Do not block
Step 2—General
This furnace should be installed in a location in which facilities for ventilation permit satisfactory combustion of oil, proper venting, and maintenance of ambient temperature at safe limits under normal conditions of use. The location should not interfere with proper circulation of air within the confined space. (See
In addition to air needed for combustion, process air shall be provided as required for: cooling of equipment or material, controlling dew point, heating, drying, oxidation or dilution, safety exhaust, and odor control.
In addition to air needed for combustion, air shall be supplied for ventilation, including all air required for comfort and proper working conditions for personnel.
The barometric draft regulator (included with furnace) shall be installed in same room or enclosure as furnace in such a manner as to prevent any difference in pressure between regulator and
Air requirements for operation of exhaust fans, kitchen ventilation systems, clothes dryers, and fireplaces shall be considered in determining the adequacy of a space to provide
The lack of a proper amount of combustion air can lead to serious furnace operational problems. Some of these problems are:
1.Excessive oil burner
2.Sooting.
3.Melted oil burner ignitor/relay control.
4.Air band or air turbulator settings more open than normal.
5.Lockouts on
The requirements for combustion and ventilation air depend upon whether furnace is located in a CONFINED or UNCONFINED space.
Step 3—Unconfined Space
An unconfined space must have at least 50 cu ft for each 1000 Btuh of total input for all the appliances (such as furnaces, clothes dryers, water heaters, etc.) in the space.
In unconfined spaces in buildings of conventional frame, brick, or stone construction, infiltration MAY be adequate to provide air for combustion, ventilation, and dilution of flue gases. This determi- nation must be made on an individual installation basis and must take into consideration the overall volume of unconfined space, the number of windows and ventilation openings, the number of doors to the outside, internal doors which can close off unconfined space, and overall tightness of building construction. Consideration must also be given to the amount of storage items (furniture, boxes, etc.) within the unconfined space which take away from the air volume. (See Table 2.)
Many new buildings and homes (and older ones that have been weatherized) MUST BE considered as being of tight construction, therefore, infiltration will not be sufficient to supply necessary air for combustion and ventilation.
Table 2—Minimum Floor Area
For Unconfined Space
58CMA FURNACE | MINIMUM SQ FT WITH |
INPUT BTUH | |
70,000 | 467 |
91,000 | 607 |
105,000 | 700 |
119,000 | 793 |
140,000 | 933 |
154,000 | 1026 |
A building can be considered as being of tight construction when:
•Walls and ceilings exposed to outside atmosphere have a continuous water vapor retarder with a rating of 1 perm or less with openings gasketed or sealed, and/or
•Weatherstripping has been added on operable windows and doors and/or
•Caulking or sealants are applied to areas such as joints around window and door frames, between sole plates and floors, between
If combustion and ventilation air must be supplied to an uncon- fined space from outside, an opening with a FREE AREA of not less than 1 sq in. per 1000 Btuh of total input of all appliances within unconfined space (but not less than 100 sq in.) must be provided. This opening must be located such that it can not be blocked at any time.
Step 4—Confined Space
A confined space has a volume of less than 50 cu ft per 1000 Btuh of the total input rating for all appliances installed in that space.
When furnace is installed in a closet or enclosure, 2 ventilation openings, with OPEN AREA as dimensioned in example below are required for combustion air. The openings should be located about 6 in. from top and bottom of enclosure at front of furnace. (See Table 3.)
Table 3—Combustion Air
From Confined Space
58CMA FURNACE | LENGTH | HEIGHT |
INPUT BTUH | (IN.) | (IN.) |
16 | 8 | |
119,000 | 20 | 10 |
|
|
|
NOTE: In calculating free area, consideration shall be given to blocking effect of louvers, grilles, or screens protecting openings. Screens used shall not be smaller than
The size of the openings depends upon whether the air comes from outside of the structure or an unconfined space inside the structure.
ALL AIR FROM INSIDE THE STRUCTURE
For a confined space, where air is taken from an interior space, 2 permanent openings of equal area are required. One opening must be within 12 in. of ceiling and the other within 12 in. of floor. Each
4
