4mm radials

[loz2754]

nowhere does OP say that the cable is in contact with insulation . i quote.

All the cables from the consumer unit descend loosely through a void in an otherwise insulated stud wall.

Ok fair comment. I may have misread read that.

 

[JonathanA]

A big thanks to everyone who replied - what a wonderful resource this is!

Let me just clarify that at no point are the cables covered in insulation. They are mostly clipped direct and exposed but for about 2m they have been boxed in with sheet timber and plasterboard. They cables are all loose within what might be thought of as trunking.

Having said that, and before it kicks off in here, I‘m sure every contributor is correct in what they say, namely:

• Is the installation safe as it is? - Yes
• Is it well-designed and compliant with the letter of the regulations? - Probably not

I have spoken to the Electrician who did the work and who issued the paperwork. He clearly had the hump being challenged and was adamant that the installation was a standard One. He said that Wylex RCBOs rated at 25A are available despite not being listed in the catalogue.

He’s willing to swap the two over if I insist but can’t do it until early April. For peace of mind, I’ll likely go this way and swallow the £200 he quoted. I’ll keep the 32A ones as back up in case the new 25A ones drive me nuts tripping all the time.

Thanks again to all.

 

[Deleted account]

Why put 25A breakers in. The 32A ones are fine.

and from wha5 you have informed us it is compliant.

 

[Dave OCD]

£200 to supply and fit two RCBOs [even Wylex] seems very steep !!

 

[telectrix]

seems very steep !!

it's the curve characteristics make it steep.

 

[JonathanA]

Paignton Pete, to be honest, it may never happen, but if it does it’ll be because I’m the sort of bloke that freak accidents do happen to!

 

[UNG]

we are the only country in the world who do rings. What does that tell you.

You haven't done much research. The ring final circuit is used in other countries as there are other countries that do use BS7671 as their electrical regulation standard

 

[mattg4321]

If the cables are not touching any insulation anywhere then 32A is fine. I’d leave as is personally.

 

[Mike Johnson]

I agree with you statement about each to their own, talking about other countries, the radials are multiple just like we had before RFC, talking in general for instance 20A radial unlimited socket outlets is IMO ridiculous. I would never create such a circuit.

I am afraid I can't remember back before we had RFC's or Ring Circuits.

Bit short sighted to think that radials will have unlimited socket outlets, they are restricted in number in all other countries that use them, legislation will change with the advent of any new regulations.

 

[stevethesparks]

in my opinion rings are potentially dangerous and I don’t do them any more. Radials every time for me.

I'd rather have a open L or N leg on a ring than an open Earth leg on a radial.

 

[Mike Johnson]

I think the other countries that use BS7671 as a guide to their countries electrical installations are ex or still are British colonies i.e. Gibraltar & Singapore spring to mind.

 

[littlespark]

I'd rather have a open L or N leg on a ring than an open Earth leg on a radial.

I’d rather not have any open legs on either.
That’s where regular testing comes in ?

rule of thumb, 4A per kW... so your 2.5kW oven takes 10A.... kettle? Maybe the same. Fridges, hood extractor etc are very little in comparison.

 

[stevethesparks]

I’d rather not have any open legs on either.
That’s where regular testing comes in ?

Agreed

 

[Mike Johnson]

I’d rather not have any open legs on either.
That’s where regular testing comes in ?

Used to see a lot of those in Amsterdam down by the canal.
And I do think they where subject to regular testing. ?

 

[stevethesparks]

Used to see a lot of those in Amsterdam down by the canal.

Spend a lot of time there?

 

[Mike Johnson]

Sure did, stunning views.

 

[richy3333]

Paignton Pete, to be honest, it may never happen, but if it does it’ll be because I’m the sort of bloke that freak accidents do happen to!

I'd recommend lightening protection and SPD's then ?

 

[timbobelfast]

Morning all,

I‘d really appreciate some advice - not a kick in the pants please - from those more knowledgeable than me!

My new kitchen and utility room are each supplied by 4mm T&E radials. Each circuit is protected by a 32A RCBO.

Kitchen

• Single oven rated at 2.5kW connected to single socket at end of radial
• Toaster, kettle, fridge and microwave connected to 3 x double sockets leaving some spare

Utility

• Washing machine connected to single socket
• Vented dryer connected to single socket
• Boiler connected to 3A fused switch
• 2 x double sockets spare

Length of radial in both cases is less than 10m so no worries there.

I was told that a 4mm radial with 32A protection is a ’standard circuit’ but there are issues with the installation that bother me, specifically:

1) The oven is not on a separate circuit so it’s not a ‘standard circuit‘ at least according to the OSG
2) The cabling for the most part is clipped direct but it is boxed in with other loose cables for a run of about 2m.
3) All the cables from the consumer unit descend loosely through a void in an otherwise insulated stud wall before going their separate ways (I suspect my OCD is kicking in with this one)

My worry of course is the possibility of the 4mm cables becoming overloaded at less than 32A.

Please understand that rewiring either of these circuits or installing new ones would involve huge disturbance which I am very keen to avoid.

I would sleep easier if the RCBOs were down rated to 25A but Wylex only make compact types for this rating which wouldn’t match the others in the CU.

I’d really appreciate your advice on this. Best response would be to tell me it’s fine, that I’m overthinking it and should get a life!

Thanks, J

From the way you have described the installation methods, the only thing I would watch out for is the 'grouping' Cg factor and that the circuits are spaced from each other in that void. Even still there is an element of diversity for the expected loads on these circuits. Personally I believe you are 'over-thinking' this! But without see the installation these are merely assumptions.