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Heatilator • NNXT33-IFT, NNXT33L-IFT, NNXT36-IFT, NNXT36L-IFT Installation Manual • 2628-980 Rev. C • 8/20
32
B. Wall Penetration Framing/Firestops
Combustible Wall Penetration
Whenever a combustible wall is penetrated, you must
frame a hole for the wall shield firestop(s). The wall shield
firestop maintains minimum clearances and prevents cold
air infiltration.
• The opening must be framed on all four sides using the
same size framing materials as those used in the wall
construction.
• SLP pipe - A wall shield firestop must be placed on each
side of an interior wall. A minimum 1-1/2 in. (38 mm)
overlap of attached heat shields must be maintained.
• DVP pipe - A wall shield firestop is required on one side
only on interior walls. If your local inspector requires a
wall shield firestop on both sides, then both wall shield
firestops must have a heat shield (refer to Section
12.A.) attached to them.
• See Section 7.F. for information for regarding the instal-
lation of a horizontal termination cap.
Non-Combustible Wall Penetration
If the hole being penetrated is surrounded by non-com-
bustible materials such as concrete, a hole with diameter
one inch greater than the pipe is acceptable.
Whenever a non-combustible wall is penetrated, the wall
shield firestop is only required on one side and no heat
shield is necessary.
A*
B*
10 in.
C
D
DO NOT PACK WITH
INSULATION OR
OTHER MATERIAL
12 in. (DVP)
10 in. (SLP)
Figure 5.2 Wall Penetration
* Shows center of vent framing hole for top or rear venting. The center of the
hole is one (1) in. (25.4 mm) above the center of the horizontal vent pipe.
A*
B*
C
D
Inches
40-1/2
24-1/2
39-1/2
23-1/2