Carrier N92ESN Installation, Start-Up, Operating And Service And Maintenance Instructions page 49

N92ESN: Installation, Start-up, Operating and Service and Maintenance Instructions
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The NATURAL GAS manifold pressure adjustments in
compensate for BOTH altitude AND gas heating value. DO NOT apply
an additional de-rate factor to the pressures show in
values in this table are NOT referenced to sea level; they are
AS-MEASURED AT ALTITUDE.
The heating content of natural gas at altitude may already provide for a
reduction in capacity of the furnace. Be sure to obtain the expected
in-season gas heating value of the gas from the gas supplier BEFORE
making any adjustments for capacity or altitude. Refer to
adjustments to the furnace may be necessary at altitude for certain gas
heating values.
Refer to the instructions provided in the factory-specified LP/Propane
conversion kit for instructions for setting gas manifold pressures for
LP/Propane applications.
In the USA., the input rating for altitudes above 2000 ft. (609.6M) must
be reduced by 2 percent for each 1000 ft. (304.8M) above sea level.
Refer to Table 19. The natural gas manifold pressures in
for BOTH altitude and natural gas heating value.
In Canada, the input rating must be reduced by 5 percent for altitudes of
2000 ft. (609.6M) to 4500 ft. (1371.6M) above sea level. The natural gas
manifold pressures in Table 19
heating value.
Table 17 – Altitude Derate Multiplier for U.S.A.
ALTITUDE
FT. M
0–2000 0-610
2001–3000 610-914
3001–4000 914-1219
4001–5000 1219-1524
5001–6000 1524-1829
6001–7000 1829-2134
7001–8000 2134-2438
8001–9000 2438-2743
9001–10,000 2743-3048
*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. (611 to 914 M) in
To adjust manifold pressure to obtain the proper input rate, first,
determine if the furnace has the correct orifice installed. At higher
altitudes or different gas heat contents, it may be necessary to change the
factory orifice to a different orifice. Tables have been provided in the
furnace installation instructions to match the required orifice to the
manifold pressure to the heat content and specific gravity of the gas. To
do this:
1. Obtain average yearly gas heat value (at installed altitude) from
local gas supplier.
2. Obtain average yearly gas specific gravity from local gas supplier.
3. Find installation altitude in
4. Find closest natural gas heat value and specific gravity in
Follow heat value and specific gravity lines to point of intersection
to find orifice size and manifold pressure settings for proper
operation.
5. Check and verify burner orifice size in furnace. NEVER ASSUME
ORIFICE SIZE. ALWAYS CHECK AND VERIFY.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
NOTICE
Table
Table
Table 19
adjust for BOTH altitude and natural gas
PERCENT DERATE
OF MULTIPLIER
DERATE FACTOR*
0 1.00
4-6 0.95
6-8 0.93
8-10 0.91
10-12 0.89
12-14 0.87
14-16 0.85
16-18 0.83
18-20 0.81
Table 17.
Table 17.
Table 19 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
19. The 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
factory-supplied orifices. See EXAMPLE 1.
EXAMPLE 1: 0 - 2000 ft. (0 - 609.6M) altitude
19. No
Heating value = 1050 Btu/cu ft.
Specific gravity = 0.62
Therefore: Orifice No. 44
Manifold pressure: 3.4-in. w.c. (847 Pa)
(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.)
NOTE: To convert gas manifold Table pressures to Pascals, multiply the
adjust
in. w.c. value by 249.1 Pa/in. w.c. (1 in. w.c. = 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. 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
Table 19.
plug must be installed to prevent gas leaks.
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
Fig. 61.
a. Refer to the correct manifold pressure table for the appropriate
model.
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NOTICE
!
Table
WARNING
!
19. Use only