3
Connect Your Wires
3
Heat Only or Millivolt
Set Installer Switch to
NORM
Rh*
Power Connection
W
Heat Relay (appears as
W1/E
on TT-P-421)
G
Fan Relay
[note 4]
C
24 Volt AC Transformer Common
[note 1]
1 HEAT / 1 COOL Single or Dual Transformer
Set Installer Switch to
NORM
Rh*
24 Volt AC Power (heating transformer)
[note 2]
Rc*
24 Volt AC Power (cooling transformer)
[note 2]
W
Heat Relay (appears as
W1/E
on TT-P-421)
Y
Compressor Relay
(
appears as
Y1
on
TT-P-421
)
G
Fan Relay
C
24 Volt AC Transformer Common
[note 1, 3]
Typical Wiring Configurations
NOTE:
The “Installer Switch” option will be configured in the next step.
Conventional Systems
NOTES - Conventional Systems
[1]
If batteries are installed the 24 Volt AC common connection is optional
[2]
Remove factory installed jumper for dual transformer systems
[3]
In dual transformer systems, transformer common must come from
cooling transformer
[4]
If needed for system
Provide disconnect and overload protection as required.
2 HEAT / 1 COOL Single Transformer (TT-P-421 Only)
Set System Type to
NORM
R
24 Volt AC Power
W1
Heat Relay Stage 1
W2
Heat Relay Stage 2
Y1
Compressor Relay Stage 1
G
Fan Relay
C
24 Volt AC Transformer Common
[note 1]
* Appears as R on TT-P-421 (single transformer).
