In article om,
mick writes:
On Fri, 18 Dec 2015 19:10:46 +0000, Tim Watts wrote:

(Spun off from Chris' thread).

Just noticed my water heater isolator (about 45A load) gets rather warm
after 15-30 mins of operation.

Tightened the terminals - but it seems to be the switch element - the
toggle base gets to perhaps 40-50C by feel. Never noticed before because
I'd never really gone around feeling shower/water isolators under high
sustained loads!

Personally I'd expect a simple switch to be stone cold even under
permanent full load.

Is this reasonable - or time to replace? It's a GET plate - only 6 years
old.

Cheers,

Tim


It's difficult to be certain. For fairly modern stuff it's "not hot
enough to cause damage to the contacts or operating mechanism"! You'd
really need to look at the manufacturers data sheet as that will indicate
stuff like derating due to ambient temperature.

Yep - datasheet (at least for professional quality parts) will tell you,
because the heat from a breaker running at full load reduces the overload
trip rating of the adjacent breakers. Hence there is sometimes a requirement
to space out breakers expected to run at full load for long periods, so
they don't overheat or take themselves or adjacent breakers too far from
the rating plate.

--
Andrew Gabriel
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