Rob asks this question about where to find guidance on good practise for earthing a 14kVA generator. It has been answered by the ECA (Cables, Wiring and Wiring Accessories):
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Question: Where can I find guidance on good practise for earthing a 14kVA generator? BS7430:2011 section 7.2 refers to impedance between the generator E-N point and ground earth, and I request a source of information on procedure.
Also, I intend to run a 16mm2 earth round a workshop with several e.g. 2HP three-phase is correct motors, and make links to the various sockets, and continue this earth to the residence, which is served by supplies from both one phase of this generator, and also by an inverter drawing off a battery bank (separate consumer units in the house, one labelled genie and the other labelled inverter).
Is there any problem with one ground earth serving two power sources? (this is an off-grid location)
To finish, are there any issues to address in (a) the domestic environment, (b) in the workshop, with the voltage differential between accessible supplies? i.e. I am aware that different phases should not be accessible in the same room in a domestic environment, and there is likelihood of a similar situation arising with different AC sources.
Answer:
In response to your first question, ENA make a guidance for connecting generators to the public distribution - ER G84 is the main document to reference. If this is a temporary installation, BS 7909 is the most relevant British Standard for this. There is a very good guide book to this by an author called James Eade, which is worth looking into. Otherwise, the manufacturer of the generator set will always have technical facilities, so it is worth calling them.
Regarding your second query, it is quite hard to comment on design on these sorts of forums, so the ECA wouldn't want to say whether what you are proposing is right or wrong. 543.1.2 does allow a protective conductor to be common across two or more circuits however.
To answer your third question, are we talking about different supplies or different phases? If you have only one supply, there should be no reason to be concerned at having different phases (lines) in an area, i.e. a room or grid switch etc. If there are multiple supplies/sources (you mentioned earlier this is an off grid system) you may need to have additional warning notices as you would do with a typical AC supply where solar panels have been provided.
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