Socket Types

tampinator · 17 Jan 2005

Double switched, single switched, double pole, single pole. What is the difference between these 'outlet' sockets and when is it appropriate to use each one ? Thanks.

securespark · 17 Jan 2005

Well the double/single bit is easy. One has one outlet and the other has two.

Basically, you use 2 gang (doubles) -which are still only rated at 13A for the whole unit (ie NOT 26A)- except where you want a 1 gang (single) for a dedicated outlet ie appliance etc...

Single Pole switching means just the live is disconn'd from the socket when switched off, double pole kills both phase conductors, live & neutral.

Careful_Bodger · 17 Jan 2005

SecureS - what are unswitched sockets/outlets for then??

I'd really like to know! Is there a specific requirement or application?

Apologies if this is perceived as 'Thread-jacking'.

Ta

ban-all-sheds · 17 Jan 2005

Careful_Bodger said:
SecureS - what are unswitched sockets/outlets for then??

They are for cheapskates.

shaggy · 17 Jan 2005

There is an argument for plugging a freezer into an unswitched socket though.

ban-all-sheds · 17 Jan 2005

Actually - fridge/freezer question aside, I guess they're OK for installing below worktops when you've got the switching above with FCUs or a grid.

Paul_C · 17 Jan 2005

Cheapskates? Possibly perceived as such only because the majority of sockets fitted in British homes are the switched variety.

There's nothing against fitted unswitched outlets throughout if you wish. Most other countries use unswitched sockets -- The idea that an integral switch should be there seems to be a peculiarly British idea (adopted also bv a handful of British-inflluenced places: Australia, New Zealand, etc.).

tampinator · 17 Jan 2005

Thanks for your responses. Why is there double and single pole? In what circumstances would you want to use double rather than single, and visa versa?

securespark · 18 Jan 2005

Careful

I didn't mention unswitched because Mr Tampinator didn't ask!

But Ban is right - any equipment you do not want switched off in error can be fed from un/sw sockets, as can equipment fed from a switch elsewhere.

They may be long forgotten by most (Aaaaaaahhhhhh!) but they still have a valid place in a well-designed installation.

Careful_Bodger · 18 Jan 2005

Mr Tampinator didn't ask!

...which is why I did..........

Thanks SecureSpark

ban-all-sheds · 19 Jan 2005

securespark said:
Basically, you use 2 gang (doubles) -which are still only rated at 13A for the whole unit (ie NOT 26A)

Now here's an interesting thing.

From a footnote in Paul Cook's Commentary, to a table summarising the results of various calculations for ring final circuits (Table 16.4.7 on pp320-321 for those of you following this at home)

(with my emphasis):

Design current based on a 20A load at the extremity and the balance to device rating (10 or 12A) evenly balanced. This equates to 25A for a 30A device. 20A is the maximum current socket-outlets to BS 1363 are required to handle.

mapj1 · 19 Jan 2005

Coming back to the poles. In most cases, switching off the live is fine, and 'unplug before changing the bulb' gets round the (small) risk of reverse supply polarity. I'm not aware of any legal binding situation for DP switching, but it is considered more 'secure' particularly if the supply is overhead, and may one-day suffer a broken neutral.
The other situation is if an applience develops an earth neutral fault, it will trip the RCD when off, if on a single pole switch, but not double pole.
In reality all these risks are rare, and both types are used interchangeably, though people who prefer 'belt and braces' will generally specify DP switching, partly as the cheaper makers dont do them!
M.

plugwash · 19 Jan 2005

changing lightbulbs live isn't exactly dangerous anyway.

if it was then pull cord switches would have to be banned as you cant tell what position they are in.

mapj1 · 19 Jan 2005

changing lightbulbs live isn't exactly dangerous anyway.

I would agree, but if you do it for work, then you should have switches known to be off, and if you cant see the switch in question while you are working then you should station a colleague by the switch, in case of accidental operation.
All over the top, as at home you can change the bulb with the juice on, and the worst that happens is it lights up...
Of course removing the stem of broken bulb is another matter entirely.

Many years ago I changed a ceiling rose and broken bulb holder in a hallway for a friend, and very carefully took out the downstairs lights fuse, and had it in my pocket while I worked. As I re-fitted the replacement lamp holder and put the bulb back in , it came on

. In one sense testament to my "work like its live even if its dead" practice, but a bit of a surprise, I'll say. Nowadays I double check that the hall light isn't on the upstairs circuit !

Incidentally the normal bayonet lamp holder is IMHO by far the most dangerous connector we have in common use, in terms of exposed live pins (rather then live holes) we have loads of them next to the bedsides of fiddly fingered kids, and yet there are very, very few accidents. Do we think the traditional bulb holder is really dangerous, and should be phased out, or that our paranoia for seeing danger in what are really very low risk circumstances is running slightly out of control?

regards M.

tampinator · 19 Jan 2005

Thanks mapj1 for your helpful contribution.
What are the pros and cons of light bulb bayonet fittings verses screw-in fittings? I lived in the U.S.A. for 13 years and can't remember a seized screw-in fitting. Of course it's possible to over-tighten them but you'd have to be ham-fisted to do that.

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Socket Types

Paul_C

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