ICP N9MSB, Service And Technical Support Manual

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SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: N9MSB
Specifications subject to change without notice.
6 440 04 4413 03
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).
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).
Table 1 Altitude Derate Multiplier for USA
ALTITUDE
FT. (M)
PERCENT
OF DERATE
DERATE MULTIPLIER
FACTOR*
0–2000
(0 − 610)
0 1.00
2001–3000
(610 − 914)
4 − 6 0.95
3001–4000
(914 − 1219)
6 − 8 0.93
4001–5000
(1219 − 1524)
8 − 10 0.91
5001–6000
(1524 − 1829)
10 − 12 0.89
6001–7000
(1829 − 2134)
12 − 14 0.87
7001–8000
(2134 − 2438)
14 − 16 0.85
8001–9000
(2438 − 2743)
16 − 18 0.83
9001–10,000
(2743 − 3048)
18 − 20 0.81
* Derate multiplier factors are based on midpoint altitude for altitude range.
NOTE : For Canadian altitudes of 2000 to 4500 ft. (610 to
1372 M), use USA altitudes of 2001 to 3000 ft. (610 to 914
M)
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. Loosen set screw on inlet tower pressure tap no more
than one full turn with a 3/32 − in. hex wrench or 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 R and W 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.
FIRE HAZARD
Failure to follow this warning could result in personal injury,
death, and/or property damage.
Inlet pressure tap set screw must be tightened and 1/8
− in.
NPT pipe plug must be installed to prevent gas leaks.
!
WARNING
14. Tighten set screw on inlet tower pressure tap with
3/32 − in. hex wrench, or if 1/8 − in. NPT plug was
removed, apply pipe dope sparingly to end of plug and
re − install in the gas valve.
Adjust Manifold Pressure
1. Adjust manifold pressure to obtain proper gas input rate.
(See Figure 3 )
a. Turn gas valve ON/OFF switch to OFF.
b. Loosen set screw on manifold tower pressure tap no
more than one full turn with a 3/32 − in. hex wrench, or
remove the 1/8 inch NPT plug from the manifold
pressure tap on the gas valve. See Figure 3
c. Connect a water column manometer or similar device
to manifold pressure tap.
d. Turn gas valve ON/OFF switch to ON.
e. Manually close blower door switch.
f. Jumper R and W thermostat connections on control
to start furnace. (See Figure 4 )
g. Remove regulator adjustment cap from gas valve
pressure regulator (See Figure 3 ) and turn adjusting
screw (3/16 or smaller flat − tipped screwdriver)
counterclockwise (out) to decrease input rate or
clockwise (in) to increase input rate.
NOTICE
DO NOT set low − heat manifold pressure less than 2.8 − in. w.c.
(697 Pa) or more than 3.8 − in. w.c. (947 Pa) for natural gas. If
required manifold pressure is outside this range, change main
burner orifices.
h. When correct input is obtained, replace cap that
conceal gas valve regulator adjustment screw. Main
burner flame should be clear blue, almost transparent
(See Figure 13 )
i. Remove jumper R to W.