Single phase electrics

Discussion in 'Electricians' Talk' started by vijay, Mar 30, 2004.

  1. vijay

    vijay New Member


    I need to run a 35 amp supply into my detached garage in order to power a car lift. At the moment I've got a 2.5mm twin & earth cable from the consumer box, with a 16amp rated fuse. This goes into another comsumer box (in the garage) where it splits into a lighting circuit and a socket circuit. The consumer box is rated at 45 amps and has a 20 amp and a 5 amp fuse inside.

    Could anyone help me with what exactly diameter cable (I assume armoured cable) and if I can still use the consumer box in the garage or will I need a new one?

    Thanks for any help,

  2. plugwash

    plugwash New Member

    i would replace the CU in the garage with a one that had a 63A switch incomer and protect it with a 50A breaker at the cu this would leave you 15A for other stuff which should be suffician't (your unlikely to use power tools at the same time as the lift anyway but i can easilly imagine a heater running at the same time as the lift)

    there should be a 30ma RCD at the house end (if not use a rcbo rather than a mcb)

    as for cable this is going to need to be pretty thick but the calculator at should be helpfull (select cable type SWA 3 core xple and wattage 11500 for a 50 amp system)
  3. plugwash

    plugwash New Member

    oh and use a metal cu in the garage so you can screw a swa gland into it

    i reccomended the 3 core steel wire armoured so you are not relying on the armour as earth but you should still be protecting it

    actually thinking about it i would forget about the rcbo as i'm not sure they all isolate double pole

    i would put the mcb on a non rcd cuircuit in the cu and put a full size 63 rcd in a metal 2 module din rail box which you can use to terminate the swa near the main CU in the house this should connect to the 50A breaker in the main box with 10mm twin and earth
  4. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    Hello m8,

    Is 35Amps the design current of your car lift or is that a rough idea?
    Any idea the run length?

    Fill us in Vijay,we will sit down,rattle some calcs out and get back to you,

  5. vijay

    vijay New Member

    Hi SF,

    The run from consumer board (house) to consumer board (garage) is about 17-18 metres. 35 Amps is what I've been told I need. Would it be a better idea to go slightly higher?


  6. unphased

    unphased Screwfix Select

    Hi vijay (scuse me butting in si-fi)

    We need to know the exact rating of the power lift to a) check that 35A is sufficint and b) to size up the cables and MCB's. We cant afford to gusess and putting in a bigger supply may not be necessary. :)

  7. vijay

    vijay New Member

    well 2 lifts that I've looked at, one supplier said that a 32amp supply is needed and the other said a 35 amp is needed. So I just thought if I went with say a 40 amp supply that would be OK.............or would it ? :)

  8. plugwash

    plugwash New Member

    it depends what else you are running out there since your existing cuircuit does not seem up to spec it would seem sensible to run one large cuircuit for everything out there split up by a cu in the garage

    power tools are not really a problem as they won't be running at the same time as the car lift

    with 40A if you plug in a fan heater because it's winter and run the lift at the same time you will be over 40A

    and most of the work is digging for the cable so imo you may as well run a 50A cuircuit the first time rather than run a 40A and later discover it is insufficiant
  9. Stoday

    Stoday New Member

    Now what we don't know is if the circuit rating includes the starting current. A dol starter takes 6X the full load current, so if the 35 or so A includes the starting current there is plenty of capacity for heaters or what-have-you.
  10. The Trician

    The Trician New Member

    30+Amps sounds a lot just for a car lift, even if it is single phase. Seen some folk use 30 or 32A rated swtichfuses and isolators because they had them 'hanging around'. Nothing wrong with this other than the switchgear being a bit ott.

    If I'm correct, most car lifts I've seen rely on a hydraulic powerpack driven by a small motor to run the pump. The hydraulic rams and the oil do all the 'umph'.

    I'd have thought that 16A would have been ample -so I would recommend that you do some further research into car-lifts and their power requirements before you begin to dig big holes!
  11. golcarbob

    golcarbob New Member

    I agree with "The Trician"
    Ive worked on car ramps and as he says they are run off a single phase motor and a hydrolic pump does all the hard work. The one i repaired recently was running off a 13a plug into a standard socket
  12. vijay

    vijay New Member

    I would love you guys to be right about not needing that many amps. I have spoken to 2 suppliers and I'm rust relaying what they have told me (32 and 35). I will call them again tomorrow and double check.

    Thanks everyone.

  13. vijay

    vijay New Member

    Hi again,

    Getting closer to fitting this lift :) The lift I will be getting needs a 22 amp supply. The current supply is 16amps and the lift guy said that should be fine, it may trip occasionally but should be ok. Any opinions on that?

    Is it worth upgrading the cable? I'm digging up the side anyway to lay some drainage, so it wouldn't be too much more digging to lay the cable. If so, what size SWA should I use?


  14. vijay

    vijay New Member

    anyone :(

  15. cpc

    cpc Member

    The lift I will be getting needs a 22 amp supply. The current supply is 16amps and the lift guy said that should be fine, it may trip occasionally

    what type of mcb do they recommend ?B,C,D.

  16. chocolateblock

    chocolateblock New Member

    have you thought about getting a 3 phase lift and running it of an invertor
  17. vijay

    vijay New Member

    CPC, to be honest I never asked. How does the B,C or D ,make a difference if your pulling more amps than the MCB?

    Chocolateblock, I did look into a 3 phase lift with an inverter but heard mixed things about the inverters which put me off :(

    Thanks guys,


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