What to do with my Frankenstein fuse box?

[JohnW2]

What are the options for kitchen sockets? ... A 20A circuit can power one full-size appliance plus smalls. So no real opportunity to exploit diversity ...

That's why, as I said, I don't really like 20A radials, anywhere.

... A 32A circuit on the other hand can power two full-sized appliances plus smalls. That means we can exploit diversity, it's unlikely that more than two appliances will be at full load at the same time, so we can cover the whole kitchen with one circuit. ... 4mm² is borderline for 32A, it will pass with method C and no derating factors, but only just, almost any derating or adverse installation methods will push you up to 6mm² ...

This is where common sense and the regs probably diverge a bit. Given we are assuming that cookers are not involved, if one applies the concept in general, I doubt that all the other appliances in a kitchen would be 'likely' (a word/concept beloved by the regs!) result in a total load over any appreciable period of time which would exceed the CCC of 4mm² cable, even if it were appreciably 'de-rated'.

Kind Regards, John

 

[flameport]

A dishwasher, washing machine or tumble dryer does not require it's own 20A circuit.
Washing machines and dishwashers use the heating element for a relatively small proportion of the wash cycle, typical power for the heater is 1.7kW to 2kW.
A direct heating tumble dryer will use the heating element most of the time, but they are around 2kW to 2.5kW, or approximately 10A.
Most smaller items in kitchens are used for very short periods, typically only a few minutes in the case of kettles, toasters and the like.

 

[securespark]

Mr Port, I have to say I am firmly in the radial camp, but this wasn't always the case.

When I started, I was working under the 14th Edition. Even though the 15th had been introduced 2 years earlier, there was much confusion over it (there was a huge format change from the 14th to the 15th), so it was agreed that sparks could elect to continue to work to the 14th Edition until 1985 happened along, when adherence to the 15th became mandatory.

I fully admit to being a sheep apprentice in the very early days and not challenging anything I was taught or told.
Ring finals were THE circuit of choice for 1363 accessories, as "that's the way we've always done it."

In smaller properties, there would be a 404 with a single ring final for the whole of the building, a single lighting circuit, an immersion and a cooker point.

Some sparks decided (sensibly IMO) that the upstairs socket circuits of larger houses did not need always need a 30A fuse and down graded it to a 20, but remained faithful to the ring final.

I guess old habits, especially perpetuated ones, die hard.

 

[JohnW2]

A dishwasher, washing machine or tumble dryer does not require it's own 20A circuit. ... Washing machines and dishwashers use the heating element for a relatively small proportion of the wash cycle, typical power for the heater is 1.7kW to 2kW.
A direct heating tumble dryer will use the heating element most of the time, but they are around 2kW to 2.5kW, or approximately 10A. ... Most smaller items in kitchens are used for very short periods, typically only a few minutes in the case of kettles, toasters and the like.

Exactly my point, which is why I don't believe that, in practice (rather than 'per regs') the cable of a single 4mm² radial supplying all of it would come to any harm, even if the cable were appreciably 'de-rated' because of installation method/grouping/whatever.

Maybe time to again wheel out the "Wiring Matters2 contribution to this discussion - not more than about 20A total for periods longer than about 30 minutes, and even the period nearer to 30A (for a short period) only if DW, WM and dryer all start more-or-less simultaneously:

Kind Regards, John

 

[EFLImpudence]

4mm² is borderline for 32A, it will pass with method C and no derating factors, but only just,

37A for 32A is hardly "borderline" or "only just".

With a ring though, you are allowed to install 20A cable on a 32A circuit.

Except T&E where you must use a 27A cable.

2.5mm² has a much bigger margin for a 20A circuit than 4mm² does for a 32A circuit and if you do have to step up due to adverse installation conditions, you are only stepping up to 4mm² which still gives room in the terminals for a spur.

...and if you install a shower circuit surrounded by thermal insulation, you will need a huge cable so don't install it that way.

 

[SUNRAY]

I don't understand what all these discussions about 'to ring or not to ring' and why go to the silly expense of 4mm² radials when 2.5mm² rings have been demonstrated time and time again to be significantly cheaper... and certainly easier to install.

