11
Response FF80
- Installation
GENERAL
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.
4
SEALED SYSTEM REQUIREMENTS - Central Heating - continued
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 6).
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 6.
Guidance on vessel sizing is given below and also in BS
7074:1 and BS 5449.
Table 6 - 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.