Johnson Controls TM9T*MP Combustion Air Source From Outdoors, Air Supply Openings and Ducts

505309-UIM-D-0511

This type of installation requires that the supply air to the appliance(s) be of a sufficient amount to support all of the appliance(s) in the area. Operation of a mechanical exhaust, such as an exhaust fan, kitchen ventilation system, clothes dryer or fireplace may create conditions requiring special attention to avoid unsatisfactory operation of gas appliances. A venting problem or a lack of supply air will result in a hazardous condition, which can cause the appliance to soot and gen- erate dangerous levels of CARBON MONOXIDE, which can lead to serious injury, property damage and / or death.

An unconfined space is not less than 50 cu.ft (1.42 m3) per 1,000 Btu/ hr (0.293 kW/h) input rating for all of the appliances installed in that area.

Rooms communicating directly with the space containing the appli- ances are considered part of the unconfined space, if doors are fur- nished with openings or louvers.

A confined space is an area with less than 50 cu.ft (1.42 m3) per 1,000 Btu/hr (0.293 kW/h) input rating for all of the appliances installed in that area. The following must be considered to obtain proper air for combus- tion and ventilation in confined spaces.

Combustion Air Source From Outdoors

The blocking effects of louvers, grilles and screens must be given con- sideration in calculating free area. If the free area of a specific louver or grille is not known, refer to Table 12, to estimate free area.

Table 12: Estimated Free Area

Wood or Metal	Wood 20-25%*
Louvers or Grilles	Metal 60-70% *
Screens+	1/4” (6.4 mm)
	mesh or larger 100%

* Do not use less than 1/4” (6.4 mm) mesh

+Free area of louvers and grille varies widely; the installer should follow louver or grille manufacturer’s instructions.

Dampers, Louvers and Grilles (Canada Only)

1.The free area of a supply air opening shall be calculated by sub- tracting the blockage area of all fixed louvers grilles or screens from the gross area of the opening.

2.Apertures in a fixed louver, a grille, or screen shall have no dimen- sion smaller than 1/4” (6.4 mm).

3.A manually operated damper or manually adjustable louvers are not permitted for use.

4.A automatically operated damper or automatically adjustable lou- vers shall be interlocked so that the main burner cannot operate unless either the damper or the louver is in the fully open position.

When a Category I furnace is removed or replaced, the original vent- ing system may no longer be correctly sized to properly vent the attached appliances.

An improperly sized vent system can cause CARBON MONOXIDE to spill into the living space causing personal injury, and or death.

Table 13: Unconfined Space Minimum Area

BTUH Input Rating				Minimum Free Area Required for Each Opening
60,000					60 in2 (387 cm2)
80,000					80 in2 (516 cm2)
100,000					100 in2 (645 cm2)
120,000					120 in2 (742 cm2)
Table 14: Free Area
			Minimum Free Area Required for Each Opening
BTUH Input			Horizontal Duct		Vertical Duct or	Round Duct
Rating					Opening to Outside
			(2,000 BTUH)			(4,000 BTUH)
					(4,000 BTUH)
60,000			30 in2 (193 cm2)		15 in2 (97 cm2)	5” (13 cm)
80,000			40 in2 (258 cm2)		20 in2 (129 cm2)	5” (13 cm)
100,000			50 in2 (322 cm2)		25 in2 (161 cm2)	6” (15 cm)
120,000			60 in2 (387 cm2)		30 in2 (193 cm2)	7” (18 cm)
EXAMPLE:		Determining Free Area.
Appliance			1 Appliance		2 Total Input
100,000	+		30,000 = (130,000 ÷ 4,000) = 32.5 Sq. In. Vertical
Appliance			1 Appliance		2 Total Input
100,000	+		30,000 = (130,000 ÷ 2,000) = 65 Sq. In. Horizontal

		Gas
Gable		Vent
Vent	Ventilated
Optional	Attic
	Top Above
Inlet (a)
	Insulation
Soffit	Outlet
Vent	Air (a)	rnaceuF
	Gas
	Water
	Heater
	Ventilated
	Crawl Space

		Gas
	Gable	Vent
	Vent
	Ventilated
	Attic
	Top Above
	Insulation
Soffit				Outlet
Vent
				Air (b)
	Heater	Furnace	Inlet	Inlet	Heater
	Gas				Gas
Inlet	Water				Water
Air (b)			Air (a)	Air (b)

Gas

Vent

	Outlet
	Air (a)
Furnace	Inlet
	Air (a)

FIGURE 38: Outside and Ambient Combustion Air

Air Supply Openings and Ducts

1.An opening may be used in lieu of a duct to provide to provide the outside air supply to an appliance unless otherwise permitted by the authority having jurisdiction. The opening shall be located within 12” (30.5 cm) horizontally from, the burner level of the appliance. Refer to “AIR SOURCE FROM OUTDOORS AND VENT AND SUPPLY AIR SAFETY CHECK” in these instructions for additional informa- tion and safety check procedure.

2.The duct shall be either metal, or a material meeting the class 1 requirements of CAN4-S110 Standard for Air Ducts.

3.The duct shall be least the same cross-sectional area as the free area of the air supply inlet opening to which it connects.

4.The duct shall terminate within 12” (30.5 cm) above, and within 24” (61 cm) horizontally from, the burner level of the appliance having the largest input.

5.A square or rectangular shaped duct shall only be used when the required free area of the supply opening is 9 in2 (58.06 cm2) or larger. When a square or rectangular duct is used, its small dimen- sion shall not be less than 3” (7.6 cm).

6.An air inlet supply from outdoors shall be equipped with a means to prevent the direct entry of rain and wind. Such means shall not reduce the required free area of the air supply opening.

7.An air supply inlet opening from the outdoors shall be located not less than 12” (30.5 cm) above the outside grade level.

Johnson Controls Unitary Products 27