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Discuss MCB Problem - Possibly needs a larger rated MCB? in the Electrical Wiring, Theories and Regulations area at ElectrciansForums.co.uk.

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  1. Daniel Nolan
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    Daniel Nolan Guest

    Hello eveyone!

    I've recently passed a DEI and 17th Edition course and I've been asked by a friend about an electrical problem and because I don't have any experience I was wondering if someone could check I've come up with the right solution please? :confused:

    The problem is this. My friend's got a washing machine, a tumble dryer, a microwave and kettle all running from the same socket circuit protected by a 16A MCB. When the washing machine and tumble dryer are running and she turns on the kettle the MCB trips.

    That's as much information as I know. My gut feeling was that the MCB is possibly too small for the loads, so I looked in BS7671 and the On-Site Guide for solutions. I think that depending on if the sockets are on a ring circuit (with a line conductor with a CSA of 2.5mm) or a radial circuit (using a line conductor with a CSA of 4mm) then the MCB should be a 32A Type B, or if the circuit is a radial with line conductor CSA of 2.5mm it should be a 20A Type B.

    So, my first question is am I right? Or have I gone completely down the wrong road? :oops:

    Secondly, if you were faced with the same problem, how would you come up with a solution? I'd like to know if I've applied what I've learnt correctly and if I if I haven't (which I suspect is likely if I'm honest :blush2:) I'd like to see how it should be done to see where I've gone wrong.

    Thanks for your time reading this!

    Danny
     
  2. bugsy
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    bugsy Guest

    w/m eleement 3kw, tumble dryer element 3kw, kettle 3kw - what do you reckon?
     
  3. Engineer54
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    Engineer54 Guest

    A 20A MCB should be OK to install.
    Whoever designed a kitchen circuit to supply all those appliances on a 2.5mm radial circuit, clearly has no idea whatsoever!! Maybe a kitchen fitter or another example from the 5WW boy's!! lol!!!
     
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  4. micknew
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    micknew Electrician's Arms

    Location:
    Kent
    You obviously have not learnt any electrical theory have you?
    Get a qualified sparks in to put it right..
     
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    Last edited: Feb 16, 2012
  5. Flyingsparks
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    Flyingsparks Regular EF Member

    Location:
    Derbyshire
    Makes you wonder what they actually teach you on these courses !
     
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  6. rich.250
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    rich.250 Electrician's Arms

    Location:
    Cornwall
    Business Name:
    Rich Williams Electrical
    I think you are overlooking a lot of factors!! Reference method, max zs combined with CPC csa to achieve this.....
    The circuit is obviously functioning correctly. Just designed wrong initially.
     
  7. rich.250
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    rich.250 Electrician's Arms

    Location:
    Cornwall
    Business Name:
    Rich Williams Electrical
    Hmmmmmm, now that is a question...... LOL
     
  8. tonycoysh
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    tonycoysh Guest

    My Brother-in-Law has this same problem. CU is on the wall above. 2.5mm radial from a 16A breaker down to a dbl socket above the worktop and a dbl socket below running exactly the same, Diswasher, Washer Dryer, Microwave and Kettle. I'm sure with the distance of cable run without measuring that Zs etc will be fine. So for this one I'll make it a ring and increase cb to 32A mainly because iof their setup it's easier in this instance than upgrading to 4mm and changing the cb to 32A.
     
  9. D80
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    D80 Guest

    Further information is needed on that circuit really.

    Is there a socket outlet on the cooker switch plate? Could plug the kettle in there if so.
     
  10. D80
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    D80 Guest

    Is it sparks or kitchen fitters putting in these 16A radials? Complete idiots!
     
  11. SimpleSimon
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    SimpleSimon Guest

    Location:
    Yateley
    Get a grip. The guys showing he's using his brain and thinking about it than asking the experts for their advice too, we all started somewhere and comments like this just discourage people.

    Sent from my GT-I9100 using Tapatalk
     
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  12. Paul.M
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    Paul.M Trusted Advisor

    Location:
    Lost in Space
    I'm sorry chaps but I have to say something on this. The op has clearly stated his quals and knowledge and has asked for help of seniors. He has given info that he had seen. I don't think we should be so quick to slag off someone that wants to learn. Just my thoughts gents. Help the lad out, I'm in a good mood tonight :).

    Ask away mate, ask away.
     
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  13. Paul.M
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    Paul.M Trusted Advisor

    Location:
    Lost in Space
    Thank-you Simon. Well said words.
     
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  14. Des 56
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    Des 56 Trusted Advisor

    Location:
    Gliese 581C
    Hello Daniel and welcome,you have asked in a very polite manner about your conclusions about an installation after doing this course
    Your gut feeling and your thoughts on loading exceeding mcb capacity seem probable with the information given to you
    mcb ratings for the type of circuits you suggest seem to be correct

    I presume that you would not be considering doing this work just yet,because of your admitted lack of experience and are asking for opinions to further your understanding

    Take a look at the install and confirm what you have been told
    Assess the loading and inspect the current set up with consideration being given to modifying the existing or installing extra capacity which will depend on 131.8 brb being satisfied, procedures for compliance with building regs also to be followed
     
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  15. Paul.M
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    Paul.M Trusted Advisor

    Location:
    Lost in Space
    I wish that more new comers would ask questions in this manner. I tip my hat to you Daniel.
     
    • Like Like x 4
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