harry wrote:
On 16 Sep, 14:37, wrote:
harry wrote:

That's just a switch, it's not difficult to buy battery isolation
switches to do the same and they don't cost more than £200 like the
one above! I can see good reasons for using something like the one
above in motorsport and similar applications but it really isn't that
necessary on a boat as long as you have a readily accessible
mechanical switch.
--
Chris Green- Hide quoted text -
- Show quoted text -
A switch and an isolator are not the same thing. Isolators are meant
to be opened under no-load conditions.
They won't last long used as switches which will interrupt their rated
current.
True, I was just meaning that it isn't an overload protection device.

It's not actually clear whether the device in question is intended to
*switch* the current or not. Given that it's a solid state device it
might actually be able to switch while on load without much distress.

--
Chris Green- Hide quoted text -

- Show quoted text -

A solid state device is not an isolator. The circuit has to be
phyisically broken in both poles to be considered to be isolated.


Well, that's not strictly true Harry. Whilst a solid-state device cannot
offer an isolation function (because it can't achieve the prescribed
"separation distance" of contacts and because the wiring regs simply
don't allow it), the isolation function does not *by definition*
require the neutral to be disconnected.

Section 537 of the wiring regs applies. You need to read the whole
section, but here's three short extracts:-

=====

"537.1.4

[...]

A main switch intended for operation by ordinary persons, e.g. of a
household or similar installation, shall interrupt both live conductors
of a single phase supply."

So, in a domestic environment, the main switch (in the consumer unit)
must be two pole.

However,

=====

"537.2.1.1

Every circuit shall be capable of being isolated from each of the
supply's live conductors. In a TN-S or TN-C-S system, it is not
necessary to isolate or switch the neutral conductor where it is
regarded as being connected to earth by a suitably low impedance."

Thus, by inference, the requirements for TT systems are different in
that, as the neutral is not "regarded as being connected to earth by a
suitably low impedance", isolation of the neutral *is* required.

=====

"537.2.2.1

A device for isolation shall isolate all live supply conductors from the
circuit concerned [...].

[...]

Semiconductor devices shall not be used as isolating devices."