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SECTION C: Installation
11
b. Where communicating with the outdoors
through horizontal ducts, each opening shall
have a minimum free area of 1 in.
2
per 2,000
BTUH (1,100 mm
2
per kW) of total input rat-
ing of all equipment in the enclosure.
2. One permanent opening, commencing within 12
in. (305 mm) of the top of the enclosure, shall be
permitted where the equipment has clearances of at
least 1 in. (25 mm) from the sides and back and 6
in. (152 mm) from the front of the appliance. The
opening shall directly communicate with the out-
doors or shall communicate through a vertical or
horizontal duct to the outdoors or spaces that
freely communicate with the outdoors, and shall
have a minimum free area of:
a. 1 in.
2
per 3,000 BTUH (740 mm
2
per kW) of
the total input rating of all equipment located
in the enclosure, and
b. Not less than the sum of the areas of all vent
connectors in the confined space.
WARNING: Do not use the “one permanent opening”
method if the equipment room may be under negative
pressure conditions.
Canadian Installations
CAUTION: All combustion air must be drawn from
the air outside of the building; the mechanical equip-
ment room must communicate directly with the
outdoors.
1. Ventilation of the space occupied by the heater
shall be provided by an opening(s) for ventilation
air at the highest practical point communicating
with the outdoors. The total cross-sectional area of
such an opening(s) shall be at least 10% of the area
required in 2. and 3. (below), but in no case shall
the cross-sectional area be less than 10 in.
2
(65
cm
2
).
2. For heaters using a barometric damper in the vent
system there shall be a permanent air supply open-
ing(s) having a cross section area of not less than 1
in.
2
per 7,000 BTUH (320 mm
2
per kW) up to and
including 1 million BTUH, plus 1 in.
2
per 14,000
BTUH (160 mm
2
per kW) in excess of 1 million
BTUH. This opening(s) shall be either located at
or ducted to a point not more than 18 in. (450 mm)
nor less than 6 in. (152 mm) above the floor level.
The duct can also “goose neck” through the roof.
The duct is preferred to be straight down and ter-
minated 18 in. (450 mm) from the floor, but not
near piping. This air supply opening requirement
shall be in addition to the air opening for ventila-
tion air required in 1. (above).
WARNING: Care must be taken to ensure that the
equipment room is not under negative pressure
conditions.
3. For heaters not using a barometric damper in the
vent system, and when air supply is provided by
natural air flow from outdoors for a power burner
and there is no draft regulator, drafthood or similar
flue gas dilution device installed in the same space,
in addition to the opening for ventilation air re-
quired in 1., there shall be a permanent air supply
opening(s) having a total cross-sectional area of
not less than 1 in.
2
for each 30,000 BTUH (74
mm
2
per kW) of total rated input of the burner(s),
and the location of the opening(s) shall not inter-
fere with the intended purpose of the opening(s)
for ventilation air referred to in 1. This opening(s)
can be ducted to a point not more than 18 in. (450
mm) nor less than 6 in. (152 mm) above the floor
level. The duct can also “goose neck” through the
roof. The duct is preferred to be straight down 18
in. (450 mm) from the floor, but not near piping.
4. Refer to B149.1 for additional information.
Water Piping
General
The heater should be located so that any water leaks
will not cause damage to the adjacent area or structures.
CAUTION: This heater requires forced water circula-
tion when the burner is operating. See Table F for
minimum and maximum flow rates for water pump
selection. The pump should be interlocked with the
heater to prevent heater operation without water circu-
lation.
NOTICE: Minimum pipe size for in/out connections is
2 in. NPT for 503 and 753 models and 2-½ in NPT for
1003 – 2003 models. Verify proper flow rates and ∆T
as instructed in this manual.