WarmFlow B-Series B70, Owner'S Manual

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Page 52
7.2 Sealed Systems
7.2.1 Expansion Vessel
Refer to BS7074: PART and BS5449 for details of expansion vessel sizing. The
values given in the table below are for total system volumes which include the
primary water capacity of the boiler which can be found in the Technical Data section
of this manual. System and Combi models up to 20 are supplied with a 2 litre
expansion vessel charged to .0 bar. This can accommodate a maximum combined
boiler and system volume of 0 litres. Where permitted by the type, size and
configuration of heating system the expansion vessel bladder pre-charge pressure
can be reduced, prior to filling the system, to 0.5 bar in order to accommodate
a total system volume of 45 litres. If these maximum total system volumes are
exceed, additional expansion capacity will be required.
When measuring the expansion vessel bladder pre-charge pressure, using a tyre
gauge, the system should be cold and the system pressure should be relieved (by
manually operating the system pressure relief valve) in order to obtain an accurate
reading.
7.2.2 System Filling
For all System and Combi boilers a filling point complete with a filling loop is supplied
fitted to the expansion vessel. The filling loop must be disconnected from the mains
supply after filling. A system pressure when cold of bar is recommended. After
filling, vent all air from the system. The plastic plugs of the auto air vent(s) factory-
fitted to the boiler must be loosened when filling the system in order to bleed the air
from the boiler.
7.2.3 System Pressure
Water loss from the system as indicated by a reduction in pressure on the pressure
gauge may be made up through the filling loop. In the first week of operation it is
normal to see a drop in system pressure. After this time the system pressure must
be rechecked and the system refilled. Failure to do so may lead to boiler faults.
7.2.4 Pressure Relief Valve
Any pressure relief valve fitted to the boiler or system must be able to discharge
externally to a drain where the discharge can be seen but cannot cause any injury
or damage. No other valves should be positioned between the relief valve and
discharge termination.
7.2.5 Low Pressure Switch
Where there is a catastrophic loss of water from the system the boiler thermostats
may fail to operate which would result in serious damage to the appliance. To
prevent this it is recommended that a low pressure cut out switch set at 0.2 bar is
fitted to the system and wired in series with the boiler limit thermostat.
25.0
32.7
46.8
300
VESSEL VOLUMES
22.9
30.0
42.9
275
20.8
27.2
39.0
250
8.7
24.5
35.
225
6.7
2.8
3.2
200
4.6
9.
27.3
75
2.5
6.3
23.4
50
0.5
3.6
9.5
25
8.3
0.9
5.6
00
6.3
8.2
.7
75
4.2
5.4
7.8
50
2.
2.7
2.9
25
0.5
.0
.5
TOTAL SYSTEM
VOLUME
INITIAL
C
HARGE