Comfort Stat CDT901 - Manual (Page 22)

CDT900 Series Touchscreen Programmable Thermostata
Table 2. Terminal Designation Descriptions.
Terminal Designation Description
Rc (see Note 1)
Power for cooling--connect to secondary side of cooling
system transformer
R (see Note 1)
Power for heating--connect to secondary side of heating
system transformer
C (see Note 2)
Common wire from secondary side of cooling system
transformer
W Heat relay
Y Compressor contactor
G Fan relay
Y2 Second stage cooling
W2 Second stage heat relay
O/B (see Note 3) Changeover valve for heat pump systems
AUX Auxiliary heat relay for heat pump systems
E Emergency heat relay for heat pump systems
L (see note 4) Equipment monitor for heat pump systems
S1, S2 Optional outdoor or indoor remote sensor
NOTES:.
1.When sed in a single-transformer system, leave metal jumper wire in place between Rc
and R. If used on a two-transformer system, remove metal jumper wire between Rc and R.
2.Common wire is optional when thermostat is used with batteries.
3. If thermostat is configured for a heat pump system in the Installer Setup, configure
changeover valve for cool (O-factory setting) or heat (B).
4.L terminal is an input (system monitor) when the System mode is in the Heat, Off, Cool or
Auto position. L terminal is a 24 Vac output when System mode is Emergency Heat. Must
connect the 24 Vac Common when using the L terminal. See LCD Indication section for more
details.
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