UDAP/APD/UDBP Venting Requirements

Form I-UD&APD Series-V-PV (5-17), P/N 195675R20, Page 11
4.6 Condensation
On units with long vent runs (over 50% of maximum vent length allowed)
or installed in low ambient conditions (below 50°F), it is recommended that
vent pipes be tted with a tee, a drip leg and a clean out cap to prevent any
moisture in the vent pipe from entering the unit. The drip leg should be
inspected and cleaned out periodically during the heating season.
Any length of vent pipe exposed to cold air or run through an unheated area or an
area with an ambient temperature of 50° or less, must be insulated along its entire
length with a minimum of 1/2” foil-faced berglass, 1-1/2# density insulation. Inspect
for leakage prior to insulating and use insulation that is noncombustible with a
rating not less than 400°F. Install a tee tting at the low point of the vent system and
provide a drip leg with a clean out cap. On horizontal vent runs, the ue pipe must
be pitched down toward the terminal end 1/4” per foot for condensate drainage.
Slope applies to the entire length of the horizontal run. Failure to pitch the vent run
properly may damage the heater due to condensate running back into the unit.
CAUTION: Exceeding the specied vent pipe diameter and length may result in
condensate forming in the vent pipe.
4.7 Vent Terminal
(Type of Pipe and
Vent Cap)
The vent terminal pipe must be UL listed Category I vent pipe. Terminate the vent
with a heater Option CC1 vent cap. A different style vent cap could cause nuisance
problems or unsafe conditions. The vent cap must be the same size as the vent pipe.
See Figure 4 for requirements of vertical vent termination.
Vertical vents must terminate a minimum horizontal and vertical distance from roof
lines and adjacent walls or obstructions. These minimum distances are outlined as
follows (based on National Fuel Gas Code requirements for vents with diameters
less than 12”):
• For double wall vent pipe and 8’ or greater horizontal distance to any vertical
wall or similar obstruction, the vent must terminate above the roof in accordance
with Figure X and Roof Slope Heights Table.
• For double wall vent pipe and less than 8’ horizontal distance to any vertical
wall or similar obstruction, the vent must terminate at least 2’ above the highest
point where it passes through a roof of a building and at least 2’ higher than any
portion of a building within a horizontal distance of 10’ (see Roof Slope Heights
Table shown below).
H (minimum)
Roof Slope ft m
Flat to 6/12 1.0 0.30
Over 6/12 to 7/12 1.25 0.38
Over 7/12 to 8/12 1.5 0.46
Over 8/12 to 9/12 2.0 0.61
Over 9/12 to 10/12 2.5 0.76
Over 10/12 to 11/12 3.25 0.99
Over 11/12 to 12/12 4.0 1.22
Over 12/12 to 14/12 5.0 1.52
Over 14/12 to 16/12 6.0 1.83
Over 16/12 to 18/12 7.0 2.13
Over 18/12 to 20/12 7.5 2.27
Over 20/12 to 21/12 8.0 2.44
Termination Locations for Gas Vents with Listed Caps
12” (300 mm) or Less in Size at Least 8’ (2.4 m) from
a Vertical Wall.
Roof Slope Heights Table