CGi Manual
Part Number 550-142-302/0520
CGi
SERIES 4 — GAS-FIRED WATER BOILER — Boiler Manual
54
Troubleshooting — control module lights (cont.)
11c
CHART 2 –– TSTAT CIRC & POWER light flashing
–– Usually indicates 48 VAC on thermostat circuit (stray voltage) –– 120
Electrical shock hazardTURN OFF POWER
• 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 aqua-
stat T-T terminals).
• Turn off power to the boiler for 1 minute.
• Turn on power and allow boiler to cycle.
Does the TSTAT and POWER
No Yes
• 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.
Yes No
• Boiler should now operate per the normal sequence of
operation (Figure 30, page 38).
• 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.
Replace
control module
.
Retest.