Benchmark Alpha CD18S Installation And Servicing Instructions page 29

8.21 PUMP - Refer to Fig. 31
Gain access behind the casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2.
Pump head
1. Remove the four socket head screws securing the pump head to the body. Withdraw the head, remove the wiring cover
and disconnect the wiring.
2. Connect the wiring to the new head as follows:-
Brown to L, Blue to N, Green/yellow to
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).
Complete pump
1. Remove the pump head as described above.
2. Unscrew the automatic air vent from the pump outlet.
3. Disconnect the pump unions and withdraw the pump body.
4. Connect the wiring as described above, ensure that pump is set to maximum and re-assemble using new sealing washers.
5. Refill and pressurise the system. (Refer to Commissioning, Section 5.1).
8.22 PRIMARY PRESSURE SWITCH - Fig. 31
1. Gain access behind the 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.
8.23 PRESSURE RELIEF VALVE - Fig. 31
1. Gain access behind the casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2.
2. Remove the four screws securing the bottom tray and remove the tray. Disconnect the pressure relief valve outlet fitting.
3. Release the screw retaining 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).
8.24 EXPANSION VESSEL - Fig. 12
Note: If there is less than 450 mm clearance above the boiler or a rear exit flue is used, it is not possible to replace the vessel,
in which case an additional vessel should be fitted external to the boiler in the central heating return pipe, as close to the boiler
as possible (see Fig. 5).
1. Gain access behind the casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2.
2. Disconnect the pipe from the pump inlet manifold and expansion vessel.
3. Remove the four screws securing the top support plate.
4. Lift the expansion vessel out of the boiler.
5. When replacing the vessel, ensure that the connection is towards the front of the boiler and re-assemble in reverse order
using new seals as necessary.
6. Refill and pressurise the system. (Refer to Commissioning, Section 5.1).
8.25 CYCLONE - Fig. 13
1. Gain access behind the casing and drain the boiler heating circuit as described in Sections 8.1 and 8.2.
2. Disconnect the unions from the cyclone and re-assemble with a new cyclone.
3. Pressurise the system. (Refer to Commissioning, Section 5.1).
8.26 CONDENSATE TRAP - Fig. 12
1. Gain access behind the casing and drain the trap as described in Sections 8.1 and 7.3, paragraph 10.
2. Disconnect the top and drain connection of the condensate trap.
3. Lift the trap out and re-assemble with a new condensate trap.
Note: Before fitting the new trap, pour 100 cc of water into the trap.
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Alpha CD18S/24S/30S - Component Replacement
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