Johnson Controls CM8M/CMLM*MP Bottom Return and Attic Installations, Horizontal Application

368261-UIM-A-0508

BOTTOM RETURN AND ATTIC INSTALLATIONS

Bottom return applications normally pull return air through a base plat- form or return air plenum. Be sure the return platform structure or return air plenum is suitable to support the weight of the furnace.

The internal bottom panel must be removed for this application.

Attic installations must meet all minimum clearances to combustibles and have floor support with required service accessibility.

HORIZONTAL APPLICATION

FIGURE 9: Horizontal Application

This furnace may be installed in a horizontal position on either side as shown above. It must not be installed on its back.

ATTIC INSTALLATION

When a furnace is installed in an attic or other insulated space, keep all insulating materials at least 12 inches (30.5 cm) away from furnace and burner combustion air openings.

SUSPENDED FURNACE / CRAWL SPACE INSTALLATION

The furnace can be hung from floor joists or installed on suitable blocks or pad. Blocks or pad installations shall provide adequate height to ensure the unit will not be subject to water damage. Units may also be suspended from rafters or floor joists using rods, pipe angle supports or straps. Angle supports should be placed at the supply air end and near the blower deck. Do not support at return air end of unit. All four sus- pension points must be level to ensure quite furnace operation. When suspending the furnace use a secure platform constructed of plywood or other building material secured to the floor joists. Refer to for typical crawl space installation.

Support

Angle IronBracket

Bracket

Line contact only permissible between lines formed by the intersection of furnace top and two sides and building joists, studs or framing

Filter rack
must be a minimum
distance	Gas Piping
of 18” (45.7 cm)
from the
furnace

Supply

Air

Vent (Maintain required clearances to combustibles)

Sheet metal in

front of furnace

combustion air

12”Openings is Recommended

12”

30” MIN. Work Area

6” Min. Between

Rod & Front of Furnace1” Max. Between

Rod & Back of Furnace

FIGURE 11: Typical Suspended Furnace / Crawl Space Installation

DOWNFLOW APPLICATION

To apply the furnace in a downflow position, it will be necessary to rotate the vent blower 90° left or right so that the vent pipe passes

Return

AirSediment

Trap

FIGURE 10: Typical Attic Installation

This appliance is certified for line contact when the furnace is installed in the horizontal left or right position. The line contact is only permissible between lines that are formed by the intersection of the top and two sides of the furnace and the building joists, studs or framing. This line may be in contact with combustible material. Refer to Figure 10, "Typi- cal Attic Installation".

through the side of the furnace casing rather than the end. See Figure 12, "Downflow Venting".

For modulating furnaces to be used in the downflow position, it is necessary to rotate the gas valve so that it is upright when the fur- nace is installed. Loosen the pipe union between the gas valve and manifold, rotate the valve as far upward as it will go, and tighten the union. See Figure 13, "Downflow Installation - Gas Valve Rotation".

Rotate vent blower 90° either way

For downflow installation,rotate

gas valve upwards, as shown

LEFT SIDE VENT RIGHT SIDE VENT

FIGURE 12: Downflow Venting

FIGURE 13: Downflow Installation - Gas Valve Rotation

Johnson Controls Unitary Products 7