LAARS Mighty Therm LO-NOx VW (Sizes 250/400) - Installation, Operation and Maintenance Instructions - Manual (Page 7)

Mighty Therm LO-NOx Volume Water Heater Page 7
Table 2. Air Openings to Outside.
Required Net Free Opening Area
Directly from Outside
At Top At Bottom
Model in. 2 cm 2 in. 2 cm 2
250 63 406 63 406
400 100 645 100 645
Note: For screens or louvers, add 50%.
Figure 20. Indoor Installation and Venting.
Notes:
1.
The drafthood must sit directly on top of the heater
as shown and must not be altered in any manner.
2. A vent cap listed or certified for the application by a
Nationally Recognized Testing Laboratory (NRTL)
such as Underwriter’s Laboratories (UL) is required to
eliminate downdraft and to allow the heater to function
properly.
3. Use approved roof fitting.
Vent terminated at
least 2 ft. (61cm)
above any
object within
10 ft. (3.0m)
10 ft.
3.0m
2 ft. 61cm
Listed Vent
Cap
Storm Collar
Roof Jack
Drafthood
1/4 in. 0.6cm
Minimum Pitch
Per Foot of
Horizontal Pipe
Figure 19. Base for Outdoor Installation.
Figure 18. Outdoor Location Installation.
Figure 17. Incorrect Outdoor Installation.
WINDOW
OR GRILL
INDOOR
ROOM
4 ft.
1.2m
10 ft.
3.0m
4 ft.
1.2m
LAARS
UNIT
(Side View)
2.4 Combustion and Ventilation
Air Supply
All indoor installations must have openings to
outside air for combustion, ventilation and dilution of
flue gases from inside the building (see Figure 20 and
Table 2 ). Laars does not recommend indoor
installations that do not provide combustion air from
outside the building.
In the United States, the most common
requirements specify that the space (enclosure) shall
communicate with the outdoors in accordance with
method 1 or 2, which follow. Where ducts are used,
they shall be of the same cross-sectional area as the
free area of the openings to which they connect.
Method 1:
Two permanent openings, one commencing
within 12" (30 cm) of the top and one commencing
within 12" (30 cm) of the bottom of the enclosure shall
be provided. The openings shall communicate
directly, or by ducts, with the outdoors or spaces that
freely communicate with the outdoors. When directly
communicating with the outdoors, or through vertical
ducts, each opening shall have a minimum free area of
1 square inch per 4000 Btu/hr (550 square mm/kW) of
total input rating of all equipment in the enclosure.
When communicating to the outdoors through
123456789012345678901234567890121234567890123456789012345678901212345
123456789012345678901234567890121234567890123456789012345678901212345
123456789012345678901234567890121234567890123456789012345678901212345
123456789012345678901234567890121234567890123456789012345678901212345
123456789012345678901234567890121234567890123456789012345678901212345
12345678901234567890123
12345678901234567890123
12345678901234567890123
Base For Outdoor Unit
Adequate
Air Supply
To Room
Top and
Bottom
5 ft.
min.
1.5m
Forced Air Inlet
Minimum Clearances
4 ft.
1.2m
3 ft.
0.9m
horizontal ducts, each opening shall have a minimum
free area of not less than 1 square inch per 2000 Btu/hr
(1100 square mm/kW) of total input rating of all
equipment in the enclosure.
OUT OF
PRODUCTION