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Operation
45RT-SVX19A-E4
Thermostat signals are as follows:
R 24VAC power to thermostat
Y1 Call for compressor 1 or first
stage cooling
Y2 Call for compressor 2 or 2nd
stage cooling
G Call for supply fan
W1 Call for heat 1
W2 Call for heat 2
Heat pump only:
X2 Call for emergency heat
O Switchover valve On = cooling,
Off = heating
T Bias for heat anticipation for those
mechanical thermostats that use
this function
Conventional thermostat –
Gas/ Electric, Electric Heat:
Input/connection
Function when
energized :
G (fan) Fan runs continuously
except during
unoccupied mode
(see next page)
Y1 (compressor 1
or economizer)
Compressor #1 runs
or economizer
operates
Y2 (compressor 2
or compressor 1
while economizing)
Compressor #2 also
runs, or #1
compressor runs
while economizing
W1 (gas / electric
heat first stage)
1st stage heat
W2 (gas / electric
heat 2nd stage)
2nd stage heat (if
available)
Conventional thermostat –
Heat Pump
T (provides heat anticipation signal for
those mechanical thermostats that use this
feature. If the thermostat used does not
have a “T” terminal, disregard this
terminal.
Input/connection
Function when
energized
Cooling mode:
G (fan) Fan runs continuously
except during
unoccupied mode
(see next page)
O (reversing valve
during cooling)
Reversing valve in
cool mode
Y1 + O
(first stage cooling)
Compressor #1 runs
or economizer
operates
Y1 + Y2 + O
(2nd stage cool)
Compressor #2 also
runs, or #1
compressor runs
while economizing.
Heating mode:
G (fan) Fan runs continuously
except during
unoccupied mode
(see below)
Y1 (both
compressors 1st
stage heat)
Both compressors
run
Y2 (during heating
– nothing happens)
No change
W2 (electric heat
2nd stage)
2nd stage (electric)
heat
X2 (electric heat
only)
Electric heat only –
no compressors