Safe practices - adding a new radial to a consumer unit

[lostaylos]

Hi.

I am looking to add a small radial circuit to my existing consumer unit. However, it is going to be difficult to isolate the supply as the 'meter' room is not within my access.

With the consumer unit switched 'off' is it safe to add circuits or is this not recommended.

If it is safe to proceed with the consumer unit off, are there suggested safe working practices?

Thank you all for your help.

Los

 

[kevindgas]

you can add a circuit to a CU that has been isolated at the main switch, but be aware that it is live at the switch and the tails will be live.
but if you have to ask a basic question like this I do question your ability to Size the MCB/Fuse, the cable and the outlets of this new circuit! also how do you intend to check the Continuity, loop impedance, insulation etc
of said circuit?
also be aware the work of this nature could be under the scope of Building Regs/Part P

if in doubt get a qualified Sparks to undertake the work!! before you injure yourself or your loved ones.

 

[OwainDIYer]

Depends how old the consumer unit is as well - some of the older ones do not adequately shield live internal parts even with the Big Switch off.

What sort of 'small radial circuit' do you need?

 

[ban-all-sheds]

And why does the fact that it's a "small" one make any difference to how safe, or easy, or neither, it is to add?

lostaylos - there are a few questions you should be able to deal with...

• For a circuit to supply a <thing> (doesn't matter what), how would you go about deciding what cable and protective device to use?
  
  
• How do you calculate maximum demand and how can diversity be used?
  
  
• What are the 3 different types of domestic single-phase supplies provided in this country, how would you recognise them, and what differences do each make to the requirements for the rest of the installation, particularly any outdoor supplies?
  
  
• Can you correctly identify all components and connections of a circuit by method of testing or otherwise? In doing so can you identify or recognise anything wrong or dangerous with the circuit?
  
  
• Do you understand how the way in which you install cables affects how much current they can carry?
  
  
• What are the rules concerning cables concealed in walls, partitions and under floors?
  
  
• What are the rules for cables run outdoors, buried in the ground or overhead?
  
  
• Where cables need to be joined, how should this be done / not be done and in what circumstances are different methods acceptable?
  
  
• Can you identify extraneous conductive parts, and do you know the requirements for main and supplementary bonding of them?
  
  
• Which circuits should be RCD protected?
  
  
• Do you know what tests you would carry out on the installation - what sequence you'd do them in and at what point you would energise the installation, and for each test do you know what is being measured, why it is important, how you would carry out the test, and with what equipment, and what sort of results you would expect to get if everything was OK?

You might also find these useful:

• //www.diynot.com/forums/viewtopic.php?p=81696#81696
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  
  
• http://www.tlc-direct.co.uk/Book/8.1.1.htm
  
  
• //www.diynot.com/wiki/electrics:part_p