Bradford-White Corp B4 Method, Outdoor Air Supply, Indoor Air Supply, Exhaust Fans or Vents

Internet Version for Reference Only

Copper Brute B4 Volume Water Heaters Page 7

	Required Net Free Opening Area
		Directly from Outside
		At Top	At Bottom
Mode	in.2	cm2	in.2	cm2
175	44	284	44	284
250	63	406	63	406
325	82	529	82	529
400	100	645	100	645

Note: For screens or louvers, add 50%.

Table 2. Air Openings to Outside.

Vent terminated at			10 ft.
least 24 in.						Listed Vent
			(3.0m)
(610mm) above							Cap
any object within
10 ft. (3.0m)			2 ft. (0.6m)			Storm Collar
	1/14 in. (6mm)						Roof Jack
	Minimum Pitch
	Per Foot of
	Horizontal Pipe
		Drafthood					Adequate
							Air Supply
							To Room
					12 in.		Top and
							Botom
				(305mm)

All Sides

Notes:

1. The drafthood must sit directly on top of the heater as shown and must not be altered in any manner.

2. An Underwriters' Laboratories listed vent cap is re- quired to eliminate downdraft and allow the heater to function properly.

3. Use approved roof fitting.

Figure 14. Indoor installation and venting.

In the United States, the most common requirements specify that the space shall communicate with the outdoors in accordance with method 1 or 2, which follow. Where ducts are used, they shall be of the same cross-sectional area as the free area of the openings to which they connect.

Method 1:

Two permanent openings, one commencing within 12" (30 cm) of the top and one commencing within 12" (30 cm) of the bottom of the enclosure shall be provided. The openings shall communicate

directly, or by ducts, with the outdoors or spaces that freely communicate with the outdoors. When directly communicating with the outdoors directly, or through vertical ducts, each opening shall have a minimum free area of 1 square inch per 4000 Btu/hr (550 square mm/kW) of total input rating of all equipment in the enclosure. When communicating to the outdoors through horizontal ducts, each opening shall have a minimum free area of not less than 1 square inch per 2000 Btu/hr (1100 square mm/kW) of total input rating of all equipment in the enclosure.

Method 2:

One permanent opening, commencing within 12" (30 cm) of the top of the enclosure shall be permitted. The opening shall directly communicate with the outdoors or shall communicate through a vertical or horizontal duct to the outdoors or spaces that directly communicate with the outdoors, and shall have a minimum free area of 1 square inch per 3000 Btu/hr (734 square mm/kW) of the total input rating of all equipment located in the enclosure. This opening must not be less than the sum of the areas of all vent connectors in the confined space.

Other methods of introducing combustion and ventilation air are acceptable, providing they conform to the requirements in ANSI Z223.1, or applicable codes.

In Canada, Table 2 does not apply. Consult local building and safety codes or, in absence of such requirements, follow CAN/CGA B149.

NOTE: Check with louver manufacturers for net free area of louvers. If screens or louvers are installed, add 50 percent for each screen/louver to the net free area Check all local codes applicable to combustion air.

2.4.1 Outdoor Air Supply

When combustion air comes directly through an outside wall, each opening must have a minimum free area of at least one square inch for each 4,000 BTU/h input of the total input rating of all appliances in the enclosed area. (In Canada, refer to CGAB149.1 and .2.)

2.4.2 Indoor Air Supply

Confined and non-confined areas have different requirements for installation. Consult the latest edition of the National Gas Code for installation requirements.

2.4.3 Exhaust Fans or Vents

Any equipment which uses air or removes air from the heater room can use up the combustion air supply or reverse the natural draft action of the venting system. This could cause flue products to build up in the heater room. More air must be supplied to make up for the decrease.