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441 01 2121 01
Return Air Connections
FIRE HAZARD
A failure to follow this warning could cause personal
injury, death and/or property damage.
Never connect return−air ducts to the back of the
furnace. Follow instructions below.
!
WARNING
Downflow Furnaces
The return−air duct must be connected to return−air opening
(bottom inlet) as shown in Figure 1. DO NOT cut into casing
sides (left or right). Side opening is permitted for only upflow
and certain horizontal furnaces. Bypass humidifier
connections should be made at ductwork or coil casing sides
exterior to furnace. (See Figure 19)
Upflow and Horizontal Furnaces
The return−air duct must be connected to bottom, sides (left
or right), or a combination of bottom and side(s) of main
furnace casing as shown in Figure 1. Bypass humidifier may
be attached into unused return air side of the furnace casing.
(See Figure 18 and Figure 20) Not all horizontal furnace
models are approved for side return air connections. (See
Figure 20)
GAS PIPING
FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
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.
!
WARNING
FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Use proper length of pipe to avoid stress on gas
control manifold and a gas leak.
!
WARNING
FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Gas valve inlet and/or inlet pipe must remain capped
until gas supply line is permanently installed to protect
the valve from moisture and debris. Also, install a
sediment trap in the gas supply piping at the inlet to
the gas valve.
!
WARNING
Gas piping must be installed in accordance with national and
local codes. Refer to current edition of NFGC in the U.S.
Installations must be made in accordance with all authorities
having jurisdiction. If possible, the gas supply line should be a
separate line running directly from meter to furnace.
NOTE: In the state of Massachusetts:
1. Gas supply connections MUST be performed by a li-
censed plumber or gas fitter.
2. When flexible connectors are used, the maximum
length shall not exceed 36 in. (915 mm).
3. When lever handle type manual equipment shutoff
valves are used, they shall be T−handle valves.
4. The use of copper tubing for gas piping is NOT ap-
proved by the state of Massachusetts.
Refer to Table 6 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. (1.8 M). Joint compound
(pipe dope) should be applied sparingly and only to male
threads of joints. Pipe dope must be resistant to the action of
propane gas.
Table 6 – Maximum Capacity of Pipe*
NOMINAL
IRON PIPE
SIZE
IN. (MM)
INTERNAL
DIA.
IN. (MM)
LENGTH OF PIPE - FT (M)
10
(3.0)
20
(6.0)
30
(9.1)
40
(12.1)
50
(15.2)
1/2 (12.7) 0.622(158) 175 120 97 82 73
3/4 (19.0) 0.824 (20.9) 360 250 200 170 151
1 ( 25.4) 1.049 (26.6) 680 465 375 320 285
1‐1/4
(31.8)
1.380 (35.0) 1400 950 770 660 580
1‐1/2
(38.1)
1.610 (40.9) 2100 1460 1180 990 900
* Cubic ft of gas per hr for gas pressures of 0.5 psig (14-In. W.C.) or less and
a pressure drop of 0.5-In. W.C. (based on a 0.60 specific gravity gas). Ref: Table 6
and 9.2 NFGC.
FIRE OR EXPLOSION HAZARD
A failure to follow this warning could result in personal
injury, death, and/or property damage.
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. Black iron pipe shall be installed at the
furnace gas control valve and extend a minimum of
2−in. (51 mm) outside the furnace.
!
WARNING
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in furnace
damage.
Connect gas pipe to furnace using a backup wrench
to avoid damaging gas controls and burner
misalignment.
CAUTION
!
An accessible manual equipment shutoff valve MUST be
installed external to furnace casing and within 6 ft. (1.8 M) of
furnace. A 1/8−in. (3 mm) NPT plugged tapping, accessible
for test gauge connection, MUST be installed immediately
upstream of gas supply connection to furnace and
downstream of manual equipment shutoff valve.
NOTE: The furnace gas control valve inlet pressure tap
connection is suitable to use as test gauge connection
providing test pressure DOES NOT exceed maximum 0.5
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