Hi,

In recent musings about generators, UPS systems etc. I have been
thinking about transfer switches.

Is there much difference between a "transfer switch" such as this:
http://www.mowers-online.co.uk/itm01417.htm

and a suitably rated contactor such as this:
http://cpc.farnell.com/MC00148/elect...-k2-30a10230ac
(rating would need to be sized according to electrical load)

Obviously one comes in a nice box, with accessories - but as long as
the contacts break before they make, surely these will both do the
same job?

I'm also unsure what extra complexity an "automatic" transfer switch
has, beyond perhaps a short time delay circuit that will activate the
contactor once the secondary supply starts up..

I've no plans to implement anything just yet, but am definitely
curious as to how much could indeed be d-i-y-able, or which parts
would still need to be purchased off the shelf.. Previous discussion
threads regarding generators, earthing etc. would of course still
apply.