Williamson-Thermoflo GWC-070 Manual page 80

GWC -
gas fired water boiler
Troubleshooting
CHART 2
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.
Is return water temperature sensor clamped
securely to the return pipe in the boiler?
Yes
• Check for stray voltage on the incoming thermostat wires.
Disconnect the two external wires connected to the boiler
thermostat wires.
• Connect a voltmeter across the two incoming wires. Close each
thermostat, zone valve and relay in the external circuit one at a
time and check the voltmeter reading across the wires. There
should NEVER be a voltage reading. If a voltage does occur
Did you find and correct a voltage across the two external thermostat circuit wires?
• Boiler should now operate per the normal sequence of op-
eration (Figure 71, page 63) if wiring was corrected.
• Remove CIRCULATORS plug (Figure 89, page 76, Item 4)
from plug receptacle of IBC.
• Place voltmeter leads across the right-side 120 VAC N and
120 VAC H pins of the CIRCULATORS receptacle.
Does the voltmeter indicate 120 VAC?
No
• Replace IBC.
• Retest.
• Replace circulator harness.
• Retest.
• Reconnect circulator harness to IBC.
• Attempt to get the circulator started by giving it a sharp rap
on the end of the circulator motor (to release a possibly
locked impeller).
• If the circulator begins to operate, allow it to operate for a
few minutes to see if the problem clears.
• If problem persists, replace the Bypass circulator.
• Retest.
80
— Boiler Manual
(continued)
TSTAT CIRC & POWER lights flashing
No
Yes
Yes
• Test wire continuity of
circulator wire harness.
Is harness ok?
No Yes
• Attach sensor to pipe with clamp provided.
• Follow return temperature sensor checking procedure
on page 74. Replace sensor if necessary.
• Retest.
under any condition, check and correct the external wiring. (This
is a common problem when using 3-wire zone valves.)
• Once the external thermostat circuit wiring is checked and
corrected if necessary, reconnect the external thermostat
circuit wires to the boiler thermostat wires and allow the boiler
to cycle.
Is boiler internal Bypass circulator operating?
No
• Check the boiler internal return pipe where it enters the
boiler sections. The TSTAT CIRC and POWER lights
will flash as long as the return water temperature is less
than 130 °F.
• Wait up to 20 minutes to give the boiler and system a
chance to respond.
Does problem persist?
No
• Boiler may now be operating normal-
ly. Verify against normal sequence of
operation (Figure 71, page 63).
• If boiler appears not to be heating, troubleshoot boiler
per CHART 8, page 86. If problem cannot be resolved,
replace water temperature sensor and retest. Then re-
place IBC (IBC) if sensor does not correct the problem.
• If boiler is heating, but the temperature at the return
pipe does not increase above 130 °F, there may be an
incorrectly-piped external circulator forcing water through
the boiler. Check external piping and correct.
No
Yes
Yes
Part number 550-142-056/0411