Troubleshooting Without Status Indicator Assistance; Troubleshooting Guide Without Status Light; Thermopile Output Check; Thermopile Output With Time - Honeywell WT8840 Installation Instructions Manual

Troubleshooting Without Status Indicator Assistance

Follow diagram in Fig. 6.

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.

TROUBLESHOOTING GUIDE WITHOUT STATUS LIGHT

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
YES
STATUS LIGHT SHOULD FLASH AFTER
1 MINUTE, LED WILL FLASH NORMAL
SINGLE BLINK, RELEASE THE DEVICE
KNOB, PILOT SHOULD REMAIN LIT
YES
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.
YES
SYSTEM OK
Fig. 6. Troubleshooting without status light.
WT8840 TRADE WATER HEATER CONTROLS
CHECK:
• INLET PRESSURE
NO
• MAKE SURE AIR IS BLED OUT OF SYSTEM
• PIEZO SPARKING TO THERMOPILE
• CLOGGED PILOT ORIFICE
• GAS LEAK IN PILOT TUBING CONNECTIONS
CHECK:
• WIRING OF THERMOPILE LEADS
NO
• FLAME COVERAGE OF THERMOPILE
– THERMOPILE OUTPUT IS TOO LOW-RUN
• THERMOPILE OUTPUT CHECK
CHECK:
NO
• EXCESSIVE INLET PRESSURE
• TANK TEMPERATURE IS AT OR CLOSE
TO SET POINT

THERMOPILE OUTPUT WITH TIME

900
800
700
600
500
400
300
200
100
0
0 1
Fig. 7. Thermopile output.
7
M29431
NORMAL RANGE
OUTPUT TOO LOW
2 3 4 5 6
TIME (MINUTES)
7 8 9 10
M22535B
34-00013EF—01