Ring vs Radial circuit, what would you do?

[dsbuds]

Hi all,

Just a question to the hive mind, I have had two different opposing answers from different electricians so wanted to see the general consensus of those in the know (one said leave as radial, other said to re-create the ring).

Currently:
Downstairs: 16A radial in 2.5T+E (was a ring when rewired, but presume tested bad so someone swapped MCB for a 16A, I found the other end still live under the floor with a single wrap of insulation tape....)
Kitchen + Garage: Joined into the same MCB as downstairs sockets (this flagged on EICR) also 2.5 T+E
Upstairs: 16A radial in 2.5T+E

The floors are still accessible, so I'm wondering if it is worth getting a spark to re-create the downstairs ring, or to leave as a radial? We already have a dedicated circuit for one electric fire (other room planned to be gas), so likely only appliances on the downstairs circuit will be low power TV/Game console/lamps/etc. I understand that a short enough radial can possibly be upped to 20A too.

Kitchen / Garage I'm going to ask the electrician to put onto their own dedicated MCBs if possible, washing machine in the kitchen and tumbler in the garage so I can see tripping if we're doing too much at once. Kettle is on the cooker socket thankfully so we've avoided that so far.

Cheers!

 

[AndyPRK]

I don’t think you will get an agreement here.

You understand downstairs will have benefits of being on a ring and if it’s easy to resolve.

Sounds like your having a new cu so plenty of spare ways. As a minimum I would want 20A. Sometimes you can get 25A which would do the kitchen well.

So if you want some sockets to carry on working under fault conditions of others, Lots of Radials with rcbo is best.

 

[endecotp]

Imagine what you will do if the central heating dies and you have to use electric heaters temporarily. That’s the worst case, does it cope?

 

[pete01]

Could you create 2 x 20 amp radials somehow?

 

[Murdochcat]

Sounds like mr DIY has been messing around a lot.

How old is the property? And the wiring?

 

[Taylortwocities]

Sounds like mr DIY has been messing around a lot.

How old is the property? And the wiring?

Mr DIY doesn’t know or care about incomplete rings and making two radials.
A spark will have been involved here.

 

[Murdochcat]

Mr DIY doesn’t know or care about incomplete rings and making two radials.
A spark will have been involved here.

Not sure in agree with this

 

[ericmark]

We consider sockets on a 32 amp supply as having a design current of 26 amp, that is 20 amp centre of ring and 12 amp even spread, so for volt drop 26 amps is used, allowing up to 106 meters of 2.5 mm² cable to be used. This would show an increase of 0.59 Ω on the loop impedance reading.

But split that into two with 20 amp overload, and we then work on the full 20 amps, so again with 2.5 mm² cable, we can have 32 meters of cable. This would show an increase of 0.79 Ω on the loop impedance reading.

Using a 16 amp overload, we can use 42 meters, with an increase of 0.97 Ω on the loop impedance reading.

This shows the whole reason for the ring final, it allowed fewer circuits to cover the same area, and saved copper on the rebuild after the second world war. There are some other advantages of having a 32 amp MCB/RCBO in that it allows a higher in rush, but this could be done by using a curve C rather than curve B. There is also the cost of the extra RCBO's at £15 to £20 each, and the larger consumer unit.

We often don't record the line - neutral loop impedance as the furthest point to the consumer unit, so it needs someone with a meter to measure it, before one can say if complying with the recommendations on volt drop, a radial can be used.

Of course, one can ignore the recommended 5% volt drop limit, and to be frank only items using a refrigeration unit with does not have an inverter drive are likely to have a problem with volt drop. This is why we are told not to run freezers etc, using an extension lead, and although our supply is 230 volts - 6% + 10% so 216.2 volt to 253 volt, in real terms we likely see around 244 volts, that is what my solar software tells me the volts are now. So volt drop to 205.39 which is the two limits added together is unlikely.

The only time I have seen a volt drop over that limit is on a caravan site.

But you are asking about Ring vs Radial, and I have explained why we use rings, and I have in the past exceeded the 16 or 20 amp maximum for a radial, but not the 32 amp for a ring.

Our regulations say

The load current in any part of the circuit should be unlikely to exceed for long periods the current-carrying capacity of the cable (Regulation 433.1.5 refers). This can generally be achieved by:
(i) locating socket-outlets to provide reasonable sharing of the load around the ring
(ii) not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit
(iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit
(iv) taking account of the total floor area being served. (Historically, limit of 100 m² has been adopted.)

