Weil-McLain CGi Series 3 Installation And Maintenance Manual page 55

CG i
GAS-FIRED wATER BOILER- sERIEs a -
Boiler Manual
llc
Troubleshooting - control module lights
(cont.J
CHART 2 - TSTAT CIRC & POWER lights flashmg
- Usually indicates 48 VAC on thermostat circuit (stray voltage) -
I&WARNINGI
Electrical shock hazard - Wherever you see .t. 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
.
If a voltage does occur under any condition, check and
thermostat leads (two black low voltage leads in J-box). correct the external wiring. (This is a common problem
Connect a voltmeter across these two incoming wires .
when using 3-wire zone valves.)
.
Close each thermostat, zone valve and relay in the external
.
Once the external thermostat circuit wiring is checked and
circuit one at a time and check the voltmeter reading corrected if necessary, reconnect the external thermostat
across the wires. circuit wires to the boiler thermostat wires and allow the
There should NEVER be a voltage reading .
boiler to cycle.
.
Did you find a voffage
across
the 1\Vo external thermostat circuit wires?
Yes
No
.
Leave external boiler thermostat connection wires
.
If no vonage is found under any condition of the external
disconnected from boiler.
thermostat circuit, connect the two boiler thermostat
connection leads together (or jumper the boiler aquastat
.
Troubleshoot the external thermostat circuit until you find
T-T terminals) .
the source of the stray voltage. (Pay close attention to
the wiring connections to 3-wire zone valves.)
~
.
Tum off power to the boiler for 1 minute.
.
Correct the problem and repeat the voltmeter test above,
Tum on power and allow boiler to cycle .
.
verifying there is no longer a voltage reading under any
condition in the external thermostat circuit.
Do the
TSTAT
and
POWER
lights
sli//tiash?
.
An isolating relay may be required .
-
No
I I
Yes
.
Boiler should now operate per the normal sequence of
I:
Replace control module .
operation shown in Figure 30, page 38.
Retest.
Part Number 550-142-780/0712 55