On 06/05/2019 17:47, Chris Green wrote:

As per the subject, if one mixes MCBs and/or RCBOs of different makes
in a consumer unit is it likely to stop it conforming to IEE rules?

Assuming they are mechanically compatible, then there is no real
practical problem. The resulting setup may not meet type approval any
more, but I can't see that being a issue.

Also I presume the new (18th edition) rules regarding flammability of
CUs would only apply if one replaces a CU and are not retrospective.

Correct.

Adding or changing MCBs to RCBOs in an existing CU wouldn't require
that the CU be upgraded to 'non flammable'.

Yup, if you install a whole new CU then it needs to be to current
standards. No requirement to change what is there.


--
Cheers,

John.

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