LAARS Heating Systems
Page 8
NOTE: Do not use sheet metal screws at the snap
lock joints of Type B double-wall gas vents.
Do not weld or bolt the vent pipe to the heater
drafthood. The weight of the stack must not rest on the
heater. The drafthood and heater top must be easily
removable for normal heater service and inspection.
WARNING
Avoid ending heater vents near air conditioning or
air supply fans. The fans can pick up exhaust flue
products from the heater and return them inside the
building, creating a possible health hazard.
Locate unit as close as practical to a chimney or
vent termination. Have horizontal runs sloping
upwards not less than 1/4 inch per foot (21mm/m)
from the boiler to the vent terminal. Support a vent
connector for the design and weight of the material
used to maintain clearances and prevent physical
damage and separate of joints.
Doivent présenter des tronçons horzontaux dont
la pente montante est d’au moins 1/4 po par pied
21mm/m) entre la chaudière et l’évent. Doivent
préciser que les sections horizontales doivent être
supportées pour prévenir le fléchissement.
Always use double-wall or insulated vent pipe
(Type B or equivalent).
WARNING
In cold weather, uninsulated outside vents can chill
the rising flue products, blocking the natural draft
action of the venting system. This can create a
health hazard by spilling flue products into the
heater room.
Avoid oversize vent piping or extremely long
runs of the pipe which may cause too much cooling
and condensation of flue gases.
When the installation of a power vent or draft fan
in the venting system is necessary, qualified personnel
should design the installation following good
engineering practices and all applicable codes. A
suitable draft switch must be wired into the heater
control circuit at the terminal designated Field
Interlock to keep the heater from firing unless there is
a positive draft.
2.5.2 Common Venting Systems
Venting Multiple Appliances
When installing venting for a Mighty Therm Lo-
NOx boiler or water heater installed as a Category I
fan-assisted appliance with other Category I appliances
through one shared duct called a “common vent”,
special care must be taken by the installer to ensure
safe operation. In the event that the common vent is
Method 2:
One permanent opening, commencing within 12"
(30 cm) of the top of the enclosure shall be permitted.
The opening shall directly communicate with the
outdoors or shall communicate through a vertical or
horizontal duct to the outdoors or spaces that directly
communicate with the outdoors, and shall have a
minimum free area of 1 square inch per 3000 Btu/hr
(734 square mm/kW) of the total input rating of all
equipment located in the enclosure. This opening must
not be less than the sum of the areas of all vent
connectors in the confined space.
Other methods of introducing combustion and
ventilation air are acceptable, providing they conform
to the requirements in ANSI Z223.1, or other
applicable codes.
In Canada, Table 2 does not apply. Consult local
building and safety codes or, in absence of such
requirements, follow CSA B149.1.
NOTE: Check with louver manufacturers for net free
area of louvers. If screens or louvers are installed,
add 50 percent for each screen/louver to the net free
area.
2.4.1 Outdoor Air Supply
When combustion air comes directly through an
outside wall, each opening must have a minimum free
area of at least one square inch for each 4,000 BTU/h
input of the total input rating of all appliances in the
enclosed area. (In Canada, refer to CSA-B149.1.)
2.4.2 Indoor Air Supply
Confined and non-confined areas have different
requirements for installation. Check the latest edition
of ANSI Z223.1 or in Canada CSA-B149.1 and all
local codes applicable to combustion air.
2.4.3 Exhaust Fans or Vents
Any equipment which uses air or removes air
from the heater room can use up the combustion air
supply or reverse the natural draft action of the venting
system. This could cause flue products to build up in
the heater room. More air must be supplied to make up
for the decrease.
2.5 Venting (Category I)
2.5.1 General Information
When installed indoors, the drafthood must be
connected to a venting system. The venting system
must be installed by a qualified installer and in
accordance with the latest edition of ANSI Z223.1. In
Canada, the installation must be in accordance with
CSA-B149.1, and any local codes that apply.
The vent pipe must have a listed vent cap, and
extend at least 2 feet (0.6 m) above any object within a
10 foot (3.0 m) radius.
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