Internet Version for Reference Only
BRADFORD WHITE
Page 6
Copper Brute B4 Volume Water Heaters Page 7
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 conned 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
Conned and non-conned 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 ue products to build up in
the heater room. More air must be supplied to make up
for the decrease.
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.
Figure 14. Indoor installation and venting.
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 tting.
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
10 ft.
(3.0m)
2 ft. (0.6m)
Listed Vent
Cap
StormCollar
Roof Jack
Adequate
Air Supply
ToRoom
Topand
Botom
1/14 in. (6mm)
Minimum Pitch
Per Foot of
Horizontal Pipe
Drafthood
12 in.
(305mm)
All Sides
Ventterminated at
least 24 in.
(610mm) above
any object within
10 ft. (3.0m)