17
441 01 2101 05
Specifications are subject to change without notice.
Figure 20
−
Horizontal Return Air Configurations and Restrictions
5
TONS
AND
GREATER
*
*
2000
CFM
AND
GREATER
AT
.6
ESP
HI
COOLING
SPEED
Gas piping must be installed in accordance with national and
local codes. Refer to current edition of NFGC in the U.S.
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 natural 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 NFPA54/ANSI Z223.1
−
2012.
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
licensed plumber or gas fitter.
2. When flexible connectors are used, the maximum
length shall not exceed 36 inches (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
approved 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.
FIRE OR EXPLOSION HAZARD
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. 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
psig (14
−
In. W.C.) stated on gas control valve. (See
Figure 48) Some installations require gas entry on right side
