Typically, when applying the new regulations (Regulations 443.4 and 443.5) the outcome in many instances will require overvoltage protection to be provided. Therefore, the presence, correct selection, erection, and correct operation of SPDs should be included as a part of the inspection process for initial verifi cation purposes and details should be included in the record of the inspector’s checks provided in the certifi cation.

Note: T ere is no specifi c test that can be performed to verify that a device is operating correctly. However, most SPDs have a status indication that should be checked to ensure the status indicates normal operating conditions – reference to manufacturer’s instructions will be necessary.

It is also worth noting from a

designer’s perspective that to satisfy requirements in larger installations it may be necessary for more than one SPD to be installed within an installation. As well as being aware of these diff erent ‘Types’ of SPD, the inspector will also need to be able to verify that they have been correctly selected and erected in line with the requirements given in Section 534. Type 1 devices are typically

installed where there is a risk of direct lightning current and will be located at the origin of the installation.

These should be expected in a building

provided with a lightning protection system to BS EN 62305. Type 2 and 3 devices may also be located downstream in such an installation close to sensitive and critical equipment, e.g. distribution equipment, comms room equipment etc. Type 2 devices however can also be found located at the origin of an installation in a building – specifi cally one without a lightning protection system and then also located downstream close to sensitive and critical equipment, e.g. near each distribution board. Type 3 would normally be found located at the end of any fi nal circuits

Note: Combined Type SPDs also exist – e.g. Type 1 and 2 – which provide high-surge-current-handling and better overvoltage protection level (Up).

What should be checked and how should the presence of SPDs be recorded? After establishing that overvoltage protection is actually necessary and has been provided, locate where the SPDs have been installed and also check the manufacturer’s instructions carefully to determine if there are any specifi c installation requirements and make sure that these have been followed.

supplying sensitive equipment, e.g. supplies to server equipment.

The details of the installed devices should be obtained during the inspection process and recorded on the circuit chart schedule of test results. The type of SPD is normally clearly visible and is indicated on the front of the device, as shown in the image on this page. In some instances, an SPD will need to be supplied via its own dedicated overcurrent protective device (OCPD). To protect it against short circuit faults and to limit the length of connecting cables to it, this OCPD should be located in the circuit way in the distribution board nearest to the incoming supply – this is outlined in guidance provided in Appendix 16 of BS 7671:2018 and is shown above in Figure 1.

Continued on page 38 >>> CABLEtalk AUGUST/SEPTEMBER 2021 37

Figure 1

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