10
L o c h i n v a r
D E S I G N E R
’
S
G U I D E
E F F I C I E N C Y
+
B O I L E R
6 1 5 - 8 8 9 - 8 9 0 0
Vertical Air Inlet
The air inlet cap for the vertical roof top
air inlet is assembled from components
purchased locally. The air inlet cap consist
of two 90° ells installed at the point of
termination for the air inlet pipe.
The point of termination for the combustion
air inlet cap
must
be at least 2 feet (0.6m)
below the point of flue gas termination
(vent cap) if it is located within 10
ft.
(3.0m)
of the flue outlet.
The termination ell on the air inlet
must
be
located a minimum of 12
”
(0.3m) above the
roof or above normal levels of snow
accumulation. It
must
not be placed closer
than 10 feet (3.0m) from an inside corner of
an L-shaped structure.
Incorrect location of the air inlet cap can
allow the discharge of flue products to be
drawn into the combustion process of the
boiler. This can result in incomplete
combustion and potentially hazardous levels
of carbon monoxide in the flue products.
Combined Air Inlet Points
The air inlet pipes from multiple boilers can
be combined into a single common
connection, if the common air inlet pipe has a
cross sectional area equal to or larger than
the total area of all air inlet pipes connected
to the common air inlet pipe.
The air inlet point for multiple boiler air inlets
shall be provided with an exterior opening
which has a free area equal to or greater
than the total area of all air inlet pipes
connected to the common air inlet. This
exterior opening for combustion air
must
connect directly to the outdoors.
The total length of the combined air inlet pipe
must
not exceed a maximum of 50
equivalent feet(15.2m). Deduct the restriction
in area provided by any screens, grills or
louvers installed in the common air inlet point.
Screens, grills, or louvers installed in the
common air inlet can reduce the free area
of the opening from 25% to 75% based on
the materials used. The air inlet cap for the
combined air supply from multiple boilers can
be purchased or fabricated in the field.
Direct Venting
A direct vent boiler uses a two pipe system,
one pipe for the flue products and one pipe
for the combustion air supply.
The flue
cannot
be combined with any other
appliance vent or common vent from multiple
boilers. The vent on a direct vent system will
have a positive pressure in the flue, which
requires all vent joints and seams to be
sealed gas-tight. The flue from a direct vent
system shall have a condensate drain with
provisions to properly collect and dispose of
any condensate that may occur in the venting
system. Direct vent systems require Category
IV vent material with AL29-4C approved
stainless steel.
The air inlet pipe connects directly to the
boiler to supply combustion air. The air inlet
pipe
must
be sealed. Choose acceptable
Lochinvar
EXAMPLE OF
COMBINED
AIR INLET
SIZING
Two 5” air inlet pipes
(19.6 in
2
area each) have
a total area of 39.2 in
2
requiring an 8” (50.3 in
2
area) common air inlet
pipe.
