Extending radial main

[franna]

I have a new conservatory and was hoping to extend the ring main into
it from the adjoining living room. Turns out my living room is on a radial main protected by a 15 amp fuse (old style fuse box). An electrician has told me you can't have more than 7 sockets on a radial main is this true?
If not is it still worth converting the existing radial into a ring main bearing in mind I want to run underfloor heating in the conservatory (electrical load 1700w)

I am not undertaking any of this work myself but have no understanding of electrics and would really appreciate any help.

 

[ban-all-sheds]

An electrician has told me you can't have more than 7 sockets on a radial main is this true?

No limit on the number of sockets, only on the floor area served:

2.5mm² 30/32A ring final - 100m²

2.5mm² 20A radial - 50m²

4mm² 30/32A radial - 75m²

BUT - if you have an old installation there may be other factors to consider.

If not is it still worth converting the existing radial into a ring main bearing in mind I want to run underfloor heating in the conservatory (electrical load 1700w)

Ring finals came into existence as a quick kludge to provide increased capacity. See what your electrician says about the cables you have, and if they need replacing. If they do, my advice would be to install a 4mm² radial, because I don't like rings, but not everyone shares my opinion.

I am not undertaking any of this work myself but have no understanding of electrics and would really appreciate any help.

Not accusing you of anything, but it's odd how many people these days ask all sorts of questions because they are interested but have no plans to do it themselves.....

 

[colport27]

Ban........could it be people ask the questions for reassurance?

On the comment you made about ring mains.......Im totally with you, testing radials is so much quicker than rings........and if we were to go the whole hog and have double pole circuit breakers, imagine how easy it would be to discover which circuit had the neutral earth fault on an rcd protected DB.

 

[Adam_151]

On the comment you made about ring mains.......Im totally with you, testing radials is so much quicker than rings........

Not actually sure about that one tbh, besides testing for bridged rings, etc, all the tests for the ring can be conducted from the CU, with a radial you have to go to a second location (the end of the radial)

and if we were to go the whole hog and have double pole circuit breakers, imagine how easy it would be to discover which circuit had the neutral earth fault on an rcd protected DB.

Have you seen Hagers new 'single pole and switched neutral' range of CUs and MCBs? designed with the application you describe in mind

 

[franna]

Cheers ban-all-sheds 50 m2 will be enough.

My cu says this radial is on 15A rather than 20A best off getting new modern cu?

Appreciate what your saying about me asking questions but I don't know any sparks and am wary about getting ripped by anyone when I have no knowledge. (this is no disrespect to electricians it happens in all trades)
I would like to appear a bit less of a dimwit when people come round to give me quotes

 

[colport27]

No Adam, I havnt..sounds like a promising idea though.
Must admit I`m an MEM or Merlin Gerin kinda guy.

 

[franna]

(coughs politely)

So will the electrician be able to wire underfloor carbon heating(1700w) into an extended radial main?

 

[colport27]

Personally I would be a little concerned adding 6-7 amps on an existing 15A radial, though I dare say there are those who would disagree.

 

[Spark123]

It depends what else is on the circuit, but to be honest, I probably wouldn't.

 

[Adam_151]

Personally I would be a little concerned adding 6-7 amps on an existing 15A radial, though I dare say there are those who would disagree.

Ditto, I would add a separate circuit for the heating personally

oh and BTW OT, http://imagehost.darkernet.co.uk/i/spsn.gif

 

[colport27]

Sorry to hijack the thread a little, whats the cost comparison like Re a basic mcb Adam?

 

[franna]

Thanks for the replies.

Appreciated

 

[Adam_151]

Sorry to hijack the thread a little, whats the cost comparison like Re a basic mcb Adam?

Unfortunatly I don't know, sorry, I've only seen them in the hager catalogue, not for sale

 

[colport27]

No worries Adam, thanks for enlightening me though. Can see them taking of big time if the price is right.

 

[rhino36]

Have heard on the electrical grapevine that within a year or two we may be going down the same route as the French in that our ring finals will become radials.