Sockets in Garage....

Discussion in 'Electricians' Talk' started by MrE, Aug 9, 2019.

  1. MrE

    MrE New Member

    Hi
    Couple of (probably obvious) questions...
    BTW I'm no electrician, so excuse the lingo (and please correct me)

    I have a detached single garage, with the lekky coming from the house (from the main board on a 16a breaker). The cable goes from the house under the concrete path to garage. Garage has two double sockets and a strip light (no breaker in garage). Looks like a 2.5mm cable for sockets and 1.5mm cable for light.

    1. Is it possible to upgrade to more than 16a (i know i might have to replace the cable)

    2. I want two more sockets in the garage (even though i probably won't exceed 16amps with the one or two things to plug in). Is it easy to add them. I know probably not easy to reply without an existing wiring diagram?

    3. Metal sockets better? SP or DP or doesn't really matter? there are only plastic ones currently.

    4. Does the length from the main board make any difference.

    Thanks, appreciate any help.

    MrE
     
    Last edited: Aug 9, 2019
  2. gas monkey

    gas monkey Well-Known Member

    mr e first thing need to know is the load then you can work out the cable
    however the lights should be ok as long as 2.5 and 1.5 are seperate
     
  3. MrE

    MrE New Member

    The load being what i want to run...in Amps? The tricky thing with that (being a non expert) is the start up load. Apparently that's higher than the running load, does that come into calculations?
    Anyway, I think about 12amps to 14Amps, so is that too close to 16Amps?

    When you say separate....I'll have to look closer at the junction box where is comes into the garage, as that's a floor level, there is then a plastic conduit going to a socket, then up the wall to the top where the conduit finishes, THEN i see the two cables.

    Hope that makes sense?

    Thanks
     
  4. Bazza

    Bazza Well-Known Member

    Let’s go back to basics.

    What is the total maximum load going to be?
    What are you planning to plug in?
    How far is the garage from the house?
     
  5. Coloumb

    Coloumb Well-Known Member

    6mm swa from the house cu on a 32a breaker to a garage cu with RCD main switch feeding a 16a for sox and a 6a for lights covers 99.9% of all garage requirements. Unless your doing something really weird, like trying to set up a dog grooming shop in your shed.
     
  6. Bazza

    Bazza Well-Known Member

    @MrE if your load is going to be less than 16A you don’t need to upgrade the cable.

    Just connect up the extra sockets and it’s done.
     
  7. dobbie

    dobbie Well-Known Member

    Does he really need all this for a garage.
    [​IMG]
     
  8. Coloumb

    Coloumb Well-Known Member

    Make sure any new sox you add are 30ma rcd protected. Such an RCD may already be in the CU with the 16a breaker.
     
  9. Coloumb

    Coloumb Well-Known Member


    Dobbie he most certainly does. Without a doubt. Lol.:D
     
  10. Tony Goddard

    Tony Goddard Active Member

    I wonder if that OP did get his grooming parlour set up with it's 60+ amp requirements!:)
     
  11. Coloumb

    Coloumb Well-Known Member

    Lol, well I noticed he hasn't been back so no doubt I bullied him into submission and so he has despaired of ever setting up his dog grooming parlour now I wrecked his dreams. ;):D
     
  12. Tony Goddard

    Tony Goddard Active Member

    Or he tried the suggestion I made of fitting a gas boiler and the garage is now blown to bits:D
     
  13. MrE

    MrE New Member

    Lots of activity thanks,
    1. Garage only 2m from the house. But House CU is about 8m form the garage (approx)

    2. Usage, usual garage stuff (no dog grooming stations), saw, sander, drill charger, grinder, small heater, man cave stuff. So checked the amps of a few things and as i mentioned maybe 12-14amps in total at any one time. Its a best guess. cant use everything at once obviously as one person and one set of arms :)

    3. No idea what sox is

    4. Pretty sure SWA is armoured cable. How would i know what cable goes from house CU to garage, when i can't see it?

    5. I know some people have an extra little breaker unit in the garage (I did in my old house, and I don't now), is it legally required or just good practise?

    6. I'll try and do a diagram of where the wiring goes because its not too obvious to me how to 'add in' a couple more sockets. I (think) I know you cant spur off of more than one socket so might have to replace some wires (which are easy to get to)

    7. Any thoughts on the metal socket question at the top (point 3)

    8. I'm pretty sure i'd have to get an electrician to sign off anything i did, even just adding a couple of sockets, right?

    maybe I'll have to get an electrician in anyway, but I'd rather do it myself if possible, more satisfying.

    Thanks guys (and any gals)
     
  14. Tony Goddard

    Tony Goddard Active Member

    1. Garage only 2m from the house. But House CU is about 8m form the garage (approx)

    Reason this is important is due to voltage drop on the cable run, sounds like you have appx 10 mtrs of cable so that will be negligable

    2. Usage, usual garage stuff (no dog grooming stations), saw, sander, drill charger, grinder, small heater, man cave stuff. So checked the amps of a few things and as i mentioned maybe 12-14amps in total at any one time. Its a best guess. cant use everything at once obviously as one person and one set of arms :)

    16A should be more than adequate, get a 2kW heater, that still gives you scope to heat and drill at the same time

    3. No idea what sox is

    Abbreviation for sockets

    4. Pretty sure SWA is armoured cable. How would i know what cable goes from house CU to garage, when i can't see it?

    "Strand wire armour", yes armoured cable, it's black and round, you should see it coming out of the ground in the garage if its fed that way, but if fed overhead, or the garage is attached to the house you probably just have standard twin and earth "flat" cable.