As for 20A kitchen radials... what stupid idiocy is that???

My own daughter was pulling her hair out where the kitchen circuit kept tripping and the electronic programs in the washing machine, tumble drier and dishwasher would crash. The coffee machine required opening the back cover each time to do a reset. Luckily the property is mostly studded walls and adding the extra few metres of cable (maybe 10) was a doddle. Why oh why did the stupid idiot who built the place mess about with peoples sanity. Annoyingly it was listed as a 32A ring on completion documents but end to end shown N/A.

 

[EFLImpudence]

I appreciate what you are saying but I don't think people are saying the only option is one 32A ring or one 20A radial.

Obviously with 2.5mm², it can be 25A (yes, I know only method C) so not much less than 32A.

Or two 20A/25A radials, or more than two 16A radials with 1.5mm² - as is done here.

It all depends on the actual situation.

 

[SUNRAY]

I appreciate what you are saying but I don't think people are saying the only option is one 32A ring or one 20A radial.

Obviously with 2.5mm², it can be 25A (yes, I know only method C) so not much less than 32A.

Or two 20A/25A radials, or more than two 16A radials with 1.5mm² - as is done here.

It all depends on the actual situation.

Mmm let me see... 2x 20A radial Vs 1x 32A ring. 2 radials will, more than likely, use more cable than a ring and 2 OCPD will cost twice as much. 2 radials will require a certain amount of load planning, for the ring it's unlikely to need to be so.
Oh yes I can see the huge... massive... advantages of radials for multiple loads in domestic properties.

 

[JohnW2]

I don't understand what all these discussions about 'to ring or not to ring' and why go to the silly expense of 4mm² radials when 2.5mm² rings have been demonstrated time and time again to be significantly cheaper...

Can you perhaps help me with some insight into the thinking behind that statement?

... and certainly easier to install.

... and that one?

Thanks.

Kind Regards, John

 

[EFLImpudence]

Mmm let me see... 2x 20A radial Vs 1x 32A ring.

Why do you not say 2 x 25A (or even 1 x 25A) when you might never notice the difference?
There are more options than you keep quoting.

2 radials will, more than likely, use more cable than a ring and 2 OCPD will cost twice as much. 2 radials will require a certain amount of load planning, for the ring it's unlikely to need to be so.

I had not realised your prime objective was cheap and simple.
Two 32A 4mm² radials would be 64 Amp; that must surely be better despite the expense.

Rings do in fact have to use oversized cables most of the time.
Perhaps the powers that be could persuaded to increase the OPD ratings for rings now MCBs are used or allow 1.5mm² T&E then you could do it even cheaper.

There must be another reason why, when CUs are replaced, one ring for the whole property is changed to several.

You are talking about kitchens - perhaps the only place where a ring might be sensible, but not always.
I suppose in a kitchen a ring with many spurs would be best but that is always greeted with "extend the ring" so cables there and back in the same place.

Oh yes I can see the huge... massive... advantages of radials for multiple loads in domestic properties.

I am not saying there is a huge, massive advantage; just no disadvantage compared to the strict limits still imposed on rings.

 

[SUNRAY]

Why do you not say 2 x 25A (or even 1 x 25A) when you might never notice the difference?
There are more options than you keep quoting.


I had not realised your prime objective was cheap and simple.
Two 32A 4mm² radials would be 64 Amp; that must surely be better despite the expense.

Rings do in fact have to use oversized cables most of the time.
Perhaps the powers that be could persuaded to increase the OPD ratings for rings now MCBs are used or allow 1.5mm² T&E then you could do it even cheaper.

There must be another reason why, when CUs are replaced, one ring for the whole property is changed to several.

You are talking about kitchens - perhaps the only place where a ring might be sensible, but not always.
I suppose in a kitchen a ring with many spurs would be best but that is always greeted with "extend the ring" so cables there and back in the same place.


I am not saying there is a huge, massive advantage; just no disadvantage compared to the strict limits still imposed on rings.

Because, IME, it's not very often calcs allow a 25A MCB on a domestic multipoint 2.5mm² radial.

