Tony asks this question, which concerns a genset supplying electrical power to a building site cabin, and the method of earthing needed. It has been answered by SELECT (Theme – Power):
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Question: Does a generator, which is supplying a site cabin, need earthing via an earth rod?
Answer: You have not mentioned rating of the generator concerned. If this is only small single-phase generator (<10 kW), then you will have to refer to manufacturer’s instructions, as there are numerous types, some of which do not require earthing via an earth electrode, and some of which do.
If it is a larger three-phase generator, then it would probably need to be earthed via an earth electrode, the resistance to the general mass of earth being 20 ohms or less.
You can refer to Chapter 55 (see also Section 717) of the Regulations (BS 7671: 2008), or Section 2.4 of the On-Site Guide.
Note that Chapter 55 covers ‘Other Equipment’, and includes requirements in Regulation 551.7 to ensure the safe connection of low voltage generating sets including small-scale embedded generators (SSEGs).
BS 7430:2011 also has a Section 7 dealing with all types of generators.
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