Modine Manufacturing HD Installation And Service Manual - page 6
6
General Instructions For Double Wall (Type B)
Terminal Pipe Installation:
1. How to attach a single wall vent cap to double wall (type B)
vent pipe:
A. Look for the “flow” arrow on the vent pipe. Attach the
vent cap to the exhaust end of the double wall vent pipe.
B. Slide the vent cap inside the pipe.
C. Drill a hole through the pipe and the vent cap. Using 3/4"
long sheet metal screws, attach the cap to the pipe.
2. How to connect a single wall vent system to a double wall
(type B) vent pipe:
A. Slide the single wall pipe inside the inner wall of the
double wall pipe.
B. Drill a hole through both walls of the double wall pipe
and through the single wall pipe. Using 3/4" sheet metal
screws, attach the two pieces of pipe. Do not over
tighten.
C. Repeat Step B drilling and inserting (2) additional
screws, evenly spaced around the pipe.
D. To seal the annular opening, run a large bead of 350°F
silastic. The “GAP” between the single and double wall
pipe must be sealed but it is not necessary to fill the full
volume of the annular area.
Additional Requirements For Horizontal Venting:
1. All HD heaters that are horizontally vented perform as
category III appliance. Category III venting has special
venting requirements as follows:
A. All residential, horizontally vented HD heaters must be
vented with an agency certified category III venting
system. Agency certified category III venting systems are
available from your local vent pipe distributor. Follow the
agency certified category III vent manufacturers
instructions for installations.
B. For commercial and industrial horizontally vented HD
heaters you may use either agency certified category III
venting systems or single wall galvanized or stainless
steel vent pipe. If uncertified single wall vent pipe is
used, all joints must be sealed with metallic tape or
silastic suitable for temperatures up to 400°F. Wrap tape
(2) full turns around the vent pipe.
2. Limit the total equivalent vent pipe length to a minimum of 3'
and a maximum of 30', making the vent system as straight
as possible. see Figure 8. (The equivalent length of a 3"
elbow is 1').
3. The vent system shall terminate at least 3' above any forced
air inlet (except direct vent units) located within 10', and at
least 4' below, 4' horizontally from, or 1' above any door,
window, or gravity air inlet into any building. The bottom of
the vent terminal shall be located above the snow line or at
least 1' above grade; whichever is greater. When located
adjacent to public walkways the vent system shall terminate
not less than 7' above grade.
4. All horizontal vents must be terminated with a Gary Steel
1092 or Breidert Type L vent cap. The vent cap must be 12"
from side of wall. Refer to Figures 6, 7, and 8.
5. When condensation may be a problem, the vent system
shall not terminate over public walkways or over an area
where condensate or vapor could create a nuisance or
hazard or could be detrimental to the operation of regulators,
relief openings, or other equipment.
6. The venting system must be exclusive to a single unit, and
no other unit is allowed to be vented into it.
7. When vented horizontally, maintain a 1/4" per foot rise away
from the heater. Place a drain tee and clean out near the
vent connector. See Figure 6. Where local authorities have
jurisdiction, a 1/4" per foot downward slope is acceptable.
Use a drain tee with a clean out near the exit of the vent, see
Figure 7, or allow the condensate to drip out the end. See
Figure 8.
8. When the vent is routed through a combustible wall, use
either an agency approved thimble, or where authorities
have jurisdiction use type B vent. See Figure 6.
INSTALLATION
Figure 4
Vertical Venting Through Flat Roof
Figure 5
Vertical Venting Through Sloped Roof
Figure 6
Horizontal Venting with Upward Pitch
2' Min
5' Min
Drip Leg
Drip Leg
2' Min
4" Min
12" Min
Downward
Slope
1
/
4
" towards drip leg.
Refer to National Fuel
Gas Code
Refer to N.F.G.C.
4" Min
Listed
Cap
4" Min to combustibles
1
/
4
" Slope up towards termination
Clean out / drip leg
6" Above snow
grade
Listed Thimble
11"
Listed Cap
12" Min
Downward
Slope
1
/
4
" towards drip leg.
Modine Specified Cap (See No.4, page 6)