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Step 11 — Install Gas Piping
Installation of the gas piping must be accordance with lo-
cal building codes and with applicable national codes. In
U.S.A., refer to NFPA 54/ANSI Z223.1 National Fuel Gas
Code (NFGC). In Canada, installation must be accordance
with the CAN/CSA B149.1 and CAN/CSA B149.2 installa-
tion codes for gas burning appliances.
This unit is factory equipped for use with Natural Gas fuel
at elevations up to 2000 ft (610 m) above sea level. Unit may
be field converted for operation at elevations above 2000 ft
(610 m) and/or for use with liquefied petroleum fuel. See ac-
cessory kit installation instructions regarding these accesso-
ries.
NOTE: Furnace gas input rate on rating plate is for installation
up to 2000 ft (610 m) above sea level. The input rating for alti-
tudes above 2000 ft (610 m) must be derated by 4% for each
1000 ft (305 m) above sea level.
For natural gas applications, gas pressure at unit gas con-
nection must not be less than 4 in. wg (996 Pa) or greater than
13 in. wg (3240 Pa) while the unit is operating. On 48FCF/
T*05-07 (high-heat) units, the gas pressure at unit gas con-
nection must not be less than 5 in. wg (1245 Pa) or greater
than 13 in. wg (3240 Pa) while the unit is operating, see
Table 3. For liquefied petroleum applications, the gas pres-
sure must not be less than 11 in. wg (2740 Pa) or greater than
13 in. wg (3240 Pa) at the unit connection, see Table 4.
Table 3 — Natural Gas Supply Line Pressure
Ranges
UNIT MODEL
UNIT SIZE
48FCD/E/S/R
04, 05, 06, 07
48FCF/T
05, 06, 07
(High Heat Units Only)
Table 4 — Liquid Propane Supply Line Pressure
Ranges
UNIT MODEL
UNIT SIZE
48FCD/E/S/R
04, 05, 06, 07
48FCF/T
05, 06, 07
(High Heat Units Only)
The gas supply pipe enters the unit at the burner access
panel on the front side of the unit, through the long slot at the
bottom of the access panel. The gas connection to the unit is
made to the
1
/
-in. FPT gas inlet port on the unit gas valve.
2
Manifold pressure is factory-adjusted for natural gas fuel
use. Adjust as required to obtain best flame characteristics.
See Table 5.
Table 5 — Natural Gas Manifold Pressure Ranges
UNIT MODEL
UNIT SIZE
48FCD/E/S/R
04, 05, 06, 07
48FCF/T
05, 06, 07
(High Heat Units Only)
NOTE: LOW FIRE, 1.7 in. wg (423 Pa), applies to the following three
phase voltage units only: 48FC*E04 and 48FCF*05/06/07.
Manifold pressure for LP fuel use must be adjusted to speci-
fied range. Follow instructions in the accessory kit to make ini-
tial readjustment, see Table 6.
MIN.
MAX.
4.0 in. wg
13.0 in. wg
(996 Pa)
(3240 Pa)
5.0 in. wg
13.0 in. wg
(1245 Pa)
(3240 Pa)
MIN.
MAX.
11.0 in. wg
13.0 in. wg
(2740 Pa)
(3240 Pa)
11.0 in. wg
13.0 in. wg
(2740 Pa)
(3240 Pa)
HIGH FIRE LOW FIRE
3.5 in. wg
SEE NOTE
(872 Pa)
BELOW
3.5 in. wg
SEE NOTE
(872 Pa)
BELOW
13
Table 6 — Liquid Propane Manifold Pressure
Ranges
UNIT MODEL
UNIT SIZE
48FCD/E/S/R
04, 05, 06, 07
48FCF/T
05, 06, 07
(High Heat Units Only)
NOTE: LOW FIRE, 5.0 in. wg (1245 Pa), applies to the following
three phase voltage units only: 48FC*E04 and 48FCF*05/06/07.
CAUTION
Failure to follow this caution may result in equipment
damage.
When connecting the gas line to the unit gas valve, the
installer MUST use a backup wrench to prevent damage to
the valve.
Install a gas supply line that runs to the unit heating sec-
tion. Refer to the NFPA 54/NFGC or equivalent code for gas
pipe sizing data. Do not use a pipe size smaller than
Size the gas supply line to allow for a maximum pressure
drop of 0.5-in. wg (124 Pa) between gas regulator source and
unit gas valve connection when unit is operating at high-fire
flow rate.
The gas supply line can approach the unit in three ways:
horizontally from outside the unit (across the roof), thru-curb/
under unit basepan (accessory kit required), or through unit
basepan (factory option or accessory kit required). Consult
accessory kit installation instructions for details on these in-
stallation methods. Observe clearance to gas line components
per Fig. 16.
9" MINIMUM CLEARANCE
FOR PANEL REMOVAL
MANUAL GAS
SHUTOFF VALVE
BASE UNIT
48" MINIMUM
BASE RAIL
ROOF
CURB
FROM
GAS
METER
LEGEND
NFGC — National Fuel Gas
Code
STEEL PIPE
NOMINAL DIAMETERS (IN.)
1
/
2
3
/
or 1
4
1
1
/
or larger
4
Fig. 16 — Gas Piping Guide
(with Accessory Thru-the-Curb Service
Connections)
FACTORY-OPTION THRU-BASE CONNECTIONS (GAS
CONNECTIONS)
This service connection kit consists of a
adapter fitting (brass), a
1
/
2
and a
3
/
-in. electrical bulkhead connector, all factory-in-
4
stalled in the embossed (raised) section of the unit basepan in
the condenser section. See Fig. 17.
HIGH FIRE LOW FIRE
10 in. wg
SEE NOTE
(2490 Pa)
BELOW
10 in. wg
SEE NOTE
(2490 Pa)
BELOW
1
/
X
GAS
*
REGULATOR
*
DRIP LEG
*
PER NFGC
FIELD-FABRICATED
*
SUPPORT
*Field supplied.
NOTE: Follow all local codes.
SPACING OF SUPPORTS
X DIMENSION (FT)
6
8
10
1
/
-in. NPT gas
2
-in. electrical bulkhead connector
-inch.
2
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