kitchen wiring

[David WE Roberts]

Yes - socket in adjacent unit so you can get at it without touching the appliance.

[Dave Plowman (News)]

The 'design' current is for a reasonable life switching that current. So I'm not clear how you think a 13 amp fuse downstream of this will stop it being exceeded? If the appliance shorts, the fuse will blow. A switch with its contacts made will handle rather more than its rated spec.

The MCB contacts get damaged when it trips?

[Tim Watts]

No - the 32A isolator that would be used in place of teh 20A that you think is inadequate.

[John Rumm]

Its most likely what they had available at the time. There is no reason that a single socket wired as a spur (switched or otherwise) needs another fuse.

[John Rumm]

The design current for an unfused spur is 20A anyway (single or double socket) - so still adequate.

(obviously a double socket might not be a good design choice in that circumstance)

[ARW]

That is not a requirement. Washing machines and dishwashers do not need emergency switching.

A push in dishwasher or washing machine can be supplied from an unswitched socket behind it and requires no other isolation.

[ARW]

There is a benefit to using the 20A switch for local authorities and landlords. If the washer blows a fuse then it is the fuse in the washers plug top that blows and not the fuse in the fused spur. It saves a calling out an electrician. The tenant is told on the phone to remove the washer and try some other appliance in the single socket. If the other appliance works then you need not send an electrician

[ARW]

I suspect that you could melt an overloaded double socket before a BS1362

13A fuse trips given the right set up:-)

[Andy Champ]

We've just had the dishwasher catching fire thread. Personally I like the idea of pulling the power without having to move a smoking machine...

Andy

[ARW]

So where is the isolator for your TV? TVs catch fire.

[F]

Thanks: I stand corrected! Wish I had known that a few years ago...

[Dave Plowman (News)]

What are you on about?

[Dave Plowman (News)]

Then the socket needs to be some way from the machine. All the installations I've seen with isolating switches seem to site the switch above the machine. So you'd have to lean over the fire to switch it off...

[S Viemeister]

An acquaintance had to redo much of her kitchen earlier this year, after her dishwasher caught fire. I made sure to have an over-the-counter switch for mine...

[Dave Plowman (News)]

If my dishwasher caught fire, I'd need an ambulance, not new kitchen.

[Tim Watts]

I might counter with the same!

Shall we start again - why did you mention the MCB - I'm only discussing the isolator switch.

You *seem* to be claiming a 20A on a circuit with a 32A protective device is not adequate.

*I* am claiming it is, on the basis that the design current (ie the max possible load) cannot exceed 13A, because of the 13A (max) fuse that can be in the single plugtop that that leg feeds.

Problems with that??

[Dave Plowman (News)]

I was discussing your incorrect statement that a 13 amp plug fuse in some way protected the permanent wiring. Which is not its purpose.

Not so.

You are allowed a double socket on a spur.

The plug fuse protects the appliance cable. The CU MCB or whatever protects the permanent wiring.

[Tim Watts]

It may not be its original purpose, but by the laws of physics it does protect the upstream single cable (that after the tee off from the ring) from *overload*.

I believe it is also accepted as valid practise to make that assumption.

If the cable that the 20A isolator is controlling *cannot exceed* 13A by design (because there is a single socket/fused plugtop downstream) then the

20A isolator can never be subjected to an overload outside of its design limits.

Noone ever suggested a double socket on the end of this spur - the original discussion was IIRC regarding a single appliance socket being fed by an isolator that did not contain a fuse as part of the isolator.

That's overload scenarios covered.

Fault scenarios I covered previously.

[Tim Watts]

For an interesting read, see here:

is not 100% conclusive, but the statement "Isn't it like 2.5mm² not being rated for 32A either - but we still use it on ring circuits & unfused spurs"

distilled it for me.

Look at some light fittings - may be fitted to a 10A lighting circuit, but have a tiny 5A button/pullcord. However, in the same way, the current through the switch cannot exceed some fraction of an amp by design (max wattage lamp the fitting will take). Same logic.

[Dave Plowman (News)]

Not so. If that were the case, you could have unlimited outlets on a spur

- after that cable would be protected by the 13 amp fuse in each outlet, by your reckoning.

You are ignoring the possibility of a fault in the socket or spur cable feeding it.