LAARS Mighty Therm2 MT2V (Sizes 500–2000 MBTU/h) - Install and Operating Manual - Manual (Page 8)

LAARS Heating Systems Page 8
( see Figure 3 ).
Use single-wall galvanized pipe, per Table 4 , for
the combustion air intake (see Table 2 for appropriate
size). Route the intake to the heater as directly as
possible. Seal all joints with tape. Provide adequate
hangers. The unit must not support the weight of the
combustion air intake pipe. Maximum linear pipe length
allowed is 50 feet (15.2m). Three elbows have been
calculated into the 50-foot (15.2m) linear run. Subtract
10 allowable linear feet (3.0m) for every additional
elbow used ( see Table 2 ). When fewer than 3 elbows are
used, the maximum linear pipe length allowed is still 50
feet (15.2m).
The connection for the intake air pipe is on the
filter box. The Mighty Therm2 appliances have venting
and combustion air ducting attached to the top.
In addition to air needed for combustion, air
shall also be supplied for ventilation, including all air
required for comfort and proper working conditions for
personnel. The Mighty Therm2 loses less than 1 percent
of its input rating to the room, but other heat sources
may be present.
2.2 Venting
2.2.1 Vent Categories
Depending upon desired Mighty Therm2 venting,
it may be considered a Category I or a Category III
appliance. In general, a vertical vent system will be a
Category I system. However, in rare instances, a vertical
vent system may be considered Category III. In the
U.S., the National Fuel Gas Code (ANSI Z223.1-Latest
Edition), or in Canada the CSA B149.1 (latest edition),
defines a Category I vent system, and includes rules and
tables to size these vent systems. If the Mighty Therm2’s
vertical vent system does not satisfy the criteria for
Category I venting, it must be vented as a Category III
system.
All Mighty Therm2 vent systems which discharge
horizontally (without the use of a power venter) are
considered Category III vent systems.
2.2.2 Category I Vent
When vented as a category I appliance, the vent
system must conform to the National Fuel Gas Code
(ANSI Z223.1-Latest Edition) in the U.S., or in Canada,
to CSA B149.1 (latest edition). The vent system must
be sized and installed for a Category I Fan-Assisted
Appliance.
If chimney height is greater than 25 feet, or if
multiple units are vented into the same vertical vent, a
barometric damper must be installed on each appliance,
such that the flue draft does not exceed (negative) 0.1"
w.c.
If using a power venter for any type of Category I
venting, the draft should be set between (negative) 0.01
and 0.10" w.c.
2.2.3 Common Venting Systems
Mighty Therm2 units are Category I fan-assisted
when vented vertically and adhering to all applicable
codes.
When common venting Mighty Therm2 fan-
assisted unit with other appliances through one shared
vertical 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 blocked, it is possible,
especially for fan-assisted devices, to vent backwards
through non-operating appliances sharing the vent,
allowing combustion products to infiltrate occupied
spaces. If the appliances are allowed to operate in this
condition, serious injury or death may occur.
WARNING
Operation of appliances with a blocked common vent
may lead to serious injury or death. If safe operation
of all appliances connected to a common vent cannot
be assured, including prevention of spillage of flue
gasses into living spaces, common venting should not
be applied, and appliances should each be vented
separately.
Proper vent sizing, construction and safety
requirements from the National Fuel Gas Code, ANSI
Z223.1 or in Canada, from CSA B149.1 as well as all
applicable local codes must be followed.
As an additional precaution, it is recommended
that a Carbon Monoxide (CO) alarm be installed in all
Figure 3. Combustion Air and Vent Through Roof.
TERM DESCRIPTION
Pipe Single-wall galvanized steel pipe, 24 gauge
minimum (either insulated or non-insulated)
Joint Permanent duct tape or aluminum tape
Sealing
Table 4. Required Combustion Air Piping Material.