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Wait 30
seconds
(prepurge)
*Loose
harness
*Defective
CB502 board
*Loose, leaking, blocked, or reversed
pressure switch tubes
*Leaks in flue collector joints
*Foreign object in fan or flue collector
* Blockage in venting system
* Vent system not installed in
accordance with installation manual
* Excessive silicone on I.D. of vent
system joints
* Damaged or missing fan gasket
* Defective fan
* Wind at horizontal vent terminal in
excess of 40 mph
*Incorrect fan outlet orifice
Pilot
light?
24 volts
between 24V
and
24V (GND) on
ign. module?
See "Intermittent
Ignition System
Troubleshooting
Chart" on page 64
Main
burners
light?
N
Do burner,
circulator and
fan shut down at
end of call for
heat?
END
Y
Does boiler shut
down when t'stat
wire is removed from
t'sat terminal
* T'stat or zone system
calling for heat
* T'stat wires shorted
* Internal boiler wiring
problem, consult
Crown representative
Y
N
Y
Do burners shut
down before
gauge temp
exceeds high limit
setting +15F?
* Defective L4080D
* Sensing bulb not bottomed
out in well
N
N
Y
N
Y
Y
N
TROUBLESHOOTING CHART FOR BOILERS WITH CB502 CONTROL SYSTEM (USING #42-502A BOARD)
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