18
Meter Time In Minutes and Seconds For Normal Input Rating of
Furnaces Equipped For Use With Natural Gas
INPUT M ETER
SIZE
HEAT
VALUE
HEAT
VALUE
HEAT
VALUE
HEAT
VALUE
Btu/hr FT
3
900 1,000 1040 1,100
M IN. SEC. M IN.SEC M IN. SEC. MIN. SEC.
1 1 21 1 30 1 33 1 39
10 13 30 15 00 15 36 16 30
1 0 54 1 00 1 03 1 06
10 9 00 10 10 10 24 11 00
1 0 41 0 45 0 47 0 50
10 6 45 7 30 7 48 8 15
1 0 32 0 36 0 37 0 40
10 5 24 6 00 6 14 6 36
1 0 27 0 30 0 31 0 33
10 4 30 5 00 5 12 5 30
120,000
40,000
60,000
80,000
100,000
In Canada, the rating plate input for the furnace apply to installations
up to 4,500 feet (1370m) above sea level. Canadian certification
applies to the installations of up to 4,500 feet above sea level.
Installations above 4,500 feet are subject to acceptance by the
local authorities having jurisdiction.
Do not derate the furnace by adjusting the manifold pressure to a
lower pressure than specified on the furnace rating plate. The
combination of the lower air density and a lower manifold pressure
will prohibit the burner orifice from drawing the proper amount of
air into the burner. This may cause incomplete combustion,
flashback, and possible yellow tipping.
In some areas the gas supplier may artificially derate the gas in
an effort to compensate for the effects of altitude. If the gas is
artificially derated, the appropriate orifice size must be determined
based upon the BTU/ft
3
content of the derated gas and the altitude.
Refer to the National Fuel Gas Code, NFPA 54/ANSI Z223.1, and
information provided by the gas supplier to determine the proper
orifice size.
Some models require a pressure switch change due to the reduced
air density above certain altitudes. Refer to the following table to
determine proper pressure switch settings for your application.
A different pressure switch may be required at high altitude
regardless of the BTU/ft
3
content of the fuel used. Contact your
distributor for appropriate altitude ranges and pressure switch
kits.
Furnace input Kbtu/hr Altitude (ft) Switch Setting (inches w.c.)
45 8000' 0.55
70 NR
90* 8000' 0.60
115 NR
140 NR
* 904BNA does not require a switch change
Pressure Switch Changes
PROPANE GAS CONVERSION
WARNING
P
OSSIBLE PROPERTY DAMAGE, PERSONAL INJURY OR DEATH MAY OCCUR IF
THE CORRECT CONVERSION KITS ARE NOT INSTALLED.
T
HE APPROPRIATE KITS
MUST BE APPLIED TO INSURE SAFE AND PROPER FURNACE OPERATION.
A
LL
CONVERSIONS MUST BE PERFORMED BY A QUALIFIED INSTALLER OR SERVICE
AGENCY.
This unit is configured for natural gas. The appropriate
manufacturer’s propane gas conversion kit, must be applied for
propane gas installations. Refer to the “Propane Gas and/or
High Altitude Installations” section for details.
Contact your distributor for a tabular listing of appropriate
manufacturer’s kits for propane gas and/or high altitude
installations. The indicated kits must be used to insure safe and
proper furnace operation. All conversions must be performed by
a qualified installer, or service agency.
GAS PIPING CONNECTIONS
GENERAL
CAUTION
TO AVOID POSSIBLE UNSATISFACTORY OPERATION OR EQUIPMENT DAMAGE
DUE TO UNDERFIRING OF EQUIPMENT, USE THE PROPER SIZE OF
NATURAL/PROPANE GAS PIPING NEEDED WHEN RUNNING PIPE FROM THE
METER/TANK TO THE FURNACE.
When sizing a trunk line, be sure to include all appliances which
will operate simultaneously when sizing a trunk line.
The gas piping supplying the furnace must be properly sized based
on the gas flow required, specific gravity of the gas, and length of
the run. The gas line installation must comply with local codes, or
in their absence, with the latest edition of the National Fuel Gas
Code, NFPA 54/ANSI Z223.1.
Natural Gas Capacity of Pipe
In Cubic Feet of Gas Per Hour (CFH)
Length of Nominal Black Pipe Size
Pipe in Feet 1/2" 3/4" 1" 1 1/4" 1 1/2"
10 132 278 520 1050 1600
20 92 190 350 730 1100
30 73 152 285 590 980
40 63 130 245 500 760
50 56 115 215 440 670
60 50 105 195 400 610
70 46 96 180 370 560
80 43 90 170 350 530
90 40 84 160 320 490
100 38 79 150 305 460
(Pressure 0.5 psig or less and pressure drop of 0.3" W.C.; Based on
0.60 Specific Gravity Gas)
CFH =
BTUH Furnace Input
Heating Value of Gas (BTU/Cubic Foot)
To connect the furnace to the building’s gas piping, the installer
must supply a ground joint union, drip leg, manual shutoff valve,
and line and fittings to connect to gas valve. In some cases, the
installer may also need to supply a transition piece from 1/2" pipe
to a larger pipe size.
The following stipulations apply when connecting gas piping.
• Use black iron or steel pipe and fittings for the building
piping.
• Use pipe joint compound on male threads only. Pipe joint
compound must be resistant to the action of the fuel used.
• Use ground joint unions.
• Install a drip leg to trap dirt and moisture before it can enter
the gas valve. The drip leg must be a minimum of three
inches long.
• Install a 1/8" NPT pipe plug fitting, accessible for test gage
connection, immediately upstream of the gas supply
connection to the furnace.
• Use two pipe wrenches when making connection to the
gas valve to keep it from turning. The orientation of the gas
valve on the manifold must be maintained as shipped from
the factory.
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