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CAP
Fig. 34: Manifold Pressure Adjustment
VISUAL INSPECTION
Flames can be observed through the sight glass
reflection below the blower motor.
flame indicates normal operation. At least every three
months a visual inspection should be made.
ELECTRICAL
Be sure that electrical service to the heater has proper
overload fuse or circuit breaker protection, wire size
and connections which comply with all applicable
codes.
CAUTION: Prior to replacing any component,
make sure that the main gas, power, and pumps
are turned OFF.
ORIFICE REMOVAL
GAS ORIFICE
Fig. 35: Orifice Location
1. Locate and close the external manual shut-off
valve.
2. Loosen the external gas union.
3. Locate and remove front door panel.
4. Locate and remove the (4) bolts & nuts holding the
gas orifice in place. See Fig. 35 above.
5. Carefully remove the gas orifice and do not mis-
place the O-rings attached to the flanges.
6. Inspect and/or replace the orifice with the correct
size.
GAS AND AIR ORIFICE SELECTION
The gas orifice and the air orifice MUST match to
attain the correct air/fuel ratio.
matched when the number of pockets on the side of
the gas orifice is the same as the number of notches
on the edge of the air orifice. The orifice selection is
based on elevation, not on the fuel used. See Table L.
The gas orifice is located on the gas train, between the
gas valve and the combustion blower. The air orifice
is located on the inlet side of the combustion blower.
ADJUSTMENT SCREW
CLOCKWISE TO INCREASE
MANIFOLD
PRESSURE TAP
-0.40" ± 0.10" W.C.
GAS VALVE
A blue-colored
BRACKET
O-RING
The orifices are
NOTE: Gas orifices for propane gas have a black
oxide finish.
MUST MATCH
FOR CORRECT
AIR/FUEL RATIO
4 POCKETS
GAS ORIFICE
Fig. 36: Orifice Orientation
Pockets / Notches
1
2
3
4
5
6
Table L: Orifice Usage
IGNITER REMOVAL
.26" MIN ALONG
LENGTH OF RODS
Fig. 37: Igniter
1. Locate and remove front door panel.
2. Locate and remove the accessible left side access
panel. You may also reach from the front of the
heater or remove the jacket top for better access.
3. Locate the igniter behind the blower.
4. Locate and disconnect the high tension spark
cable from the igniter.
5. Using a 5/16" socket, remove the (2) bolts holding
the igniter down.
6. Using a flat screw driver, loosen the igniter bracket
from the combustion chamber, preferably on both
sides.
7. Carefully remove the igniter from its location. The
ceramic is fragile, so handle with care.
8. When replacing or inspecting the igniter, the gap
between the ground & spark tips should be 0.18"±
0.03". The gap between the rods should be no
less than 0.26" along their entire length.
41
4 NOTCHES
AIR ORIFICE
Model
Elevation
409B
0-2000 ft
259B
0-2000 ft
409B
2000-5000 ft
259B
2000-5000 ft
409B
5000-7000 ft
259B
5000-7000 ft
.18" ± .03"
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