Weil-McLain 550-141-850/0599, GOLD DV WATER BOILER Chart 2 Tstat Circ & Power lights flashing

• Installation • Start-Up • Parts • Maintenance

CHART 2 — TSTAT CIRC & POWER lights flashing

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.

Is return water temperature sensor clamped securely to the return pipe in the boiler?

Yes No

•Attach sensor to pipe with clamp provided.

•If problem persists, replace return water temperature sensor.

•Retest.

• Check for stray voltage on the incoming thermostat wires.	does occur under any condition, check and correct the
Disconnect the two external wires connected to the boiler	external wiring. (This is a common problem when using 3-wire
thermostat wires.	zone valves.)
• Connect a voltmeter across the two incoming wires. Close •	Once the external thermostat circuit wiring is checked and
each thermostat, zone valve and relay in the external circuit	corrected if necessary, reconnect the external thermostat
one at a time and check the voltmeter reading across the	circuit wires to the boiler thermostat wires and allow the boiler
wires. There should NEVER be a voltage reading. If a voltage	to cycle.

Did you find and correct a voltage across the two external thermostat circuit wires?

Yes

No

•Boiler should now operate per the normal sequence of operation shown in Figure 22 if wiring was corrected.

•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

Is boiler internal Bypass circulator operating?

No Yes

• 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?

•Replace GCM (control module).

•Retest.

•Replace circulator harness.

•Retest.

•Test wire continuity of circulator wire harness.

Is harness ok?

No Yes

No Yes

• Boiler may now be operating

normally. Verify against

Figure 22, sequence of

operation.

•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.

• 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.

Part number 550-141-850/0699 75