LAARS Mighty Therm VW (Sizes 2000-5000) - Installation, Operation and Maintenance Instructions - Manual (Page 6)

LAARS Heating Systems
Page 6
3. Avoid long horizontal runs of the vent pipe, and
too many 90° elbows, reductions and
restrictions. Horizontal runs should have at least
a 1/4" rise per foot in the direction of flow. A
vent connector shall be supported for the design
and weight of the material employed to maintain
clearances and prevent physical damage and
separation of joints.
4. Avoid terminating heater vents near air
conditioning or air supply fans. The fans can
pick up exhaust flue products from the heater
and return them inside the building, creating a
possible health hazard. A minimum of 4 feet
horizontal distance must be maintained from
electric meters, gas meters, and relief equipment.
5. Always use double-wall or insulated vent pipe
(Type B or equivalent). In cold weather,
uninsulated outside vents can chill the rising flue
products, blocking the natural draft action of the
venting system. This can create a health hazard
by spilling flue products into the heater room.
6. Avoid oversize vent piping or extremely long
runs of the pipe which may cause excessive
cooling and condensation. Rule of Thumb: The
total length of the vent, including the connector
and any offset, should not exceed 15 feet for
every inch of vent diameter. Longer total lengths
shown in venting tables are based on maximum
capacity, not condensation factors.
7. When the installation of a draft fan is necessary
in the venting system to which a Laars heater is
to be connected, the installation should be
engineered by competent personnel following
good engineering practices. The draft fan
supplier should be consulted for correct size.
The installation should be in accordance with the
latest edition of ANSI Z223.1 and any local
codes having jurisdiction. In Canada follow
CAN1-B149 standard. When a draft fan is
installed, a suitable draft switch must be used
and wired into the heater control circuit at
terminal designated “Field Interlock,” to prevent
firing of the heater unless a positive draft has
been established (see Figure 3).
2.3 Installation of Outdoor Heater
Caution
Outdoor installations are not recommended in areas
where the danger of snow blockage exists.
1. Standard outdoor units are shipped with two vent
stacks and vent caps that must be installed on the
vent outlets.
2. Locate the heater to provide the minimum
clearances as listed in Section 2A, “Placement of
Heater.”
3. Do not locate the heater in an enclosure or wall
recess. Avoid location where wind deflection off
structures might cause down draft. When such
wind conditions are possible, locate the heater at
least three (3) feet from the structures.
4. Never install the heater under any kind of roof
overhang. Do not locate the heater below or
adjacent to any doors, windows, louvers, grills,
etc. which communicate in any way with an
inhabited area of a building. Even though such
communication might be through another
structure such as a garage or utility room (see
Figure 4).
Control Wiring for Draft Fan
Figure 4. Incorrect Outdoor Installation.
Figure 3. Draft Inducer/Power Venter.
2.4 Gas Supply and Piping
Review the following instructions before
proceeding with the installation.
1. Verify that the heater is fitted for the proper type
of gas by checking the rating plate. Laars heaters
are normally equipped to operate below a 2000
foot altitude. Heaters equipped to operate at
higher altitudes have appropriate stickers or tags
attached.