Sealed Systems
22
6 Sealed Systems
6.1 Sealed System
Requirements
All Grant Spira boilers are suitable for
use with sealed systems complying with
the requirements of BS5449.
The system must be provided with the
following items:-
• Diaphragm expansion vessel
complying with BS 4814.
• Pressure gauge.
• Pressure relief (safety) valve.
• Approved method for filling the
system.
Expansion vessel
The expansion vessel can be fitted in
either the return or flow pipework in any
of the recommended positions as
shown in Figure 6-1. To reduce the
operating temperature of the expansion
vessel diaphragm, position it below the
pipe to which it is connected.
The expansion vessel may be
positioned away from the system,
providing the connecting pipe is not
less than 13 mm diameter. If the
expansion vessel is connected via a
flexible hose, care must be taken to
ensure that the hose is not twisted.
The pressure gauge must have an
operating range of 0 to 4 bar.
It must be located in an accessible
place next to the filling loop for the
system
Safety Valve
The safety valve (provided with the
boiler) is set to operate at 2.5bar. It
should be fitted in the flow pipework
near to the boiler.
The pipework between the safety valve
and boiler must be unrestricted, i.e. no
valves. The safety valve should be
connected to a discharge pipe which
will allow the discharge to be seen, but
cannot cause injury to persons or
property.
Filling Loop
Provision should be made to replace
water lost from the system. This can be
done manually (where allowed by the
local water undertaking) using an
approved filling loop arrangement
incorporating a double check valve
assembly.
The filling loop must be isolated and
disconnected after filling the system.
Heating System
The maximum temperature of the
central heating water is 75°C. Refer to
Section 1.1.
An automatic air vent should be fitted to
the highest point of the system.
If thermostatic radiator valves are fitted
to all radiators, a system by-pass must
be fitted. The by-pass must be an
automatic type.
All fittings used in the system must be
able to withstand pressures up to 3 bar.
Radiator valves must comply with the
requirements of BS 2767(10):1972.
One or more drain taps (to BS 2879)
must be used to allow the system to be
completely drained.
6.2 Filling the Sealed System
Filling of the system must be carried out
in a manner approved by the local
Water Undertaking.
Figure 6-1: Sealed heating system components
Figure 6-2: Heating system Pressure Gauge
Only ever fill or add water to the
system when it is cold and the boiler
is off. Do not overfill.
!
WARNING
!
NOTE
Ensure that the expansion vessel
used is of sufficient size for the
system volume.
Refer to BS 7074:1:1989 or The
domestic Heating design Guide for
sizing the required vessel.
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