Type C MCB for Volex Consumer Unit.

Fitting a type C MCB won't get around the problem of nuissance trippin on the death of a light bulb. This is becasue the current surge is in the magnetic 'instant' part of the breaker's spec.

Subject to the wiring being adequate a cartridge fuse (if they make holders for your CU) might help. Also going to low voltage or any form of fluorescent lighting will avoid the problem.

Not so sure. I had a type C trip the other day when an RO80 blew. On a circuit which was nowhere near fully loaded - only 200 watts at the time.

Type Cs may not be a panacea, but they do require higher i x t to trip than type Bs, even in the magnetic portion of the curve iirc, so they should give an improvement. Wire fuses are much better in this respect.

NT

Oh-oh, now you've got all scientific on me. I don't know anything about this but I have read several topics from this newsgroup suggesting type 'C' MCB's might help. Certainly it's likely to be a cheap and easy option and can't do any harm to try, but it's irrelevant if I can't get them to fit my consumer unit anyway.

Are all MCB's basically the same size/shape, can I fit another manaufacturers MCB's into my Volex consumer unit.

This question comes up at regular intervals, do a Google newsgroup search for "DIN MCB consumer unit" in uk.d-i-y. There was a thread very recently, it might be one your news server still holds.

In brief, you may be lucky but it's by no means certain. Some makes of MCB will fit in other makes of consumer unit but it's really a bit of a "suck it and see" process. Since MCBs only cost two or three pounds a few "don't fits" aren't too costly.

MCBs have two independent trip mechanisms. One is thermal (i.e. bimetalic strip of some sort) and designed to clear prolonged overloads

- how long it takes to operate will depend on how big the overload, but we are talking minutes or even hours here. The second mechanism is based on a solonoid that will open the breaker very quickly on occurance of a "fault" i.e. a massive overload like that caused by a short circuit.

When tripping due to thermal overload a MCB will respond not unlike a fuse. However in the event of a fault (which a failing bulb can momnentarily cause), they will open very quickly due to their solonoid (magnetic) mechanism. So your type C which will withstand overload for longer, is still able to respond the afault very quickly.

Never tried a volex CU, so can't say for sure.

See thread here:

Thanks all, especially John for the straight-forward explanation that even I can understand.