Specifications

3.5
Air supPlY
Detailed
recommendations
for air
supply
are
given in
BS 5440
:
2.
The
following
notes
are
intended
to
give general
guidance.
3.5.1
Room
or
internal
space
air supply
The
room
or
space
in which
the
boiler
is
located
must
have
a
permanent air
vent'
This
vent
must
be
either
direct
to the
outside
air
or
to
an adiacent
room
or
internal
space
which
must
itself
'have
a
permanent
air
vent of
at
least
i-n" same
sizd
direct
to
the
outside
air.
The
minimum
effective
area
of
permanent
air
vent(s)
is specified
below
and
is
related
to
the
maximum
rated
heat
input
of
the unit.
The balanced
flued
combi
boiler,
VCW-sine,
does
not
require
the
room
or
internal
space
to
have a oermanent
air
vent.
Appliance
cmz
in.2
vcw20/1
vcw25/1
108
130
16
20
3.5.2
Cupboard
or
compartment
air supply
Where
the
combi
boiler
is to be
installed
in a
cuoboard
or
compartment,
permanent air
vents
are
required
(for
cooling
purposes and
in
the
case
6f
open
flued
appliances
also
for
combustion
and
flue dilution)
in the
cupboard
or
compaftment
at
high and
low level'
These air
vents
must
either
communicate
with
the
room
or
internal
space
or be
direct
to outside
air.
The
minimum
etfective
areas
of
the
permanent
air
vents
required
in the
cupboard
or
compartment
are specified
below
(Tab. 1)
and
are ielated
to the
niaximum
rated
heat
input
of
the unit.
Pos.
of
air
vents
Air
vent areas
Airfrom
room
or
internal
space
cmz
,
(inr)
Airdirectfrom
outside
cm2
I
(inr)
High
Level
vcw20/1
vcw25/1
VCW-sine
280
320
235
{42)
(50)
(36,5)
140
160
120
(21)
(25)
(18,5)
LOW
Level
vcw20/1
vcw25i1
VCW-sine
560
640
,235
(84)
(1
00)
(36,5)
280
320
120
(42)
(50)
(18,5)
Tab.1
Note:
Both
air
vents
must
communicate
with
the
same
room
or
internal
space
or
must
be
both
on
the
same
wall
to
the outside
air.
Where
cupboard
or
compartment
air
vents
communichte
with
the
room
or
internal
space
the
room
or
internal
space
must
itself
have
a
permanent air
vent(s)
as
specified
in 3.5.1.
3.5.3
Effect
of
an
extract
fan
lf there
is anv
tvpe
of
extract
fan
fitted
in
the
oremises
there
i6
the
possibility
that
if adequate
iir
inlet
area
from
outside
is not
provided
ipittag"
of
the
products from
the
open
flued
combi
boilers
flue
could
occur
when
the
extract
fan
is
in operation.
Where
such
installations
occur
a spiilage
test
as
detailed
in
BS 5440.:
1
must
be carried
out
and
any
necessary
actlon
taken.
3.6
Water
circulation
system
Detailed
recommendations
for
the
water
circulation
system
are
given in BS
5376
:2'
BS
5449
:1
(Jor
small
bore
and
micro
bore
central
heatinq
svstems)
and
CP
342-
the
following
notes
ire
of
particular importance.
Pipework
not forming
pbrt
ot
the
useful
heating
surface
should
belnsulated
to
help
prevent heat
loss
and
possible
freezing,
particularly
where
pipes
6
are
run
through
roof
spaces
and
ventilated
underfloor
sPaces.
Draininq
taps
must
be
located
in accessible
oosition-s
which
permit
the
draining
of
the
whole
svstem
including
the combi
heater
and
the
hot
water
system.
Dlaining
taps
should
be
at
least
1/2 in.
nominal
size
and
be
in accordance
with
BS
2879.