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Horizontal Thru-wall Direct Vent
System (Category III) Installation
These installations utilize the heater mounted blower
to draw combustion air from outdoors and vent com-
bustion products to the outdoors.
The total length of the thru-wall exhaust vent cannot
exceed forty (40) feet in length for the flue outlet. Each
elbow used is equal to ten (10) feet of straight pipe.
This will allow installation in one of the three following
combinations.
· 40’ of straight flue pipe.
· 30' of straight flue pipe and one elbow.
· 20' of straight flue pipe and two elbows.
The total length air supply pipe cannot exceed forty
(40) feet in length for the combustion air inlet. Each
elbow used is equal to ten (10) feet of straight pipe.
This will allow installation in one of the three following
combinations.
· 40’ of straight combustion air pipe
· 30' of straight combustion air pipe and one elbow.
· 20' of straight combustion air pipe and two elbows.
The flue exhaust direct vent cap is not considered in
the overall length of the venting system.
Care must be taken during assembly that all joints are
sealed properly and are airtight.
The vent must be installed to prevent the potential
accumulation of condensate in the vent pipes. It is rec-
ommended that:
a) The vent be installed with a slight downward slope
of not more than 1/4" per foot of horizontal run to
the vent terminal.
b) The vent be insulated through the length of the
horizontal run.
For appliances installed in extreme cold climate, it is
recommended that:
a) The vent be installed with a slight upward slope of
not more than 1/4" per foot of horizontal run to the
vent terminal. In this case, an approved conden-
sate trap must be installed per applicable codes.
b) The vent be insulated through the length of the
horizontal run.
Horizontal Thru-wall Direct Vent
Termination
The flue exhaust direct vent cap MUST be mounted on
the exterior of the building. The direct vent cap cannot
be installed in a well or below grade. The direct vent
cap must be installed at least one (1) foot above
ground level and above normal snow levels.
Multiple direct vent caps MUST NOT be installed with
one combustion air inlet directly above a direct vent
cap. This vertical spacing would allow the flue prod-
ucts from the direct vent cap to be pulled into the
combustion air intake installed above. This type of
installation can cause non warrantable problems with
components and poor operation of the unit due to the
recirculation of flue products. Multiple direct vent caps
should be installed in the same horizontal plane with a
three (3) foot clearance from the side of one vent cap
to the side of the adjacent vent cap(s).
Combustion air supplied from outdoors must be free of
particulate and chemical contaminants. To avoid a
blocked flue condition, keep the vent cap clear of
snow, ice, leaves, debris, etc.
The Stainless Steel flue exhaust direct vent cap
must be furnished by the heater manufacturer in
accordance with its listing. Use only the special gas
vent pipes listed for use with category III gas burning
heaters, such as the stainless steel vent by Heat Fab
Inc (800-772-0739), Protech Systems, Inc. (800-766-
3473) or Z-Flex (800-654-5600). Pipe joints must be
positively sealed. Follow carefully the vent manufac-
turers installation instructions.
WARNING: No substitutions of flue pipe or vent
cap material are allowed. Such substitutions would
jeopardize the safety and health of inhabitants.