In article , David Looser
wrote:
"Jim Lesurf" wrote

My experience is that almost any type of conventional relay will end
up causing problems if the unit is used for many years. Avoid if at
all possible. Solid state relays would be much better if you can find
one that suits your purpose.


I don't share your jaundiced view of relays. Whilst they are not
suitable for every switching requirement, there are many applications
for which they are the most logical choice. I suspect your negative
view is based on the effects of cost-cutting by equipment
manufacturers.

Based also on kit I designed myself and where I chose relays. The problems
may take decades, but in my experience eventually turn up. If you think
about it, physical contacts all eventually wear or corrode, springs weaken,
etc.

SSRs are a lot more expensive than ordinary relays and
they have their own limitations. They only make economic sense when
very many operate-release cycles are expected over the equipment life.

I might cite the two relays in the control box of my 30-year old central
heating boiler. The boiler is well past it's sell-by date and due for
replacement in 2010 (esp if I can get Gordon Brown to chip in £400 :-),
but the relays have never been any trouble.

However the problem Ian is converned with is a safety issue, and for all I
know might affect users in some decades time from now.

And FWIW I had to change the controls for our central heating some time
ago.

Slainte,

Jim

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