LAARS Mighty Therm LO-NOx PW (Sizes 500-1825) - Install and Operating Manual - Manual (Page 5)

Mighty Therm Lo-NOx Page 5
See Table 2 for recommended opening sizes
pertaining to Method 1.
Method 2: One permanent opening, commencing
within 12 inches (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/h (700 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, provided they conform
to the requirements in the applicable codes.
In Canada, consult local building and safety
codes or, in absence of such requirements, follow
CAN/CGA B149.
An improperly ventilated equipment room can
get excessively hot and cause accelerated
deterioration of controls and electrical components.
In Canada, Table 2 does not apply. Consult local
building codes or, in the absence of such requirements,
follow CGA requirements and/or CAN/CGA B-149
standard.
2.2.1.b Forced-Air Ventilation
In the United States: any equipment which
exhausts air from the heater room can deplete the
combustion air supply or reverse the natural draft
action of the venting system. This could cause flue
products to accumulate in the heater room. Additional
air must be supplied to compensate for such exhaust.
The information in Table 2 is not applicable in
installations where exhaust fans or blowers of any
type are used. Such installations must be designed by
qualified engineers.
In Canada: follow Canadian standard, CAN/
CGA B-149 or local codes.
If a blower or fan is used to supply air to the
heater room, the installer should make sure it does not
create drafts which could cause nuisance shutdowns.
If a blower is necessary to provide adequate
combustion air to the heater, a suitable switch or
interlock must be wired into the heater control circuit
to prevent the heater from firing unless the blower is
operating.
The heater must be completely isolated and
protected from any source of corrosive chemical fumes
such as trichlorethylene, perchloroethylene, chlorine, etc.
2.2.2 Venting
IMPORTANT NOTE: Mighty Therm LO-NOx
units are not fan-assisted. They are natural draft
appliances. The fans on the Mighty Therm LO-NOx
units are for combustion assistance only. Venting
systems must be sized as natural draft, atmospheric
vent, and not as fan-assisted vent systems.
1.
Laars heaters have built-in draft diverters for
natural draft operation and must not be
connected to any portion of a mechanical draft
system under positive pressure. The flue outlet
must be connected to a clear, unobstructed vent
of adequate capacity ending above the highest
point of the building with an approved vent cap.
The venting system should be installed
according to Category 1, Natural Draft per the
latest edition of ANSI Z223.1 and/or, in Canada,
CAN/CGA B-149 and any local codes having
jurisdiction.
2. Do not weld or fasten the vent pipe to the boiler
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.
IMPORTANT NOTE: Do not use sheet metal
screws at the snap lock joints of Type B gas vents.
3. Avoid using long horizontal runs of the vent
pipe, and too many 90° elbows, reductions or
restrictions. Horizontal runs should have at least
a 1/4" (6mm) rise per foot in the direction of
flow. A vent connector should be supported for
the design and weight of the material used to
maintain clearances and prevent physical
damage and separation of joints.
Figure 4. Typical Heater Installation on Concrete Slab.
Table 2. Minimum Recommended Air Supply to Heater,
Per Method 1.
Heater Each Opening*
Size square inches square cm
500 125 807
715 179 1155
999 250 1613
1010 253 1632
1200 300 1936
1430 358 2310
1825 457 2950
* Net Free Area.
Check with louver manufacturers for net free area of louvers.
Correct for screen resistance to the net free area if a screen is
installed. Check all local codes applicable to combustion air.
Area indicated is for one of two openings: one at floor level
and one at the ceiling, so the total net free area could be
double the figures indicated. For special conditions refer to the
latest edition of ANSI Z223.1.
Consult factory if openings do not communicate directly
through the walls with the outdoors.