5165699-BIM-C-0516
Johnson Controls Unitary Products
3
SECTION III: UNIT INSTALLATION
LOCATION
Access for servicing is an important factor in the location of any furnace.
Provide a minimum of 24” (61 cm) in front of the furnace for access to
the heating elements and controls. This access may be provided by a
closet door or by locating the furnace 24” (61 cm) from a facing wall or
partition.
FURNACE CLEARANCE
Electric furnace is approved for zero (0) in. clearance to combustible
material on all or any part of the furnace exterior and the inlet or outlet
duct work. For furnaces installed in upflow application, there must be
1” (2.54 cm) clearance from the outlet duct work for a distance of 3 feet
(91.4 cm) from the supply air opening.
RETURN AIR
In order for the furnace to work properly, a closet or alcove must have a
certain total free area opening for return air.
For Heating Only Furnace
Minimum 200 sq. in (1290 sq. cm) free area opening. Use any return
Grille with minimum 200 sq. in free opening.
For up to 4 Ton AC and 3.5 Ton HP Applications (Standard
Blower)
Minimum 250 sq. in (1613 sq. cm) free area opening. The standard
blower assembly supplied with the furnace is capable of handling up 4
Ton AC and 3.5 Ton HP applications. Use any return grille with mini-
mum 250 sq. in (1613 sq. cm) free area opening.
For 5 Ton AC and 4 Ton HP Applications (Accessory
Blower)
Minimum 350 sq. in (2129 sq. cm) free area opening. Use 5 Ton AC/4
Ton HP blower accessory 3500-7901/A. Use accessory louvered door
3501-9311 or any return grille with a minimum 350 sq. in (2129 sq. cm)
free area opening.
The return air opening can be located in a closet front door or a sidewall
above the furnace casing, or in a louvered door on the furnace. If open-
ing for the return air is located in the floor, side walls or closet door any-
where below furnace casing height, 6” (15.2 cm) minimum clearance
must be provided on the furnace side where return is located to provide
for proper air flow. See Figure 2. The 6” (15.2 cm) minimum clearance
is not required if there is a return grille installed above the furnace
height. This return grille cannot start more than three feet above the fur-
nace height.
For Upflow installations, a closet 32” (81.3 cm) wide by 30” (76.2 cm)
deep with a 30” (76.2 cm) wide door is necessary. See Figure 3.
When installing furnace in a separate closet or room which is accessi-
ble only through an outside door, a minimum of 200 in
2
(1290 cm
2
) free
opening for return air must be provided. The supply and return air must
be ducted, securely attached and be sealed to the furnace casing if
there are grilles in the outside door to the closet. Openings where ducts
pass through walls, the floor or the ceiling must be sealed to prevent air
leakage into or from closet and the living area.
Provisions shall be made to permit the return of circulating air from all
rooms and living spaces, except the bathroom(s) to the circulating air
supply inlet of the furnace. Failure to comply may cause improper heat-
ing and may cause the furnace to cycle on the limit.
DUCT SYSTEM DESIGN
Electric furnace is designed to operate at a given static pressure.
In order to assure proper air flow through the furnace, the distribution
system must be designed so that the static pressure external to the fur-
nace does not exceed the static pressure rating shown on the furnace
rating plate.
The number, size and placement of registers should be such that even
distribution of heat is provided throughout the home.
SECTION IV: DOWNFLOW FURNACE
INSTALLATION
7900 SERIES DUCT CONNECTOR
We have designed our duct connector to eliminate a sub-base require-
ment. Table 1 will help you in deciding the part number of the duct con-
nector you need.
Provide adequate clearance for servicing.
1.
Locate furnace conveniently away from wall facing or partitions to
permit easy removal of components.
2.
A six (6) inch space minimum should be maintained between the
furnace and closet door when door is used for return air.
3.
Two (2) feet of space must be available in front of furnace for
future servicing (blower, element or furnace removal, etc.).
FIGURE 2:
Upflow Closet Clearances
30”
32”
30”
Wide Door
Closet
25-1/2””
Return Air
Pass Through
Frame Width
1-5/8” Min., 2-3/8 Max.
