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circuit-breaker allegedly "getting more sensitive"

Former Community Member
Former Community Member
OK, usual caravan park issues with more pitches than incoming supply, so client has acknowledged this by installing 10 A circuit-breakers for each 16 A outlet. With 24 pitches on a presumed 80 A single-phase cut-out, he has got away with it..... so far, but he doesn't close for winter....


He has a few regulars that complain about the 10 A circuit-breaker being too sensitive so client believes them and has fitted new 10 A circuit-breakers ready for this weekend.


Considering that a 10 A circuit-breaker will run at 11.3 A continuously and 16 A for about 10 minutes, I'm more inclined to think that the "shed puller's" use of the 2 kW built in heater, 2 kW supplementary fan heater, fridge and domestic 3 kW kettle plus entertainment equipment are more likely....


But, has anyone carried out any tests on circuit-breakers to prove/disprove the alleged reduced rating? Or links to any such reports?


Regards


BOD
  • 0
    I was under the impression Alcomax that the thermal element of the circuit-breaker (CB) was the same irrespective of it being B, C or D and only the magnetic in-rush was different. The replacement of the CB with a C or D wouldn't alter the time of an overcurrent caused by too many heaters/kettles etc but would only help if say a tool transformer or welder were connected by not responding to the high inrush current.


    Yes Bod, but the anecdotal consideration was for instantaneous operation, not time for an overload, as, in practice, the [bodge] remedy does result in less claims of the MCB being "too sensitive" for campsites. Not very BS7671, but the wiring and points are already in and the customers want the electric to stay on more often than not. It is not  just the number of potential loads that may "overload", it is overload of a very short duration when everything is on demand at the same time. So 30 amps instantaneous, a C type is more likely to stay in than a B type.  Your client has "10 amp " points, that is fairly typical of an owner using the CB as a means of limiting how much electric  a pitch is using for the usual fixed nightly sum, so there is a trade off.
  • 0
    perspicacious:
    I will post further if I can find the information in my files that are now in the loft.


    Thank you Mike. I'm sure others will find this "derating" of interest!


    Regards


    BOD


    Bod


    Found it!! Not sure if this applies directly to your situation, but, this may go some way to helping you.

    Quote from Wylex NM CU Installation Instructions - have scanned & pasted below:



    Ambient Temperature Considerations

    The  NH  Range  of  MCB's  are  calibrated  to  meet  the 30°C   Ref   Calibration   Temperature   

    requirements   of BSEN 60898.

    At   other   temperatures   the   following   rating   factors should be used:

    At 60°C  0.9        At 20°C  1.0         At 0°C  1.1

    Adjacent    thermal-magnetic    MCBs   should    not    be continuously  loaded or approaching

    their nominal rated currents  when  mounted in  enclosures.     It  is  good    I!

    engineering practice to apply generous  derating factors or   make   provision   for   adequate   

    free   air   between· devices.  In these situations, and in common with other; manufacturers, we

    recommend a 60% diversity factor is applied  to  the  MCB  nominal  rated  current  where  it is

    intended  to load the MCB' s continuously  (in excess of 1 hour)

    Before fitting the front cover, check the tightness of  all connections,


    Hope this helps


    Regards


    Mike


  • 0
    Merlin Gerin (Schneider) have similar temperature de-rating info.

    e.g See pages 8/3 to 8/5

    http://www.farnell.com/datasheets/1694097.pdf
  • 0
    If it’s the only MCB in the pitch socket enclosure why would you derate it?
  • 0
    Okay, the pitch box might have four devices in it, but why would you derate them and replace them?

    https://www.fastlec.co.uk/rolec-tre4-four-way-caravan-hook-up-consumer-unit-with-sockets-outdoor
  • Former Community Member
    0 Former Community Member
    https://www.fastlec.co.uk/rolec-tre4-four-way-caravan-hook-up-consumer-unit-with-sockets-outdoor


    Do these meet the requirement of 708.55.1.1?


    Regards


    BOD
  • Former Community Member
    0 Former Community Member
     In these situations, and in common with other; manufacturers, we

    recommend a 60% diversity factor is applied  to  the  MCB  nominal  rated  current  where  it is

    intended  to load the MCB' s continuously  (in excess of 1 hour)


    Hmm, so a EICR carried out on my dwelling with a 16 A circuit-breaker on my 3 kW immersion heater in a 210 litre cylinder would result in what code? Assuming naturally that the rest of my dwelling electrics are perfect.................................


    Regards


    BOD
  • 0
    perspicacious:
    https://www.fastlec.co.uk/rolec-tre4-four-way-caravan-hook-up-consumer-unit-with-sockets-outdoor


    Do these meet the requirement of 708.55.1.1?


    Regards


    BOD


    Features and Benefits



           


    • Built in MCB, RCD or RCBO protection

    • 30 milliamp fault current protection

    • Enclosure is manufactured in IP56 weatherproof material

    • Enclosure drilling to suit bespoke incoming cable systems

    • Manufactured to 17th Edition IEE Wiring Regulations

    • Internally wired

    • Built-in cable terminals


  • Former Community Member
    0 Former Community Member
    Aren't we working to the 18th now Andy?


    Regards


    BOD
  • 0
    ?

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