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Matrix Installation and Operation Instructions
Figure 3.5 Installing Venting Below Grade
3.3 Venting Rules and Guidelines
1. It is highly recommended that the vent terminal be located where it will not be exposed to normal prevailing winds.
2. The exhaust must be a minimum of 18” above the air inlet, and the air inlet must always be a minimum of 12” plus snow
allowance above any surface that will support snow. (Two feet plus snow allowance is highly recommended). Consult your weather
office for the maximum typical snowfall for your region. Example: New Brunswick Canada the typical maximum snowfall is 19”,
Thus in figures of Section 3.3, the inlet must be (12”+19”) = 31” off the ground, the exhaust must be (31”+18”) = 49”.
3. Under normal operating conditions this appliance will produce a plume of white gases, and should be taken into consideration
when selecting an adequate location. A 3’ diameter stainless, plastic, or vinyl shield can be used to flash the exterior of the
residence.
4. If the horizontal distance between the inlet and exhaust is more then 12”, increase minimum vertical separation by the same
amount. (If horizontal distance is greater then 6’, no additional vertical spacing is required). Example, horizontal separation equal to
24” requires a minimum vertical separation of 18”+(24”-12”) =30”. (Vertical separation is never required to be greater then 36”)
5. Elbows on outside of wall must be no greater than ½” away from the wall.
6. All indoor exhaust piping must be on a slope back to the boiler a minimum of ¼” per linear foot of vent. For applications where
excessive condensation is possible ½” per linear foot is recommended. (See illustration in Figure 3.1)
6. Exhaust vent pipe can be secured to the wall for more rigidity.
7. In all roof applications the discharge must point away from the pitch of the
roof.
8. Install adequate flashing where the pipe enters the roof, to prevent water
leakage.
9. Install and seal a rain cap over existing chimney openings, in vacant
chimney applications.
10. For installations that exit the wall below grade. Excavate site as shown in
Figure 3.5, to a point below where the pipes are to exit. Ensure that the wall is
fully sealed where the pipes penetrate the wall. The vent piping MUST be
secured to the side of the building above grade, as shown, to provide rigidity.
NTI provides a mounting bracket, PN:82075, for securing the exhaust pipes.
Ensure that the vent clearances are maintained (Inlet minimum 12” plus snow
allowance from grade, exhaust outlet 18” minimum above inlet)
11. Install the vent screens provided into both the inlet and exhaust vent
terminal elbows. The screen must be on the outside of the last elbow. Install
the screen into the female opening of the elbow. Then cut a small piece of
pipe to sandwich the screen into the elbow. NOTE be sure that the small piece
of pipe cut, does not extend past the end of the elbow. Two screens are provided in the package.
12. It is extremely important that the intake and exhaust piping be adapted to the appropriate size immediately upon exiting the
boiler cabinet.
13. All interior vent pipe shall be supported a minimum of every 36”.
