Viessmann VR2 Series - Page 9

Fresh Air
9
Combustion Air Supply (Continued)
Unconfined spaces
Where the boiler is located in an
unconfined space in a building having
insufficient infiltration, additional air for
combustion and ventilation shall be
obtained from outdoors or from spaces
freely communicating with the
outdoors. Under these conditions,
permanent opening(s) shall be provided
so that the total air received through
these openings will be at least as much
as would be admitted by openings
having a total free area of 1 in
2
/5000
Btu/h or 4.5 cm
2
/kWh of the total input
rating of all oil-fired appliances.
Confined spaces
If the boiler is located in a confined
space and that obtains all of its air for
combustion and ventilation from within
the conditioned space, the building shall
be provided with two permanent
openings, one near the top of the
enclosure and another near the bottom.
Eachopeningshallhaveafreeareaof
not less than 1 in
2
/1000 Btu/h or
19.5 cm
2
/kWh of the total input rating
of all appliances in the enclosure, freely
communicating with interior areas that
have in turn adequate infiltration from
the outside.
If the boiler is located in a confined
space and that obtains all of its air for
combustion and ventilation from
outside, the building shall be provided
with two permanent openings, one near
the top of the enclosure and another
near the bottom. Each opening shall
communicate directly or by means of
ducts with the outdoors or to such
spaces (such as a crawl space) that
freely communicate with the outdoors,
and shall be sized in accordance with
the following methods:
H Vertical duct(s) with a free area of not
less than 1 in
2
/4000 Btu/h or
5.5 cm
2
/kWh of the total input rating
of all appliances in the enclosure,
H Horizontal duct(s) with an equivalent
lengthoflessthan50ft/15m,
havingafreeareaofnotlessthan
1in
2
/2000 Btu/h or 11 cm
2
/kWh of
the total input of all appliances in the
enclosure,
H Air openings that communicate
directly with the outdoors, having a
free area of not less than
1in
2
/4000 Btu/h or 5.5 cm
2
/kWh of
the total input rating of all appliances
in the enclosure.
Louvres and grilles
In calculating free area as specified
above, consideration shall be given to
the blocking effect of louvers, grilles, or
screens that protect openings. Screens
used shall be not smaller than
¼” / 6 mm mesh and s hall be readily
accessible f or cleaning. If the free area
through a design of louvre or grille is
known, it s hall be used in calculating
the size of opening required to provide
the free area specified. If the design
and free area are not known, it shall be
assumed that wood louvres have
20-25% free area and metal louvres
and grills have 60-75% free area.
Installation
Install a combustion air opening. Round
duct diameters are as follows:
Boiler Model
Model No. VR2-40 VR2-50 VR2-63
Round duct for combustion air supply
*1
Ø” 6 6 7
*1
Round duct dia meter given is a minimum.
Ensure that all code requirements are met.
5285 838 v2.1