51
GENERAL VENTING REQUIREMENTS AND
GUIDELINES
Ve
nting
Vent terminations for both Non-Direct and Direct-Vent in-
stallations must adhere to guidelines specified by the latest
edition of ANSI Z21.47
Gas-Fired Central Furnaces
.
These are clearly detailed in
Figure 21
for Non-Direct-Vent
installations and
Figure 32
for Direct-Vent installations. In
addition to these requirements, the installation and venting
must also comply with the National Fuel Gas Code (U.S.)
and CSA-B149.1; Canadian Natural Gas and Propane In-
stallation Code (Canada) and the following requirements
must also be met:
NOTE:
Screens of any kind on the inlet or exhaust pipes
are not permitted and will void the manufacturer’s war-
ranty.
In addition to the requirements shown in
Figure 21
for
Non-Direct venting and
Figure 32
for Direct-Venting, the
vent must be installed with the following minimum clear-
ances:
1. The vent terminal shall have a minimum horizontal
clearance of 4 feet from electric meters, gas meters,
regulators and relief equipment.
2. Locate the furnace combustion air inlet a minimum of 3
feet from the vent of any other gas or fuel-burning appli-
ance or clothes dryer to prevent recirculation of the flue
gases into the furnace combustion air inlet. The only
exception to this requirement is the case of multiventing
two or more furnaces, which is covered in the section
on multiventing of these instructions.
In addition to the minimum clearances listed above and in
Figure 21
(Non-Direct Vent) and
Figure 32
(Direct-Vent),
the vent location should also be governed by the following
guidelines.
1. Avoid terminating under any kind of patio or deck. How-
ever, if necessary, vent piping may be installed under a
deck as long as the termination(s) is (are) not under the
deck.
2. If installing the vent under a deck, insulate it to insure
that no condensate freezes and blocks the pipes.
3. Do not terminate in any area or behind any obstruction
that may allow the flue products to become stagnant
and/or re-circulate.
4. Do not locate on the side of a building with prevailing
winter winds. This will help prevent moisture from
freezing on the walls and overhangs (under eaves).
5. If extending vent through a brick or masonry surface, a
sleeve between the wall and venting is suggested to
protect against damage from thermal expansion and
contraction.
6. A corrosion-resistant sheet metal or plastic backing
plate on the wall behind the vent is suggested to pre-
vent exhaust gases and condensate from contacting
the wall.
7. Avoid locating too close to shrubs as condensate may
stunt growth or kill them.
TERMINATION REQUIREMENTS
!
CAUTION
THE COMBUSTION PRODUCTS AND MOISTURE IN
THE FLUE GASES WILL CONDENSE AS THEY
LEAVE THE TERMINATION. THE CONDENSATE
CAN FREEZE ON THE EXTERIOR WALL, UNDER
THE EAVES AND ON SURROUNDING OBJECTS.
SOME DISCOLORATION TO THE EXTERIOR OF
THE BUILDING IS TO BE EXPECTED. HOWEVER,
IMPROPER LOCATION OR INSTALLATION CAN RE-
SULT IN FINISH DAMAGE TO THE BUILDING AND
MAY RE-CIRCULATE THE PRODUCTS OF COM-
BUSTION INTO THE COMBUSTION AIR TERMINAL
AND FREEZE.
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