Why would an earthed frame cause problems if it were bonded to neutral? Surely it would only be an issue if, as already stated, the earth were centre tapped rather than electrically seperated and truly 'floating'.
If the frame is connected to the centre tap on the winding - as it often is on small generators - you will short circuit half the winding if you earth one of the outers (what you are calling a neutral) Try it - the generators are quite cheap these days .
Please note that any attempt to earth the 'neutral' end of the winding will end in tears if the generator earth connects internally to its frame . icon_eek.gif
I have also come across generators with centre tap. Designed for duel voltage 110/230 with two winding either parallel (110) or series (230) one winding being centre tapped to earth. OK in 110 format but in 230 volt mode gives 57-0-173 volt.If the frame is connected to the centre tap on the winding - as it often is on small generators - you will short circuit half the winding if you earth one of the outers (what you are calling a neutral) Try it - the generators are quite cheap these days .
I suggest you read BS 7430:1998 (18.2.5) and search for the HSE guidance on this subject.
Please note that any attempt to earth the 'neutral' end of the winding will end in tears if the generator earth connects internally to its frame .
With a centre tapped system that is floating with respect to true earth an RCD can provide protection but not against shocks to true earth.
The exposed-conductive-parts of the installation (food van) are connected as usual to the earth terminal of the generator. Any faults within the installation between either outer conductor and the exposed-conductive-parts will operate the RCD.
What will not happen is protection against faults to true earth. This is because we have not referenced to true earth. Should a 'first fault' occur that does reference the system to true earth a hazard will occur.
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