Williamson-Thermoflo GWC-070 Manual page 87

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Troubleshooting
CHART 7
Electrical shock hazard — Wherever you see TURN OFF POWER, follow the instructions. Failure to follow
instructions could result in severe personal injury, death or substantial property damage.
• Has it been at least 5 minutes since setting thermostat to
call for heat? If not, wait 5 minutes. Is system heating?
• Is thermostat set to call for heat? Remove thermostat
wires at boiler and check continuity across the two wires. If
circuit isn't closed, check external thermostat (zone valve,
relay, etc.) wiring. Correct problems and retry.
• Reconnect external thermostat wiring at boiler.
Is thermostat circuit closed (continuity across wires)?
No
• Boiler is in standby.
Are all red lights off?
• Set thermostat to call for heat
No Yes
• Verify sequence of operation,
• Wait 30 seconds.
Are all red lights
• Check block switch on top of
off?
No Yes
• Replace IBC.
• Retest.
• Wait for cast iron
block to cool to room
temperature.
Are block switch
contacts closed?
No Yes
• Check across thermal fuse
• Replace
switch.
• Retest.
• Replace
thermal fuse.
• Retest.
• Excessive block temperature has been reduced to safe op-
erating level. Check for low water level or mineral deposits
in sections. Correct before proceeding.
• Restart boiler and check sequence of operation (Fig-
ure 71, page 64).
Part number 550-142-786/0712
-
fired water boiler
(continued)
Insufficient heat or no heat to system (POWER light on steady)
Yes
and recheck operation.
Figure 71, page 64.
boiler with continuity checker.
Are contacts closed?
No Yes
• Check across limit
switch contacts with
continuity checker.
Are contacts closed?
Yes No
leads with continuity checker.
Is circuit closed?
No Yes
• Replace IBC.
• Retest.
— Boiler Manual
Is boiler System circulator operating?
No
• Remove system circulator harness plug from CIR-
CULATORS plug receptacle (long harness) (see
Figure 90, page 78, Item 4). Check with voltmeter
across left-side 120 VAC N and 120 VAC H pins of
receptacle.
Does voltmeter show 120 VAC across pins?
No
• Replace IBC.
• Retest.
• Wait 5 minutes.
No
• If you have sufficient heat — boiler should follow normal
operating sequence (Figure 71, page 64).
• If you have less than sufficient heat —
Is vent or combustion air piping free of blockage?
No
• Correct conditions and
recheck operation. See
sequence of operation, Fig-
ure 71, page 64.
• Wait for boiler water to cool to temperature 20 to 30 °F
lower than temperature set on the limit.
• Are limit switch contacts closed?
No
• Replace limit switch.
• Retest.
• Boiler water temperature exceeded setting on limit switch
with thermostat calling for heat. Boiler is OK. (See se-
quence of operation, Figure 71, page 64)
• Also check operation of setting limit (should be above
140°F.).
Yes
Yes
• Repair/replace circula-
tor. Retest.
• Repair/replace wiring.
Retest.
Is FLAME light on?
Yes
Yes
• Contact your William-
son-Thermoflo sales
representative.
Yes
87