Williamson GWI-047, Manual

Page: 35 / 48

35 Part Number 550-142-785/0812
GWI Series 2 Gas-Fired Water Boilers – Boiler Manual
12 Troubleshooting
continued
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.
CHART 2
— TSTAT CIRC & POWER lights flashing
No Yes
Did you find a voltage across the two external thermostat circuit wires?
No Yes
•
Leave external boiler thermostat connection wires
disconnected from boiler.
•
Troubleshoot the external thermostat circuit until you find
the source of the stray voltage. (Pay close attention to
the wiring connections to 3-wire zone valves.)
•
Correct the problem and repeat the voltmeter test above,
verifying there is no longer a voltage reading under any
condition in the external thermostat circuit.
•
An isolating relay may be required.
•
Disconnect the two external wires connected to the boiler
thermostat leads (two black low voltage leads in J-box).
•
Connect a voltmeter across these 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.
•
Boiler should now operate per the normal sequence of
operation shown in
Figure 18 , page 23.
•
If no voltage is found under any condition of the external
thermostat circuit, connect the two boiler thermostat
connection leads together (or jumper the boiler aquastat
T-T terminals).
•
Turn off power to the boiler for 1 minute.
•
Turn on power and allow boiler to cycle.
Do the TSTAT and POWER lights still flash?
•
Replace control module.
•
Retest.
— Usually indicates 48 VAC on thermostat circuit (stray voltage) —