raden wrote:

The earth needs to be fairly close to neutral for flame sensing to work

sounds like the flame sense signal is getting lost

Yep, it sounds to me as if the generator output is completely floating
(IT system). The OP needs to earth one side of its output to define a
neutral point and create a TN-S system. As someone else said you
mustn't rely solely on an earth provided by the public mains, but
there's no reason not to connect your means of earthing in parallel with
a supplier's earth (unless you intentionally have the house as a TT
installation).

Section 551 of BS 7671 refers.

http://groups.google.com/group/uk.d-...e=source&hl=en
has further information.

--
Andy