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P/N 42-9470 11/07 Copyright 2007 Mestek, Inc.
Cast iron condensing boiler
Cast iron condensing boiler
— Installation and operation manual
Figure 30
Removing boiler jacket top
Figure 31
Gas valve adjustments
Starting the boiler
(continued)
When is low fi re adjustment required?
Adjust the gas valve low-fi re sett ing
ONLY
if the fl ame is unacceptable,
the CO2, O2 or CO are out of acceptable range or you are changing
fuels. You will need to remove the boiler jacket top and adjust the gas
valve low-fi re sett ing as described below.
The boiler jacket top must be removed
when it is necessary to access the gas
valve low-fi re adjustment screw or other interior components, such as the blower mo-
tor. Use the procedure below.
Removing the boiler jacket top
See Figure 30.
Remove the three thumb screws securing the fi lter access plate.
Remove and set aside the fi lter access cover and gasket.
Pull back on the fi lter clamp and remove the fi lter.
Hold the fi lter clamp back as in Figure 30.
Squeeze the conical grommet sides and maneuver the grommet out of the opening
in the jacket top.
If there is no air pipe att ached to the air inlet, leave the air inlet plate in place.
If air is piped to the air inlet plate, remove the air inlet plate and gasket by removing the
four screws that secure it to the jacket top. Make sure the air piping is properly supported.
Remove the seven Phillips-head screws securing the jacket top to the jacket sides.
Lift off the jacket top. (Leave the wire harnesses connected.)
Move the insulation aside if necessary.
Adjusting the low-fi re setting
DO NOT
adjust the low-fi re sett ing unless low-fi re fl ame or combustion
are unacceptable.
See Figure 31 for the location of the gas valve low-fi re adjustment. Use a 2-mm
hex wrench.
When adjusting the low-fi re sett ing, make changes in half-turn increments. Allow
the fl ame to stabilize before adjusting each time. (Reduce gas input if the fl ame or
burner appears red.)
If CO
2
is too
HIGH
(O
2
too low):
REDUCE
gas by turning the adjustment
COUNTERCLOCKWISE
(one
half turn at a time). Recheck the analyzer and fl ame aft er each half turn.
4. If
CO
2
is too
LOW
(O
2
too high):
INCREASE
gas by turning the adjustment
CLOCKWISE
(one half turn at a
time). Recheck the analyzer and fl ame aft er each half turn.
Replace the boiler jacket top
To replace the jacket top, reverse this order above. Make sure insulation is in place.
Slide the conical grommet over the blower inlet Th
en seat the grommet ring into
the hole in the jacket top.
Reatt ach the air inlet plate if it was removed. Inspect the air piping to make sure it
was not displaced.
Pull the air fi lter clamp back. Replace the fi lter, gasket and access cover. Secure with
the three thumbscrews. Replace the gas valve cover plate if removed.
Remove the low-fi re jumper from the connection board. Replace the electrical
panel cover.
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