Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 38 replies
  • Subscribers 33 subscribers
  • Views 14245 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

EICR C3 mixed manufacturer breakers

Martyn
I know this will have been discussed in the past but we are on Amd 1 of the 18th now so I thought I would renew it.


The Best practice guides list mixed manufacturer breakers in a consumer unit or distribution board as a C3.


As far as I am aware Bs7671 does not have a Reg on it beyond manufacturers instructions and given EICR's are based on this standard perhaps it is justified on that basis.


Most on here will be familiar with the 16kA 'rule' in BSEN61439 Annex ZB or its predecessor BSEN60439 Annex ZA


I avoid C3's like the plague because they give all the wrong signals to a client and clearly by definition are for things which are a breach of the regs, I'm not too keen on the insurance risk of a C3 either.


My question here would be what fault rating can one apply to an enclosure where there are mixed breakers given a manufacturer will only have certified their equipment with their devices?


Enjoy!


Martyn
  • 0
    I would think that each manufacturer would be happy to have the same form of own breakers in adjoining spaces particularly with regards to hotspots and lines of magnetism and therefore ventilation. Thereby affecting safe ratings and good operation. With differing designs of different manufacturers then poss not. I suspect that, in practice, the same plant manufactures the same designs but differi.ng badges. I`d say at least a C3 and poss a C2.

    Martyn you say you don`t like C3s  . What about, for example, wrong colour coding of conductors?

    Any one of us opening a lightswitch sees all sorts of wrong colour coding often.  The electric in the circuit does not care, it still works as safely (or unsafely) as it would in a correctly coloured cct. Anyone opening up the switch should be competant enough to know that, otherwise they should not open it.
  • 0
    Interestingly, WISKA also state that the enclosures I refer to have passed the 'glow test' too.

    Personally, when it comes to a high energy disintegration of an overloaded mcb, I would reckon that all enclosures, be they of metal or plastic construction, are built to the same standard in terms of their ability to withstand a violent discharge and to contain the fall-out.

    Mcbs are now all pretty much made to BSEN 60898 so should have that commonality too,

    A cynic might suspect that the manufacturers are just doing what manufacturers do - protecting their revenue streams by utilising a measure which includes some dubious pseudo-scientific reasoning behind it.

    When it comes down to the hard science, exactly what is it that may cause a catastrophic failure if 2 mcbs from different makers are sitting happily side by side in an enclosure?

    Let us say for the sake of the exercise, that both mcbs have the same form factor, that the top and bottom terminal spacings are identical and that the busbar is not deformed during tightening.

    What's to go wrong?

    Just exactly how can a mcb from maker A undermine an enclosure and the other mcb from Maker B when they are all fitted together?
  • 0
    missed the edit window...

    A better example.
  • 0
    Given that a (say) 6kA breaker is guaranteed to break a 6kA fault and be reset.

    During type approval, there is a test that requires the operation of the breaker to be verified again after breaking the full  fault current at least once.

    If operated repeatedly, it must break the fault safely each time after it has been reset, but does not have to reset.- so it has to fail to a safe state where it cannot be reset.

      During all the testing up to that point the presence or absence of a case around it is in is cosmetic, and does not affect the ability to operate.

    It is however allowed to fail at the containment at higher fault currents - and that  is when qualifying the whole assembly comes in, as the outer box may contain the flames and flying bits, so the rating for the breaker in the box, is higher than for the breaker 'bare'. Also at this point the glow wire tests start to matter as when one breaker blows up, you do not want the neighbours catching fire.


    There are a few type approval test reports on the web, that give a flavour of typical results.

    random example 

  • 0
    or more.
  • 0

     





    As an aside, What is the point in comparing to current regs and having C3 codes? The two things seem mutually exclusive, a C3 also seems an insurance risk, second guessing of the regulation it fails And deciding that one doesn't really matter if you like.


    Cheers


    Martyn

     


     




    You don’t have to code the plastic consumer unit enclosure, even though it could to coded 3.


    Andy B.

  • 0
    That is a good question. I would expect so, but a manufacturer may have other ideas! 


    Regards,


    Alan.
  • 0

    Alan Capon:




    Martynduerden:

    But what about the enclosure itself Alan? Clearly the devices have a certified kA rating and that is fairly easy to ascertain but the enclosures kA rating is manufacturer certified subject to use of their prescribed devices . . . 




    That is where the entertainment begins. In theory an mcb used at or below its rated fault current will trip on a fault as everyone expects every time. If the mcb is used above it’s rated current, it may trip correctly, or it may fail catastrophically. The idea of the conditional “rated assembly” is that if the device fails attempting to trip, the enclosure will contain all the bits, including the explosion until the upstream protective device (the supplier’s cutout for example) clears the fault. If the type-tested assembly fails, then the manufacturer may be liable. If they can then prove the presence of another manufacturer’s device or a device of theirs that was not included in the testing was fitted, then it is likely they have no liability. 


    My reason for not giving a definite response, is that a catastrophic failure of a type-tested assembly would have to be examined in a court of law for an absolute judgement. 


    Regards,


    Alan. 


     




    That is my reading too Alan, although you have also prompted the question, Will a manufacturer honour their individual device kA ratings where that device is outside its intended location? 


    Cheers 


    Martyn 

  • 0

    John Peckham:

    Martyn


    The Regulation you are looking for is 536.4.203 for mix and match circuit breakers . A C3 unless the board has been mutilated, bus bars bent, cover cut away then a C2. 






    Cheers John, 


    A ‘new’ one in the 18th. 


    I wonder if a manufacturer would honour the kA rating of a device if sited next to another manufacturers? I suspect not. 


    The question still remains what kA rating(s) can be relied upon for devices and enclosures where they are installed beyond their design? 


    Personally this always gets a C1 from me for the simple reason that PFC will always be greater than zero kA and the only rating I can apply to the enclosures and devices is zero kA, unless I test the enclosure etc 


    As an aside, What is the point in comparing to current regs and having C3 codes? The two things seem mutually exclusive, a C3 also seems an insurance risk, second guessing of the regulation it fails And deciding that one doesn't really matter if you like.


    Cheers


    Martyn

     

  • 0
    Martyn


    The Regulation you are looking for is 536.4.203 for mix and match circuit breakers . A C3 unless the board has been mutilated, bus bars bent, cover cut away then a C2.

Community Rules & Guidelines