Horizontal Through-the-Wall Direct Venting (Category III)
Horizontal Through-the-Wall Venting
Horizontal Through-the-Wall Direct Venting
CAUTION: This venting system requires the
installation of a condensate drain in the vent piping
per the vent manufacturer’s instructions. Failure to
install a condensate drain in the venting system will
void all warranties on this heater.
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 equipment room in accordance with
the NFGC (U.S.) or B149 (Canada).
The total length of the horizontal through-the-wall flue
system should not exceed 80 equivalent ft in length. If
horizontal run exceeds 80 equivalent ft, an appropri-
ately sized variable-speed extractor must be used.
Each elbow used is equal to 10 ft of straight pipe. This
will allow installation in one of the four following
arrangements:
• 80’ of straight flue pipe
• 70’ of straight flue pipe and one elbow
• 60’ of straight flue pipe and two elbows
• 50’ 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 flue gas leakage.
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 required that:
1. The vent must be installed with a condensate
drain located in proximity to the heater as directed
by the vent manufacturer.
2. The vent must be installed with a slight upward
slope of not less than 1/4 inch per foot of horizon-
tal run to the vent terminal.
3. The vent must be insulated through the length of
the horizontal run.
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