5m tails from meter, and is isolator required?

[gwebstech]

Hi all

Im looking at buying the tails to go from my meter to my CU. I need to buy 25mm ones is that correct?

Also ive read some saying i DO need an isolator if using over 3m tails and some saying i dont - does anyone actually know whats legally required? and if i do, is it an 80amp DP isolator i need thats fitted just after the meter?

Lastly, do the tails require any form of protection, or are they ok just clipped to the internal blockwork?

thanks

 

[AndyPRK]

Usually a switch fuse is requested above 3m

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/183951437498

25mm sounds ok.
I would leave them exposed so no one drills thru them

 

[Adam_151]

1. Likely 25mm, but if you only had a 60A supply then 16mm may work out ok

2.Generally DNOs want you to porvide your own *overcurrent protection* if more than 3m, that means a switchfuse not just an isolator, there is nothing in law to say so, BS7671 (which itself is not law) allows you to rely on the DNOs overucrrent protection only if they agree do, most have a policy that they agree so for tails of less than 3m. Find out teh policy for your local DNO, nots not law, but you'll cause yourself problems if you want to go against it.

3. Ah, We are taking about mechnical protection here, Well they could be clipped to the wall, but if you then conceal them (I'm guessing thats your intention) they would have to be both in safe zones and provided with 30mA additional RCD protection (you don't want to do that, as they'll not discriminate with the ones in your CU).

Who is installing these tails? who is signing for design of the installation?

 

[flameport]

I need to buy 25mm ones is that correct?

Possibly. Depends on the load and the fuse.

Also ive read some saying i DO need an isolator if using over 3m tails

A switchfuse is required if the tails are more than 3m long. An isolator on it's own is not suitable.

Lastly, do the tails require any form of protection

Depends on where and how they are installed.

 

[sparkwright]

When you say clipped to the internal blockwork, I take it the blockwork won't be plastered over?

 

[gwebstech]

thanks for the replies guys. An electrician i know of - through his brother - is going to be signing all this off, but im buying all the equpiment, and ill do as much routing of cable as i can

as regards routing the tails, i think ill be able to get them from inside the cavity from the meter, up and take them over the doorway (still inside the cavity) and then bring them out of the block wall, along near the ceiling and clipped down the wall to the CU which will be boarded over with plasterboard and it may be dot and dabbed but i might use CLS and screw the plasterbords to it (this will help route some plumbing too). Would that be safe enough or is the cavity insulation going to cause an issue with warmth/heat of cables?

thanks

 

[flameport]

An electrician i know of - through his brother - is going to be signing all this off,

You will need to ask them about any installation details if they are 'signing it off' - which they almost certainly should not be doing. A highly dubious and questionable situation already.

Where cables are installed in insulation, their current carrying capacity is reduced significantly, up to 50% in some cases. If they really must be put there, significantly larger cables will be required.

Concealing the tails behind plasterboard is not permitted.

 

[gwebstech]

You will need to ask them about any installation details if they are 'signing it off' - which they almost certainly should not be doing. A highly dubious and questionable situation already.

i dont understand mate, all the electrics will need to be signed off at the end of the job- whats dubious about it?

i will be asking him when i can, but i also like to understand how things work myself thats all.

And if tails are not allowed to be left behind plasterboard, that means ill have to put the CU inside a cupboard then and leave the wiring showing. So what do they do in other new houses?

thanks

 

[flameport]

What exactly do you mean by 'signed off' and what do you expect to get once whatever that is has been done?

 

[gwebstech]

i mean a certificate or whatever its called, as required by the building inspector. Its a brand new house so everthing needs to be certified

 

[JohnD]

you might like to have a look at a certificate, and see what the statements are that somebody has to sign.

 

[gwebstech]

you might like to have a look at a certificate, and see what the statements are that somebody has to sign.

well id imagine he takes responsibility for the installation is the gist - which is what im paying him for. He will do whatever he needs to do to sign it so hes taking that stress off of me. Hes been doing it long enough and for a lot bigger customers than me so i dont see an issue with it.

 

[sparkwright]

i dont understand mate, all the electrics will need to be signed off at the end of the job- whats dubious about it?

i will be asking him when i can, but i also like to understand how things work myself thats all.

And if tails are not allowed to be left behind plasterboard, that means ill have to put the CU inside a cupboard then and leave the wiring showing. So what do they do in other new houses?

thanks

In new houses, they tend to put the consumer unit back to back with the meter kiosk.

This way the tails can be minimal length, running in the cavity.

Careful consideration is made so both the meter and consumer unit are in sensible locations.

 

[gwebstech]

In new houses, they tend to put the consumer unit back to back with the meter kiosk.

This way the tails can be minimal length, running in the cavity.

Careful consideration is made so both the meter and consumer unit are in sensible locations.

thank you mate, i can do this as a last resort. The meter box is right outside the kitchen - i was just looking at ways to avoid having the CU in a kitchen cupboard when theres a utility room next door. The meter box would have gone outside the utility room but there will be a lot of pipework there so it wasnt ideal, but as ive learned you try and solve one issue and create another.

 

[sparkwright]

If you can make a boxing with the cables more than 50mm from the surface I can't see any major issues.