"Cursitor Doom" wrote in message
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On Thu, 02 Jan 2014 08:37:33 +0000, harryagain wrote:

"Chris Crinkle" wrote in message
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I have a 7 day timer, with a max load of 13A at 240V.
However reading the instructions its states there is an inductance
current of 3A. What does this mean ?

Inductive loads (motors, coils etc.) have stored energy in their coils
which means the current you have to break can be much higher than is on
the rating plate.

So any switch rated for a non-inductive load (lights, heater) will be
down rated for inductive loads.
Some are not suitable at all for inductive loads.

I don't really understand why peeps here are describing heaters as non-
inductive loads. They most certainly ARE inductive; not so much as
motors, but significantly inductive nevertheless. Reason being the
resistance wire used in them is bunched up in coils to save space and
where you have a coil you have inductance. In fact even a straight wire
has a tiny amount of inductance but that's another story.
Coils store energy in the form of a magnetic field and when the current
is switched off, this field collapses generating a back EMF (a voltage
spike). This can be several thousand volts in some cases, causing arcing
of the switch terminals and shortening their life. You therefore have to
'de-rate' the current to allow for this.

The inductive effect is insignificant in electric heaters with a few dozen
turns of conductor in air.

Significant inductors have hundreds of turns of wire wound onto iron cores
which store significant energy in the form of a changing magnetic field.