364861-UIM-B-0708

When a Category I furnace is removed or replaced, the original venting 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 12: Unconfined Space Minimum Area in Square Inch

BTUH Input Rating

Minimum Free Area in Square Feet

Required for Each Opening

 

 

 

40,000

40 (258 cm2)

60,000

60 (387 cm2)

80,000

80 (516 cm2)

100,000

100 (645 cm2)

120,000

120 (742 cm2)

130,000

130 (838 cm2)

Table 13: 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)

 

40,000

20 in2 (129 cm2)

10 in2 (64 cm2)

4” (10 cm)

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)

130,000

65 in2 (419 cm2)

33 in2 (213 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

Gable

Vent

 

Ventilated

Optional

Attic

Top Above

Inlet (a)

Insulation

 

Soffit

Outlet

Vent

Air (a)

 

Gas

 

Water

 

Heater

 

Ventilated

 

Crawl Space

Gas

VentGable

Vent

Ventilated

Attic

Top Above

Insulation

Soffit

Vent

Furnace

Gas

 

 

Water

Inlet

Heater

Air (b)

 

Gas Vent

Furnace

Gas

Vent

Outlet

Air (b)

Inlet

Inlet

Heater

Furnace

 

 

Gas

 

 

 

Water

 

Air (a)

Air (b)

 

 

 

 

 

Outlet Air (a)

Inlet

Air (a)

FIGURE 36: 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 appli- ance. Refer to “AIR SOURCE FROM OUTDOORS AND VENT AND SUPPLY AIR SAFETY CHECK” in these instructions for additional information 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 in (30.5 cm) above, and within 24 in (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 in (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.

Combustion Air Source from Outdoors

1.Two permanent openings, one within 12 in (30.5 mm) of the top and one within 12 in (30.5 mm) of bottom of the confined space, Two permanent openings, shall communicate directly or by means of ducts with the outdoors, crawl spaces or attic spaces.

2.One permanent openings, commencing within 12 in (30.5 mm) of the top of the enclosure shall be permitted where the equipment has clearances of at least 1 in (2.54 cm) from the sides and back and 6 in (15.24 cm) from the front of the appliance. The opening shall communicate directly with the outdoors and shall have a min- imum free area of:

a.1 square in per 3000 Btu per hour (6.45 cm3 per 0.879 kW) of the total input rating of all equipment located in the enclosure.

b.Not less than the sum of all vent connectors in the confined space.

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 blocking effects of louvers, grilles and screens must be given consideration in calculating free area. If the free area of a specific louver or grille is not known. Refer to Table 11, "Estimated Free Area".

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Johnson Controls Unitary Products

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Johnson Controls TG9S*MP, GG9S*MP installation manual Air Supply Openings and Ducts, Free Area

TG9S*MP, GG9S*MP specifications

Johnson Controls has long been at the forefront of building efficiency solutions, and their TG9S*MP and GG9S*MP series exemplify this commitment. These two-stage, multi-position gas furnaces are designed for optimal comfort and performance in residential applications, and they come packed with a variety of features that enhance their efficiency and operational capabilities.

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In conclusion, the Johnson Controls TG9S*MP and GG9S*MP furnaces provide homeowners with efficient, reliable, and comfortable heating solutions. With advanced features such as two-stage operation, impressive AFUE ratings, and modern technology integrations, these models stand out in the market as dependable options for both energy savings and year-round comfort. Whether you're a homeowner looking to upgrade your heating system or a contractor seeking high-quality products for your clients, these furnaces represent a smart choice.