Boiler Manual
Part Number 550-110-593/1099 55
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.
No Yes
Did you find a voltage across the two external thermostat circuit wires?
NoYes
• 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.
• 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 24, page 37.
• 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) —
Chart 3 — Spark-ignited pilot —TSTAT CIRC & POWER lights flashingcontinued