Should an earth spike be used when a generator is used to power class 1
equipment that normally needs an earth? (thinking of safety and ignoring
EMC). I should know the answer to this but can see two sides of the coin
and can't choose between the two.
On one side it would be good to tie the gen and neutral down to Earth,
but on the other side it would seem sensible to let the whole lot float.
... and how would an RCD cope?
The particular case is using a gen to provide power for an outdoor PA
system (and maybe a band).

Dave