VI Air for Ventilation

WARNING

OUTDOOR COMBUSTION AIR MUST BE PIPED TO THE AIR INTAKE. NEVER PIPE COMBUSTION AIR FROM AREAS CONTAINING CONTAMINATES SUCH AS SWIMMING POOLS AND LAUNDRY ROOM EXHAUST VENTS. CONTAMINATED COMBUSTION AIR WILL DAMAGE THE BOILER AND MAY CAUSE PROPERTY DAMAGE, PERSONAL INJURY OR LOSS OF LIFE.

Air for combustion must always be obtained directly from outdoors, however sufﬁcient air for ventilation must still be provided in the boiler room. Air for ventilation is required to keep various boiler components from overheating and is always obtained from indoors. To ensure an adequate ventilation air supply, perform the following steps:

Step 1: Determine whether the boiler is to be installed in a conﬁned space - A conﬁned space is deﬁned by the National Fuel Gas Code as having a volume less than 50 cubic feet per 1000 BTU/hr input of all appliances installed in that space. To determine whether the boiler room is a conﬁned space:

•Total the input of all appliances in the boiler room in thousands of BTU/hr. Round the result to the next highest 1000 BTU/hr.

•Find the volume of the room in cubic feet. The volume of the room in cubic feet is: Length (ft) x width (ft) x ceiling height (ft)

In calculating the volume of the boiler room, consider the volume of adjoining spaces only if no doors are installed between them. If doors are installed between the boiler room and an adjoining space, do not consider the volume of the adjoining space, even if the door is normally left open.

•Divide the volume of the boiler room by the input in thousands of BTU/hr. If the result is less than 50, the boiler room is a conﬁned space.

Example:

A FCM120 and a water heater are to be installed in a room measuring 6 ft – 3 in x 7 ft with an 8 ft ceiling. The water heater has an input of 30000 BTU/hr:

Total input in thousands of BTU/hr = (120000 BTU/hr + 30000 BTU/hr) / 1000 = 150 MBTU/hr Volume of room = 6.25 ft x 7 ft x 8 ft = 350 ft3

350/150 = 2.33. Since 2.33 is less than 50, the boiler room is a conﬁned space.

Step 2a: If the boiler is to be placed in a conﬁned space, provide two openings into the boiler room, one near the ﬂoor and one near the ceiling. The top edge of the upper opening must be within 12” of the ceiling and the bottom edge of the lower opening must be within 12” of the ﬂoor (Fig 6.1). The minimum opening dimension is 3 inches.

•If the FCM boiler is the only gas-burning appliance in the boiler room, these openings must each have a minimum free area of 100 square inches.

•If other gas-burning appliances are in the boiler room, size the openings in accordance with the appliance manufacturer’s instructions or the National Fuel Gas Code. Minimum opening free area is 100 square inches even if opening requirements for other appliances are less.

•If the total volume of both the boiler room and the room to which the openings connect is less than 50 cubic feet per 1000 BTU/hr of total appliance input, install a pair of identical openings into a third room. Connect additional rooms with openings until the total volume of all rooms is at least 50 cubic feet per 1000 BTU/hr of input.

•The “free area” of an opening takes into account the blocking effect of mesh, grills, and louvers. Where screens are used, they must be no ﬁner than ¼” (4 x 4) mesh.

Step 2b: If the boiler is to be placed in an unconﬁned space the natural inﬁltration into the boiler room will provide adequate air for ventilation without additional openings into boiler room.