Part number 550-143-010/1021
79
GV90+
series
2
gas-fired water boiler – boiler manual
Troubleshooting
(continued)
INDICATOR LIGHT
CONDITION
POWER
Flashes once per second
120 VAC connection to boiler
reversed or there is insufficient
earth ground.
Flash code 2*
Internal fault, microprocessor or
memory.
Flash code 3*
LWCO circuit.
Flash code 4*
Unused.
Flash code 5*
Internal fault, water thermistors
disagree.
Flash code 6*
Flashes once per second
Internal fault, gas valve circuit.
* Flash code pattern: POWER LED flashes 2, 3, etc. times rapidly
followed by 2 seconds off, then repeats.
Control indicator lights —
HARD LOCKOUT Summary (Flashing LED’s)
MAY remove 120VAC power for more than 2 seconds to clear lockout OR
ignition control will automatically restart sequence of operation after 1 hour
waiting period after fault condition is cleared.
P
OWER light flashing alone
• Usually indicates reversed polarity of 120 VAC power wires.
POWER and TSTAT/CIRC lights flashing
• Usually indicates stray voltage on external thermostat circuit wires or
return water temperature entering boiler sections has not reached 130°F
within 30 minutes.
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 blower starting.
POWER and FLAME lights flashing
• Flame sensed without a call for heat or out of sequence during ignition trial.
• Usually indicates control has had three unsuccessful ignition attempts
or sensed flame when it shouldn’t be there. Boiler may not be properly
grounded.
FLAME lights flashing
• Flame loss, or flame not sensed during trial for ignition. Boiler may not
be properly grounded.
Solid LWCO light
• Low water condition occurred.
LWCO light flashing alone
• Three (3) rapid pulses indicates LWCO requires maintenance.
IBC indicator lights — non-lockout modes
TSTAT/CIRC light flashing alone
(Freeze Protection)
• Usually indicates return water temperature sensor detects water at boiler
return pipe less than 40°F. Both internal circulators will run continuously,
even with no call for heat, until temperature rises.
LIMIT light flashing alone
• Usually indicates an open or shorted return water or supply tempera-
ture/LWCO sensor.
Troubleshooting the IBC
• See
for location of harness plug receptacles and plugs
on the IBC.
Integrated Boiler Control (IBC)
Make sure
ground wiring
is installed per wiring
diagram. Good grounding is extremely important for
proper operation.
Solder or water
splatter between plugs
and circuit board can cause improper
operation of IBC. Place a shield over the
boiler internal controls and components
during installation. Failure to comply
could result in severe personal injury,
death or substantial property damage.
IBC indicator lights — lockout
modes
• See Charts 1 through 8 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 ther-
mostats. Wait 45 seconds. Then restore power and
call for heat.
• After an over-temperature lockout (POWER and
LIMIT lights flashing), the control will only reset
after interruption of 120VAC for 45 seconds. (And
temperature at return water temperature sensor
must be below 240°F.)
Figure 92
GV90+ Integrated Boiler Control (IBC)