LAARS Mighty Therm PH (Sizes 500-1825) - Installation, Operation and Maintenance Instructions - Manual (Page 8)

LAARS Heating Systems
Page 8
Figure 9. Alcove Installation.
4. If a blower or fan is used to supply air to the
heater room, the installer should make sure it
does not create drafts which could cause
nuisance shutdowns of the pilot. If a blower is
necessary to provide adequate combustion air to
the boiler, a suitable switch or equivalent must
be wired into the boiler control circuit to prevent
the boiler from firing unless the blower is
operating.
5. The boiler must be completely isolated and
protected from any source of corrosive chemical
fumes such as trichlorethylene, perchlorethylene,
chlorine, etc.
2B-2. Venting
1. Laars boilers have built-in draft diverters for
natural draft operation and must not be
connected to any portion of a mechanical draft
system under positive pressure. The flue outlet
must be connected to a clear, unobstructed vent
of adequate capacity ending 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/or, in Canada, CAN1-13149 requirement
and any local codes having jurisdiction.
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 using long horizontal runs of the vent
pipe, and too many 90° elbows, reductions or
restrictions. Horizontal runs should have at least
a 1/4" rise per foot in the direction of flow. A
vent connector should be supported for the
design and weight of the material used to
maintain clearances and prevent physical
damage and separation of joints.
4. Avoid ending heater 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 (1.2m) horizontal
distance must be maintained from electrical
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 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 (4.6m)
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 connecting a venting system to a Laars boiler,
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/or, in Canada, CAN 1-B149
requirement and any local codes having
jurisdiction. When a draft fan is installed, a
suitable draft switch must be wired into the
boiler control circuit at terminal designated
“Field Interlock” to prevent firing of the boiler
unless a positive draft has been established.
8. When an existing boiler is removed from a
common venting system, the common venting
system is likely to be too large for proper venting
of the appliances remaining connected to it.
At the time of removal of an existing boiler, the
following steps shall be followed with each
appliance remaining connected to the common
venting system placed in operation, while the