Please can someone tell me, is comparing 4mm and 2.5mm cable the same as comparing a chainsaw and a blender?

[PotatoSoup]

The maximum foreseeable load was the reason a ring final could be used for all the sockets in the kitchen. Fixed loads ( oven, induction hob and fitted microwave ) are on a radial.

The reason the rest of the cottage is on radials is due to constraints that ancient building impose on cable routings.

Got it - thank you

 

[PotatoSoup]

We have 16A circuits and 16A sockets.
No need for fuses everywhere nor polarity in the sockets, plugs and appliances because the overcurrent protection device is always in the line conductor.

That might seem horrible to you but it is only the UK ring circuit and its 32A capacity that brought about the need for the plug fuses and polarity restrictions in order to bring everything back to, in effect, the same as the 16A (for some reason 13A) circuit.

Definitely doesn't seem horrible to me

Thank you for the explanation

 

[PotatoSoup]

I'm going to start a new thread as my original query has been answered and I've got a new one. Thank you so much, Folks!!

 

[EFLImpudence]

Don't forget that the beloved 32A 2.5mm² ring circuit is, in fact, two 2.5mm² radial circuits which in the right conditions (buried in masonry) could each be 25A.

 

[JohnW2]

A 4 mm² radial can have up to approx 40 meters of cable, where a 2.5 mm² can have 106 meters of cable approx, ...

As I tell you (and, more importantly, others) every time you (frequently) post that statement, I think that it isi potentially pretty misleading ...

(a) ... those figures derive from consideration of ('recommended', not 'mandated') voltage drop under the most extreme situation of loading of the circuit (which situation will virtually never arise in practice), and

(b) ... the numbers themselves are misleading. 106 metres sounds dramatically more than 40m, but that 106 metres figure ignores the fact that a ring is a ring. With a ring final, a cable length of 106 metres means that the farthest socket could never be more than 53m from the origin of the circuit, which is not dramatically different from the 40m in the case of a 4 mm² radial circuit.

Kind Regards, John

 

[JohnW2]

Do you really expect to need multiple circuits with 7kW or more connected to them?
The vast majority of domestic electrical items have tiny power requirements.

Pragmatically, I agree.

However, a similar argument would probably say that it is exceedingly unlikely that, in a standard domestic setting, a 2.5mm² (or maybe even 1.5 mm²) radial protected by a 32A (or higher) OPD would result in any harm.

Returning to the OP, the difference between 32A and 40A (assuming Method C) is pretty trivial.

Kind Regards, John

 

[Risteard]

Ring final circuits are far superior to 4mm^2 radials. Either go for multiple 20A radials, or utilise 32A ring final circuits.

 

[JohnW2]

Ring final circuits are far superior to 4mm^2 radials.

In what sense?

Either go for multiple 20A radials, or utilise 32A ring final circuits.

Opinions vary. As I always say, I am personally no fan of 20A radials, particularly in areas such as kitchens - but I have no strong feelings either way as regards 32A ring finals vs. 32A 4mm² radials in such situations.

Kind Regards, John

 

[Risteard]

In what sense?

Opinions vary. As I always say, I am personally no fan of 20A radials, particularly in areas such as kitchens - but I have no strong feelings either way as regards 32A ring finals vs. 32A 4mm² radials in such situations.

Kind Regards, John

4mm^2 in very many circumstances isn't suitable for a 32A radial, along with 2*2.5mm^2 being easier to terminate. Plus 4mm^2 T&E has only a 1.5mm^2 cpc. Quite often 4mm^2 would be installed on a 25A protective device.

 

[JohnW2]

4mm^2 in very many circumstances isn't suitable for a 32A radial, ...

You mean when it's not installed by Method C? If so, whether that is the case in "very many circumstances" is probably open to ebate?

along with 2*2.5mm^2 being easier to terminate.

Again, open to debate. In general, I personally find 4mm² T+E nicer to work with than 2.5mm², and I've never had problems terminating 2 x 4 mm² conductors in any accessory (3 x 4 mm² can sometimes be more difficult).

Plus 4mm^2 T&E has only a 1.5mm^2 cpc.

It does, but if it results in an adequately low Zs, then it results in an adequately low Zs.

Quite often 4mm^2 would be installed on a 25A protective device.

That may depend upon where you're talking about and what you mean by "quite often". In England, 25A MCBs are "quite often" not available for a particular CU - and, indeed, when they are available, they are (possibly 'quite often') used to protect 2.5mm² (Method C) radials!

I do not regard any of the above as indicating that 2.5mm² ring finals are 'far superior' to 32A 4mm² radials, when the latter are possible. Such radials are obviously not possible if the installation method is such that CCC is less than 32A or the CPC size is such vthat Zs is greater than the permitted maximum - but if those problems don't exist, such that a compliant 32A 4mm radial is possible, then I see no reason to regard a 2.5mm² ring final as being "far superior" to it.

Kind Regards, John

 

[FrodoOne]

See

AND
the opinions therein expressed !

 

[FrodoOne]

We have 16A circuits and 16A sockets.

