moving D/B 10m away from main cut out

[BristolSpark]

Got a question

Got a lady who has a c/u and main service fuse under her brand new kitchen cupboards. She now wants house rewired. Nice.

Problem is its virtually impossible to work under kitchen cupboard. So was wondering if I moved the board and placed in a better position in hallway or what ever. What would your suggestions be regarding the tails. and what type of cable to run to supply the new board.

Any suggestions would nice.

The run from service fuse is someone between 10 - 15m although it could possible go on the adjacent which would bring it into an alcove in the living room which they said they did not mind. making the route then about 3m max

 

[Wotsit]

I would use SWA, if you use tails you would need to provide mech protection or surface clip.

 

[baldsparkies]

As per wotsit, with the inclusion of a switchfuse at the mains position

 

[BristolSpark]

is there a problem running 16mm t+e plus separate main earth if service fuse is 63amp. or would you still use 25mm swa.

 

[Mac]

Main tails have to be 25mm.Can't you put the CU in a position that suits you.Easy to relocate.Easy for you mate.End of the day,you need to try and keep the job simple as poss for yourself

 

[baldsparkies]

Factors I would consider are mechanical protection,maximum demand and associated volt drop along with discrimination with regards to the suppliers cut out ( hence switchfuse) you are effectively running a submain from the mains position.

 

[sparks1234]

Not necessary to install a switchfuse, an isolator is fine as long as the cable is equivelent to the incoming fuse rateing

 

[Spudnik]

Not necessary to install a switchfuse, an isolator is fine as long as the cable is equivelent to the incoming fuse rateing

Really?

I have always been told by the DNO that a switchfuse MUST be installed if the tails are longer than there specified maximum.

The isolator would only be installed for convenience, if requested, not for tails protection.

 

[sparks1234]

Really?

I have always been told by the DNO that a switchfuse MUST be installed if the tails are longer than there specified maximum.

The isolator would only be installed for convenience, if requested, not for tails protection.

why would you need a fuse as well, the tails are protected by the boards fuse, you just need isolation

 

[Spudnik]

Regs (now 434.2.1) allows up to 3m of cable not to have protection against faults (subject to a number of conditions).

In the old days when meter tails were sized just according to the load and usually there were several switch fuses rather than one nice neat CU, each set of tails could be rated at a lot less than the DNO's fuse. These days with 25mm2 tails on a 100A fuse, there's less of an issue.

On the other hand, the DNO's fuse isn't part of the consumer's installation, so there's debate over whether the BS7671 side can rely on it - the DNO could choose to uprate it to suit their own purposes - like they've done in the past putting 100A fuses in what were originally 40A/60A/80A installations on 16mm2 or smaller tails.

The other way to look at it is via 434.3 (iv) - which allows fault protection to be omitted if the supplier agrees that their device provides protection. Hence the DNO get a say on the size/length of tails they're willing to protect - which will depend on their idea of fault loop impedance, and hence perhaps local network conditions.

 

[baldsparkies]

A 10-15 meter run from the mains has all the characteristics of a submain so definately provide your own over current protection and isolation,would not rely on suppliers cut out myself, Jasons post provides the rest. I noted you mention an alcove 3 meters away in the living room closer to the mains position the better and you could just about use tails. why not go for that.

 

[ICE]

I have been in this situation many times over the years , I have used a 25mm SWA and a good quality metal cased switch fuse which allows for a good solid termination of the gland and it has passed test and Inspect everytime without question...

 

[800fsbgang]

Regs (now 434.2.1) allows up to 3m of cable not to have protection against faults (subject to a number of conditions).

In the old days when meter tails were sized just according to the load and usually there were several switch fuses rather than one nice neat CU, each set of tails could be rated at a lot less than the DNO's fuse. These days with 25mm2 tails on a 100A fuse, there's less of an issue.

On the other hand, the DNO's fuse isn't part of the consumer's installation, so there's debate over whether the BS7671 side can rely on it - the DNO could choose to uprate it to suit their own purposes - like they've done in the past putting 100A fuses in what were originally 40A/60A/80A installations on 16mm2 or smaller tails.

The other way to look at it is via 434.3 (iv) - which allows fault protection to be omitted if the supplier agrees that their device provides protection. Hence the DNO get a say on the size/length of tails they're willing to protect - which will depend on their idea of fault loop impedance, and hence perhaps local network conditions.

The DNO would not choose to uprate fuse's anymore,you are more likely to get it downrated to 80A regardless of MD- I work for supplier's and every job we do ,we will drop the fuse regardless.

 

[stretchyboy]

Good post Jason.... says it all ;-)

 

[johnnyb]

I agree with Jason, after the specified max run for d/ins tails, in my veiw its a matter for an swa to be run thus becoming a sub-main which does have to have a sw/fuse and would also need to go down on the test sheet as a sub-main.