are branching radials okay ?

Discussion in 'Electricians' Talk' started by lensman, Dec 9, 2003.

  1. lensman

    lensman New Member

    I've got a small room (3x3m), currently on the main house ring main, that I'd like to put on a separate circuit (it's a home-office, also with computer server equipment). I doubt it'll draw more than a couple of amps.

    It would make rewiring simpler if I did it as a radial
    in 4mm cable, connected directly to a 20A MCB at the CU.
    Is there any problem with this, or reasons that I should
    run a full ring-main ?

    If it is run at a radial, the cable paths would be shortest if the radial split at a JB where it enters the South side of the room, to go to sockets on the East and West sides. Again, is there a problem (practical or regs)
    with doing this?
     
  2. supersparky

    supersparky New Member

    do radial, 32amp braeker for 4mm cable mate, if its for computer equipment it should have a clean earth, either a 2.5mm single earth, run in conduit, or a 6mm earth which you can run however suits you, it it connected to the last socket, so you have an earth loop, as opposed to a dsingle earth thats in the cable, this is now required where there is alot of electronic equipment
    donet worry about cable run, run it how its ment to be, into first socket, loop to next, to next and so on...

    BR
     
  3. unphased

    unphased Screwfix Select

    Seems a little innappropriate to have a separate circuit just for one room. Why do you want to break off from the ring main for this? Would be best left on it.

    Hardly worth the bother of clean earths for a couple of items of IT equipment. Really intended for companies with loads of IT equipment (due to high earth leakage currents)
     
  4. supersparky

    supersparky New Member

    He said he had alot, a CE must be fitted where the leakage exeds 3mA, but i have never herd of it in domestic, unless an office, i appologise, ive only gone back to work this afternoon...ill start being more realistic now...

    BR
     
  5. lensman

    lensman New Member

    Seems a little innappropriate to have a separate
    circuit just for one room. Why do you want to break
    off from the ring main for this? Would be best left
    on it.

    Part of my job involves providing 24x7 cover for critical medical IT systems. A lot of it can be done from home on a broadband connection - which is very handy when there's a glitch at 1am or I'm officially on holiday (the department doesn't recognise holidays if the main system croaks). Hence I want to make my home computer systems as robust as possible - got UPS, but that's only good for 15 minutes if the power dies. Since I'm going to be decorating/restructuring bits of my new place for the next couple of years I want to be able to cut the main house power whenever necessary without losing the computers.
     
  6. supersparky

    supersparky New Member

    if its that critical you thaught about a backup system?
    you could arrange it to cut in using relays, and an inverter and a battery pack...could give you a few hours if you were on holiday....yes that also sounds like a pretty important system....put a claean earth in anyway, it will make the computers last longer...

    BR
     
  7. jj

    jj New Member

    I also run a home office and 24/7 cover/callout (check the time of some of my posts !!), My main work PC is a laptop with external keyboard & monitor, the battery on that lasts 3+ hours in the event of a power failure. I have a UPS but only for the broadband modem (which has a small current drain, so lasts hours too). I also have ISDN2 and dial-up as a back-up to that too which are line powered, so no power loss issues there. The office/room is on it's own ring - non rcd.

    I'm not sure the work I do is as critical as yours, but if it were I would think about investing in a compact petrol generator ? (unless you live in a flat ??) You could use in your spare time to run a hot-dog stall !!
    ;)
     
  8. lensman

    lensman New Member

    but if it were I would think about investing in a
    compact petrol generator ?

    I've always got the backstop of getting on my bike and heading into work at any ungodly hour, so the inconvenience of setting up a generator or filling the house with heavy batteries probably outweighs the benefits given that a separate circuit will only fail very rarely (and hopefully not a times when it's needed). Thanks for all the advice though.
     

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