UTICA BOILERS MGB 100, Installation, Operation & Maintanance Manual

6

VeNtilatioN aND coMBUstioN air

When directly communicating with the outdoors, each 

1. 

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

When communicating with the outdoors by means of 

2. 

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

(DUCT ENDS 1 FT. 
ABOVE THE FLOOR)

CHIMNEY OR 
TYPE B VENT 
PIPE

If horizontal ducts are used, each opening and duct shall 

3. 

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)

Figure #4

CHIMNEY OR 
TYPE B VENT 
PIPE

One permanent opening, commencing within 12 inches 

A. 

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.

In calculating free area using louvers, grilles or screens 

4. 

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.