Weil-McLain EG 6 Series Manual page 31

Universal Control Systems
Troubleshooting – (EG water boilers)
– Spark-ignited pilot – TSTAT/CIRC & POWER light flashing
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.
• Disconnect the two external wires connected to the boiler
thermostat leads. (two (2) black low voltage leads in J-box).
• 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.
• Leave external boiler thermostat connection wires
disconnected from boiler.
• Trouble shoot the external thermostat circuit until you
find the source of the stray voltage. (Pay close atten-
tion to the wiring connections to 3-wire zone valves.)
• Correct the problem and repeat voltmeter test above,
verifying there is no longer a voltage reading under any
condition in the external thermostat circuit.
• Boiler should now operate per the normal sequence of
operation shown in Figure 1, page 6.
Part Number 550-142-304/1220
– Usually indicates 48 VAC on thermostat circuit (stray voltage) –
Did you find a voltage across the two external thermostat circuit wires?
Yes
continued
• If a voltage does occur under any condition, check and cor-
rect 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.
• 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?
No
No
Yes
• Replace control module.
• Retest.
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