International comfort products F9MXT0401410A Service And Technical Support Manual page 6

SERVICE AND TECHNICAL SUPPORT MANUAL
5. Check and verify burner orifice size in furnace. NEVER
ASSUME ORIFICE SIZE. ALWAYS CHECK AND
VERIFY.
NOTICE
If orifice hole appears damaged or it is suspected to have been
redrilled, check orifice hole with a numbered drill bit of correct
size. Never redrill an orifice. A burr−free and squarely aligned
orifice hole is essential for proper flame characteristics.
6. Replace orifice with correct size, if required by Table 3.
Use only factory−supplied orifices. See EXAMPLE 1.
EXAMPLE 1:
0 - 2000 ft. (0 - 609.6M) altitude
Heating value = 1050 Btu/cu ft.
Specific gravity = 0.62
Therefore: Orifice No. 44
(Furnace is shipped with No. 44 orifices. In this example, all
main burner orifices are the correct size and do not need to be
changed to obtain proper input rate.)
Manifold pressure: 3.4-in. w.c. (847 Pa) for high heat, 1.4-in.
w.c. (349 Pa) for low heat
NOTE: To convert gas manifold Table pressures to Pascals,
multiply the in.w.c. value by 249.1 Pa/in. w.c. (1 in. wc. = 249.1
Pa).
Check Inlet Gas Pressure
The inlet gas pressure must be checked with the furnace
operating in maximum heat. This is necessary to make sure the
inlet gas pressure does not fall below the minimum pressure of
4.5 in. w.c.
1. Make sure the gas supply is turned off to the furnace and
at the electric switch on the gas valve.
2. Remove the 1/8 in. NPT plug from the inlet pressure tap
on the gas valve.
3. Connect a manometer to the inlet pressure tap on gas
valve.
4. Turn on furnace power supply.
5. Turn gas supply manual shutoff valve to ON position.
6. Turn furnace gas valve switch to ON position.
7. Jumper the R to W/W1 and W2 thermostat connections
at the furnace control board.
8. When main burners ignite, confirm inlet gas pressure is
between 4.5 in. w.c. (1125 Pa) and 13.6 in. w.c. (3388
Pa).
9. Remove jumper across thermostat connections to
terminate call for heat. Wait until the blower off delay is
completed.
10. Turn furnace gas valve electric switch to OFF position.
11. Turn gas supply manual shutoff valve to OFF position.
12. Turn off furnace power supply.
13. Remove manometer from the inlet pressure tap of the
gas valve.
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in personal injury,
death, and/or property damage.
Re−install manifold pressure tap plug in gas valve to
prevent gas leak.
14. Apply pipe dope sparingly to end of inlet gas pipe plug
and re−install in the gas valve.
6
Adjust Manifold Pressure
1. Adjust manifold pressure to obtain low fire input rate.
(See Figure 3)
a. Turn gas valve ON/OFF switch to OFF.
b. Remove manifold pressure tap plug from gas valve.
d. Turn gas valve ON/OFF switch to ON.
e. Move setup switch SW−1 (TT) on furnace control to
g. Jumper R and W/W1 thermostat connections on
h. Remove regulator adjustment cap from low heat gas
DO NOT set low−heat manifold pressure less than 1.3−in. w.c.
(324 Pa) or more than 1.7−in. w.c. (423 Pa) for natural gas. If
required manifold pressure is outside this range, change main
burner orifices.
Figure 3
1/2" NPT Inlet
1/8" NPT Inlet
Pressure Tap
2. Adjust manifold pressure to obtain high fire input rate.
(See Figure 3)
a. Jumper R to W/W1 and W2 thermostat connections
b. Remove regulator adjustment cap from high−heat
Specifications subject to change without notice.
Gas Furnace: (F/G)9MXT
c. Connect a water column manometer or similar device
to manifold pressure tap.
ON position to lock furnace in low−heat operation.
(See Figure 4 and Figure 15)
f. Manually close blower door switch.
control to start furnace. (See Figure 4)
valve pressure regulator (See Figure 3) and turn
low−heat adjusting screw (3/16 or smaller flat−tipped
screwdriver) counterclockwise (out) to decrease input
rate or clockwise (in) to increase input rate.
NOTICE
Redundant Automatic Gas Control
Valve (2−Stage)
ON/OFF Switch
i. Install low−heat regulator adjustment cap.
j. Move setup switch SW−1 (TT) to off position after
completing low−heat adjustment.
k. Leave manometer or similar device connected and
proceed to Step 2.
on furnace control. This keeps furnace locked in
high−heat operation.
gas valve pressure regulator (See Figure 3) and turn
high heat adjusting screw (3/16−in. or smaller
flat−tipped screwdriver) counterclockwise (out) to
decrease input rate or clockwise (in) to increase input
rate.
Regulator Seal Cap
Regulator Adjustment
Regulator Seal Cap under Cap
1/2" NPT Outlet
1/8" NPT Manifold
Pressure Tap
A11152
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