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Connect Your Wires
Conventional Systems
Typical Wiring Configurations
NOTE: The "Installer Switch" option will be configured in the next step.
Heat Only or Millivolt
Set Installer Switch to NORM
Rh* Power Connection
W Heat Relay (appears as W1/E on TT-N-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-N-421)
Y
Compressor Relay (appears as Y1 on TT-N-421)
G Fan Relay
C 24 Volt AC Transformer Common [note 1, 3]
2 HEAT / 1 COOL Single Transformer (TT-N-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]
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.
*Appears as R on TT-N-421 (single transformer)
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