot gas to a reheat coil downstream of the evaporator. A gas heat unit is required for Super-
market Reheat and a Humiditrol
operation except for Supermarket Reheat operation ECTO 4.24 option 1.
6.2.

Supermarket Reheat Operation

ECTO 4.24 Option 1 De−Humidistat Control
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 9) but do not connect the global
input (P297−9).
An optional de−humidistat is required. Refer to figure 5.
24 V POWER
R
C
G
W1
B
W2
Y1
A
Y2
OCP
TO PROVIDE SUPERMARKET REHEAT SCHEME, USE
S86 DEHUMIDISTAT AND K55 RELAY
Figure 5. Supermarket Reheat Diagram (ECTO 4.24 Option 1)
ECTO 4.24 Option 2 RH Sensor Control
A relative humidity sensor will bring on first−stage cooling based on the setpoint set with ECTO 4.25 or from the L Connection
network. First−stage cooling will de−energize when RH drops to ECTO 4.25 minus 4.26. A room thermostat or zone sensor
will energize heating to maintain indoor temperature.
An optional RH sensor is required. Refer to figure 6.
A91 HUMIDITY SENSOR
Two separate shielded cables required.
®
unit is required for Humiditrol Reheat. Economizer operation is disabled during reheat
TO M2 THERMOSTAT INPUTS
TO R
2
7
TO G
K55−1
S86
5
TO Y1
ALL OTHER THERMOSTAT
SIGNALS REMAIN CONNECTED
AS SHOWN ON THE RIGHT.
0 − 10VDC = 0−100% RH
A91
GND
One wire of the two
pairs is not connected.
Figure 6. Reheat Sensor Diagram
J297A P297
1
R
C 2
B
G 3
4
W1
5
W2
Y1 6
Y2 7
OCP 8
C
9
10
J298A
1
2
B
VIN
3
4
C
VO
5
6
7
D
8
9
10
Page 19
6. Reheat Operation
A55
P298
R
C
AI−1
HUM
TMP
DO−1
C
DO−2
PRODIGYT M2 UNIT CONTROLLER