Type C...

Discussion in 'Electricians' Talk' started by Not Too Sure, Jun 14, 2019 at 5:44 PM.

  1. Not Too Sure

    Not Too Sure Member

    Hi,

    I recently purchased a car lift to put in my garage and what I found is that if I plug it into a socket indoors (via. an extension lead) everything is fine, but as soon as I plug it into my garage plugs it trips the garage electrics, so all the plugs and lights go off.

    The installer who put the car ramp in said that this was often the case (he said it even before he started installing) and that I needed to change the Eaton 16A Type B to a 20A Type C mcb. I have four flick mcb switches - two of which are marked ‘lights’ and the other ‘sockets’.


    I changed the socket one to the one the installer said to use and it still doesn’t work - so I wanted to check...

    1) is the change I’ve done already a usual thing (16A type b to 20A type c) - don’t just want to take the installers word for it?

    2) Would I also have to change the light mcb to 20A Type C - I didn’t do it as assumed they were on different circuits.

    3) if the answer to 1 is fine to change and 2 is no the light mcb doesn’t need changing, then do I need to increase the socket mcb from 20A or something?

    PS Rang the car ramp place and they said try a 32A C breaker - I’m worried that they are just blindly telling me to increase it, what about the impact on my electrics overall, I don’t want to compromise safety!!!


    Thank you.
     
  2. unphased

    unphased Screwfix Select

    Yes, type C and type D breakers are used where there is a surge or pull at switch on, usually for motors, lifts and welding gear. So your type C should be okay. If it isn't then you may need a higher rated circuit, like 32A, and that will require larger cable on the garage sockets. What is the actual rating of the lift? You don't need to worry about the other circuits, just the one you are using for your lift.
     
  3. W. Axl Rose

    W. Axl Rose Member

    You shouldn't have altered the circuit protection without verifying that the change would adequately protect the installation.
     
  4. Not Too Sure

    Not Too Sure Member

    Thanks both - in my simplistic mind, my main worry is that sticking something in that is higher rated could stop the tripping process working as it should in an emergency (say accidentally cutting the electrical cable on a strimmer for example)? Also I don’t want the plug wires to get damaged / overheat.

    I’m not sure if I’m over-thinking this - the house is about 10 years old, so fairly recent wiring?
     
  5. Not Too Sure

    Not Too Sure Member

    Also the fuse box in the garage isn’t the one turning off, it’s the one in the utility which is marked as ‘garage’ - I changed the fuse in the garage...but left the utility one alone...wonder if that is the one I was supposed to put the 20A C breaker into!!!
     
  6. unphased

    unphased Screwfix Select

    Ah, then that is the problem. You have two breakers in series so both would need to, be type C.
     
    Not Too Sure likes this.
  7. Not Too Sure

    Not Too Sure Member

    Thanks - will do that, the one in the utility is a 16a type b - I noticed all the other fuses in that box are 32a...

    Out of interest, why are there two boxes - is that just for ease in case you want to isolate the garage ?
     
  8. unphased

    unphased Screwfix Select

    It is a common way of providing a power supply to a garage. If it were known at the outset that a car lift would be installed, that would have been put on its own circuit separate to the garage. It is usually expected that just a couple of sockets and a light would be present.
     
    Not Too Sure likes this.
  9. Not Too Sure

    Not Too Sure Member

    Thank you - will try tomorrow and hopefully it works!

    Next time I get an electrician out I will ask him to install a stand-alone plug and fuse for the ramp.

    Really appreciate your help.
     
  10. masterdiy

    masterdiy Active Member

    One small point, I'm not an electrician, but I had this problem a few years ago.
    Couldn't find why the circuits kept cutting out. (Using car ramp).
    After an electrician had checked it out, he said no fault found.
    Any way, long storey...
    In the end (this is the short bit) I installed an extra earth lead (heavy) & all was well.
    So, point is, make sure you have an adequate earth.
     
  11. Coloumb

    Coloumb Well-Known Member

    Where did you install the extra earth from and to?
     
  12. HappyHacker

    HappyHacker Active Member

    Changing MCB types and values without knowing the supply characteristics, cable sizes & lengths, installation method etc is a bad idea. While it will usually work it may not be safe in the event of a fault. You need an electrician to work out what you need and to install and test it.
     
  13. ajohn

    ajohn Active Member

    I suspect an important question is did it come with a plug on it or did the op add one?

    John
    -
     
  14. masterdiy

    masterdiy Active Member

    CU to Earth steak.
     
  15. W. Axl Rose

    W. Axl Rose Member

    A nice juicy bleu Earth steak.

    I'll have a 36 Oz one.
     
  16. Coloumb

    Coloumb Well-Known Member

    So you put an earth rod in for the garage CU?
     
  17. masterdiy

    masterdiy Active Member

    Well, all steaks come from the earth, so putting one back seems quite natural. :D

    And, it looked just like this.

    [​IMG]
     
    W. Axl Rose likes this.
  18. Not Too Sure

    Not Too Sure Member

    20a type c in the fuse box (on whatever they are called now!) and the same again in the garage outside has fixed the issue.

    I have asked a friend to pop over next week once he is back from hols, as he is a sparky to double check, but so far it seems to be working fine and no overheating on any wires or fuses.

    Thanks for all your help and responses.
     
  19. MGW

    MGW Well-Known Member

    There are a number of considerations as to circuit protection, volt drop, cable size and prospect current.
    The MCB comes in three flavours, the thermal bit is same for all, but B = 3 to 5 times rated current for magnetic protection, C is 5 to 10 times, and D is 10 to 20 times, so with a B32 MCB it will need 5 x 32 = 160 amp to ensure it will trip with a short circuit, simple ohms law 230/160 = 1.44 ohms, because the volts can drop we add 5% so 1.365625 is the max permitted figure used today.

    This figure is for both line - neutral and line - earth unless a RCD is used, with a RCD it is only the line - neutral which is important, the line - neutral can rise above that, but the same applies before changing a MCB one has to measure the prospective short circuit current or loop impedance which are directly related to each other using ohms law.

    Many meters auto measure line - earth when switched to loop impedance and line - neutral when switched to fault current, but not all.

    There is some debate as to what to allow for the supply, with a 100 amp supply to stay within the +6% -10% means there is a limit to the loop impedance, this is normally considered as 0.35 ohm, should the supply be under that figure there is no guarantee it will remain low.
     

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