13Table 4 – Opening Dimensions -- IN. (mm)FURNACECASINGWIDTHAPPLICATION PLENUM OPENING FLOOR OPENINGA B C D14–3/16(360)Upflow Applications on Combustible or Noncombustible Floor-ing (KGASB subbase not required)12--- 11/16(322)21--- 5/8(549)13--- 5/16(338)22--- 1/4(565)Downflow Applications on Noncombustible Flooring (KGASBsubbase not required)12--- 9/16(319)19(483)13--- 3/16(335)19--- 5/8(498)Downflow applications on combustible flooring (KGASB sub-base required)11--- 13/16(284)19(483)13--- 7/16(341)20--- 5/8(600)Downflow Applications on Combustible Flooring with CNPV,CNRV, CAR, or CAP Coil Assembly or KCAKC coil box(KGASB subbase not required)12--- 5/16(319)19(483)13--- 5/16(338)20(508)17–1/2(445)Upflow Applications on Combustible or Noncombustible Floor-ing (KGASB subbase not required)16(406)21--- 5/8(549)16--- 5/8(422)22--- 1/4(565)Downflow Applications on Noncombustible Flooring (KGASBsubbase not required)15--- 7/8(403)19(483)16--- 1/2(419)19--- 5/8(498)Downflow applications on combustible flooring (KGASB sub-base required)15--- 1/8(384)19(483)16--- 3/4(425)20--- 5/8(600)Downflow Applications on Combustible Flooring with CNPV,CNRV, CAR, or CAP Coil Assembly or KCAKC coil box(KGASB subbase not required)15--- 1/2(394)19(483)16--- 1/2(419)20(508)21(533)Upflow Applications on Combustible or Noncombustible Floor-ing (KGASB subbase not required)19--- 1/2(495)21--- 5/8(549)20--- 1/8(511)22--- 1/4(565)Downflow Applications on Noncombustible Flooring (KGASBsubbase not required)19--- 3/8(492)19(483)20(508)19--- 5/8(498)Downflow applications on combustible flooring (KGASB sub-base required)18--- 5/8(473)19(483)20--- 1/4(514)20--- 5/8(600)Downflow Applications on Combustible Flooring with CNPV,CNRV, CAR, or CAP Coil Assembly or KCAKC coil box(KGASB subbase not required)19(483)19(483)20(508)20(508)24--- 1/2(622)Upflow Applications on Combustible or Noncombustible Floor-ing (KGASB subbase not required)23(584)21--- 1/8(537)23--- 5/8(600)22--- 1/4(565)Downflow Applications on Noncombustible Flooring (KGASBsubbase not required)22--- 7/8(581)19(483)23--- 1/2(597)19--- 5/8(498)Downflow applications on Combustible flooring (KGASB sub-base required)22--- 1/8(562)19(483)23--- 3/4(603)20--- 5/8(600)Downflow Applications on Combustible Flooring with CNPV,CNRV, CAR, or CAP Coil Assembly or KCAKC coil box(KGASB subbase not required)22--- 1/2(572)19(483)23--- 1/2(597)20(508)HORIZONTAL INSTALLATIONFIRE, EXPLOSION, AND CARBON MONOXIDEPOISONING HAZARDFailure to follow this warning could result in personalinjury, death, and/or property damage.Do not install the furnace on its back or hang furnace withcontrol compartment facing downward. Safety controloperation will be adversely affected. Never connectreturn--air ducts to the back of the furnace.! WARNINGThe furnace can be installed horizontally in an attic or crawl spaceon either the left--hand (LH) or right--hand (RH) side. The furnacecan be hung from floor joists, rafters or trusses or installed on anon--combustible platform, blocks, bricks or pad.Suspended Furnace SupportThe furnace may be supported under each end with threaded rod,angle iron or metal plumber’s strap as shown. (See Fig. 15 and16.) Secure angle iron to bottom of furnace as shown.Heavy--gauge sheet metal straps (plumber’s straps) may be usedto suspend the furnace from each bottom corner. To preventscrews from pulling out, use 2 #8 x 3/4--in. screws into the sideand 2 #8 x 3/4--in. screws in the bottom of the furnace casing foreach strap. (See Fig. 15 and 16.) If the screws are attached toONLY the furnace sides and not the bottom, the straps must bevertical against the furnace sides and not pull away from thefurnace sides, so that the strap attachment screws are not intension (are loaded in shear) for reliable support.Platform Furnace SupportConstruct working platform at location where all required furnaceclearances are met. (See Fig. 2 and 17.) For furnaces with 1--in.clearance requirement on side, set furnace on noncombustibleblocks, bricks or angle iron. For crawl space installations, if thefurnace is not suspended from the floor joists, the groundunderneath furnace must be level and the furnace set on blocks orbricks.Roll--Out ProtectionProvide a minimum 17--3/4 in. X 22 in. piece of sheet metal forflame roll--out protection in front of burner area for furnacescloser than 12--in. (305 mm) above the combustible deck orsuspended furnaces closer than 12--in. (305 mm) to joists. Thesheet metal MUST extend underneath the furnace casing by 1--in.(25 mm) with the door removed.The bottom closure panel on furnaces of widths 17--1/2 in. (445mm) and larger may be used for flame roll--out protection whenbottom of furnace is used for return air connection. See Fig. 17for proper orientation of roll--out shield.Bottom Return Air InletThese furnaces are shipped with bottom closure panel installed inbottom return--air opening. Remove and discard this panel whenbottom return air is used. To remove bottom closure panel,perform the following:1. Tilt or raise furnace and remove two screws holding bot-tom filler panel. (See Fig. 9.)2. Rotate bottom filler panel downward to release holdingtabs.58DL