LAARS Mighty Therm VW (Sizes 2000-5000) - Installation, Operation and Maintenance Instructions - Manual (Page 5)

Page 5 Mighty Therm Volume Water Heaters
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 heater, a suitable switch or equivalent must
be wired into the heater control circuit to prevent
the heater from firing unless the blower is
operating.
5. The heater must be completely isolated and
protected from any source of corrosive chemical
fumes such as emitted by trichlorethylene,
perchlorethylene, chlorine, etc.
2.2.2 Venting
1. Laars heaters 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 heater
draft hood. The weight of the stack must not rest
on the heater. The draft hood and heater top
must be easily removable for normal heater
service and inspection.
2. 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" (30 cm) of the top and one
commencing within 12" (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 directly, or through vertical
ducts, each opening shall have a minimum free
area of 1 square inch per 4000 Btu/hr (550
square mm/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 (1100 square mm/kW) of total
input rating of all equipment in the enclosure.
Method 2:
One permanent opening, commencing within 12"
(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 (734 square mm/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, Table 2 does not apply. Consult
local building and safety codes or, in absence of
such requirements, follow CAN/CGA B149.
3. Exhaust Fans or Vents: Any equipment which
exhausts air from the heater room can deplete the
combustion air supply or reverse the natural
draft action of the venting system. This could
cause flue products to accumulate in the heater
room. Additional air must be supplied to
compensate for such exhaust. The information in
Table 2 is not applicable in installations where
exhaust fans or blowers of any type are used.
Such installations must be designed by qualified
engineers.
Indoor Each Opening*
Size (Square Inches)
2000 .......................................................... 500
2450 .......................................................... 613
3050 .......................................................... 763
3500 .......................................................... 875
4050 ......................................................... 1013
4500 ......................................................... 1125
5000 ......................................................... 1250
Net Free Area in Square Inches*
*Area indicated is for one of two openings; one at floor
level and one at the ceiling, so the total net free area
would be double the figures indicated. For all other
conditions, refer to latest edition of ANSI Bulletin 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 2– Minimum Recommended Air Supply
To Heater Room.