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75Part number 550-141-850/0699
• Installation • Start-Up • Parts • Maintenance
Electrical shock hazard — Wherever you see
▲
TURN OFF POWER
▲
, follow the instructions. Failure to follow
instructions could result in severe personl injury, death or substantial property damage.
CHART 2
—
TSTAT CIRC
&
POWER
lights flashing
• Remove CIRCULATORS plug (
Figure 34, Item 4
) from
plug receptacle of control module.
• 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 Yes
• Attach sensor to pipe with clamp provided.
• If problem persists, replace return water temperature
sensor.
• Retest.
• Replace GCM (control
module).
• Retest.
• Replace circulator
harness.
• Retest.
• Reconnect circulator harness to GCM.
• 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.
No Yes
Is boiler internal Bypass circulator operating?
NoYes
Is return water temperature sensor clamped
securely to the return pipe in the boiler?
Did you find and correct a voltage across the two external thermostat circuit wires?
• Test wire continuity of
circulator wire harness.
Is harness ok?
No Yes
NoYes
• Boiler should now operate per the normal sequence of
operation shown in Figure 22 if wiring was corrected.
• 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 Yes
• Boiler may now be operating
normally. Verify against
Figure 22, sequence of
operation.
• If boiler appears not to be heating, troubleshoot boiler per
CHART 8
(no heat problems). If problem cannot be
resolved, replace water temperature sensor and retest.
Then replace GCM (control module) 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.
• 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 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.