Laars NTH1000, Installation And Operation Instructions Manual, Page: 14 / 140

LAARS Heating Systems Page 10
Method 2 : One permanent opening, commencing
within 12” (300 mm) 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 the applicable codes
listed above.
In Canada, consult local building and safety codes
or, in absence of such requirements, follow CAN/
CSA B149.
3.1.2 Ducted Combustion Air
The combustion air can be taken through the wall, or
through the roof. When taken from the wall, it must
be taken from out-of-doors by means of the LAARS
horizontal wall terminal, shown in Table 3a. See
Table 2 to select the appropriate diameter air pipe.
When taken from the roof, a field-supplied rain cap
or an elbow arrangement must be used to prevent
entry of rain water. (See Fig. 7).
Use ABS, PVC, CPVC, polypropylene, stainless
steel, or galvanized pipe for the combustion air
intake. (See Table 4.) The intake must be sized per
Table 2. Route the intake to the boiler as directly
as possible. Seal all joints. Provide adequate
hangers. The unit must not support the weight of the
combustion air intake pipe. The maximum linear
pipe length allowed is 100 feet (39 m). Subtract 5
allowable linear ft. (1.5 m) for every elbow used.
When using polypropylene or stainless steel
materials in horizontal duct configurations, a single
elbow must be installed on the end of the air inlet
to act as an outdoor terminal. In vertical duct
Fig. 7 - Combustion Air and Vent Through Roof
Table 5 - Required Exhaust Vent Material
Installation Standards
Material United States Canada
Stainless steel UL 1738 Venting must be ULC-S636 certified for use as
venting material. The venting material class must
be chosen based upon the intended application
of the boiler, and must be installed according to
the maximum flue gas temperature and the vent
manufacturer’s instructions.
PVC*, sch 40 ANSI/ASTM D178
CPVC, sch 40 ANSI/ASTM F441
Polypropylene UL-S636 Class 2C
* PVC cannot be used for the first 12 inches of vent material
applications, two elbows must be installed on the
end of the inlet to act as a vent terminal. In both
installation types, Laars part number CA008500 (for
Model 1,000) or CA011300 (for Model 1,700) can
then be installed into the elbow to prevent foreign
objects from entering the air inlet system. The
elbow(s) required to complete the vent terminal is
not included.
The connection for the intake air pipe is on the back
panel.
In addition to air needed for combustion, air shall
also be supplied for ventilation, including air
required for comfort and proper working conditions
for personnel. Refer to the applicable codes.
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*
*
*
*
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*
In Canada, refer to CAN/CSA B199.1