Bryan Boilers Forced Draft Steam Boilers - Manual (Page 6)

1.6 ELECTRICAL CONNECTION
IMPORTANT: All electrical connections must
conform to the National Electrical Code and to all
other applicable State and Local Codes. Forced
draft boilers may require a high voltage
connection. See boiler wiring diagram and
equipment list for
details.
Equipment Grounding - The boiler must be
grounded in accordance with the American
National Standard Electrical Code, ANSI/NFPA
#70-1981.
1.7 COMBUSTION AIR SUPPLY
IMPORTANT: Positive means for supplying an
ample amount of outside air, allowing complete
combustion of the gas, must be provided.
Movable combustion air dampers, automatic or
manually adjustable, must be electrically
interlocked with the boiler to prevent boiler
operation if the dampers are closed.
Combustion air openings must never be blocked
or obstructed in any manner.
The boiler room must be at a positive or neutral
pressure relative to the outdoors. A negative in
the boiler room will result in downdraft problems
and incomplete combustion due to lack of air.
WARNING!
Failure to provide an adequate air supply will
result in boiler damage and hazardous conditions
in the building (fire and asphyxiation hazard as
well as equipment damage).
COMBUSTION AIR: Complete combustion of
natural or propane gas requires approximately
ten cubic foot of air (at sea level and 70 F) for
each 1000 Btu of boiler input. In reality, additional
air is required to achieve complete combustion.
Air is also required for the proper operation of the
appliance draft diverter or barometric damper.
The combustion air opening recommendations
below are designed to provide the air needed for
atmospheric gas fired boilers which are equipped
with either draft diverters or barometric dampers.
Combustion air openings for boilers which are
equipped with forced draft burners may be
reduced to 70% of that required for atmospheric
gas fired boilers. This is because the forced draft
boiler is not equipped with a draft control device
(so no air is required for draft control).
COMBUSTION AIR OPENINGS - AREA
REQUIRED:
Openings directly through outside wall -
One opening within 12 inches of the ceiling plus
one opening within 12 inches of the floor. Each
opening must have a minimum free area of 1
square inch per 4,000 Btu of total input of all air
using appliances in the room.
Example: A boiler room having two boilers with
500,000 Btu input would require two openings
through an outside wall, and each opening must
have at least 250 square inches of free area.
Openings through vertical ducts -
One duct in the ceiling plus one duct terminating
within 12 inches of the floor. Each opening must
have a minimum free area of 1 square inch per
4,000 Btu of total input of all air-using appliances
in the room.
Example: A boiler room having four boilers with
250,000 Btu input would require two ducts, one in
the ceiling and one terminating near the floor,
each opening having at least 250 square inches
of free area.
Openings through horizontal ducts -
One duct opening within 12 inches of the ceiling
plus one duct opening within 12 inches of the
floor. Each opening must have a minimum free
area of 1 square inch of per 2,000 Btu of total
input for all equipment in the room. NOTE: No
rectangular duct may have a dimension of less
than 4 inches.
Example: A boiler room having 1 million Btu total
input would require two ducts, one in the ceiling
and one near the floor, each opening must having
at least 500 square inches of free area.