20
VENTING (continued)
5. Any run of single wall vent pipe passing through an
unheated space must be insulated with an insulation
suitable to 550°F.
6. The vent system must be installed to prevent col-
lection of condensate. Pitch horizontal pipes down-
ward 1/4" per foot (21mm/m) toward the vent
cap to facilitate drainage. Vertical vent pipes should
be piped as depicted in Figures 7A & 7B.
7. The equivalent length of the vent system must not
be less than 5' (1.5m) and must not exceed 50'
(15.2m). Equivalent length equals the total length of
straight pipe plus 10' (3.05m) for each 90° elbow
and 4' (1.22m) for each 45° elbow.
8. Each slip joint must be secured with at least three
corrosion resistant screws. Two full turns of 3m #425
Aluminum Foil tape or its equivalent must then be
used to seal each joint. General Electric RTV-108,
Dow-Corning RTV-732 or an equivalent may be
used instead of the tape.
9. For horizontal vent systems longer than 5' (1.5m),
the system must be supported from over-head
building structures at 3' (1m) intervals.
10. The exhaust vent system must remain at a minimum
distance of 6" (152mm) from all combustible
materials. Any part of the vent system that passes
through a combustible material must be properly
insulated.
NOTICE: Increasing the clearance distances may be
necessary if there is a possibility of distortion or
discoloration of adjacent materials.
For a VERTICAL vent pipe section that passes through
a fl oor or roof, an opening 4" (102mm) greater in diam-
eter is required (see Table 1). The opening must be insu-
lated and fl ashed in accordance with applicable instal-
lation codes. See Figure 7B.
A HORIZONTAL section of an exhaust vent system that
passes through a combustible wall must be constructed
and insulated as shown in Figures 8A & 8B.
Figure 7A - Vertical Intake/Vent Installation
* 2 FT. Min plus max snow depth for area.
** If excessive condensation develops, a drip leg with
a condensate drain may be required. Insulating the
pipes may eliminate the problem.
CAT-2764C
