28
Horizontal Thru-wall Venting
System (Category III) Installation
These installations utilize the heater-mounted blower
to vent the combustion products to the outdoors.
Combustion air is taken from inside the room and the
vent is installed horizontally through the wall to the out-
doors. Adequate combustion and ventilation air must
be supplied to the mechanical room in accordance
with the NFGC or, in Canada, the B149 Installation
Code.
The total length of the horizontal thru-wall exhaust
vent system should not exceed seventy (70) feet in
length. If horizontal run exceeds 70 feet, an appropri-
ately sized extractor must be used. To maintain proper
operation pressure reading must be between -.01 to -
.08 in. WC as measured 12 in. from the appliance flue
outlet. Each elbow used is equal to ten (10) feet of
straight pipe. This will allow installation in one of the
four following combinations.
· 70’ of straight flue pipe.
· 60' of straight flue pipe and one elbow.
· 50' of straight flue pipe and two elbows.
· 40' of straight pipe and three elbows.
The vent cap is not considered in the overall length of
the venting system.
The vent must be installed to prevent the flue gas leak-
age. Care must be taken during assembly to ensure
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. The
Raypak supplied flue exhaust direct vent cap must be
utilized.
The Stainless Steel direct vent cap must be fur-
nished 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 manufacturers installation instruc-
tions.
WARNING:
No substitutions of flue pipe or vent
cap material are allowed. Such substitutions would
jeopardize the safety and health of inhabitants.
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