32
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
A heat pump thermostat with
three stages of heat
is required
to properly use a two-stage furnace in conjunction with a
heat pump. Refer to the fossil fuel kit (AFE18-60A) installa-
tion instructions for additional thermostat requirements.
H
IGH
A
LTITUDE
D
ERATE
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 B149.1-15 in Canada, and informa-
tion provided by the gas supplier to determine the proper orifice
size.
P
ROPANE
G
AS
C
ONVERSION
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
.
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
installer, or service agency.
G
AS
V
ALVE
This unit is equipped with a 24 volt gas valve which modu-
lates by pneumatic linkage to the combustion air blower.
Taps for measuring the gas supply pressure and manifold pres-
sure 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.
G
AS
P
IPING
C
ONNECTIONS
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
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 B149.1-15 in
Canada.
Natural Gas Capacity of Pipe In Cubic Feet of Gas Per Hour (CFH)
Nominal
½
¾
1
1¼
1½
2
2½
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
137
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 w ith 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.)
CFH =
BTUH Furnace Input
Heating Valve of Gas (BTU/Cubic Foot)
To connect the furnace to the building’s gas piping, the in-
staller 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.
Refer to
Gas Piping Connections
figure for typical gas line
connections 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.
