OT: School kitchen electrics

[Dave Plowman (News)]

It might have grease and all sorts in it from a pro kitchen. You mostly see industrial plugs and sockets in these because of this.

[Andy Cap]

They're actually moved out into the school hall Dave, which is not a dedicated dining room, so that's not the situation here. Could be chewing gum perhaps.

[dennis]

Like I said they aren't very durable.

15,000 is a pathetic number of cycles for a switch.

Poor design if you can hold the contacts there by hand.

[Andy Wade]

Well it is the minimum required by the standard. The better makes (MK, etc.) probably exceed it by a fair margin.

[Arcing]

Good design to avoid unnecessary toggle mechanisms which add would only add complexity and cost.

BS 1363 and the ring circuit system that seems to bother you so much has stood the test of time quite well. It's been in use for 60 years now - long enough, most people would think, for all significant problems to have shaken out. There have been a few changes of course, but not that many since the standard was first published in 1947.

[Dave Plowman (News)]

How many failed switch sockets have you replaced?

The vast majority are replaced for fashion reasons rather than that.

[Tournifreak]

I've replaced a dozen or so that have literally stopped working. They were all from Screwfix - their cheapest offering about 4-5 years ago (sub =A31 I think). About 10% never worked, and the rest followed pretty soon afterwards. I can't believe *they* passed the BS1363 endurance test Andy mentioned.

I thought it was just one batch, but foolishly/stupidly bought a couple more a couple of years back - one of those has failed too.

I've since bought a few dozen Crabtree ones - problem solved!

Jon.

[David Hansen]

On Thu, 19 Jul 2007 20:52:26 +0100 someone who may be "dennis@home" wrote this:-

As has been said, a different mechanism would add to complexity and cost. Would this be worthwhile? I suspect not. Would we really want to see people priming the mechanism like an item of high voltage switchgear and then tripping it?

[The Natural Philosopher]

Yes. One learns stuff like that eventually.

13A plugs with simple split pin fuseholders that bend and never make contact.

13A sockets that have soft flimsy contacts that arc after a few insertions.

Light bulbs that fail the week after they are fitted.

Its not always the cheap stuff either.

[Lyndon]

On some old switches (early 1950s?) the contacts moved apart gradually as you operated the switch. So it was possible to achieve any gap you wanted between closed and fully open. On a modern switch, as you operate the switch there is no movement of the contacts until you reach a point where the contacts snap open. I would call that a 'toggle' operation, and believe this is what Dennis was referring to. I do not believe that with a modern switch it would be possible to achieve any gap between fully closed and fully open.

[David Hansen]

On Fri, 20 Jul 2007 12:01:47 +0100 someone who may be "Lyndon" wrote this:-

Indeed, IIRC these are frowned upon if not disallowed these days.

In theory.

[Dave Plowman (News)]

For cheap I use these:-

They appear to be the old MK design - or at least match it if extending an installation. Not had any problems with them.

[dennis]

More than I should need to if those figures were correct.

[Dave Plowman (News)]

So none, I take it?

[dennis]

More can not equal none!

[Andrew Gabriel]

Contacts are deliberately slow break so that inductive loads don't cause high voltage spikes which damage wiring and accessories, but arc across the opening contacts instead, which they are designed to handle.

The 'click' in the switch action is mainly for user feedback of the switching operation, and often isn't actually the electrical switching point of the switch mechanism.