So if we look at appliances which are not portable (over 18 kg with no wheels) that are over 2 kW then we have.
Dishwasher
Tumble drier
Washing machine
as well as cookers, ovens and hobs. Plus the immersion heater, which normally is on a dedicated circuit. OK washing machine may be on wheels, and the tumble drier if heat pump type is under 2 kW. And the Dishwasher and Washing machine only use over the 2 kW for a short time. However, that leaves the tumble drier unless heat pump type, which tend to draw 2 kW for over an hour, so coming close behind the immersion heater, and likely worse than an oven.

So we are looking at nuisance tripping due to too many items being used together of high power usage. So if I look at my own house, each ring covers half of the house, arranged so should one fail, one would not be temped to run extension leads up/downstairs, and the load on each ring is reasonably equal, so side to side of the house. So, the living room, and two bedrooms above it, are unlikely to get anywhere near 16 amps, never mind 32 amps, but the kitchen, dinning room, and two bedrooms above, are very likely to exceed 16 amps, even 20 amps, so really need that circuit to be as a ring final.

Yes, this is because I am braking the rules, and my kitchen/utility room has washing machine, tumble drier and dishwasher on the circuit, which is one reason why the freezers have been moved to a dedicated circuit, so should the ring final fail, well even if the DNO supply fails, the freezers and central heating will continue to run, supplied from my battery (6.4 kWh) and the solar panel inverter.

I like the ring final, but I have tried to give the reasons why, not just a statement, the problem for you is, until someone has measured the loop impedance, you don't know if within the rules to use two radials. So no one who knows the rules can really tell you to use two radials until they have tested, so it can't be answered on a forum as we don't know what the volt drop is.

 

[securespark]

If your question was contemplating a ring or radial from scratch I would probably say 20A radial, depending on the appliances.
I would no longer entertain a 16A radial.

However, as you have presented me with a mangled ring final circuit, I would investigate that with a view to fixing the issues and reinstating the ring.

Sometimes it is possible to create two useable radial circuits from a ring, but often, you find one is very short with only a few outlets and the other is very long, so not an even split.

 

[dsbuds]

I don’t think you will get an agreement here.

Sounds like your having a new cu so plenty of spare ways. As a minimum I would want 20A. Sometimes you can get 25A which would do the kitchen well.

Property was rewired in early 2010s, but seemingly poorly, non mf jbs inaccessible, left aluminium stranded cable in use, one short section of VIR (now changed). No mention of new CU except for info in EICR about it not being metal. There are plenty of spare ways.

Sounds like mr DIY has been messing around a lot.

How old is the property? And the wiring?

We've only been here 6 months, EICR flagged a few things and I had found things that concerned me so asked the chap doing the EICR (for instance, sockets all came off non-MF junction boxes off the main cable run under the floor, think a centipede, with lots of loose connections!), but they seemed happy with the radials. Another spark came for our bathroom and was of the opinion the ring should be recreated before our laminate flooring goes down to give us the extra capacity.

 

[JohnW2]

Not sure in agree with this

As TTC has said, very few DIYers would know anything about splitting rings (or the reason it might be done) - and, as you often observe, a DIYer would rarely have the means and/or knowledge to undertake the testing that could lead to the decision to split a ring.

 

[Murdochcat]

Property was rewired in early 2010s, but seemingly poorly, non mf jbs inaccessible, left aluminium stranded cable in use, one short section of VIR (now changed). No mention of new CU except for info in EICR about it not being metal. There are plenty of spare ways.



We've only been here 6 months, EICR flagged a few things and I had found things that concerned me so asked the chap doing the EICR (for instance, sockets all came off non-MF junction boxes off the main cable run under the floor, think a centipede, with lots of loose connections!), but they seemed happy with the radials. Another spark came for our bathroom and was of the opinion the ring should be recreated before our laminate flooring goes down to give us the extra capacity.

Rewired by whom? Bob the builder?

 

[Murdochcat]

As TTC has said, very few DIYers would know anything about splitting rings (or the reason it might be done) - and, as you often observe, a DIYer would rarely have the means and/or knowledge to undertake the testing that could lead to the decision to split a ring.

I’ve been called in to “fault find” after such work - generally by the wife who tells me the husband did it

 

[pete01]

I’ve been called in to “fault find” after such work - generally by the wife who tells me the husband did it

I find that situation a bit stressful...maybe thats just me.

 

[dsbuds]

Rewired by whom? Bob the builder?

A seemingly proper electrician, and it came complete with EIC that looks genuine enough to me. That's how I know it was originally a ring and someone has changed it since (before our ownership).