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4. Combustion
Air
Requirements
WARNING
Be Sure to Provide Enough Fresh
Air for Combustion
You must provide for enough fresh
air to assure proper combustion.
The fire in the unit uses oxygen.
The air in a house contains only
enough oxygen to supply the bumer
for a short time. Outside air must
enter the house to replace that used
by the burner. Study the following
examples to determine your fresh
air requirements.
EXAMPLE 1: UNIT LOCATION IN
UNCONFINED
SPACE
If your unit is in an open area in a
conventional house, the air that
leaks through the cracks around the
door and windows will usually be
adequate to provide air for combus-
tion. The doors should not fit tightly.
Do not caulk the cracks around the
windows.
EXAMPLE 2: UNIT LOCATED IN A
HOUSE HAVING TIGHT CON-
STRUCTION
If the house is of tight construction
with weathemtripped windows, not
enough outside air will enter for safe
combustion. Install a duct or pipe
from a point near the burner to a
ventilated attic or crawl space or the
outside where fresh air is freely
available. Vertical ducts should
have a net free area of 1 square
inch for each 4,000 BTU per hour
input of all gas appliances and for
each 2,000 BTUihr. if horizontal
ducts are used. Screen the open-
ings to keep animals and birds from
entering. This is also required if the
boiler is installed near an exhaust
fan or clothes dryer.
Provisions for combustion and venti-
lation air in accordance with section
5.3, Air for CombustTon'_nd
Ventilation, of the National Fuel Gas
Cede, ANSI Z223.1-Latest Edition,
or applicable provisions of the local
building codes.
5. Vent Pipe
Connections
Check Your Chlmney
This is a very important part of your
heating system. It must be clean,
the dght size, propedy con_ed
and in good condition. No boiler can
function properly with a bad chim-
ney. If your chimney is just big
enough for your new boiler, it will
not have extra capacity for other
gas appliances.
When two or more appliances are
vented into the same chimney, the
cress-section area inside the chim-
ney must be at least equal to the
area of the largest vent PLUS ½ the
area of each additional vent.
For example, if your boiler vent has
a diameter of 5 inches (area 19.6
square inches), the water heater
vent, a diameter of 4 inches (12.6
square inches), the minimum chim-
ney area must be 19.6+ ½ of 12.6 or
25.9 square inches. They will
require a 6" diameter round chim-
ney.
When removing a boiler from a
common venting system the venting
system is likely to be too large:for
proper venting of the remaining
appliances connected to it.
At the time of removal of an existing
boiler, the following steps shall be
followed with each appliance
remaining connected to the com-
mon venting system placed in oper-
ation, while the other appliances
remaining connected to the com-
mon venting system are not in oper-
ation.
(a) Seal any unused openings in
the common venting system.
(b) Visually inspect the venting
system for proper size and hori-
zontal pitch and determine there
is no blockage or restriction, leak-
age, corrosion and other deficien-
cies which could cause an unsafe
condition.
(c) Insofar as is practical, close
all building doors and windows
and all doors between the space
in which the appliances remaining
connected to the common venting
system are located and other
spaces of the building. Turn on
clothes dryer and any appliance
not connected to the common
venting system. Turn on any
exhaust fans, such as range
hoods and bathroom exhausts,
4
so they will operate at maximum
speed. Do not operate a summer
exhaust fan.
(d) Place in operation the appli-
ance being inspected. Follow the
lighting instructions. Adjust ther-
mostat so appliance will operate
continuously.
(e) Test for spillage at the draft
hoed relief opening after 5 min-
utes of main burner operation.
Use the flame of a match or can-
dle, or smoke from a cigarette,
cigar or pipe.
(f) After it has been determined
that each appliance remaining
connected to the common vent-
ing system propedy vents when
tested as outlined above, return
doors, windows, exhaust fans,
fireplace dampers and any other
gas burning appliance to their
previous conditions of use.
(g) Any improper operation of the
common venting system should
be corrected so the installation
conforms with the National Fuel
Gas Code, ANSI Z223.1-Latest
Edition. When resizing any por-
tion of the common venting sys-
tem, the common venting system
should be resized to approach
the minimum size as determined
using the appropriate tables in
Appendix G in the National Fuel
Gas Code, ANSI Z223.1-Latest
Edition
Connect the Vent Pipe
WARNING
NEVERINSTALLA
MANUALLY
OPERATED DAMPER IN THE
VENT PIPE OFANY GAS APPLI-
ANCE.
1. Do not modify draft diverter fur-
nished with the boiler.
2. Vent pipe must be same size as
outlet collar on draft diverter.
3. Slope pipe up from b_ler'to chim-
ney not less than ¼" per foot.
4. Run pipe as directly as possible
with as few elbows as possible.
5. Do not connect to fireplace flue.
6. The sections of vent
pipe
should
be fastened with sheet metal screws
to make the piping rigid. Use
stovepipe wires to support the pipe
from above.
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