G.
Gas Piping
Gas piping must be installed in accordance with national and local codes. Refer to current edition of NFGC in the United States. Canadian
installations must be made in accordance with NSCNGPIC and all authorities having jurisdiction. Gas supply line should be a separate line running
directly from meter to furnace, if possible. Refer to Table 5 for recommended gas pipe sizing. Risers must be used to connect to furnace and to
meter. Support all gas piping with appropriate straps, hangers, etc. Use a minimum of 1 hanger every 6 ft. Joint compound (pipe dope) should be
applied sparingly and only to male threads of joints. Pipe dope must be resistant to propane gas.
WARNING: FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in fire, explosion, personal injury, or death.
-Connect gas pipe to furnace using a backup wrench to avoid damaging gas controls.
-Gas valve shutoff switch MUST be facing forward or tilted upward.
-Never purge a gas line into a combustion chamber. Never test for gas leaks with an open flame. Use a commercially available soap
solution made specifically for the detection of leaks to check all connections.
-Use proper length of pipe to avoid stress on gas control manifold.
-If a flexible connector is required or allowed by authority having jurisdiction, black iron pipe shall be installed at furnace gas valve and
extend a minimum of 2 in. outside furnace casing.
Install a sediment trap in riser leading to furnace. Trap can be installed by connecting a tee to riser leading to furnace so straight-through section
of tee is vertical. Then connect a capped nipple into lower end of tee. Capped nipple should extend below level of gas controls. Place a ground
joint union between gas control manifold and manual gas shutoff valve. (See Fig. 30.)
If local codes allow the use of a flexible gas appliance connector, always use a new listed connector. Do not use a connector which has previously
served another gas appliance.
WARNING: FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could result in serious injury, death or property damage.
Never test for gas leaks with an open flame. Use a commercially available soap solution made specifically for the detection of leaks
to check all connections. A fire or explosion could result causing property damage, personal injury or loss of life.
An accessible manual shutoff valve MUST be installed external to furnace casing and within 6 ft of furnace. A 1/8-in. NPT plugged tapping,
accessible for test gauge connection, MUST be installed immediately upstream of gas supply connection to furnace and downstream of manual
shutoff valve.
NOTE:
The gas valve inlet pressure tap connection is suitable to use as test gauge connection providing test pressure DOES NOT exceed
maximum 0.5 psig (14-in. wc) stated on gas valve. (See Fig. 48.)
Piping should be pressure and leak tested in accordance with NFGC in the United States or NSCNGPIC in Canada, local, and national plumbing
and gas codes before the furnace has been connected. After all connections have been made, purge lines and check for leakage at furnace prior
to operating furnace.
If pressure exceeds 0.5 psig (14-in. wc), gas supply pipe must be disconnected from furnace and capped before pressure test. If test pressure is
equal to or less than 0.5 psig (14-in. wc), turn off electric shutoff switch located on furnace gas valve and accessible manual shutoff valve before
test.
The gas supply pressure shall be within the maximum and minimum inlet supply pressures marked on the rating plate with the furnace burners
ON and OFF.
PROCEDURE 5—ELECTRICAL CONNECTIONS
See Fig. 31 for field wiring diagram showing typical field 115-v and 24-v wiring. Check all factory and field electrical connections for tightness.
Field-supplied wiring shall conform with the limitations of 63°F (35°C) rise.
WARNING: ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in serious injury or death.
Blower access panel door switch opens 115-v power to control center. No component operation can occur. Do not bypass or close
switch with panel removed.
CAUTION: FURNACE MAY NOT OPERATE
Failure to follow this caution may result in furnace operation stopping and water pipes freezing during cold weather.
Furnace control must be grounded for proper operation or control will lock out. Control is grounded through green/yellow wire routed
to gas valve and burner box screw.
Table 5—Maximum Capacity of Pipe*
NOMINAL IRON PIPE SIZE
(IN.)
INTERNAL DIAMETER
(IN.)
LENGTH OF PIPE (FT)
10
20
30
40
50
1/2
0.622
175
120
97
82
73
3/4
0.824
360
250
200
170
151
1
1.049
680
465
375
320
285
1-1/4
1.380
1400
950
770
660
580
1-1/2
1.610
2100
1460
1180
990
900
* Cubic ft of gas per hr for gas pressures of 0.5 psig (14-in. wc) or less, and a pressure drop of 0.5-in. wc (based on a 0.60 specific gravity gas).
Ref: Table 9.2 NFPA 54-2002
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