No my prime objective is not cheap. Yes I certainly try to keep it simple which for me is usually the ring option which is usually cheaper.

32A 4mm² radials to replace 32A 2.5mm² rings would frequently be non-compliant and/or harder work.

Two 32A 2.5mm² rings would be 64 Amp, why is that be worse?

Actually 40A rings are not banned.

IME the usual reason for increasing the number of power circuits is to bring the installation up to a more sensible state with the increased loads in the property since its initial design. I wouldn't automatically advocate making the change unless I thought it was required.

I'll usually try to maintain the ring, mainly to reduce the number of wires in a terminal, but I'd not go out of my way to do so.

When I read recent posts I get the impression some members feel rings are some sort of draconian blot on the landscape which serve no purpose in modern society. I believe they can be/are very much a sensible option.

I am not saying there is a huge, massive advantage of rings but IME there are less strict limits than imposed on radials.

 

[JohnW2]

Because, IME, it's not very often calcs allow a 25A MCB on a domestic multipoint 2.5mm² radial.

What 'calcs' are they? Provided only that thee CCC of the cable, as installed, is at least 25A, it can be as 'multipoint' (I presume you mesn multiple sockets) as you wish.

Actually 40A rings are not banned.

Indeed not - nor 6mm², 16mm² or whatever ones, provided only that you could find some accessories that could accommodate the conductors!!. However, there would be 'no point' in terms of the regs.

The only 'point' of 2.5mm² ring finals is that, by virtue of a 'special dispensation in the regs, one is specifically allowed to have cable with a CCC as low as 20A protected by a 30/32A OPD. There is no similar dispensation for OPDs >30/32A, so the maximum allowed rating for a hypothesised 4mm² ring would be no different from (no greater than) that allowed for a 4mm² radial - so (unless VD or EFLI were a perceived problem) nothing would be different if you cut your 4mm² ring in the middle, turning it into a radial which branched at the DB/CU.

When I read recent posts I get the impression some members feel rings are some sort of draconian blot on the landscape which serve no purpose in modern society. I believe they can be/are very much a sensible option. I am not saying there is a huge, massive advantage of rings but IME there are less strict limits than imposed on radials.

I don't know whether you are including me as one of those 'some members'? My views are in no way polarised. In virtually all situations, I don't think it makes hardly any difference which type of circuit one uses, the only caveat being that, as I've said, I personally don't really like the idea of 20A multi-socket radials, anywhere.

Kind Regards, John

 

[Risteard]

The AEI splitter, do not know why, but most people still call them a Double pole Henley block even though as in your case most nowadays are not made by Henley, they also make single pole versions.
Think the proper name nowadays is just a 100amp Single or Double pole connecter block.

We call what you call "Henley blocks" ISCOs here.

 

[SUNRAY]

What 'calcs' are they? Provided only that thee CCC of the cable, as installed, is at least 25A, it can be as 'multipoint' (I presume you mesn multiple sockets) as you wish.
Kind Regards, John

A survey a couple of years ago we quoted to install 6 13A DSSO's every 3m on block wall. We were not able to run tube at socket level however there was an existing steel trunking such that the new conduit drops were 1.875m (half a length). DB ~4m to first socket, total length of cable to end socket 38.375m not allowing for inside enclosures. Total length of ring 59.25m.
We used an on-line calculator...

 

[JohnW2]

A survey a couple of years ago we quoted to install 6 13A DSSO's every 3m on block wall. We were not able to run tube at socket level however there was an existing steel trunking such that the new conduit drops were 1.875m (half a length). DB ~4m to first socket, total length of cable to end socket 38.375m not allowing for inside enclosures. Total length of ring 59.25m.

That's a very specific, and (for domestic) almost uncommon enough to be described as 'irrelevant', anecdote - so I struggle to understand how your response in any way addresses my question (to which your were apparently replying, since you quoted it) (with my emboldening)...

Because, IME, it's not very often calcs allow a 25A MCB on a domestic multipoint 2.5mm² radial.

What 'calcs' are they? ...

What am I missing ?

Kind Regards, John