9
All Lennox thermostats can be used as an external control if
used with a SPDT relay. The recommended relay is Catalog
No. 69J79. See
Figures 21 & 22
for wiring with SPDT.
NOTE:
The NC NO slide switch should remain in the NO
position.
When an external control is enabled, “EXTERNAL” will be
displayed on the dehumidifier control. External controls are
recommended when the dehumidifier is installed in an attic
and is ducted to the HVAC system.
If an external control is used in a zoned application, it must
be located in the Primary Zone (refer to
TWO ZONE –
PRIMARY AND SECONDARY
zoned installation on page
15 for details).
NOTE: When using an external control, there is a 3
minute delay at start-up or whenever power is cycled
to the dehumidifier. As with any configuration, the
compressor has a 3 minute minimum on and off time.
NOTE:
All Lennox thermostats use reverse logic for
dehumidification. There is 24VAC between the DH and
C terminals when there is no call for dehumidification.
Figures 21 & 22
show relay position when there is a call
for dehumidification and 0VAC between the DH and C
terminals.
Figure 21. 24VAC Thermostat Connections
Figure 22. Communicating Thermostat Connections
Figure 20. Lennox 24VAC Touchscreen Thermostat
Figure 19. Lennox Communicating Thermostats
+ - A B ODT
FLOA
T
Switch
DH
DH
Gh
Rf
Cf
Gs
Y
W
HV
AC EQUIP
.
HVAC
Unit
NC NO
NC
NO
24VAC
Thermostat
SPDT RELAY
R
C
G
Y
W
R
C
G
DH
Y
W
+ - A B ODT
FLOA
T
Switch
DH
DH
Gh
Rf
Cf
Gs
Y
W
HV
AC EQUIP
.
DH
C
G
R
R
I+
I-
C
iComfort
Enabled
HVAC Unit
NC NO
NC
NO
R
I+
I-
C
iComfort
Thermostat
SPDT RELAY
90-1989
90-1979
Lennox Control
iComfort
®
S30 Ultra
Smart Thermostat
(Catalog No. 12U67)
iComfort
®
M30
Smart Thermostat
(Catalog No. 15Z69)
ComfortSense
®
7500 Touchscreen
Thermostat
(Catalog No. 13H14)
iComfort
®
E30
Smart Thermostat
(Catalog No. 15S63)
