UTICA BOILERS MGB50 Installation, Operation & Maintanance Manual page 6

National Excelsior Company
www.excelsiorhvac.com
1. When directly communicating with the outdoors, each
opening shall have a minimum free area of 1 square inch
per 4,000 Btu per hour of total input rating of all equip-
ment in the enclosure. (Figure #2)
Figure #2
CHIMNEY OR
TYPE B VENT
PIPE
2. When communicating with the outdoors by means of
vertical ducts, each opening shall have a minimum free
area of 1 square inch per 4,000 Btu per hour of total input
rating of all appliances in the enclosed space. (Figure #3)
Figure #3
CHIMNEY OR
TYPE B VENT
PIPE
VENTILATION AND COMBUSTION AIR
(DUCT ENDS 1 FT.
ABOVE THE FLOOR)
Subject to change without notice.
3. If horizontal ducts are used, each opening and duct shall
have a minimum free area 1 square inch per 2,000 Btu
per hour of total input rating of all appliances in the en-
closed space. (Figure #4)
CHIMNEY OR
TYPE B VENT
PIPE
A. One permanent opening, commencing within 12 inches
of the top of the enclosure, shall be permitted where the
equipment has clearances of at least 1 inch from the
sides, 1 inch from the back, and 6 inches from the front
of the boiler. The opening shall directly communicate
with the outdoors or shall communicate through a verti-
cal or horizontal duct to the outdoors or spaces (crawl
or attic) that freely communicate with the outdoors. The
openings must have a minimum free area of 1 square
inch per 3000 Btu per hour of the total input rating of all
equipment located in the enclosure. The free area must
be no less than the sum of the areas of all vent connec-
tors in the confined space.
4. In calculating free area using louvers, grilles or screens
for the above, consideration shall be given to their block-
ing effect. Screens used shall not be smaller than 1/4 inch
mesh. If the free area through a design of louver or grill is
known, it should be used in calculating the size opening
required to provide the free area specified. If the design
and free area is not known, it may be assumed that wood
louvers will have 20-25% free area and metal louvers and
grilles will have 60-75% free area. Louvers and grilles
should be fixed in the open position or interlocked with the
boiler so they are opened automatically during the boiler
operation.
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Figure #4