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Table 2. Terminal Designation Descriptions
Terminal
Designation
Description
Rc
(see note 1)
Power for cooling−connect to secon-
dary side of cooling system trans-
former.
R
(see note 1)
Power for heating−connect to secon-
dary side of heating system trans-
former.
Y Compressor output.
C
(see note 2)
Command wire from secondary side
of cooling system transformer.
W Heat relay.
G Fan relay.
W2 Second stage heat relay.
Y2 Second stage cooling.
O/B
(see note 3)
Changeover valve for heat pumps.
Terminal not used with Lennox com-
mercial equipment.
A
(see note 4)
Economizer/Time−of−Day (TOD) out-
put−powered via R terminal.
S1
(see note 5)
Optional outdoor or indoor remote
sensor.
S2
(see note 5)
Optional outdoor or indoor remote
sensor.
L Powers red LED behind plastic in
upper right corner of the thermostat.
NOTES −
1 When used in a single−transformer system, leave
metal jumper wire in place between Rc and R. If used
on a two−transform system, remove metal jumper
wire between Rc and R.
2 Common wire is optional when thermostat is used
with batteries. When using separate transformer for
heating and cooling, the common must come from
the cooling transformer.
3 Lennox commercial heat pumps do not use this
terminal to energize the reversing valve. Thermostat
will always be conventional type.
4 Reference economizer literature for wiring details.
When set for economizer operation, the A terminal
provides the occupancy signal. (Power indicates oc-
cupied.)
5 Sensor wires must have a cable separate from
the thermostat control cable.
WALLPLATE
WALL OPENING
WIRE
SHADED AREA
Figure 6. Restrict Wires to Shaded Area of Wire
Hole
Terminal A Wiring Details for Economizers
S Wire the A" terminal as shown in diagrams in
figures 7, 8, 9 and 10.
S The A" signal is powered from the R" termi-
nal and energizes the economizer to signal
occupied status and drive the damper to the
set minimum position.
UNIT TB1A2 THERMOSTAT
Figure 7. Wire LG/LC/LH/SG/SC Units.
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