Australia "gets by" with (unfused) 10 A Socket Outlets on 20 A (2.5 mm²) Radials - and "Ring" Circuits are not permitted.
(15 A Sockets can be installed on such Radials, if required.
This used to be done for "Window Air Conditioners")

Kitchens are usually supplied by two separate 20 A circuits, (with 10 A Socket Outlets)
BUT
each of these circuits usually supply other rooms as well. (Bed Rooms, Lounge, Laundry, Garage etc . [Diversity])

Most average homes "get by" with three to four 20 A Radial circuits, plus one or two "Lighting Circuits" - of 10 A (1.5 mm²)
(Hence,, no "Winston" problems with using 10 A Socket-Outlets on Lighting Circuits" !)
Ovens,
Air Conditioners etc. are (each) supplied separately, with "Radials" dimensioned according to the current required.


Below is pictured a CU in a two bedroom house.
Typical, except that it has "over voltage" protection - which is not yet common

 

[JohnW2]

See

....
AND
the opinions therein expressed !

I'm not sure what point you are trying to make. In that video, flameport (as he's known here!) gives a very good description/explanation of what the "UK ring final circuit is" for those who do not 'know', but says nothing that most of us don't know, and the only 'opinions' he expresses are the very few at the very end, where he indicates that there really isn't any 'need' for such circuits (with which I think most of us would agree), and offers the always-cited downside of them being that of an unnoticed break in the ring.

... and, in any event, one man's opinion is one man's opinion.

Although a small number of people have strong (sometimes passionate!) views in one direction or the other, I think it is apparent from the amount of discussion ones sees that there really is not very much to choose between ring finals and 32A radials - certainly no 'right' and 'wrong'.

Kind Regards, John

 

[JohnW2]

Australia "gets by" with (unfused) 10 A Socket Outlets on 20 A (2.5 mm²) Radials

In the absence of fused plugs or sockets, what is the meaning of a "10A socket Outlet" (on a 20A circuit)?

Kind Regards, John

 

[ericmark]

I was watching a video of electrics in Italy, seems the total supply is often 6 kW, and I have read similar in France, it seems you are charged depending on the maximum you want to use, so a 25 amp supply is a lot cheaper than a 50 amp supply, and it would be hard to get a 100 amp supply, this means their whole outlook is different, they really had a problem with Smart meters, before they had a fuse, so exceed 25 amp for a short time no problem, but with Smart meters even a short over load caused the meters to disconnect.

However they use gas a lot more, often bottled gas for cooking, and open fires to burn waste wood from vines etc. The whole outlook is different, they can't do as we do with kettles, tumble driers, washing machines, dishwashers, immersion heaters, and the use of fan heaters and oil filled radiators.

How the home is split does change things, in the main most of the load is on the ground floor, so sensible split is side to side of the house, this also means should a circuit fail, temporary extension leads do not go up/down stairs, and we use less cable so the loop impedance is better, however what we don't want is if there is a fault on the socket supply, like some one touching some thing which gives them a shock, for the lights to also fail, so when RCD protection first came out, before we moved to RCBO's to split the home the same for lights and sockets mean you could arrange it so no room had lights and sockets on the same RCD, which resulted in many homes being split upper and lower floors.

Today with RCBO's it can return to the old method of side to side split, so the total on each circuit is reduced, so there is a case for the 20 amp radial circuit, the 32 amp radial is not really practical as the sockets with many makes simply don't have terminals which can take 2 x 6 mm² plus a 2.5 mm² for a spur, but will take 3 x 2.5 mm² which does not matter when installed, but may for future changes.

So the big question is how long with a circuit exceed 20 amp for? I have two 3 kW kettles plugged into the same extension lead and used them for quite some time like that, both boil a cup at a time, so they do not over load the 13 amp fuse long enough for it to rupture, the same will be true for a 20 amp radial, it needs to be overloaded for some time to trip a 20 amp MCB/RCBO, I know my son could run his washing machine on a 40ºC cycle on his narrow boat with a 6 amp type B MCB, so time does matter, but also what needs to be done to reset them if they trip, mothers house popping under the stairs to reset no real problem, my last house going outside into garage more of a problem, and this house going outside and down a set of steps to under the house not some thing I want to do when there is ice or snow on the ground. Case of crampons and ice pick.

So I have the tumble drier and washing machine in the same utility room, not tested but would assume both are plugged into the same ring final, and likely the same ring final supplies the kitchen, so could also have two kettles switched on at the same time, oven etc is on it's own supply, but seems likely during the adverts we could swap washing around and make coffee so four 2 to 3 kW devices switched on around the same time, so likely 40 amp load on the ring final, but only for a short time, so never tripped the 32 amp RCBO.

As to if it would trip a 20 amp, who knows? But is it worth taking the chance? I have tripped my 16 amp caravan supply, and we had to consider what we were using at the same time, one soon learns to turn off the central heating before starting to cook with electric, or turn one of them to gas, but the problem devices are the automatic devices, like a under sink water heater, you don't know when it will switch on.

A Quooker for example is between 1600 watt and 2900 watt, and it heats a tank of water, so you don't know when it is going to switch on, we are moving towards these auto systems, and heat up time 10 to 20 minutes depending on model, it uses power for a lot longer than a kettle as it holds more water, between 3 and 7 litres where a kettle is normally less than 2 litres, and mine only boil a cup at a time.

I am not saying you will fit one, but I am saying how we use electric does change, and the 13 amp socket has traditionally allowed the changes with the ring final over the years, and if not broke, why fix it? My grandad had the old 15 amp sockets, and I have seen a home with radials, and no desire to return to those days.