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ventilated to a room, the room itself must have an air vent
dtrect to the outside air of a minimum effective area of
1 DO
em'
(15 in.'). Details of essential features of cupboard/compartment
design, including airing cupbaord installation, are given in
BS
6798:1987
3.
If
there is any type of extract fan fttted m the premises. spiltage
of the products from the appliance flue could occur when the
fan is operating unless an adequate air inlet area from outside
is provided.
4.
A
spillage test as detailed in BS 5440:1 must be carried out and
any remedial action taken to ensure the installation meets
these standards
Table 4
Position
Air from
Air direct
Air Vents
room
from outside
H1gh Level
264 em'
132 em'
(41 in')
(20.5 in 'I
Low Level
528 cm
1
264 cm
1
(82 m.')
(41 in.')
Additional information in respect of air supply and installation data
is given in BS 6798 and BS 5440:Part 2.
7. SYSTEM CONSIDERATIONS
1.
For circuit design purposes it is most important that the flow
rate and pressure drop across the appliance corresponding to
the system temperature differential and maximum heating
output chosen, should be as given in Table 3
2.
The appliance includes a central heating circulating pump and
no other circulatmg pump
IS
required. When fitting a room or
frost thermostat refer to Section 11--Eiectrical. The appliance
will operate sat1sfactonly on a two pipe small bore or microbore
system
3.
The heatbank contains two finned copper heat exchangers
which provide domestic hot water A control system is incor-
porated that gives priority to the domestic hot water and the
central heating will be turned off when a demand for hot water
IS
made. For large quantities of hot water the Hot Water Tem-
perature Control Knob should be set at maximum and after use
a few minutes may be reqmred to re-heat the heatbank. The
central heating will remain off during this period
4.
The appliance
IS
supplied suitable for direct connection to a
sealed system
5.
It
is essential that the fittings and joints in a sealed system are
capable of maintaining the chosen system pressure.
It
is generally advisable to fit a by-pass to all systems.
8. SEALED PRIMARY SYSTEM
See Figs. 5 and 6
1.
GENERAL
The installation must comply with the requirements of BS
6798:1987 and
BS
5449:1 For sizes of flow and return pipe
work refer to Section 2-Technical Data and Fig. 2
The open end of the combined feed and vent pipe must be
sealed
IMPORTANT: The pipe connect10ns made throughout the
system must be capable of sustaining a pressure of up to 3 bar
When the appliance is fitted to an existing installation and that
system is upgraded to a sealed system then the water con-
nections must be checked and replaced if necessary
2.
SAFETY VALVE
The spring loaded safety valve is set to operate at 3 bar
(45 p.s.i.). The discharge pipe must be so arranged that the
discharge of water or steam from the tundish pipe cannot
create a hazard to occupants of the premises or cause
7
damage to electrical components and wiring. See Section 13
- Installation.
The safety valve complies with the general requirements of
BS759.
3.
PRESSURE GAUGE
A pressure gauge fitted to the appliance covers the range 0-4
bar (0-60 p.s.i.)
4.
THE EXPANSION VESSEL
The appliance incorporates a
1
2 litre diaphragm type expan-
sion vessel charged to 0.5 bar. The expansion vessel is charged
with air and is fitted wtth a Schraider type valve. The charge
pressure !S therefore adjustable by using a tyre pump and
pressure gauge and should be increased if necessary.
The charge pressure must not be less than the static head at the
point of connectiOn (i.e. height of the top point of the system
above the expansion vessel)
The vessel as supplied is, therefore, SUitable for systems with a
static heat of 0.5 bar whtch 1S equivalent to 5 metres (17ft.)
5.
SYSTEM VOLUME
The expansion vessel accommodates differing system volumes
depending upon the initial charge pressure and pre-pressurisa-
tion of the system if any. Reference should be made to Table 5
to establish the approximate system volume that can be
accommodated under different conditions with the standard
expansion vessel.
If
it is found that the system volume is in
excess of that catered for by the expansion vessel supplied,
then an extra vessel can be added as close to the return con-
nection of the appliance as possible so that the total expansion
volume is sufficient Refer to BS 5449:1 and BS 6798:1987 for
further information.
Table 5
TOTAL SYSTEM VOLUME IN LITRES (Gallons)
Initial System
Initial Charge Pressure (bar)
Pressure (bar)
0.5
1 0
15
0.5
156
-
-
(35)
1.0
96
122.5
-
(21)
(27)
15
51.5
69.5
85
(11.5)
(155)
(185)
2.0
24
32.5
395
(5.5)
(7)
(9)
NOTE. Because of the increased primary· capacity of this appliance
care should be exercised over the correct sizing of the expansion
vessel In order to check that the standard vessel (or standard vessel
together with any supplementary vessel) capacity is adequate, first
ensure that with the system cold the initial system pressure is
correctly set. Allow the system
to
heat fully with the hot water and
central heating thermostats set to maxtmum. Check that the system
pressure has not exceeded 2.6 bar If the system pressure has
exceeded 2.6 bar a supplementary vessel should be fitted as
described previously or if one has already been fitted then this
should be increased 1n size.
6.
MAKE·UP
Provision must be made for replacing water lost from the
system either from a make-up vessel mounted in a position
h1gher than the top point of the system and connected through
a non-return valve to the system on the return side on the
heating circuit. See Fig. 5. Or, where access to a make-up vessel
would be difficult, provision for make up can be made by pre-
pressurisation of the system.
The appliance must not be operated without the system
being full of water and properly vented. Repeated venting
will
reduce the quantity of water in the system.
It
is essential
that this water is replaced and the system pressure main-
tained.
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