22
rETurn air & DuCTinG inSTallaTiOn rEQuirEMEnTS
*1 - Special clearances for discharge grills. Refer to installation and instruction Manual.
*2 - Return air should be 142” if 4 ducts are used. May be reduced to 88” if 5 ducts are used.
*3 - Bottom duct required. SF42/42Q uses KiT# 520753, SH42 and SHD-2542 uses KiT# 520864.
*4 - For Vertical mount furnace, review the table below for ducting requirements. The duct requirements must be followed in order to assure proper operation of the furnace. The minimum open duct areas
listed below must be maintained through the entire duct system, including through register.
NOTE:
0” clearance is to spacer (flanges)
MODElS
Clr
FrOnT
Clr
TOp
Clr
bTM
Clr
baCK
Clr
lEFT
Clr
riGhT
DuCTS
rEQ’D
bTM DuCT
SQ inCh
TOp DuCT
SQ inCh
l & r SiDE DuCT
SQ inCh
rETurn air
SQ inCh
SFV 20/20F
1”
1”
0”
0”
1”
1”
SEE *4
52”
SEE *4
SEE *4
55”
SFV 25/25F
1”
1”
0”
0”
1”
1”
SEE *4
52”
SEE *4
SEE *4
55”
SFV 30/30F
1”
1”
0”
0”
1”
1”
SEE *4
52”
SEE *4
SEE *4
55”
SFV 35/35F
1”
1”
0”
0”
1”
1”
SEE *4
52”
SEE *4
SEE *4
55”
SFV 42/42F
1”
2”
0”
0”
1”
1”
SEE *4
52”
SEE *4
SEE *4
142”
MODElS
TOp anD FrOnT DuCTS
(4” round)
bOTTOM
lEFT DuCT
riGhT DuCT
Minimum Duct area
Minimum Duct area
Minimum Duct area
SFV 20/20F
*Optional
Required 52 SQ. IN.
*Optional
*Optional
SFV 25/25F
*Optional
Required 52 SQ. IN.
*Optional
*Optional
SFV 30/30F
*Optional
Required 52 SQ. IN.
*Optional
*Optional
SFV 35/35F
48 SQ. IN. (Bottom Front Duct
Not to be Used)
52 SQ. IN.
56 SQ. IN.
DO NOT USE
SFV 42/42F
48 SQ. IN. (Top Front Duct Not
to be Used)
52 SQ. IN.
56 SQ. IN.
72 SQ. IN.
*use of these ducts are in addition to the required use of the bottom duct
