12.0 Changing Components
36
12.20
Central Heating Differential Valve
(Figs. 63 & 64)
1. Drain the primary circuit.
2. Undo the screw securing the microswitch to
the differential valve. Allow the microswitch to
rest to one side.
3. Undo the pressure gauge capillary nut and
heating flow pipe nut from the valve.
4. Prise off the bypass connecting clips and
disconnect the heating flow tap. Undo the screws
securing the valve to the boiler bottom panel.
Remove the valve.
5. Remove the screws securing the cover from
the valve body. Examine the condition of the
diaphragm, spring and pushrod, replacing as
necessary.
6. If required the complete valve assembly can be
replaced.
7. Examine the sealing washers and ‘O’ ring on
the pipes and capillary, replacing as necessary.
12.21
Central Heating Differential Valve
Microswitch
(Fig. 64)
1. Remove the two wires from the microswitch.
2. Undo the screw securing the microswitch to
the valve body.
3. Reassemble in reverse order.
12.22
Pressure Relief Valve
(Fig. 65)
1. Drain the primary circuit.
2. Disconnect the discharge pipe from the valve.
Using a suitable hexagon key undo the grub
screw sufficiently to release the valve.
3. Note the orientation of the valve, rotate it and
withdraw it from the manifold.
4. Fit the new valve and ‘O’ ring seal and set to
the previously noted orientation. Reassemble in
reverse order.
Microswitch
Bracket
Diaphragm
Fig. 63
Fig. 64
Pressure Relief Valve
Grub Screw
‘O’ ring seal
Discharge Pipe
Fig. 65
Summary of Contents for Performa System 12e
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