SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: N9MSB
Specifications subject to change without notice.
20 440 04 4413 03
18. Check igniter resistance. Nominal resistance is 40 to 70
ohms at room temperature and is stable over the life of
the igniter.
19. Clean burner with a brush and a vacuum.
20. Clean the flame sensor with fine steel wool (0000 grade).
Do not use sand paper or emery cloth.
Figure 9 Burner Assembly
BURNER ASSY
FLAME SENSOR
(
BELOW BURNER)
FLAME ROLL−OUT SWITCH
BURNER SUPT. ASSY
L11F064
Representative drawing only, some models may vary in appearance.
To reinstall burner assembly:
1. Install the Hot Surface Igniter (HSI) and bracket in burner
assembly.
2. Install flame sensor on burner.
3. Align the edges of the one-piece burner with the slots in
the burner assembly and slide the burners forward until
they are fully seated in the burner assembly.
4. Align the orifices in the manifold assembly with the
support rings on the end of the burner.
5. Insert the orifices in the support rings of the burners.
NOTE: If manifold does not fit flush against the burner, do not
force the manifold on the burner assembly. The burners are not
fully seated forward in the burner assembly. Remove the
manifold and check burner positioning in the burner assembly
assembly before re-installing the manifold.
6. Attach the green/yellow wire and ground terminal to one
of the manifold mounting screws.
7. Install the remaining manifold mounting screws.
8. Check the igniter alignment. See Figure 9, Figure 10
and Figure 11.
Figure 10 Igniter Position − Top View
A11405
2-1/2-in.
(64.4)
1-1/4-in.
(31.8)
Figure 11 Igniter Position − Side View
L12F041
2ïin.
2.5 mm
3/8ïin.
3/16ïin.
+0.8
ï1.5 mm
50 mm
9.6 mm
4.6 mm
1/10ïin.
+ 1/32
ï 1/16ïin.
9. Attach the wires to the roll-out switches.
10. Align the burner assembly with the openings in the
primary cell inlet panel and attach the burner assembly to
the cell panel.
11. Connect the wire for the flame sensor.
12. Connect the wire for the Hot Surface Igniter.
NOTE: Use propane-resistant pipe dope to prevent leaks. Do
not use Teflon tape.
13. Install the gas pipe to the gas valve.
! WARNING
FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in personal injury,
death, and/or property damage.
Never purge a gas line into a combustion chamber. Never
test for gas leaks with an open flame. Use a commercially
available soap solution made specifically for the detection of
leaks to check all connections. A fire or explosion may result
causing property damage, personal injury or loss of life.
14. Check for gas leaks with a commercially available soap
solution made specifically for the detection of leaks.
15. Turn gas on at electric switch on gas valve and at
external shut-off or meter
16. Turn power on at external disconnect, fuse or circuit
breaker.
17. Run the furnace through two complete heating cycles to
check for proper operation
18. Install control door when complete.
Servicing Hot Surface Igniter
The igniter does NOT require annual inspection. Check igniter
resistance before removal. Refer to Figure 9, Figure 10 and
Figure 11.
1. Turn off gas and electrical supplies to furnace.
2. Remove control door.
3. Disconnect igniter wire connection.
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