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2. Power Venting, Indoor Combustion Air in Confined or
Unconfined Space
This boiler requires fresh, uncontaminated air for safe operation
and must be installed in a mechanical room where there is
adequate combustion and ventilating air. NOTE: To prevent
combustion air contamination, see Table 2.
Combustion air from the indoor space can be used if the space
has adequate area or when air is provided through a duct or
louver to supply sufficient combustion air based on the boiler
input. Never obstruct the supply of combustion air to the boiler.
If the boiler is installed in areas where indoor air is contaminated
(see Table 2) it is imperative that the boiler be installed as
direct vent so that all combustion air is taken directly from the
outdoors into the boiler intake connection.
Unconfined space is space with volume greater than 50 cubic
feet per 1,000 BTU/hr (4.8 cubic meters per kW) of the total
input rating of all fuel-burning appliances installed in that space.
Rooms connected directly to this space through openings not
furnished with doors are considered part of the space. See
Venting Section for details.
Confined space is space with volume less than 50 cubic feet per
1,000 BTU/hr (4.8 cubic meters per kW) of the total input rating
of all fuel-burning appliances installed in that space. Rooms
connected directly to this space through openings not furnished
with doors are considered part of the space.
When drawing combustion air from inside a conventionally
constructed building to a confined space, such space should be
provided with two permanent openings: one located 6" (15 cm)
below the space ceiling, the other 6" (15cm) above the space
floor. Each opening should have a free area of one square inch
per 1,000 BTU/hr (22cm
2
/kW) of the total input of all appliances
in the space, but not less than 100 square inches (645cm
If the confined space is within a building of tight construction, air
for combustion must be obtained from the outdoors as outlined
in the Venting section of this manual.
When drawing combustion air from the outside into the
mechanical room, care must be taken to provide adequate
freeze protection.
WHL-016 Rev. 4.14.16
Failure to provide an adequate supply of fresh combustion
air can cause poisonous flue gases to enter the living space,
resulting in severe personal injury or death. To prevent
combustion air contamination, see Table 2.
I. Prevent Combustion Air Contamination
Install intake air piping for the boiler as described in the
Venting Section, this manual. Do not terminate exhaust in
locations that can allow contamination of intake air.
Ensure that the intake air will not contain any of the
contaminants in Table 2. Contaminated air will damage the
boiler, resulting in possible substantial property damage,
severe personal injury, or death. For example, do not pipe
intake air near a swimming pool or laundry facilities. These
areas always contain contaminants.
J. Removing a Boiler from a Common Vent System
Do not install the boiler into a common vent with any other
appliance. This will cause flue gas spillage or appliance
malfunction, resulting in possible substantial property
damage, severe personal injury, or death.
Failure to follow all instructions can result in flue gas spillage
and carbon monoxide emissions, causing severe personal
injury or death.
When removing an existing boiler, follow the steps below.
1. Seal any unused openings in the common venting system.
2. Visually inspect the venting system for proper size and
horizontal pitch to determine if there is blockage, leakage,
corrosion, or other deficiencies that could cause an unsafe
condition.
3. If practical, close all building doors, windows, and doors
between the space in which the boiler remains connected to
the common venting system and other spaces in the building.
Turn on clothes dryers and any appliances not connected to
the common venting system. Turn on any exhaust fans, such
as range hoods and bathroom exhausts, at maximum speed.
Do not operate a summer exhaust fan. Close all fireplace
dampers.
4. Place in operation the appliance being inspected. Follow the
lighting instructions. Adjust the thermostat so the appliance
will operate continuously.
5. Test for spillage at the draft hood relief opening after 5
minutes of main burner operation. Use the flame of a match
or candle or smoke from a cigarette.
6. After it has been determined that each appliance remaining
connected to the common venting system properly vents
).
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when tested as outlined, return doors, windows, exhaust fans,
fireplace dampers, and any other gas burning appliances to
their previous condition of use.
7. Any improper operation of the common venting system
should be corrected to conform to the National Fuel Gas
Code, ANSI Z223.1. When resizing any portion of the common
venting system, the system should approach the minimum
size as determined using the appropriate tables in Appendix
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