32
Table M: Horizontal Thru-wall Direct Venting without Add-on
Secondary Condensing Heat Exchanger
Horizontal Thru-wall Direct Venting
System (Category III) Installation
These installations utilize the boiler mounted blower to
draw combustion air from outdoors and vent combus-
tion products to the outdoors.
The total length of the thru-wall exhaust vent cannot
exceed forty-five (45) 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 fol-
lowing combinations:
· 45
′
of straight flue pipe.
· 35
′
of straight flue pipe and one elbow.
· 25
′
of straight flue pipe and two elbows.
The total length air supply pipe cannot exceed forty-
five (45) 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 fol-
lowing combinations:
· 45
′
of straight combustion air pipe
· 35
′
of straight combustion air pipe and one elbow.
· 25
′
of straight combustion air pipe and two elbows.
The 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 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.
ÁDB-1501
Summary of Contents for 751
Page 2: ...2...
Page 6: ...6 Component Locations Fig 1 Component Locations...
Page 15: ...15 Fig 6 Dual Boiler Piping Fig 7 Dual Boiler Piping with CHX...
Page 20: ...20 Fig 13 Single Boiler Pool Application Fig 14 Single Boiler Pool Application with CHX...
