In message , Andrew Gabriel
writes

snip

Thanks Andrew - there is certainly a longish run to the workshop but a
700W heater - it's one of those ones with a bulb like thing and a
hyperbolic reflector - is hardly going to load anything significantly,
and this is at the half power setting.
I didn't realise that toroidal transformers were that sensitive. I
did guess it was a non-sinusoidal supply problem but I was surprised
that a 30A+ supply would be affected by a 'dirty' 1.5A load, and
further the lights and power are on separate mcbs on the local split
distribution CU
The 2kw fan heater makes no difference to the lights - the 3kw
circular saw does on start up.

Well, this might not be the correct explanation, but it was
all I could think of. It would be interesting to know how
the 350W switch works. It's probably really a 'dirty' 3A load.
If the 2kw fan heater doesn't cause any dimming of the lights
when you switch it on, I'm rather stumped.

A friend with an American camper van (mobile home:-) complained of
something similar.

In his case the toroidal step up transformer seemed to be affected by
the current load when the microwave cooker was in use. The most
noticeable effect was serious smoke from the diesel generator.

regards


--
Tim Lamb