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12.0 Changing Components
38
12.21 Plate Heat Exchanger (Fig. 67)
1. Drain the primary circuit.
2. While supporting the heat exchanger undo the
screws securing it to the brass manifolds.
3. Withdraw the heat exchanger upwards and to the left
of the gas valve, taking care not to damage any wires or
controls.
Seals
4. There are four rubber seals between the manifolds
and heat exchanger which may require replacement.
5. Ease the seals out of the manifolds. Replace carefully,
ensuring that the seal is inserted into the manifold
parallel and pushed fully in.
6. When fitting the new heat exchanger note that the
left hand location stud is offset towards the centre more
than the right hand one.
7. Reassemble in reverse order.
12.22 Diverter Valve Assembly
(Figs. 68 & 69)
The diverter valve assembly comprises of a central
heating pressure differential valve and a domestic hot
water pressure differential valve. These are connected
to a manifold which is joined to the plate heat
exchanger.
DHW Pressure Differential Valve Diaphragm
(Figs. 68 & 69)
1. Turn off the mains water inlet tap and drain the
domestic hot water by turning on a hot tap.
2. Prise off the spring clip retaining the microswitch. Pull
the switch away.
3. Undo the sensing pipe nut from the valve and slacken
the nut at the inlet manifold. Ease the pipe away from
the valve.
4. Undo the screws securing the differential valve cover.
5. Carefully draw off the cover and remove the
diaphragm, noting the orientation.
6. Fit the new diaphragm and reassemble in reverse
order.
Plate Heat Exchanger
Rubber Seal
Rubber Seal
DHW Pressure
Differential Valve
Microswitch
Sensing Pipe
Thrust Plate
Pushrod
Diaphragm
Spring
Diaphragm
Fig. 67
Fig. 68
Fig. 69
Spring Clip
DHW Pressure
Differential Valve
Cover
Offset Stud