WT8840 TRADE WATER HEATER CONTROLS
7
34-00013EF—01
Troubleshooting Without Status Indicator Assistance
Follow diagram in Fig. 6.
Fig. 6. Troubleshooting without status light.
Thermopile Output Check
1.
Turn device knob to OFF.
2.
Disconnect thermopile leads.
3.
Turn device knob to PILOT, hold down knob to
light pilot burner. Hold the knob down for five or
more minutes.
4.
After five minutes, check thermopile output by
connecting the voltmeter to the positive red lead
and negative white lead.
5.
Output should be at least 350 mV. (See Fig. 7.)
Connect the 3.6 ohm resistor between the two
thermopile leads, the voltage should be at or
higher than one half of the open circuit voltage.
6.
The terminal housing prevents miswiring of
positive and negative leadwires.
7.
Flame must envelop thermopile at Hot Junction
(3/8 in. below tip).
8.
Keep heat away from cold junction (brass sleeve
of the thermopile) for maximum output.
Fig. 7. Thermopile output.
TURN DEVICE KNOB FROM OFF TO
PILOT, PRESS DOWN KNOB AND HOLD,
LIGHT PILOT BY DEPRESSING PIEZO
IGNITION BUTTON, PILOT SHOULD
LIGHT.
– WATER TEMPERATURE IS BELOW
THE CUT-OUT LIMIT
CHECK:
• WIRING OF THERMOPILE LEADS
• FLAME COVERAGE OF THERMOPILE
– THERMOPILE OUTPUT IS TOO LOW-RUN
•
THERMOPILE OUTPUT CHECK
STATUS LIGHT SHOULD FLASH AFTER
1 MINUTE, LED WILL FLASH NORMAL
SINGLE BLINK, RELEASE THE DEVICE
KNOB, PILOT SHOULD REMAIN LIT
TURN DEVICE KNOB TO DESIRED
TEMPERATURE SETTING, BURNER WILL
TURN ON ONLY IN ACTIVE CALL FOR
HEAT (WATER TEMPERATURE IS LESS
THAN TEMPERATURE SETTING MINUS
DIFFERENTIAL); LED FLASHES 1 TIME
EVERY 3 SECONDS WHILE IDLE AND
STROBES EVERY 3 SECONDS DURING
A CALL FOR HEAT.
SYSTEM OK
CHECK:
• EXCESSIVE INLET PRESSURE
• TANK TEMPERATURE IS AT OR CLOSE
TO SET POINT
NO
NO
NO
YES
YES
YES
M29431
TROUBLESHOOTING GUIDE WITHOUT STATUS LIGHT
CHECK:
• INLET PRESSURE
• MAKE SURE AIR IS BLED OUT OF SYSTEM
• PIEZO SPARKING TO THERMOPILE
• CLOGGED PILOT ORIFICE
• GAS LEAK IN PILOT TUBING CONNECTIONS
M22535B
TIME (MINUTES)
OUTPUT (mV)
THERMOPILE OUTPUT WITH TIME
500
600
400
300
200
100
0
0
1
2
3
4
5
6
7
8
9
10
900
800
700
NORMAL RANGE
OUTPUT TOO LOW
