On Wed, 03 Dec 2008 17:36:58 +0000, John Rumm wrote:

Even if that were true (which I doubt), a large proportion are unlikely
to ever be heated via the immersion, given the added cost compared to
doing it with the boiler.

I come across a number of places where I find the immersion heater
switched on despite the central heating system working. To many
householders it's just a switch in the airing cupboard that does something
magical and if it happens to be switched on and everything works, they
leave it that way.

Having the main thermostat and the safety cutout both fail to danger is
extremely unlikely and I'm sure the probability of any given unvented
installation being subjected to these conditions is very, very remote.
However as the number of unvented installations - and installations that
aren't safety checked periodically - increases, so the probability of
*some* of those installations failing to danger increases. And the
*consequence* of such failure is Not Good (tm).


--
John Stumbles -- http://yaph.co.uk

Many hands make light work. Too many cooks spoil the broth.