General Provisions

(1) Before arranging for the selection or installation of large gas equipment, the licensed plumber or gas fitter shall check with the serving gas supplier as to the availability of gas, specifying the gas input rating and the gas pressure required at the entrance to gas train. (See 248 CMR 7.03: Figure 3). (2) Combustion Air Supply and Ventilation. (a) General. 1. Figure 3 in Positive means for supplying an ample amount of outside air to permit combustion of the gas shall be provided. Automatic or manually adjustable control devices for outside air intake shall be interlocked with the burner. 2. To determine air requirements at the equipment, under standard atmospheric conditions (60EF and 30 inches mercury), the following minimum factors apply: a. For equipment with draft hoods - 30 cubic feet per 1000 Btu input; b. or equipment directly connected to a chimney without neutralizing air openings - 12 cubic feet per 1000 Btu input. 3. When equipment is located in an inside room or space, air supply shall be provided through ducts or openings leading to the outside air. 4. Openings to the outside shall be unobstructed and screens, if used, shall have a minimum of ½ inch mesh. 5. When a room or space in which equipment is installed is ventilated by mechanical means, air sufficient to replace that exhausted and consumed by combustion shall be supplied from a safe, uncontaminated source. The means for ventilation shall not create an unsafe pressure condition in the boiler room. 6. In addition to the combustion air required, sufficient air shall be supplied to the room to make the room safe for occupancy and proper operation of equipment. (b) Equipment Equipped with Draft Hoods. 1. The effective cross-sectional area of the permanent outside air opening(s) to the room where equipment is located shall be large enough to supply the air required in that room. 2. For supplying combustion air, the area of the opening shall be of a size at least equal to the equipment breeching but not less than one square inch of free area per 5,000 Btu per hour input (approximately equal to 1.4 square feet per million Btu), except as noted in 248 CMR 7.02(2)(e). (c) Equipment Utilizing Barometric Dampers. 1. The effective cross-sectional area of the permanent outside air opening(s) to the room where the equipment is located shall be large enough to supply the air required in that room. 2. For supplying air, the area of the opening shall be of a size at least equal to the equipment breeching but not less than one square inch of free area per 14,000 Btu per hour input (approximately equal to 0.5 square foot per million Btu), except as noted in 248 CMR 7.02(2)(e). (d) Equipment Directly Connected to Chimney without Neutralizing Air Openings. 1. The effective cross-sectional area of the permanent outside air opening(s) to the room where the equipment is located shall be large enough to supply the air required in that room. 2. For supplying air, the area of the opening shall be of a size at least equal to the equipment breeching but not less than one square inch of free area per 17,500 Btu per hour input (approximately equal to 0.4 square foot per million Btu), except as noted in 248 CMR 7.02(2)(e). (e) Exceptions. 1. Ducts to a Room where Equipment is Located: In determining the cross-sectional area of duct(s) used to convey air from the outdoors to the boiler room, the resistance to air flow imposed by the duct(s) shall be considered. 2. Forced Air Supply to a Room where Equipment is Located: If mechanical means for room air supply are used, the size of the duct or opening may be reduced to not less than that needed to provide the required quantity of air. (3) Accessibility for Cleaning and Inspection. Sufficient and reasonable accessibility shall be offered for Inspection, cleaning, repair and replacement of all burners, combustion controls, safety devices and boiler components. (4) Venting of Flue Gases. (a) Chimneys. 1. All equipment shall be securely connected to a chimney in good condition and of proper construction and ample size to carry away the flue gases and permit satisfactory burner operation under all weather and operating conditions. 2. The chimney shall be designed and built to sufficiently remove the maximum volume of flue gases which may be produced by the equipment connected to it, as well as any other combustion equipment, under the least conditions of draft which can be encountered. The design should also provide proper construction to resist wind forces, weathering, interior corrosion and flue gas temperatures. 3. The chimney shall be pre-inspected and, if necessary, tested to determine whether it is in suitable condition to handle the flue gases to be dispersed. Any defects shall be corrected. 4. An existing chimney shall be checked as to cross-sectional area, arrangement, and height to determine if it will sufficiently remove the volume of flue gases produced by the equipment, under the least condition of draft that may be encountered. This shall include consideration of pressure and temperature conditions at which the flue gases enter the chimney and the effect of flue gases which may be fed into the chimney from other combustion equipment. (b) Chimney Connectors. 1. Connectors from equipment to a chimney shall be of noncombustible material capable of withstanding the corrosion effects and temperatures of the flue gases to be handled. They shall have sufficient strength to withstand the physical stresses likely to occur under the conditions of use and shall be securely supported. 2. The connector shall be installed so as to avoid excessive turns or other construction features which create unnecessary resistance to flow of flue gases. 3. The joint between the connector and the chimney shall be sealed to prevent gas leakage or air infiltration. 4. A connector shall not extend into a chimney beyond the inner wall of the chimney flue. 5. The connector shall be sized as recommended by the equipment or burner manufacturer. If the manufacturer's recommendations are not available, the connector shall be the size of the flue collar, or if a draft hood is used, shall be the size of the outlet of the draft hood unless the connector is designed and installed in accordance with industry recognized and approved engineering methods. 6. On multiple installations, separate connectors should be run to the chimney. When this is not practical, each connector shall be y-connected to a common breeching, the cross-sectional area of which shall be not less than the combined areas of the individual connectors. (c) Draft Control. 1. Equipment requiring controlled chimney draft shall be capable of automatically regulating the draft as recommended by the equipment manufacturer. Such controls may be of the barometric type which regulates the draft in the breeching or the mechanically operated damper type which controls the pressure in the equipment firebox or the draft hood type which is nonadjustable. 2. A double-acting barometric draft regulator, if used, shall be equipped with a device with a manual reset which will automatically shut off the fuel to the burner in the event flue gas spillage exceeds 60 seconds. 3. Mechanically operated dampers shall be designed to maintain a safe damper opening at all times and be arranged to prevent firing of the burner unless the damper is in the proper position. 4. Draft Control: a. When a draft control device is used, it shall be installed without alteration in accordance with the manufacturer's instructions. b. In no case shall a barometric draft control device be installed in a false ceiling, in a different room or in any place or manner that will permit a difference in pressure between a draft relief opening and the combustion air supply. c. A draft control device shall be installed in the position for which it was designed with reference to the horizontal and vertical planes and shall be located so that a relief opening is not obstructed. d. When induced or forced draft devices are used, provision shall be made to prevent flow of gas to the burners upon failure of these devices. 5. Adjustable manual dampers should be removed except when a damper must be used to control excess chimney draft. Positive means shall then be provided to lock the damper in the proper position by welding or riveting. As an alternate, a portion of the damper can be removed to prevent full closure. 6. Full closing outlet isolation dampers shall be interlocked so that the boiler firing system cannot be operated unless its isolation damper is in the proper open position. 7. Adjustable (modulating) dampers, shall be arranged to maintain a safe fuel-air ratio over the full operating range. Linkage shall be arranged to resist accidental damage and disengagement. Any counter-balancing arms or weights attached to the damper shall be located or shielded as to prevent personal injury or damage to equipment in case of breakage. 8. When a draft hood is used, it shall be installed without alteration in accordance with the manufacturer's instructions. In no case shall a draft hood be installed in a false ceiling, in a different room, or in a manner that will permit a difference in pressure between the draft hood relief opening and the combustion air supply.