Question for the " ELECTRICUTIONISTS"

[MdB]

A max of 8 double wall sockets per 32a ring circuit.

My understanding that this isn't the rule. You can have as many double sockets as you like - the rule is that there is maximum length of wiring per ring. Not having too many sockets is a good rule of thumb - some people say 10 double sockets - but it isn't in the regs. I could be wrong on this, I don't have a copy of the regs to hand to check.

 

[middi]

A max of 8 double wall sockets per 32a ring circuit.

My understanding that this isn't the rule. You can have as many double sockets as you like - the rule is that there is maximum length of wiring per ring. Not having too many sockets is a good rule of thumb - some people say 10 double sockets - but it isn't in the regs. I could be wrong on this, I don't have a copy of the regs to hand to check.

Your understanding may be better than mine. I installed the wiring circuits prior to a detailled conversation with a qualified electrician ( a family friend ) as to what the rules were. He eventually fitted all the plugs and the RCB.

Middi

 

[Flyfisher]

I've always understood there was no regulatory limit to the number of sockets on a ring, though I've also understood this was mainly in the context that many sockets allowed for more flexible room layouts rather than all of them ever being used. Thus, for example, a socket in every corner of a room allows flexible positioning of a television and a standard lamp. The 'diversity thing' means that it's very unlikely that someone would have a television, or an electric fire (etc), in every corner of the room.

But times change and the proliferation of electrical gadgets means that the modern house is likely to be woefully short of sockets; PCs, printers, phone chargers, iPod chargers etc, can easily mean that connectivity is the main concern rather than power provision. Hence the ubiquity of those plug-in socket strips in every DIY shed. I'm sure nobody would really like six or eight fixed sockets in every corner of their rooms, yet any room used as a study these days could easily require such a number.

Fortunately, all these modern devices require relatively little power so running a PC, screen, printer, powered speakers, scanner, mobile phone charger, wireless phone, desk lamp, shredder and iPod charger from socket strips connected to a single wall socket is perfectly safe, even for continuous operation.

But a kitchen has completely different characteristics, as discussed above.

 

[Lime]

There is no specific number limit of outlets allowed.
There is no restriction of a specific length of cable used to wire the ring final circuit.
However the particular electrical criteria required of all the outlets, the cable and the circuit protection restrict the length of cable and number of outlets that are possible.

The cable is limited by virtue of its electrical resistance.
If a ring is very long the 2.5mm cable may be inadequate and requires 4mm to be used for example.

If many appliances are expected to be used at any one time that fact limits the outlet number in the design stage.

As has been discussed, the domestic kitchen presents a potential high load area which also needs to be considered when installing a ring circuit.
In my kitchen (not wired by myself) I have a separate circuit for my fridge/freezer, a ring main limited to the kitchen area and a separate cooker outlet and socket.
If I had wished to use more equipment in my kitchen I would have had 2 ring mains wired in.

 

[middi]

In the room to be converted in new kitchen there are 12 double sockets, 8 on one ring and 4 on another ring.

Middi

 

[robgil]

I always thought it was 50 meters max on a ring main?

A good tip also is , sometimes or most times an electrician will separate the upstairs from the down stairs on two different rings, also with the lighting circuit.
This is not ideal and splitting the house down in half is a much better way of doing it.
Should the lights go out you wont be left in the dark on either floor, if that makes sense?

This is how this cottage is done and if the upstairs lights trip I wont be fumbling around in the dark and perhaps fall down the stairs, although I have fallen down the stairs more than once, and it wasn't even dark.

 

[robgil]

In a situation like this where someone may wish to make wiring changes in a room, and that room is not a kitchen yet, but may by some strange coincidence suddenly get converted into a kitchen fairly soon after the wiring changes have been made, .......... which rules apply?

The problem would come when you came to sell the place, or if Building Control were to need to see a certificate for the wiring once the new kitchen was finished, I think you'd get raised eyebrows if you said "well when we wired that it wasn't a kitchen!"

I dont understand how building control would even know it was a new install? How do they know the kitchen wasn't always there?

 

[Zebra]

The introduced the new cable colours at the same time as they introduced Part P. Anything wired in new colours is therefore known to have been done after Part P was introduced. But what I meant was if the kitchen building work was major enough to require BC to visit, which I realise might not be the case.

 

[Lime]

The introduced the new cable colours at the same time as they introduced Part P. Anything wired in new colours is therefore known to have been done after Part P was introduced. But what I meant was if the kitchen building work was major enough to require BC to visit, which I realise might not be the case.

No, the new colours were available for sometime before part p came into effect.

 

[Penners]

not many people plug an appliance into every socket of a ring main

Then there are the others who....

 

[middi]

Thanks mr P, I will show that picture to Mrs M.

Middi

 

[Lime]

A double socket?
Luxury!

 

[MdB]

Then there are the others who....

That is only 6 appliances in two sockets.

In my office at the moment, I have a total of 17 appliances plugged into 6 double sockets. (If everything was switched on at once then the load will come to about a 1.5kW so it isn't anywhere near overloaded.)

 

[Flyfisher]

I'm sure Penners' photo was in jest, but as long as everything is properly fused then no harm will come of such things, as MdB rightly points out (apart, perhaps, from the trip hazard). The worst that will happen is a fuse will blow to protect the wiring from overheating, which is its role in life.

On the other hand, silver foil wrapped around fuses, multiple fuse-wire in re-wireable fuses and power sockets spurred off lighting sockets are all things to be avoided - or in our case fixed when discovered. :shock:

 

[Penners]

multiple fuse-wire in re-wireable fuses

Now that raises a question that I, in my electrical ignorance, have often wondered about. If you fit, say, three strands of 5A fuse wire into a rewireable fuse holder and then load it by 15A, will they share the load to the tune of 5A each and remain intact, or will they all melt simultaneously when the total load exceeds 5A?

 

[MdB]

multiple fuse-wire in re-wireable fuses

Now that raises a question that I, in my electrical ignorance, have often wondered about. If you fit, say, three strands of 5A fuse wire into a rewireable fuse holder and then load it by 15A, will they share the load to the tune of 5A each and remain intact, or will they all melt simultaneously when the total load exceeds 5A?

It depends if the wire has a positive or negative rate of change of resistance with temperature.

If the wire increases in resistance with temperature then the three wires will load share and it will fail at something a bit less than 15A (a bit less due to mutual heating).

If the wire decreases in resistance with temperature then it won't load share and each wire will fail quickly in turn at a bit over 5A (a bit more due to a bit of load sharing which will occur).

 

[Penners]

Thanks, MdB. I should have known better than to ask, really!

I was talking about standard fusewire - what does that do when its temperature increases?

 

[Lime]

In the old days of domestic wired fuses, the use of multi-strand fuse wire (not twisted together but spaced) in a fuse was a method to make the fuse more sensitive and accurate.
It is still used in larger fuses today.
The electricity company's main house fuse (probably 60 to 100 amp) is made using multi-strand silver wire.
Multiple strands makes the fuse more resistant to continuous high load (more wires spread over larger area dissipates heat better) with the added bonus of a greater sensitivity to slight over-load.

 

[Lime]

Thanks, MdB. I should have known better than to ask, really!

I was talking about standard fusewire - what does that do when its temperature increases?

Copper fusewire's resistance increases with a rise in temperature (positive temperature coefficient) .

 

[MdB]

I was talking about standard fusewire - what does that do when its temperature increases?

I don't know and wiki didn't tell me. Sorry.

edit - beaten to it by Lime who appears to know a lot more than I...