    5. I know some people have an extra little breaker unit in the garage (I did in my old house, and I don't now), is it legally required or just good practise?

    Not required on a 16A breaker in the house, it would be needed if you had a bigger supply to protect the sub circuits in the garage. The lights should ideally be fused lower than 16A, usually in your set up by a FCU (fused spur) with a 5A fuse.

    6. I'll try and do a diagram of where the wiring goes because its not too obvious to me how to 'add in' a couple more sockets. I (think) I know you cant spur off of more than one socket so might have to replace some wires (which are easy to get to)

    It sounds like a radial circuit, so you can branch off to your hears content in whichever way is practical.

    7. Any thoughts on the metal socket question at the top (point 3)

    Metal sockets are best in this kind of settings, use plastic stuffing glands or grommets where the cables enter.

    8. I'm pretty sure i'd have to get an electrician to sign off anything i did, even just adding a couple of sockets, right?

    Best to get it tested, he will have the kit to make sure the all important earth is functional (what we call Zs or loop test) - you also need the circuit to be RCD protected, if it isn't already.

    maybe I'll have to get an electrician in anyway, but I'd rather do it myself if possible, more satisfying.

    Indeed, very satisfying - but work safe, remember to turn everything off before you get started - sounds obvious but a common error, even pro sparks occasionally forget!

    Thanks guys (and any gals)
     
  15. Bazza

    Bazza Well-Known Member

    Tony is absolutely correct.
    The circuit you have is adequate for your projected load. No need to do anything more than add the extra sockets you wish.

    The only point I would add is on point 5.
    It is essential that these sockets are protected by a 30mA RCD. Is there one in the house consumer unit that protects the SWA garage circuit?
     
  16. ajohn

    ajohn Well-Known Member

    Depending on who and when it was done it may pay to check that swa is used. People have been known to bury hose pipe or what ever and run any old cable or even swa through it. If it is swa the armour in the cable should be connected to earth at least at the house cu usually done via a special gland. The armour may also be used to provide earth in the garage via another gland. It will be 2 core swa if that has been done.

    Glands look like this but an interior ones are simpler
    https://www.toolstation.com/gland-kit-cw-exterior/p99816

    Some electricians use earth straps instead but shouldn't really
    https://www.toolstation.com/earth-clamp-12-32mm/p88231

    There will be pictures of what swa looks like on the web showing the armour. Size I understand is usually marked on the covering but not sure. If you can describe the copper that comes out of it a spark may be able to tell you the size - how many strands maybe. The diameter over the outer insulation and how many cores can be a rough guide.

    I'm wondering why it has a 16amp breaker which I assume is an mcb however as mentioned your load is ok and if significantly overloaded an mcb will trip anyway.

    Maybe a garage cu has been mentioned - "had one in previous house". There isn't a strict need for one providing the cable is correctly protected in the house cu - an mcb (miniature circuit breaker) and an rcd ( residual current device ). It will be if a modern cu. ;) I hope. Garage cu's are often sold populated with mcb's and an rcd fitted. Trying to make those work independently of a house cu is an entirely different ball game and needs totally different things doing. Personally I feel that when one isn't fitted and isolation switch in the garage would be good idea but isn't on the face of it needed.

    John
    -
     
  17. MrE

    MrE New Member

    Thanks guys, OK these might help..

    House CU
    House CU.JPG

    Exit from House (about shoulder height, metal conduit to under concrete path
    Exit from House to garage.JPG


    Coming back up and entering garage

    Entrance to garage.JPG


    Cable enters garage and up to first double socket

    Entering garage at floor.JPG



    Above last socket image, then the cables spread to strip light, switch and another socket.

    switch above socket in last pic.JPG
     
    Last edited: Aug 10, 2019
  18. Bazza

    Bazza Well-Known Member

    OK. The garage circuit is properly RCD protected. Doesnt look like SWA cable, as you say its in metal conduit and nobody in their right mind would run SWA inside metal conduit (OK, there's bound to be one or two on here)
    Would like to see what's behind the cover plate on the round box in photo 2. (Note there is a securing screw missing on the lid. (They are 4mm if it is lost).
    I'll bet its straight T&E cable run in metal conduit. Thats OK if the conduit is earthed, and it is run all the way to the garage like that..

    Not sure where you want the additional sockets, but you can just connect to either the first or second socket. Its a radial circuit, so you can connect any way you want.
    The existing cabling is run in PVC conduit in the garage. You may want to do that as well, to protect the cable. Plastic sockets will be fine, you only doing light work/doing man cave things in there.
     
  19. MrE

    MrE New Member

    Thanks Bazza, you got eagle eyes, I didn't even notice the screw missing lol Ill take the cover off tomorrow, when hopefully its not blowing a hooly outside. Is that metal trunking a normal thing? or a cheep shortcut or an old method? I didn't know you could get metal trunking.

    Thanks again
     
  20. Bazza

    Bazza Well-Known Member

    If it is steel conduit, that was a standard way that electric cabling was installed in just about every commercial installation.
    Most council houses used it as a wiring method back in the day.
    Lots still used. And available
    https://www.tlc-direct.co.uk/Main_Index/Conduit_Steel_Index/

    C&G electrician courses used to include conduit installation as part of the practical skill. Pipe bending, pipe screw cutting etc were among the fun things that electricians had to master. Not now, of course. :(
     
    Last edited: Aug 10, 2019

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