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UHA STANDARD UNIT HEATER INSTALLATION OPERATION AND SERVICE MANUAL
24 of 51
10.5 UHA[X][S] Series Internal Wiring Diagram
Blue
Black
Black
Orange
Yellow
Brown
Black
White
White
L2
L1
Black
Black
Green
White
White
Green
Green
Blue
Black
Black
Black
White
Green
Blue
Green
24 VAC
HOT
GROUND
Flame
Black
Black
Black
6
3
4
5
2
1
45
31
SENSE
ELECTRODE
LIMIT
SWITCH
PRESSURE
SWITCH
AXIAL FAN
GAS VALVE
IGNITION
MODULE
TRANSFORMER
AXIAL FAN (UHA 300,
350, 400) ONLY)
LIMIT
SWITCH
(UHA
300,350,
400 ONLY)
MANUAL RESET LIMIT SWITCH
(UHA 30 - 125 ONLY)
THERMOSTAT INPUT:
FIELD SUPPLIED
R = 24 VAC TO THERMOSTAT (RED)
G = MANUAL FAN INPUT FROM THERMOSTAT (GREEN)
W = HEAT DEMAND INPUT FROM THERMOSTAT (WHITE)
C = COMMON SIDE OF TRANSFORMER
FLUE
BLOWER
R
G
W
C
ACC
L1
CMB
Blower
Yellow
Orange
Orange
Orange
NOTE:
For field wiring into service junction box, or if any of the original wire supplied with the heater
must be replaced, it must be replaced with wiring material having a temperature rating of at least 105° C
(221° F) and 600 volts. For supply connections use No. 14 AWG or larger wires.