Baxi Bermuda BBU 15 HE Installation & Servicing Instructions Manual page 13

Pressure
Safety
Gauge
Valve
Pump
Expansion
Vessel
Boiler
System Drains at
Low Point
Fig. 6
Vessel Charge Initial System
Pressure (Bar) Pressure (Bar)
0.5
1.0
0.5
1.5
2.0
1.0
1.0
1.5
2.0
1.5
1.5
2.0
Example :- System Volume = 75 litres
Vessel Charge Pressure = 1.0 bar
Initial System Pressure = 1.5 bar
Then : - 75 x 0.152 = 11.4 litres
Expansion Vessel Volume
NOTE
Where a vessel of the calculated size is not obtainable then
the next available larger size should be used.
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3 Litre
Top Up Bottle
Air
(if required)
Vent
Filling
Point
Radiator
Circuit
Max Boiler Flow
Temp = 75° C
Multiply Total
Water Content Of
System By (Litres)
0.067
0.112
0.207
0.441
0.087
0.152
0.330
0.125
0.265
Fig. 7
4.0 System Details
4.7 Sealed Systems (Figs. 6, 7 & 8)
1. SAFETY VALVE - A safety valve complying with the
requirements of BS 6750 Part 1 must be fitted close to
the boiler on the flow pipe by means of a horizontal or
vertically upward connection with no intervening valve
or restrictions and should be positioned to facilitate
testing. The valve should be pre-set and non-adjustable
to operate at a pressure of 3 bar. It must be arranged
to discharge any water or steam through a pipe to a
safe outlet position.
2. PRESSURE GAUGE - A pressure gauge of minimum
range 0-4 bar with a fill pressure indicator must be fitted
to the system, preferably at the same point as the
expansion vessel in an easily visible position.
3. EXPANSION VESSEL - An expansion vessel
complying with the requirements of BS 4814 must be
fitted to the system by means of a connection close to
the inlet side of the circulating pump in accordance with
the manufacturers instructions, the connecting pipe
being unrestricted and not less than 15mm nominal size.
The volume of the vessel should be suitable for the
system water content and the nitrogen or air charge
pressure should not be less than the system static head
(See Fig. 7).
Further details of sealed system design can be obtained
from BS 5449 and the British Gas publication entitled
'Specifications for Domestic Wet Central Heating
Systems'.
13