10
Response 80 / 100 / 120
- Installation
GENERAL
4
SEALED SYSTEM REQUIREMENTS - Central Heating - continued
5. Filling the system
Fill the system through a temporary hose connection
from a draw-off tap supplied from a service pipe under
mains pressure. Where the mains pressure is excessive
a pressure reducing valve shall be used to facilitate filling.
The following fittings shall form a permanent part of the
filling system:
A double non-return valve with at least 1 isolation valve,
which is used as a temporary connection to fill the system
from the mains, after which it should be disconnected
and left with the installation.
Proceed with the following:
•
Thoroughly flush out the whole of the system with
cold water before fitting the boiler.
•
Fill and vent the system until the pressure gauge
registers 1.5 bar (22 lb/in
2
). Examine for leaks.
•
Release water from the system until a pressure of
1 bar (15 lb/in
2
) is reached. To avoid getting debris
on the valve seat, do not use the safety valve to do
this.
•
Light the boiler and heat the system to the
maximum working temperature. Examine for
leaks.
•
Turn off the boiler and drain the system while still
hot.
•
Refill and vent the system.
•
Re-pressurise the system to the desired charge
pressure (see table below ).
CH Return
Ecl 6053
Hose unions
Mains
water supply
Temporary hose
(disconnect after filling)
Additional
stop valve
Double check valve
assembly
(
note direction of flow
)
6. Size of expansion vessel
For the system water expansion to be contained by the
8-litre expansion vessel fitted to the boiler the cold
system volume must not exceed:
119 litres when pressurised to 0.5 bar (cold)
107 litres when pressurised to 0.7 bar (cold)
91 litres when pressurised to 1.0 bar (cold)
If the pressure exceeds 2.65 bar when the boiler is up
to temperature with all radiators in use then an
additional expansion vessel MUST be installed on the
return pipework.
For expansion volumes see table below.
Guidance on vessel sizing is given below and also in
BS 7074:1 and BS 5449.
Vessel sizing / Expansion volumes
System charge pressure (bar)
0.5
0.7
1.0
Safety valve setting (bar)
3.0
Vessel pre-charge pressure (bar)
0.5
0.7
1.0
System volume litres
Volume of expansion vessel in
addition to 8-litre unit fitted to boiler
75
None
None
None
100
None
None
0.8
125
0.4
1.3
3.0
150
2.1
3.1
5.1
175
3.8
4.1
7.3
200
5.4
6.8
9.5
225
7.1
8.7
11.7
250
8.8
10.5
13.9
275
10.6
12.4
16.1
300
12.2
14.2
18.4
Multiply this factor by system volume and
deduct 8 litres to obtain size of additional
0.067
0.074
0.088
vessel for other system volumes.
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