LAARS Mighty Therm HH (Sizes 2000-5000) - Installation, Operation and Maintenance Instructions - Manual (Page 7)

Mighty Therm Hydronic Boiler Page 7
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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 boiler 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 boiler 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 boiler control circuit at
terminal designated “Field Interlock,” to prevent
firing of the boiler unless a positive draft has
been established (see Figure 5).
2C. Installation of Outdoor Boilers
Caution
Outdoor installations are not recommended in areas
where the danger of snow blockage exists.
1. Locate the boiler to provide the minimum
clearances as listed in Section 2A, “Placement of
Boiler.”
2. Do not locate the boiler in an enclosure or wall
recess. Avoid location where wind deflection off
structures might cause down draft. When such
2B-2. Venting
1. Laars boilers have built-in draft diverters for
natural draft operation and must not be
connected into any portion of a mechanical draft
system under positive pressure. The flue outlet
must be connected to a clear, unobstructed vent
of adequate capacity terminating above the
highest point of the building with an approved
vent cap. The venting system should be installed
according to the latest edition of ANSI Z223.1
and any local codes having jurisdiction and/or in
Canada follow CAN1-B149 standard.
IMPORTANT NOTE: Do not use sheet metal
screws at the snap lock joints of Type B gas vents.
2. Do not weld or fasten the vent pipe to the boiler
draft hood. The weight of the stack must not rest
on the boiler. The draft hood and boiler top must
be easily removable for normal boiler service
and inspection.
3. Avoid long horizontal runs of the vent pipe, and
too many 90° elbows, reductions and restrictions.
Horizontal runs should have at least a ¼" 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 boiler vents near air
conditioning or air supply fans. The fans can
pick up exhaust flue products from the boiler 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.
Figure 7. Method of Installing a Tee Sediment Trap.
Figure 6. Incorrect Outdoor Installation of Boiler.