47
Part Number
550-110-290/0219
CGt
GAS-FIRED WATER BOILER — Series 2 —
Boiler Manual
12b
Troubleshooting — components
Control module
Solder or water
splatter between plugs and circuit board
can cause improper operation of control module. Place
a shield over the boiler internal controls and compo-
nents during installation. Failure to comply could result
in severe personal injury, death or substantial property
damage.
Make sure
ground wiring
is installed per wiring diagram.
Good grounding is extremely important for proper
operation.
Control indicator lights —
LOCKOUT modes
See
Charts 1
through
7
in this section for detailed trouble-
shooting procedures.
To reset control after a lockout, turn off power at the 120VAC
service switch or turn down all thermostats. Wait 45 seconds.
Then restore power or call for heat.
POWER light flashing alone
Usually indicates reversed polarity of 120VAC power wires.
POWER and TSTAT CIRC lights flashing
Usually indicates stray voltage on external thermostat circuit
wires (usually due to miswired 3-wire zone valve).
POWER and PRESS SWITCH lights flashing
Usually indicates pressure switch is closed when it should
not be, or pressure switch failed to close within 5 minutes of
inducer starting.
POWER
and FLAME lights flashing
Usually indicates false flame sense or flame sensed when it
shouldn’t be there.
Control indicator lights —
NONLOCKOUT modes
POWER light on and FLAME light flashing
Usually indicates pilot flame was not established within 15
seconds from application of spark. Control will flash light, but
will continue to cycle indefinitely until flame is established or
problem is corrected.
POWER light on and PRESS SWITCH light flashing
Usually indicates pressure switch opened during the run cycle.
Troubleshooting the control module
See Figure 33, page 48
,
for location of harness plug receptacles
and plugs on the control module.
Figure 32 Control module
3-Way valve
The 3-way valve redirects water flow in the circuit.
Normally the valve allows water to flow through the
bypass to maintain the heat in the boiler for the tankless
heater. The 3-way valve lever is up in the normal
position. When the heating thermostat calls for heat, the
3-way valve actuator lever drops which allows water to
flow to the space heating system. Check for proper 3-way
valve operation as follows:
Tankless operating limit calls for heat, boiler turns on
when temperature drops approximately 10 degrees below
tankless limit setting (differential). Boiler shuts off when
temperature reaches tankless limit setting. The 3-way
valve lever stays up all during domestic heating cycle.
Space heating thermostat calls for heat. 3-way valve lever
drops and boiler fires providing space heat.
NOTE : If the boiler temperature drops below tank-
less limit setting minus 10 degree differential, the 3-way
valve lever will raise to reheat boiler to tankless limit
setting. Then the 3-way valve lever will drop and boiler
will resume providing space heating until thermostat is
satisfied, boiler limit setting is reached, or temperature in
boiler drops below tankless limit setting minus 10 degree
differential. Verify valve is installed and wired correctly.
Tankless low limit calls for heat, but boiler does not turn
on — Check power to 3-way valve and valve end switch.
Tankless low limit calls for heat, boiler turns on, but there
is not enough domestic water supply — Check 3-way valve.
It may be stuck in the space heating position.
Thermostat calls for heat, boiler turns on, but there is no
flow of hot water to the space heating system — Check
whether 3-way valve is stuck in domestic water heating
position. Verify valve is installed and wired correctly.
