Slant/Fin CB-45 Installation And Operating Instructions Manual page 27

TROUBLESHOOTING PROCEDURES
Note: All of the procedures below require the removal
of some of the boiler jacket panels.
Checking flame sensing current
• Turn power OFF and remove lead from flame sensor.
• Connect one microampmeter lead to the flame
sensor wire lead; connect other microampmeter lead
to the flame sensor. (Meter is in series.)
• Turn power ON. Once the gas valve opens, and
ignition occurs at the burner, the microampmeter
must read at least 1 microamp to keep the gas valve
open. Typically, the reading is between 5 and 10
microamps. (If no reading, polarity may be wrong -
reverse leads.)
Flame sensor removal
• Turn power OFF and remove lead from flame sensor.
• Remove flame sensor hold-down bracket.
• Carefully pull out flame sensor.
Hot surface ignitor removal
• Turn power OFF and remove ignitor hold-down
bracket.
• Carefully pull out ignitor (handle with care, fragile).
DO NOT CUT WIRES TO REMOVE IGNITOR.
Ceramic burner/Kanthal ground bar removal
• Turn power and gas supply OFF.
• If burner enclosure not accessible from the rear of
the boiler, remove sheet metal tray under blower and
leg support brace behind blower.
Figure 22. Ceramic burner/Kanthal ground bar removal
• Disconnect wires to gas valve. May be necessary to
disconnect gas supply line to gas valve to move
assembly slightly.
• Disconnect air adapter from burner enclosure.
• Remove air filter box cover to access blower
mounting studs and nuts. Remove the four nuts and
drop blower down to move out of way.
• Remove nuts around perimeter of burner enclosure,
drop down off of studs and remove enclosure.
• Allow burner enclosure to drop down low enough to
access burner bracket. Remove and clear tubing, if
necessary, but mark location of each tube for
reassembly.
• While supporting underside of burner bracket to keep
from falling, undo knurled nuts at either end of burner.
• Drop burner down off studs gently. Pull down burner
gasket with burner without ripping it.
• Ceramic burner is only attached to the burner bracket
by the ground wire, unscrew the wire tab to remove.
• Ground bar is held to burner with a weld stud through
the burner, remove the nuts and washers from the
underside of the burner to disassemble.
• To reassemble, follow this procedure in reverse,
carefully relocating all items removed in their proper
location at tightness noted in removal.
Pressure switch calibration check
• Turn power OFF.
• Remove wire leads from pressure switch terminals.
• Hookup resistance meter between normally open
(N.O.) and common (C) terminals.
• With blower off, the switch should be open, meter
reading is infinity. If not, switch is defective.
• If switch is open, check cutout pressure with blower
running, as described in following steps.
• Hookup differential pressure gauge in same manner
as to set blower air flow - high side to blower outlet,
low side to burner enclosure. The switch and gauge
both read the same air flow differential pressure.
• Turn on power and raise thermostat.
• Note pressure reading on gauge when blower is
running. Reading should be higher than the pressure
switch cutout pressure, which is marked on the
pressure switch label.
• If the pressure switch terminals are still open with the
blower running and the gauge reading is at least
2.54mm (.10") higher than the pressure switch setting,
the switch is defective.
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