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MODU-FIRE® FORCED DRAFT
Gas-Fired Boiler Installation
3.6.1 Venting Components
The connection from the boiler to the vent should be
made using an adapter that is designed to fit the OD
of the boiler outlet. The vent manufacturer’s
adapter must be sealed to the boiler outlet with seal-
ant listed for use with the vent material. The first
turn from horizontal to vertical should be made with
a tee. A tee cover with a condensate drain shall be
provided at the bottom of the tee. The condensate
drain line from the boiler must be connected to the
stack drain upstream of the stack trap using stainless
steel tubing or piping. The stack trap shall have a
minimum height of 4 inches. The condensate must
be routed to a suitable drain that complies with all
local codes.
WARNING! The boiler condensate drain line can
get as hot as the stack. This may be up to 400ºF.
This line should be insulated to prevent thermal in-
jury or burns.
WARNING! Do NOT use copper or plastic for the
boiler condensate line, as these may fail and allow
exhaust gas to leak into the room.
3.6.2 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.)
3.6.3 Automatic Vent Damper
WARNING!
This equipment MUST NOT be used with an auto-
matic vent damper.
3.6.4 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. Provisions must be made for supports to
prevent contact of the vent with combustible sur-
faces.
This boiler operates under a positive vent pressure.
Do not connect any portion of the vent system of
this boiler into a vent system operating under natural
draft.
Stack Drain
w/Trap
4” min height
Tee/Boot Tee
w/Drain
Boiler Condensate
Drain (stainless steel)
Pitch Towards Boiler
¼
”
per foot min
Building
Sidewall
Bird Screen Not
Recommended
Boiler Outlet
8” OD
Notice: 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 manu-
facturer's requirements.
3.6.5 Clearances
Provide clearances between combustion air intake,
exhaust vent, roof and window and snow line as
shown in the following diagrams. The exhaust vent
termination must not be less than 7 feet above grade
in accordance with ANSI Z221 (NFPA 54), section
10.3.4.6, 2002 edition. The exhaust may not be
vented directly above a public walkway per section
10.8.4 of the above standard. It must also have a
minimum 6 foot horizontal and 6 foot vertical clear-
ance (above or below) any electric meters, gas
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