LAARS Mighty Therm2 MT2V (Sizes 500–2000 MBTU/h) - Install and Operating Manual - Manual (Page 7)

Mighty Therm 2
Page 7
1.7 Locating Pump-Mounted Boiler with
Respect to Return/Supply Header
For the best results, a pump-mounted Mighty
Therm2 Boiler should be located within 15 feet (4.6m)
of the supply and return headers. The pump is sized for
30 feet (9.1m) of piping.
If the appliance must be installed with longer
piping runs, then larger diameter tubing shall be used.
Consult the factory for assistance.
1.8 Locating Appliance for Correct
Horizontal Vent/Ducted Air Distance
from Outside Wall
The forced draft combustion air blower/blowers
in the appliance has/have sufficient power to pull air
and vent properly when the following guidelines for
horizontal air and vent are followed ( see Table 2 ).
NOTE: The vent collar size is larger than the size of
the vent pipe that can be used. Vent collar size and
horizontal pipe diameters can be found in Table 2 . The
larger vent collar size is to accommodate Category I
(vertical) vent systems.
NOTE: When located on the same wall, the Mighty
Therm2 combustion air intake terminal must be installed
a minimum of 12" (30cm) below the exhaust vent
terminal and separated by a minimum of 36 inches
(91cm) horizontally.
The air intake terminal must be installed high
enough to avoid blockage from snow, leaves and other
debris.
SECTION 2.
Venting and Combustion Air
2.1 Combustion Air
Mighty Therm2 boilers and water heaters must
have provisions for combustion and ventilation air
in accordance with section 5.3, Air for Combustion
and Ventilation, of the National Fuel Gas Code, ANSI
Z223.1, or Sections 7.2, 7.3 or 7.4 of CSA B149.1,
Installation Codes, or applicable provisions of the local
building codes.
A Mighty Therm2 appliance may receive
combustion air from the space in which it is installed,
or it can be ducted directly to the unit from the outside.
Ventilation air must be provided in either case.
2.1.1 Combustion Air From Room
In the United States, the most common
requirements specify that the space 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 inches (30 cm) of the top and one
commencing within 12 inches (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
when communicating to the outdoors through vertical
ducts, each opening shall have a minimum free area of
1 square inch per 4000 BTU/hr (5.5 square cm/kW) of
total input rating of all equipment in the enclosure. When
communicating to the outdoors through horizontal ducts,
each opening shall have a minimum free area of not less
than 1 square inch per 2000 BTU/hr (11 square cm/kW)
of total input rating of all equipment in the enclosure.
Table 3 shows data for this sizing method, for each
Mighty Therm2 model.
Method 2: One permanent opening, commencing
within 12 inches (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 (7 square cm/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 CSA B149.1.
2.1.2 Intake 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 ( see Table 2 ). When taken
from the roof, a field-supplied rain cap or an elbow
arrangement must be used to prevent entry of rain water
UNIT EACH OPENING*
SIZE SqUARE INCHES SqUARE CM
500 125 807
750 188 1213
1000 250 1613
1250 313 2020
1500 375 2420
1750 438 2826
2000 500 3226
*Net Free Area in Square Inches / Square cm
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.
This chart is for use when communicating directly with the
outdoors. For special conditions and alternate methods, refer to the
latest edition of ANSI Z223.1.
Note: 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.
Table 3. Combustion Air Openings.