WIRING
8
5
Terminal Designations on Base Module
Terminal Designations on T955W Master Thermostat
Terminal
2 Heat 2 Cool
Conventional System
2 Heat 2 Cool
Heat Pump System
3 Heat 2 Cool
Heat Pump System
RC
RH
C
B
O
G
W/E
Y
Y2
W2
Transformer power
(cooling)
Transformer power
(heating)
Transformer common
Energized in heating
Energized in cooling
Fan relay
First stage of heat
First stage of cool
Second stage of cool
Second stage of heat
Transformer power
(cooling)
Transformer power
(heating)
Transformer common
Heat pump changeover valve
energized in heating
Heat pump changeover valve
energized in cooling
Fan relay
Emergency heat relay
First stage of heat & cool
Second stage of cool
Auxiliary heat relay,
second stage of heat
Transformer power
(cooling)
Transformer power
(heating)
Transformer common
Heat pump changeover valve
energized in heating
Heat pump changeover valve
energized in cooling
Fan relay
Emergency heat relay
First stage of heat & cool
Second stage of cool
& second stage of heat
Auxiliary heat relay,
third stage of heat
This thermostat is shipped from the factory to operate a conventional heating and cooling system. This thermostat will
also operate a heat pump system. See the “heat pump” configuration step on page 12 of this manual to configure the
thermostat for heat pump applications.
Warning:
All components of the control
system and the thermostat
installation must conform to
Class II circuits per the NEC Code.
Powering the T955W Master Thermostat
If you add remote sensors (R250W or R251W) to this wireless system you must hardwire theT955W
master thermostat.
Note:
In many heat pump systems with no
emergency heat relay a jumper can be
installed between E and W2.
Wiring
If you are replacing a thermostat, make
note of the terminal connections on the
thermostat that is being replaced. In some
cases the wiring connections will not be
color coded. For example, the green wire
may not be connected to the
G
terminal.
Loosen the terminal block screws. Insert
wires then retighten terminal block screws.
1.
2.
Wire specifications
Use shielded or non-shielded
18 - 22 gauge thermostat wire.
Terminal
2 Heat 2 Cool
Conventional System
2 Heat 2 Cool
Heat Pump System
3 Heat 2 Cool
Heat Pump System
R
C
24 VAC Transformer power
Transformer common
24 VAC Transformer power
Transformer common
24 VAC Transformer power
Transformer common
