Wiring Conventional Systems: Forced Air And Hydronics; Wiring Heat Pump Systems - Honeywell T4 Pro Installation Instructions Manual

Wiring conventional systems: forced air and hydronics

1H/1C System (1 transformer)
R Power [1]
Rc [R+Rc joined by Slider Tab] [2]
Y
Compressor contactor
C 24VAC common [3]
W
Heat relay
G
Fan relay
Heat-only System
R Power [1]
Rc [R+Rc joined by Slider Tab] [2]
C 24VAC common [3]
W
Heat relay
Heat-only System (Series 20) [5]
R Series 20 valve terminal "R" [1]
Rc [R+Rc joined by Slider Tab] [2]
Y
Series 20 valve terminal "W"
C 24VAC common [3]
W Series 20 valve terminal "B"
Heat-only System
(power open zone valve) [5]
R Power [1]
Rc [R+Rc joined by Slider Tab] [2]
W
Valve
C 24VAC common [3]

Wiring heat pump systems

1H/1C Heat Pump System
R Power [1]
Rc [R+Rc joined by Slider Tab] [2]
Y Compressor contactor
C 24VAC common [3]
O/B Changeover valve [7]
G Fan relay
NOTES
Wire specifications: Use 18- to 22-gauge thermostat wire. Shielded cable is not required.
[1] Power supply. Provide disconnect means and overload
protection as required.
[2] Move R-Slider Tab on UWP to the R setting. For more
information, see "Setting Slider Tabs (built-in jumper)" on
page 3
[3]
Optional 24VAC common connection.
[4] Common connection must come from cooling transformer.
1H/1C System (2 transformers)
R Power (heating transformer) [1]
Rc Power (cooling transformer) [1]
Y
Compressor contactor
C 24VAC common [3, 4]
W
Heat relay
G
Fan relay
Heat-only System with Fan
R Power [1]
Rc [R+Rc joined by Slider Tab] [2]
C 24VAC common [3]
W
Heat relay
G Fan relay
Cool-only System
R Power [1]
Rc [R+Rc joined by Slider Tab] [2]
Y Compressor contactor
C 24VAC common [3]
G Fan relay
2H/1C Heat Pump System (TH4210U only)
R Power [1]
Rc [R+Rc joined by Slider Tab] [2]
Y Compressor contactor
C 24VAC common [3]
O/B Changeover valve [7]
G Fan relay
AUX Auxiliary heat
E
Emergency heat relay
L
Heat pump fault input
[5] In ISU set Heat system type to Radiant Heat. Set number of
cool stages to 0.
[7] In Installer Setup, set changeover valve to O (for cool
changeover) or B (for heat changeover).
4