54
440 01 4542 00
Specifications subject to change without notice.
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.
!
WARNING
Adjustments
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death and/or property damage.
DO NOT bottom out gas valve regulator adjusting screw.
This can result in unregulated manifold pressure and result
in excess overfire and heat exchanger failures.
!
WARNING
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in reduced furnace
life.
DO NOT redrill orifices. Improper drilling (burrs,
out--of--round holes, etc.) can cause excessive burner noise
and misdirection of burner flames. This can result in flame
impingement of heat exchangers, causing failures. See Fig.
60.
CAUTION
!
BURNER
ORIFICE
A93059
Fig. 60 -- Orifice Hole
For proper operation and long term reliability, the Furnace input
rate must be /--2 percent of input rate on furnace rating
plate, or as adjusted for altitude.
The gas input rate on rating plate is for installations at altitudes up
to 2000 ft. (609.6M).
The NATURAL GAS manifold pressure adjustments in Table
20 compensate for BOTH altitude AND gas heating value.
DO NOT apply an additional de--rate factor to the pressures
show in Table 20. The 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 Table 20. No 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.
NOTICE
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 20. The natural gas manifold pressures in
Table 19 adjust 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 20 adjust for
BOTH altitude and natural gas heating value.
Table 18 – Altitude Derate Multiplier for U.S.A.
ALTITUDE
PERCENT
OF
DERATE
DERATE
MULTIPLIER
FACTOR*
FT.
M
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 2000 ft. (611 to 914 M) in Table
20.
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 Table 20.
4. Find closest natural gas heat value and specific gravity in
Table 20. 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.
