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Pressure
Safety
Gauge
Valve
Boiler
System Drains at
Low Point
Fig. 13
expansion vessel volume for sealed systems
Vessel Charge
Pressure (Bar)
0.5
1.0
1.5
Example :-
Table. 1
Then :-
Where a vessel of the calculated size is not obtainable then
the next available larger size should be used.
DHW
Mains
Fig. 14
Inlet
© Baxi Heating UK Ltd 2006
Air
Vent
Filling
Point
Pump
Expansion
Vessel
Max Boiler Flow
Temp = 82° C
Method of determining minimum valve of
using Baxi Boilers
Initial System
Pressure (Bar)
0.5
1.0
1.5
2.0
1.0
1.5
2.0
1.5
2.0
System Volume = 75 litres
Vessel Charge Pressure = 1.0 bar
Initial System Pressure = 1.5 bar
75 x 0.152 = 11.4 litres
Expansion Vessel Volume
NOTE
Double
Stop
Check
Stop
Valve
Valve
Valve
Temporary
Hose
3 Litre
Top Up Bottle
6.7
(if required)
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 (45 Ibf/in
arranged to discharge any water or steam through a pipe
Radiator
to a safe outlet position.
Circuit
2. PRESSURE GAUGE - A pressure gauge of minimum
range 0-4 bar (0-60 Ibf/in
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 (
The volume of the vessel should be suitable for the
system water content and the nitrogen or air charge
Multiply Total
pressure should not be less than the system static head
(See Table. 1).
Water Content Of
System By (Litres)
Further details of sealed system design can be obtained
from BS 5449 and the British Gas publication entitled
0.067
'Specifications for Domestic Wet Central Heating
0.112
Systems'.
0.207
4. FILLING POINT - A filling point connection on the
0.441
central heating return pipework must be provided to
facilitate initial filling and pressurising and also any
0.087
subsequent water loss replacement / refilling. The sealed
0.152
primary circuits may be filled or replenished by means of
0.330
a temporary connection between the primary circuit and
a supply pipe provided a 'Listed' double check valve or
some other no less effective backflow prevention device
0.125
is permanently connected at the inlet to the circuit and
0.265
the temporary connection is removed after use. The
filling method adopted must be in accordance with all
relevant water supply regulations and use approved
equipment.
Your attention is drawn to, for GB: Guidance G24.2 and
recommendation R24.2 of the Water Regulations Guide.
for IE: the current edition of I.S. 813 "Domestic Gas
Installations".
5. MAKE UP SYSTEM - A method of replacing water
lost from the system should be provided either by
means of a make up vessel of not more than 3 litres (5
pints) capacity, mounted above the highest point of the
system, or by re-pressurisation of the system.
6. VENTING - A method of venting the system during
filling and commissioning must be provided by fitting
automatic air vents or by venting manually.
7. HOT WATER STORAGE - The hot water storage
vessel must be of the indirect coil type. All components
used in the system must be suitable for operation at
110°C (230°F) and at the pressure allowed by the safety
valve.
CH
Return
6.0 System Details
Sealed Systems
(Fig. 13)
2
) with a fill pressure indicator
2
). It must be
1
/
in) nominal size.
2
15
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