Page 17
Installer’s Guide
Gas Pressure Set-up Precautions
IMPORTANT:
Do not connect gas piping to the unit until a line
pressure test has been completed. This unit should never be
exposed to gas line pressure in excess of 14 inches water column
(1/2 PSIG). The furnace and its equipment shutoff valve must be
disconnected from the gas supply piping system during any pres-
sure testing of that system at test pressures in excess of 1/2 psi.
The furnace must be isolated from the gas supply piping system
by closing its individual manual shut-off valve during any pressure
testing of the gas supply piping system at test pressures less than
or equal to 1/2 psig (3.48 kPa).
Gas Supply Line Pressure
Before connecting the unit to the gas supply line, be sure to deter-
mine the gas pressure in the line.
If the gas supply pressure is excessive (above 14 inches water
column or 1/2 psig), install a pressure regulator either at the supply
source or in the branch circuit serving the unit. Once the regulator
is installed, set it to provide a pressure of 7 inches water column
with the unit operating and no greater than 14 inches water column
with the unit not operating.
NOTE:
Gas pressure in excess of 14 inches water column
(1/2 psig) may damage the regulator, while improper regulation
may result at pressures lower than 5.5 inches water column at
the unit inlet.
If the supply line pressure is below the minimum supply pressure
indicated on the unit nameplate, contact the gas supply company.
Follow these steps to complete the installation of the unit gas pip-
ing. See Figure 17.
NOTE:
The shut-off gas cock must be installed outside of the
unit and should meet the specifications of all applicable national
and local codes
.
Table 2. Natural Gas Only
TABLE OF CUBIC FEET PER HOUR OF GAS
FOR VARIOUS PIPE SIZES AND LENGTHS
PIPE
SIZE
(inch)
LENGTH OF PIPE (feet)
10
20
30
40
50
60
70
1/2
132
92
73
63
56
50
46
3/4
278
190
152
130
115
105
96
1
520
350
285
245
215
195
180
1-1/4
1050
730
590
520
440
400
370
THIS TABLE IS BASED ON PRESSURE DROP OF 0.3 INCH W.C.
AND 0.6 SP.GR. GAS
IMPORTANT
:
Before making the gas pipe connection give serious
consideration to providing the clearance necessary to remove the
access panels on the unit (e.g., economizer and filter access panels).
NOTE
: In the absence of local codes, the installation must con-
form with American National Standard--Z223.1--National Fuel
Gas Code, Latest Revision.
The available gas supply must agree with the required gas supply
marked on the unit nameplate. Minimum permissible gas supply
pressure for purpose of
input adjustment
must be at least 7.0 in. w.
c. (inches water column) for natural gas and 11 in. w. c. for LP Gas.
Pipe Delivery Schedule
NOTE:
The following procedure and tables apply to Natural
Gas
only.
1. Obtain from the gas company the heating value and specific
gravity of the gas delivered.
2. Determine the exact length of pipe needed.
3. Read BTUH input nameplate on the furnace.
4. Use the multiplier opposite the specific gravity of the gas given
in Table 1 below and insert in the following formula:
5. Using Table 2, select the pipe length nearest to calculated size.
Table 1
. Specific Gravity Multiplier
DEALER INSTALLED
GROUND UNION
1/8" N.P.T.PLUGGED
ACCESS FOR TEST
GAUGE CONNECTION
FROM
GAS SUPPLY
FIELD SUPPLIED MAIN
GAS VALVE, MUST BE
INSTALLED BY DEALER
OUTSIDE OF UNIT.
UNIT
TO MAIN
CONTROL
VALVE
6"
MIN
DRIP LEG
(6" MIN)
Figure 17. Gas Pipe
NOTE:
If this is an LP Gas application, consult your LP Gas
supplier for pipe sizes and deliveries.
6. Follow this line vertically down to the exact CFH found in Step 4
above or the next highest value.
7. Read horizontally to the left of this column for the required pipe
size diameter.
Furnace Input in BTUH
Gas Heat Contne in BTU/Cu. Ft. X Multiplier
CFH =
1. Install a tapped, Style A (1/8-inch NPT tap) shut-off gas cock at
the end of the gas supply line near the unit. Be sure the tapped
gas cock is downstream of the pressure regulator, if used.
2. Install a ground union joint downstream of the shut-off cock.
This joint must also be installed outside of the unit.
3. Install a drip leg at least six (6) inches in depth next to the union
as shown in Figure 17. This drip leg is required to collect any
sediment that may be deposited in the line.
SPECIFIC
GRAVITY
MULTIPLIER
MULTIPLIERS TO BE USED
WHEN THE SPECIFIC GRAV-
ITY OF THE GAS IS OTHER
THAN 0.60
.50
1.10
.55
1.04
.60
1.00
.65
.962
