Figure 2: Minimum Clearances
Volume [ft³](m3) = Length [ft](m) x Width [ft](m) x Height [ft](m)
b.Determine Total Input of all appliances in space. Round result to nearest 1,000 Btu per hour (Btuh).
c.Determine type of space. Divide Volume by Total Input.
i. If result is greater than or equal to 50 ft³ (1.4m3) per 1,000 Btuh, space is considered an unconfined space.
ii. If result is less than 50 ft³ (1.4m3) per 1,000 Btuh, space is considered a confined space.
d. Determine building type. A building of unusually tight construction has the following characteristics:
i. Walls and ceiling exposed to outside atmosphere have a continuous water vapor retarder with a rating of 1 perm or less with openings gasketed and sealed, and
ii.
iii. Caulking or sealants applied in joints around window and door frames, between sole plates and floors, between wall- ceiling joints, between wall panels, at plumbing and electrical penetrations, and at other openings.
e.For boiler located in a building of other than unusually tight construction, adequate combustion and ventilation air is normally provided by fresh air infiltration through cracks around windows and doors.
f.For boiler located in building of unusually tight construction, provide outdoor air through two permanent openings which communicate directly or by duct with the outdoors or spaces (crawl or attic) freely communicating with the outdoors. Locate one opening within 12 inches (30.5cm) of top of space. Locate remaining opening within 12 inches (30.5cm) of bottom of space. Minimum dimension of air opening is
3 inches (7.6cm). Size each opening per following:
i. Direct communication with outdoors. Minimum free area of 1 square inch (6.5cm2) per 4,000 Btu per hour input of all equipment in space.
ii. Vertical ducts. Minimum free area of 1 square inch (6.5cm2) per 4,000 Btu per hour input of all equipment in space. Duct
iii. Horizontal ducts. Minimum free area of 1 square inch (6.5cm2) per 2,000 Btu per hour input of all equipment in space. Duct
g.Ventilation Duct Louvers and Grilles. Equip outside openings with louvers to prevent entrance of rain and snow, and screens to prevent entrance of insects and rodents.
Louvers and grilles must be fixed in open position or interlocked with equipment to open automatically before burner operation. Screens must not be smaller than ¼ inch mesh.
Consider the blocking effect of louvers, grilles and screens when calculating the opening size to provide the required free area. If free area of louver or grille is not known, assume wood louvers have
8.Connect gas service from Meter to gas control assembly in accordance with Local Piping Codes and requirements of Gas Company, see Figure 1. They may require piping of larger size than Control Assembly
Connection, especially if run from meter is long or includes several elbows. (See Figure 1 for size of Gas
Connection to gas control assembly).