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MACH® Series
Gas-Fired Boiler Installation
Page 8
If air is taken from another interior space, each
opening should have a net free area of 1 square inch
for each 1,000 Btu per hour of boiler input (450 square
inches for a 450,000 Btu per hour.)
3.6
FLUE VENTING
This boiler requires a special vent system. This boiler
is not certified for use with Type "B" vent.
This boiler is Category IV (condensing – positive
pressure) as it is defined in ANSI Z21.13/CSA 4.9,
latest edition. The vent material must be listed
Category IV vent pipe (316L or AL29-4C Stainless
Steel) and comply with UL 1738 or UL103. In
Canada it must comply with ULC-636. The exhaust
vent can be run horizontally or vertically.
Vent installations shall be in accordance with Part 10,
Venting of Equipment, of the National Fuel Gas Code,
ANSI Z223.1 or CSA B.149 code, or applicable
provisions of the local building codes.
The venting system and the horizontal portions of the
venting system shall be supported to prevent sagging.
The vent must be sized according to the vent
manufacturer’s recommendations. Consult your vent
supplier for correct sizing and structural support
requirements. Design calculations should be based on
a maximum of 0.22" W.C. total frictional resistance in
the stack (measured at the boiler flue gas discharge),
with a stack temperature of 210° F (gross) and a CO
2
level of 9% (natural gas) or 10.4% (propane). These
values are to be used for vent sizing calculations.
The installation of a bird screen on the vent
termination is recommended. Consult your local vent
manufacturer for proper sizing.
3.6.1 Barometric Damper
WARNING!
Do not use a barometric damper with this
boiler. (This is a positive pressure system;
combustion gas may leak into the room.)
3.6.2 Flue Connection
The connection from the boiler to the vent should be
as direct as possible and the upward slope of any
horizontal breaching should be at least 1/4 inch per
linear foot. The 300 and 450 vent connection
incorporates a 4° slope toward the boiler to facilitate
pitching of the vent for condensate collection. This
boiler should not be connected into any portion of
another mechanical draft system operating under
positive pressure without consulting your local
venting representative. Provisions must be made for
supports to prevent contact of the vent with
combustible surfaces.
Note: If the vent is erected directly behind the boiler,
make sure that the weight of the vent is not
supported by the boiler vent collar. The collar is
not designed to support the weight of the vent.
Structural support and spacing from combustible
surfaces must be in accordance with the vent
manufacturer's requirements.
Flue Connection at Boiler
3.6.3 Required Clearances
Provide clearances between combustion air intake,
exhaust vent, roof and wall surfaces, doors and
window, and snow line as shown in the following
diagrams. The exhaust vent termination must be 14
feet above grade when located adjacent to a public
walkway. It must also have a minimum 6 foot
horizontal and 6 foot vertical clearance (above or
below) any electric meters, gas meters, regulators, or
relief equipment.
Sidewall
Pitch toward
boiler 1/4" per
foot minimum.
4 degree slope
toward boiler,
approx. ¾” per
foot.