Benchmark Alpha CD18S Installation And Servicing Instructions page 20

5.5 CHECK THE BURNER PRESSURES - Figs. 23, 24
Turn the boiler off. Remove the two pressure test point screws at the top of the boiler and connect a differential pressure gauge
to P1 and P2 as shown in Fig 24. Allow the boiler to run for 10 minutes and check the differential burner pressures.
1. Set the boiler selector switch to 'ON'.
2. The burner will light at the ignition rate and will increase to the factory pre-set maximum output after 1 minute.
Note: The burner pressure settings have been factory set and do not require adjusting. If incorrect, check that the inlet gas
pressure is 20 mbar.
If the inlet gas pressure is not 20 mbar, either the pipework is too small or the gas supply to the house is insufficient, in which
case contact your gas supplier.
3. Turn off the boiler. Disconnect the pressure gauge and tighten the test point screws.
Test for gas soundness using suitable leak detection fluid.
Note: Refer to Technical Data, Section 2.1 for the required differential burner pressures.
Differential
Burner
pressure
5.6 FINAL COMMISSIONING
1. Allow the heating system to heat up, then balance the system to achieve the necessary temperature difference across the
heating flow and return pipes at the boiler and check the system volume and pressure. (Refer to Technical Data, Sections
2.2 and 2.8).
2. Turn off the boiler.
3. Thoroughly flush out the water pipework (refer to Section 3.9) and with no pressure in the boiler heating circuit, empty the
cyclone at it's drain point (see Fig. 13) of any debris.
4. Re-pressurise the system as described in Section 5.1.
5.7 FINAL ASSEMBLY
1. Raise the control panel and secure in position with the screws provided.
2. If the boiler is to be left in service with the User, set the controls, clock (if fitted, see User's Operating manual) and room
thermostat (if fitted) to the User's requirements.
3. If the boiler is not to be handed over immediately, close the boiler gas service cock and switch off the electrical supply.
4. If there is any possibility of the boiler being left during frost conditions, then the boiler and system should be drained (refer to Section
8.2). It is recommended that a label is attached to the boiler drawing attention to the fact that the system has been drained.
5. Complete the details of the installation in the Benchmark Checklist on page 35.
Fig. 23 Fig. 24
Alpha CD18S/24S/30S - Commissioning 19