Installation Guide
32
Inlet gas supply pressures must be maintained within the ranges
specified in the following table. The supply pressure must be con-
stant and available with all other household gas fired appliances
operating. The minimum gas supply pressure must be maintained
to prevent unreliable ignition. The maximum must not be ex-
ceeded to prevent unit overfiring.
HIGH ALTITUDE DERATE
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 or CAN/CSA B149.1 in Canada, and information provided by the
gas supplier to determine the proper orifice size.
PROPANE GAS CONVERSION
As shipped, this unit is configured for natural gas. The LPM-09
is required to convert this furnace to operate on LP gas.
The correct kit must be used to insure safe and proper furnace
operation. All conversions must be performed by a qualified in-
staller, or service agency.
GAS VALVE
This unit is equipped with a 24 volt gas valve which modulates by pneumatic linkage to the combustion air blower. Taps for
measuring the gas supply pressure and manifold pressure are provided on the valve. This is a non-convertible, non-adjustable gas
valve equipped for natural gas.
The gas valve has a manual ON/OFF control located on the valve itself. This control may be set only to the “ON” or “OFF” position.
Refer to the lighting instructions label or the Startup Procedure & Adjustment section of this manual for use of this control during
start up and shut down periods.
GAS PIPING CONNECTIONS
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 or CAN/CSA B149.1 in Canada.
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. Re-
fer to Gas Piping Connections figure for typical gas line connec-
tions to the furnace.
• Gas piping must be supported external to the furnace
cabinet so that the weight of the gas line does not distort
the burner rack, manifold or gas valve.
• Use black iron or steel pipe and fittings for building piping.
Where possible, use new pipe that is properly chamfered,
reamed, and free of burrs and chips. If old pipe is used, be
sure it is clean and free of rust, scale, burrs, chips, and old
pipe joint compound.
• Use pipe joint compound on male threads ONLY. Always use
pipe joint compound (pipe dope) that is APPROVED FOR ALL
GASES. DO NOT apply compound to the first two threads.
• Use ground joint unions.
Natural Gas Minimum: 4.5" w.c. Maximum: 10.0" w.c.
Propane Gas Minimum: 11.0" w.c. Maximum: 13.0" w.c.
Inlet Gas Supply Pressure
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
ENSURE
SAFE
AND
PROPER
FURNACE
OPERATION
. A
LL
CONVERSIONS
MUST
BE
PERFORMED
BY
A
QUALIFIED
INSTALLER
OR
SERVICE
AGENCY
.
T
O
AVOID
POSSIBLE
UNSATISFACTORY
OPERATION
OF
EQUIPMENT
DAMAGE
DUE
TO
UNDERFIRING
OR
EQUIPMENT
,
USE
THE
PROPER
SIZE
OF
NATURAL
/
PROPANE
GAS
PIPING
NEEDED
WHEN
RUNNING
PIPE
FROM
THE
METER
/
TANK
TO
THE
FURNACE
.
WARNING
Nominal ½¾11¼1½22½
Actual ID: 0.622 0.824 1.049 1.380 1.610 2.067 2.469
Length (ft)
10 170 360 678 1390 2090 4020 6400
20 118 247 466 957 1430 2760 4400
30 95 199 374 768 1150 2220 3530
40 81 170 320 657 985 1900 3020
50 72 151 284 583 873 1680 2680
60 65 1370 257 528 791 1520 2430
70 60 126 237 486 728 1400 2230
80 56 117 220 452 677 1300 2080
90 52 110 207 424 635 1220 1950
100 50 104 195 400 600 1160 1840
125 44 92 173 355 532 1020 1630
150 40 83 157 322 482 928 1480
175 37 77 144 296 443 854 1360
200 34 71 134 275 412 794 1270
250 30 63 119 244 366 704 1120
Capacity in Cubic Feet of Gas per Hour
This chart refers to natural gas with an inlet pressure of less than 2 psi and a pressure
drop of 0.5" W.C. Specific gravity is 0.60.
Pipe Size (in.)
Natural Gas Capacity of Pipe In Cubic Feet of Gas Per Hour (CFH)
CFH = BTUH Furnace Input
Heating Valve of Gas (BTU/Cubic Foot)