8. Open Vent Primary Water System
See
Fig
. 7
8.1
The
size of the
flow
and return pipework
is
given
in
Section
3 -
Thble
4.
The
components required to connect the appliance
to an open vent system are available as an optional extra
kit.
8.2
The
feed and expansion cistern should be arranged
so
that
there
is
a minimum static head of 0.3 metres (12in.) above the
top of the appliance
or
above the highest point
in
the heating
circuit, whichever
is
the higher. See F
ig
. 6.
8.3 The feed and vent pipe should be 22 mm diameter
and
rise
continuously
from
the appliance to the feed and expansion cis·
tern.
Fig.
6. Open ventwater system.
Feed
and
expansion
tank
8.4 Apressure relief valve is not required on an open vented sys·
tern.
If
the
pressure relief valve
is
left
in
position then a discharge
pipe must be fitted which terminates
in
a position such
that
any
water or steam discharge does not cause a hazard to the occu·
pants or damage electrical components.
8.5 Air w
it
hin the appliance
will
be expelled via the feed
and
vent connection or dissipated into the rest of the system which
must be fitted with manual air vents
at
any high point.
8.6 The pump is set to maximum and must not be reset.
8.7
To
make use of the extra heating ava
il
able from the appli·
ance
at
the end of any demand,
it
is
recommended
that
a single
small radiator be left permanently open.
-
Overflow
.
S.H
.-
Mnmum
statiC
hud
300
mm
11
2
111
.1
me85Uied
from
the
top
surface
of
the
appliance
or
t.ghest
point
in
the
heattng
system
to
the
wat
er
level
in
the
feed
ill1d
expansiOn
tank
.
-r
·- ·- ·- ·
:-_-:_-==:
-·- ·r
S
.H
.
j
Primary
feed
ill1d
vent
S.H.
;~-;--;jj
1
-
1
jl
r-
--
-
----,
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.
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.
Radllltor
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l
tlll
llll
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llllllll
Nott
.A
dr0111
cock
should
be
InStalled
at
the
lo
west
poont
of
the
heat
tng
c1r
cut
ill1d
beneath
the
appliance
.
9. Domestic Hot Water
9.1 The following are gener
al
requirements and,
if
necessary,
reference should be made to the local Water Company before
fit
·
ti
ng the appliance.
9.2
MAINS
COLD
WATER
INLET
. Devices capable of preventing
the
flow
of expansion water must not be fitted unless separate
arrangements have been made.
An
expansion vessel connection
point
is
provided within the appliance.
A 15mm connection is provided on the domestic
water
inlet
elbow. A Zilmet Z160 is the preferred type. A thread
sealant
compatible with potable water must be used.
9.3
The
final
600 mm ofthe mains cold water connection to the
appliance should be made
in
copper tube only.
9.4
The
appliance is suitable
for
a mains pressure of up to 10
bar (150 lb/
in
").
I
I
8
Central
h
ea
un
g
-·
Water
to
Wate
r
h
eat
ex
changer
by
-
pass
ad
ju
ste
r-
~±--t+-1----'
,
F
ill
point
--
---'
Heating
return
Heat
ing
f
low
.
'
Nota
.
The
ma.ns
cold
1
nle1
connection
to
the
appfta
nce
must
come
before
any
other
connection
from
the
cold
supp
ly
.
Domest
ic
cold
water
.
._.
B
rinsn
St
andard
stop
valve
.
Fixed
spindle
type
.
....
Waterma
111
.
9.5 The appliance is fitted with a mains supply isolating valve.
9.6
The
maximum
domestic
hot
water
flow
rate
is 8.5
litres/min (±15
%)
(1
.87 gallons/min).
9.7
In
winter (when the mains inlet water temperature is lower)
a reduced
flow
rate at the taps
will
be required to achieve the
maximum hot water delivery temperature available
in
warmer
weather.
9.8
It
is
a requirement
that
long pipe runs
to
the taps
or
shower
should be insulated to prevent the rapid cooling of domestic hot
water
after
a
tap
or
shower
has
been
turned
off. Refer
to
BS5546:1990.
Pipe diameter: up
to
12mm. Max.length 20 metres.
Pipe
diameter: up to
22mm
. Max. length 12 metres.
9.9 Hot and cold taps
and
mixing valves used with this appli·
ance must be suitable
for
operating at a pressure of
up
to 10
bar
(150
lb/in
').
