16
Step 11 — Install Gas Piping
Installation of the gas piping must be accordance with local
building codes and with applicable national codes. In U.S.A., re-
fer 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 installation codes for gas burning
appliances.
This unit is factory equipped for use with natural gas (NG) 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 accessory kit installation
instructions regarding these accessories.
NOTE: Furnace gas input rate on rating plate is for installation up
to 2000 ft (610 m) above sea level. In U.S.A., the input rating for
altitudes above 2000 ft (610 m) must be derated by 4% for each
1000 ft (305 m) above sea level. In Canada, the input rating must
be derated by 10% for altitudes of 2000 ft (610 m) to 4500 ft
(1372 m) above sea level.
For natural gas applications, gas pressure at unit gas connection
must not be less than 4 in. wg (996 Pa) or greater than 13 in. wg
(3240 Pa) while the unit is operating. On 48HCF/N/T*05-06
(high-heat) units, the gas pressure at unit gas connection 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 pressure must not be less than
11 in. wg (2740 Pa) or greater than 13.6 in. wg (3390 Pa) at the
unit connection. See Table 4.
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
/
2
-in.
FPT gas inlet port on the unit gas valve.
Manifold pressure is factory-adjusted for natural gas fuel use.
Adjust as required to obtain best flame characteristics. See
Tables 5 and 6.
Install a gas supply line that runs to the unit heating section. Refer
to the NFPA 54/NFGC or equivalent code for gas pipe sizing data.
Do not use a pipe size smaller than
1
/
2
-in. Size the gas supply line
to allow for a maximum pressure drop of 0.5 in. wg (124 Pa) be-
tween 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: horizon-
tally from outside the unit (across the roof), through-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 installation methods.
Observe clearance to gas line components per Fig. 20.
Fig. 20 — Gas Piping Guide
(with Accessory Thru-the-Curb Service Connections)
FACTORY OPTION THRU-BASE CONNECTIONS (GAS
CONNECTIONS)
This service connection kit consists of a
1
/
2
-in. electrical bulkhead
connector and a
3
/
4
-in. electrical bulkhead connector, connected to
an “L” bracket covering the embossed (raised) section of the unit
basepan in the condenser section (see Fig. 21 for shipping posi-
tion). The
3
/
4
-in. bulkhead connector enables the low-voltage con-
trol wires to pass through the basepan. The
1
/
2
-in. bulkhead con-
nector allows the high-voltage power wires to pass through the
basepan. See Fig. 22 and 23.
Table 3 — Natural Gas Supply Line Pressure Ranges
UNIT MODEL UNIT SIZE MIN. MAX.
48HCD/E/L/M/S/R 04, 05, 06
4.0 in. wg
(996 Pa)
13.0 in. wg
(3240 Pa)
48HCF/N/T
(High Heat Units Only)
05, 06
5.0 in. wg
(1245 Pa)
13.0 in. wg
(3240 Pa)
Table 4 — Liquid Propane Supply Line Pressure
Ranges
UNIT MODEL UNIT SIZE MIN. MAX.
48HCD/E/L/M/S/R 04, 05, 06
11.0 in. wg
(2737 Pa)
13.0 in. wg
(3240 Pa)
Table 5 — Natural Gas Manifold Pressure Ranges
UNIT MODEL UNIT SIZE HIGH FIRE LOW FIRE
48HCD/E/L/M/S/R 04, 05, 06
3.5 in. wg
(872 Pa)
1.7 in. wg
(423 Pa)
48HCF/N/T
(High Heat Units Only)
05, 06
3.5 in. wg
(872 Pa)
1.7 in. wg
(423 Pa)
Table 6 — Liquid Propane Manifold Pressure Ranges
UNIT MODEL UNIT SIZE HIGH FIRE LOW FIRE
48HCD/E/L/M/S/R 04, 05, 06
10.0 in. wg
(2488 Pa)
5.0 in. wg
(1244 Pa)
CAUTION
EQUIPMENT DAMAGE
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.
X
BASE UNIT
BASE RAIL
ROOF
CURB
9” MINIMUM CLEARANCE
FOR PANEL REMOVAL
MANUAL GAS
SHUTOFF VALVE
*
GAS
REGULATOR
*
48” MINIMUM
DRIP LEG
PER NFGC
*
FIELD-FABRICATED
SUPPORT
*
FROM
GAS
METER
LEGEND *Field supplied.
NOTE: Follow all local codes.
NFGC —
National Fuel Gas
Code
STEEL PIPE NOMINAL
DIAMETERS (in.)
SPACING OF SUPPORTS
X DIMENSION (ft)
1
/
2
6
3
/
4
or 1 8
1-
1
/
4
or larger 10
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