Alpha CD25C Installation And Servicing Instructions page 29

8.20 TEMPERATURE SENSORS - Refer to Fig. 28 and 32
Note that both sensors are the same.
1. Gain access as described in Section 8.1 and drain (heating circuit for primary sensor or hot water circuit for DHW sensor)
as described in Section 8.2.
2. Primary Sensor - The primary sensor is positioned on the bottom right hand side of the heat exchanger, see Fig. 28.
Disconnect the wiring and unscrew the sensor. Re-assemble in reverse order with a new sensor and sealing washer.
2a. DHW Sensor - The DHW sensor is positioned in the hot water outlet pipe, see Fig. 32. Close the mains cold water inlet valve
and open the lowest hot water tap to drain the DHW system. Disconnect the wiring and unscrew the sensor from the hot water
outlet pipe. Re-assemble in reverse order with a new sensor, replacing the sealing washer if necessary.
8.21 AUTOMATIC AIR VENT - Fig. 32
1. Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2.
2. Remove the retaining clip from the manifold and lift out the automatic air vent. Fit a new one using a new 'O' ring.
3. Refill and pressurise the system. (Refer to Commissioning, Section 5.1).
8.22 PUMP - Refer to Fig. 32
Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2.
Pump head
1. Using a 5 mm Allen key remove the four socket head screws securing the pump head to the body. Withdraw the head,
remove the wiring cover and disconnect the plug.
2. Connect the plug to the new head. Ensure the pump is set to maximum (3) and re-assemble in reverse order.
3. Refill and pressurise the system. (Refer to Commissioning, Section 5.1).
8.23 PRIMARY PRESSURE SWITCH - Fig. 32
1. Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2.
2. Disconnect the wiring from the pressure switch.
3. Unscrew the switch from the primary flow pipe.
4. Using the new washer supplied, re-assemble in reverse order.
When connecting the wiring to the new switch the polarity of the wires is not important.
8.24 PRESSURE RELIEF VALVE - Fig. 32
1. Gain access behind the front casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2.
2. Disconnect the pressure relief valve outlet fitting.
3. Release the two screws and the retaining clip securing the pressure relief valve and pull out the valve.
4. Re-assemble in reverse order.
5. Refill and pressurise the system. (Refer to Commissioning, Section 5.1).
8.25 DHW HEAT EXCHANGER
1. Gain access behind the front casing and drain the boiler heating and hot water circuits as described in Sections 8.1 and 8.2.
2. Release the nut securing the condensate pipe and remove the flexible condensate pipe from the condensate trap. Rotate
the pipe to clear.
3. Remove the diverter valve motor as described in Section 8.14.
4. Using a 4 mm Allen key unscrew the two socket head capscrews securing the DHW heat exchanger and withdraw the
heat exchanger from the boiler, lifting it upwards and tip it forwards to remove.
Note: Be careful not to allow water to drip onto any electrical components.
5. Re-assemble in reverse order making sure that the words on the heat exchanger are at the top when fitted and that the
seals are in position in the manifold.
6. Refill and pressurise the system. (Refer to Commissioning, Section 5.1).
Alpha CD25C/28C/35C - Component Replacement
29