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107272-UIM-B-1105
30 Unitary Products Group
The building structure should not be weak end by installation for the gas
piping. The piping should not be supported by the other piping, but
should be firmly supported with pipe hooks, straps, bands, or hanger.
Butt or lap welded pipe should not be bent.
The gas piping should be so installed so as to prevent an accumulation
of condensation and it must be protected against freezing. A horizontal
pipe should be pitched so that it grades toward the meter and is free
from sags. The pipe can not be run through or in an air duct or clothes
chute.
The appliance and its individual shut-off valve must be disconnected
from the gas supply piping system during any pressure testing of the
system at test pressure in excess of 1/2 (3447 PaG) psig.
The appliance 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 equal to or less than
1/2 (3447 PaG) psig. Refer to Figure 40.
GAS PIPING INSTALLATION
Properly sized wrought iron, approved flexible or steel pipe must be
used when making gas connections to the unit. If local codes allow the
use of a flexible gas appliance connection, always use a new listed con-
nector. Do not use a connector that has previously serviced another gas
appliance.
Some utility companies or local codes require pipe sizes larger than the
minimum sizes listed in these instructions and in the codes. The furnace
rating plate and the instructions in this section specify the type of gas
approved for this furnace - only use those approved gases.
IMPORTANT: An accessible manual shut-off valve must be installed
upstream of the furnace gas valve and within 6 feet (1.8 m) of the fur-
nace.
TESTING PIPING FOR LEAKS
Before turning on gas under pressure into piping, all openings from
which gas can escape should be closed. Immediately after turning on
gas, the system should be checked for leaks. This can be done by
watching the 1/2 cubic feet (0.14 m
3
) test dial and allowing 5 minutes to
show any movement, or by soaping each pipe connection and watching
for bubbles. If a leak is found, make the necessary repairs and repeat
the above test.
DEFFECTIVE PIPES OR FITTINGS SHOULD BE REPLACED AND
NOT REPAIRED. NEVER USE A FLAME OR FIRE
IN ANY FORM TO
LOCATE GAS LEAKS, USE A SOAP SOLUTION.
TABLE 16:
Gas Line Piping Size and Length
Length of Pipe in
Feet (Meter)
Nominal Diameter of Pipe in Inches (mm)
3/4 (19.05) 1 (25.4) 1-1/4 (31.75) 1-1/2 (38.1) 2 (50.8)
Capacity-Cu. Ft. (m
3
) Per Hr. with a 0.6 Sp. Gr. Gas and Pressure Drop of 0.3 in. (74.72 Pa) Water Col.
15 (4.572) 172 (4.87) 345 (9.77) 750 (21.24 — —
30 (9.144) 120 (3.4) 241 (6.82) 535 (15.15) 850 (24.07) —
45 (13.72) 99 (2.8) 199 (5.64) 435 (12.32) 700 (19.82) —
60 (18.29) 86 (2.44) 173 (4.90) 380 (10.76) 610 (17.27) —
75 (22.86) 77 (2.18) 155 (4.34) 345 (9.77) 545 (15.43) —
105 (32) 65 (1.84) 131 (3.71) 285 (8.07) 450 (12.74) 920 (26.05)
120 (36.58) — 120 (3.4) 270 (7.65) 420 (11.89) 860 (24.35)
180 (54.86) — 100 (2.83) 225 (6.37) 350 (10.76) 720 (20.39)
FIGURE 40: Manual Shut-off Valve/Gas Piping
Tee
Control
Manifold
Pipe Cap
Union
Direction
of Flow
3.00 Min.
(72.6)
Manual
Shutoff Valve
(Close this valve during pressure
testing of the gas line)
1/8” NPT Plugged
Tapping Pressure
Gauge Port
Floor Level
LOCATION OF UNION AND DRIP LEG FOR
CONNECTING BURNER TO HOUSING PIPING
Black
Iron Pipe
Drip
Leg
Gas Line
Shutoff
Valve
Gas Piping
From Meter
To Gas
Valve
TABLE 17:
Length of Standard Pipe Threads in Inches (mm)
PIPE SIZE
EFFECTIVE LENGTH
OF THREAD
OVERALL LENGTH
OF THREAD
3/8 (9.53) 3/8 (9.53) 9/16 (14.29)
1/2 (12.7) 1/2 (12.7) 3/4 (19.05)
3/4 (19.05) 1/2 - 9/16 (14.29) 13/16 (20.64)
1 (25.4) 9/16 (14.29) 1 (25.4)
FIGURE 41: Proper Piping Practice
If the gas input to the furnace is too great because of excessive
gas pressure, wrong size orifice, high altitude, etc., the burner
flame will be sooty and may produce carbon monoxide, which
could result in unsafe operation, explosion, and/or fire or
asphyxiation.
Leave 2 End
Threads Bare
2 Imprerfect
Threads