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MCB and RCD mix and match of makes 536.4.203

Stewart Mason
Just wondering what peoples thoughts are to mixing makes of MCB's and RCD's in consumer units. I went to a callout the other night and the culprit was a faulty 61008 RCD. To get the power back on I replaced the faulty Item with a different make of 61008 RCD. The next day I raised a job to have the right make of RCD fitted. It turns out the QS at work isn't concerned about the incorrect make of RCD and is more concerned about IP ratings being met. Am I right in wanting to fit the correct make of RCD?


What would you code this as on a EICR?
  • 0
    Most important is does it fit the terminals properly and not put strain on the enclosure or adjacent breakers ?

    in general the risk of mix and match is small, if it is done properly, and you are not right on the edge of PSSC spec. or relying on co-ordination of cascaded breakers.

    However, if you want to cover yourself liability wise with maker's type testing, you can bet that combination is not covered, and if it caught fire you'd have no comeback.

    But you'd  almost certainly have not got much out of them  anyway, even following instructions to the letter, unless your legal team is as good as theirs.
  • 0

    mapj1:

    in general the risk of mix and match is small, if it is done properly, and you are not right on the edge of PSSC spec. or relying on co-ordination of cascaded breakers.




    Very good advice from mapj1. If I was designing the protections system those are the aspects I would be concerned with (and in that order). If the MCBs and RCDs meet the standards and have the same characteristics there should be little to worry about, particularly as no designer in their right mind would spec breakers right on the edge of their PSSC (though it has been done by some....).

    The maker's type testing will generally only confirm the breaking characteristics of the CB and not the coordination which will be achieved through review of the different CB tripping curves, unless the CB/RCD combination is specifically sold as a coordinated pair. However, as mapj1 says, you may want to ensure you cover yourself as the manufacturers are unlikely to confirm that mixing someone else's breakers is satisfactory - why would they when it will impact sales?

  • 0
    One of the biggest problems with using different makes of device, in say a consumer unit, is that of old the screw terminals did not always exactly line up for the busbar. This could put strain on devices when the terminals were tightened. Of course late at night during an emergency situation it has been known for electricians to "graunch" in a different make of device in place to get the customer out of trouble. I have heard that M.C.B.s of a different make to the consumer unit have been placed at the end of the row of existing M.C.B.s and the bus bar cut short, and a suitable short cable link used to connect the new M.C.B. (So, I've heard like). Most R.C.D.s these days seem to be compatible and interchangeable in most cases.  I have myself successfully undertaken some on site modification engineering with no problems.


    Z.
  • 0
    http://www.beama.org.uk/resourceLibrary/beama-technical-bulletin---safe-selection-of-devices-for-installation-in-assemblies.html

    Please look into the BEAMA report above and mix and match at your own risk.


    Topper

  • 0
    For several years I have been flagging pick and mix protective devices in consumer units when I have been preparing EICRs at change of tenancy for a housing association, before the 18th Edition was published. I’m told that currently they are getting a national contractor to go through the whole site to do periodic EICRs for every flat, since the introduction of the 18th I have coded the issue as a three, I would like to know what the national contractors guys are saying about them.


    Andy
  • 0
    I should point out that some manufacturers stipulate that you can only install equipment and devices from THE CURRENT CATALOGUE.


    So once they withdraw an item from stock that’s it as far as they are concerned, you should not use up your own old stock of unused devices or buy from others, so reusing devices is a complete no, no if you play by the rules some manufacturers set out.


    That means the housing association I mentioned above has thousands of consumer units that cannot to serviced, repaired or have circuits added to them and should be replacing consumer units as a matter of routine on a daily basis for example to install a shower rather than using a spare way in the existing consumer unit or replacing the entire consumer unit because one device has failed within it.


    That’s not happening.


    Andy
  • 0
    Hi Andy,

    Firstly the Manufacturers instructions are paramount and should be followed and to be fair if non type-tested accessories i.e. MCB's are installed the EICR is worthless (not to manufacturers instructions). To be honest the MCB's should be changed and a Minor Works certificate should be issued.

    Worse case scenarios a C3 placed on a condition report if all the markings are visible on the breaker etc. and the occupier informed, if no markings are visible on the breaker FI should be indicated and this would be unsatisfactory and would fail the EICR.


    Dave
  • 0
    Interesting BEAMA report. It seems to give a succinct summary of the situation regarding 'mix and match'. I think the "In Conclusion" section sums it up:
    • It is the responsibility of the installer who intends to mix devices / components in an assembly, to undertake appropriate verification and ensure conformity with the relevant standard.


    This is not the same as saying it must not be done. It is putting the responsibility on the person making the change to ensure the appropriate verification is done (BS EN 61439-3, section 10 for domestic consumer units).
  • 0
    I phoned two manufacturers to ask if I could put a RCBO made by one into the other one's consumer unit as it needed a B32/30mA type A RCBO due to tripping issues and the original consumer unit manufacturer does not make type A RCBO or RCDs.


    What response do you think I received?


    Andy
  • 0
    These manufacturing companies are multinational and have access to a huge amount of resouces. Surely it would be to everybodies interest for them to test their equipment accross a wide range of protective devices. It is obvious that much of this nonsence would disappear as well as providing useful data to electricians......


    Legh

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