Sealed Systems
Page 23
fi ll pressure (cold) should be 0.2 - 0.3 bar greater than the
vessel charge pressure – giving typical system fi ll pressures of
approx 0.5 bar for a bungalow and 1.0 bar for a two storey
house.
Refer to the Domestic Heating Design Guide for further
information if required.
8. Repeat steps 4 and 5 as required until system is full of water at
the correct pressure and vented.
9. Water may be released from the system by manually operating
the safety valve until the system design pressure is obtained.
10. Close the fi ll point and double check valves either side of the
fi lling loop and disconnect the loop.
11. Check the system for water soundness, rectifying where
necessary.
7.3
VENTING THE PUMP
For those heating circulating pumps fi tted with a vent plug, it is
important that the pump is properly vented to avoid an air lock and
also prevent it running dry and damaging the bearings.
Unscrew and remove the plug from the centre of the pump motor.
Using a suitable screwdriver, rotate the pump spindle about one
turn. Replace the plug in the motor. Do not over tighten.
7.4
PRESSURE RELIEF (SAFETY)
VALVE OPERATION
Check the operation of the pressure relief (safety) valve as follows:
1. Turning the head of the valve anticlockwise until it clicks. The
click is the safety valve head lifting off its seat allowing water to
escape from the system.
2. Check that the water is escaping from the system.
3. Top-up the system pressure, as necessary.
undertaking) using an approved fi lling loop arrangement
incorporating a double check valve assembly.
The fi lling loop must be isolated and disconnected after fi lling the
system.
7.1.5 HEATING
SYSTEM
The maximum ‘setpoint’ temperature for the central heating water is
75°C. Refer to Section 1.1.
An automatic air vent should be fi tted in the fl ow and return pipes of
the highest point of the system.
If thermostatic radiator valves are fi tted to all radiators, a system by-
pass must be fi tted. The by-pass must be an automatic type.
All fi ttings used in the system must be able to withstand pressures up
to 3 bar. Radiator valves must comply with the requirements of BS
2767.
One or more drain taps (to BS 2879) must be used to allow the
system to be completely drained.
7.2
FILLING THE SEALED SYSTEM
Filling of the system must be carried out in a manner approved by
the local Water Undertaking.
The procedure for fi lling the sealed system is as follows:
1. Check the air charge pressure in the expansion vessel BEFORE
fi lling the system.
The expansion vessel charge pressure should always be slightly
greater than the maximum static head of the system, in bar, at
the level of the vessel (1 bar = 10.2 metres of water). Refer to
Figure 7-2.
The charge pressure must not be less than the actual static head
at the point of connection.
Check that the small cap (or screw) on all automatic air vents
is open at least one turn. The cap (or screw) remains in this
position from now on.
2. Ensure that the fl exible fi lling loop is connected and that the
double check shut off valve connecting it to the water supply is
closed. A valve is open when the operating lever is in line with
the valve, and closed when it is at right angles to it.
3. Open the fi ll point valve.
4. Gradually open the double check valve from the water supply
until water is heard to fl ow.
5. When the needle of the pressure gauge is between 0.5 and
1.0 bar, close the valve.
6. Vent each radiator in turn, starting with the lowest one in the
system, to remove air.
7. Continue to fi ll the system until the pressure gauge indicates
between 0.5 and 1.0 bar. Close the fi ll point valve. The system
Automatic fi ll valves should not be used
NOTE
Automatic fi ll valves should not be used and
will invalidate the warranty
NOTE
The air charge pressure may be checked using
a tyre pressure gauge on the expansion vessel
Schraeder valve.
The vessel may be re-pressurised, when
necessary, using a suitable pump. When
checking the air pressure, the water in the
heating system must be cold and the system
pressure reduced to zero.
NOTE
Some heating circulating pumps are not fi tted
with a vent plug so it is not possible to vent
these pumps in the manner described above.
Refer to pump manufacturers own instructions
for further details.
NOTE
