Sears 9MPD125L20B1 - Manual (Page 31)

Table 9
LPG or PROPANE GAS MANIFOLD PRESSURE (" w . c .)
FOR THE 80,000 BTUH MODELS
HEATING VALUE
at ALTITUDE
BTU/CU. FT.
MEAN ELEVATION FEET ABOVE SEA LEVEL
0 to
2000
2001 to
3000
3001 to
4000
4001 to
5000
5001 to
6000
6001 to
7000
7001 to
8000
2500 10.0 8,9 8.4 10,0 10.0 10,0 10,0
Orifice Size #55 #55 #55 шпштггт тпжжат Ü 5 G mnwëÈvmm
NOTE: Propane data is based on 1.53 specific gravity. For fuels with different specific gravity consult the National Fuel Gas Code ANSI Z223.1 -2002/NFPA
54-2002 or National Standard Of Canada, Natural Gas And Propane Installation Code CSA B149.1 -00.
NOTE: The derating of these furnaces at 2% (Natural Gas) and
4% (Propane Gas) has been tested and design-certified by CSA.
General Derating Rules
These furnaces may be used at full input rating when
installed at altitudes up to 2,000’. When installed above
2,000', the input must be decreased 2% (natural) or 4% (LP)
for each 1000’ above sea level. See Table 10 for required
high altitude input rate.
Tablo 10
High Altitude Input Rate =
Nameplate Sea Level Input Rate x (Multiplier)
Elevation
High Altitude Multiplier
Natural Gas LP Gas
2001 ' - 3000' 0.95 0.90
3001 ' - 4000' 0.93 0.86
4001 ' - 5000' 0.91 0.82
5001 ' - 6000' 0.89 0.78
6001 ' - 7000' 0.87 0.74
7001 ' - 8000' 0.85 0.70
* Based on mid-range of elevation.
2. For operation with natural gas at altitudes above 2,000’, ori­
fice change and/or manifold pressure adjustments may be
required for the gas supplied. First consult your local gas
supplier, then refer to Table 6 (50,000, 75,000, 100,000
and 125,000 BTUH models) or Table 8 (80,000 BTUH mod­
els) for required pressure change and/or orifice change for
high altitudes.
3. For operation with LP gas, gas orifices MUST be changed
and manifold pressure MUST be maintained as per Table 7
(50,000, 75,000,100,000 and 125,000 BTUH models) or
Table 9 (80,000 BTUH models). Orifices can be ordered
through our distributor. (See Figure 29)
4. In cases where Table 6, Table 7, Table 8 or Table 9 is not
applicable, eg. alternate input rate application, refer to
Table 10 for required high altitude input rate.
High Altitude Air Pressure Switch
Altitudes over 4,000’ may require a different air pressure switch
than the one installed at the factory. Check parts list for pressure
switch and consult your distributor for part number and availability.
In Canada, provincial codes may govern installation of switch.
Check with governing authorities.
Changing Orifices for High Altitude
WARNING
ELECTRICAL SHOCK, FIRE OR EXPLOSION
HAZARD
Failure to properly install orifices could result in
death, personal injury and/or property damage.
Turn OFF electric power (at disconnect) and gas
supply (at manual valve in gas line) when instailing
orifices. Installation of orifices requires a quaiified
service technician.
NOTE: Main burner orifices can be changed for high altitudes.
1. Disconnect gas line from gas valve.
2. Remove manifold from furnace.
3. Remove the orifices from the manifold and replace them
with properly sized orifices.
4. Tighten orifices so it is seated and gas tight. (See
Figure 29)
5. Reinstall manifold. Ensure burners do NOT bind on new ori­
fices.
Natural Gas Input Rating Check
NOTE: The gas meter can be used to measure input to furnace.
Rating is based on a natural gas BTU content of 1,000 BTU's per
cubic meter. Check with gas supplier for actual BTU content.
1. Make sure burner compartment door is in place before per­
forming the following steps.
2. Turn OFF gas supply to all appliances and start furnace.
Example
Natural Gas No.of Seconds Time Per Cubic BTU Per
BTU Content Per Hour Foot in Seconds Hour
1,000 3,600 48 75,000
1,000x 3,600-48 = 75,000 BTUH
440 01 1020 04 Ш1