19
accessories. All accessories MUST be connected to duct external
to furnace casing.
FIREHAZARD
Afailure to follow thiswarning could result in personal
injury,or deathand/or property damage.
Never connect return--air ducts to the back of the
furnace. Follow instructions below.
!WARNING
Return Air Connections
DownflowFu rnaces
The return--air duct must be connected to return--airopening
(bottominlet) as shownin Fig. 19. DO NOT cut intocasing sides
(leftor righ t).S ide opening is permitted for only upflow and mo st
horizontal furnaces. (See Fig. 19.) By pass humidifier connections
should be made at ductwork or coil casing sides exteriorto
furnace.
Upflowand Horizontal Furnaces
The return--air duct must be connected to bottom, sides(left or
right), or a combinationof bottom and side(s) of main furnace
casing asshown in Fig. 18 and 20. Bypass humidifier maybe
attachedinto unused return air side of thefurnace casing. (See
Fig.18 and 20.)
Not all horizontal furnaces are approved for side return air
connections.(See Fig. 20.)
GASPIPING
FIREOR EXPLOSION HAZARD
Failure to follow this warning could result in personal
injury,death,and/or property damage.
Never purgea gas line into a combustion chamber. Never
test for gas leaks with an open flame. Use acomm ercially
available soap solution made sp ecifically for the detection
ofleak sto ch eck allco nnections.
!WARNING
FIREOR EXPLOSION HAZARD
Failure to follow this warning could result in personal
injury,death,and/or property damage.
Use proper lengthof pipe to avoid stress on gas control
manifold and a gas leak.
!WARNING
Gas piping must be installed in accordance with national and
local codes. Refer to current edition of NF GC.
Installations must be made in accordance with all auth orities
having jurisdiction.If possible, the gas supply line should be a
separateline runningdirectly from meterto furnace.
NOTE: In the state of Massachusetts:
1. Gas supply connections MUST be performed by a li-
censed plumber or gas fitter.
2. When flexibleconnectors are used, the maximum length
shall not exceed 36 inches (915 mm).
3. When lever handle type manualequipment shutoff valves
areused, they shall be T--handlevalves.
4. The use of copper tubing forgas piping is NOT approved
by the state of Massachusetts.
Referto Table6 for recommended gaspipe sizing. Risersmust be
used to connectto furnace and to meter.Support all gas piping
withappropriate straps,hangers, etc. Use a minimum of 1 hanger
every6 ft. (1.8 M) Jointcompound (pipe dope) should be applied
sparinglyand only to male threads of joints.Pipe dope must be
resistantto the actionof propane gas.
Table6—Maximum Capacityof Pipe
NOMINAL
IRONPIPE
SIZE
IN.(MM)
INTERNAL
DIA.
IN.(MM)
LENGTHOF 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 pressuresof 0.5 psig (14---In.W.C.)
orle ss and a pressure drop of 0.5---In.W.C. (based on a0.60 spe cific
gravitygas). Ref: Table 6 and ANSI Z223---2009/NFPA54 ---2009.
FIREOR EXPLOSION HAZARD
Failure to follow this warning could result in personal
injury,death,and/or property damage.
If local codes allow the useof a flexible gas appliance
connector,always use a new listedconnector. Do not use a
connector which has previously served another gas
appliance.Black iron pipe shall be installedat the furnace
gascontrol valve and extend a minimum of 2 in. (51mm)
outside the furnace.
!WARNING
FURNACEOVERHEAT HAZARD
Failureto follow this cautionmay result in unit component
damage.
Connect gas pipe to gasvalve using a backup wrench to
avoiddamaging gas controlsand burner misalignment.
CAUTION
!
An accessible manual equipment shut off 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
testgauge connection, MUST be installed immediatelyupstream
of gassupply connection to furnace and downstreamof manual
equipmentshutoff valve.
NOTE: The furnace gas valve inlet pressuretap connection is
suitableto use as test gauge connection providing testpressure
DOES NOT exceed maximum 0.5 psig (14 --In.W.C.) stated on
gascontrol valve. (See Fig.42.)
Some installationsrequire gas entry on right side of furnace(as
viewedin upflow.) (SeeFig. 21.)
Install ased iment trap in riser leading to furnace as shown in Fig.
22.Connect a capped nippleinto lower end of tee.Capped nipple
shouldextend below level of furnacegas controls. Place a ground
joint union between furnace gas control valve and exterior
manual equipment gas shutoffvalve. A 1/8--in. (3 mm) NPT
pluggedtapping, accessible fo r test gauge connection, MUST be
installed immediately upstream of gas supply connection to
furnaceand downstream of manualequipment shutoff valve.
310AAV