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2) If the heater room is located against an outside wall
and air openings can communicate directly with the
outdoors, the two openings on the outside wall
must each have a net free area, in square inches as
follows:
Model Sq. In. Of Free Area
0090 24
0135 35
0195 50
Location of the openings is the same as in the
previous case - that is, within 12 inches of the top, and
within 12 inches of the bottom of the enclosure. If
horizontal ducts are used, the area must be doubled and
the duct area shall not be less than the area of the
openings they connect, and in no case shall the smallest
dimension be less than 3 inches.
VENTING CONNECTIONS
These heaters have built-in drafthoods. Vent piping
the same size or larger than the draft hood outlet is
recommended; however, when the total vent height
(drafthood outlet to vent terminal) is at least ten (10) feet,
the vent pipe size may be reduced by one size
only as
specified in Chapter 10 of the latest edition of the National
Fuel Gas Code, ANSI Z 223.1. As much as possible
avoid long horizontal runs of vent pipe and too many
elbows. If installation requires horizontal runs, the vent
pipe must have a minimum of 1/4 inch per foot rise and
should be supported at not less than five foot intervals.
Maximum vent connector horizontal length shall be 1-1/
2 feet (18 inches) for each inch of connector diameter as
follows.
Heater Size Vent Connector Max Horizontal
Diameter Length - FT
90 5" 7.5
135 6" 9
195 7" 10.5
Gas Vents supported only by the flashing and
extending above the roof more than five feet should be
securely guyed or braced to withstand snow and wind
loads. We recommend use of insulated vent pipe spacer
through the roofs and walls.
For protections against rain or blockage by snow, the
vent pipe must terminate with a listed vent cap which
complies with the local codes or, in the absence of such
codes, to the latest edition of the National Fuel Gas Code,
ANSI Z 223.1.
The discharge opening must be a minimum of two
feet vertically from the roof surface and at least two (2) feet
higher than any part of the building within ten (10) feet.
Vent stack shall be at least five (5) feet in vertical height
above the drafthood outlet. The vent cap location shall
have a minimum clearance of four (4) feet horizontally
from, and in no case above or below, unless a 4-foot
horizontal distance is maintained, from electric meters,
gas meters regulators and relief equipment.
The weight of the vent stack or chimney must not rest
on heater draft hood. Support must be provided in
compliance with applicable codes. The heater top and
draft hood must be readily removable for maintenance
and inspection. Vent pipe should be adequately sup-
ported to maintain proper clearances from combustible
construction.
Type "B" double wall (or equivalent vent pipe is
recommended. However single wall metal vent pipe may
be used as specified in the latest edition of the National
Flue Gas Code ANSI Z 223.1.
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