10.8 kw Shower & MCB in Newlec Consumer Unit

multidrop · 8 Nov 2005

Have had a Mira 10.8 kw shower put in loft conversion, 6mm t&e cable 9m run 32amp mcb keeps tripping, presumably should have had 45 amp fitted, however, the newlec cu only has newlec 40 or 50 amp mcb's to fit (they don't do a 45amp mcb) What size should I fit?

theshogun · 8 Nov 2005

Upgrade the cable to 10mm then use 50 amp mcb, make sure your isolating switch has a current rating of 50amps as well.

multidrop · 8 Nov 2005

Thanks for quick response, so sparky who fitted it got it wrong, it even says in the instructions use a 45amp mcb! Perhaps it would be easier to get him to change the cu for one that will take a 45amp mcb? getting new 10mm cable in would be a problem

the instructions from Mira do say 6mm is ok for a run of that length. The electrics were all checked and a certificate issued NICEIC by another electrician, shouldn't he have at least spotted the mcb was the wrong size????! Argh.

ban-all-sheds · 8 Nov 2005

multidrop said:
The electrics were all checked and a certificate issued NICEIC by another electrician, shouldn't he have at least spotted the mcb was the wrong size????! Argh.

Yes.

Complain to NICEIC.

pdcelec · 8 Nov 2005

But what did the NICEIC cert say on it? A 32A mcb protecting 6mm cable is ok (most of the time). What should have been picked up was that the functional test did not pass.

theshogun · 8 Nov 2005

You could always replace the shower with a lower powered unit

multidrop · 9 Nov 2005

Functional Test? So the shower should have been tested, left on to see if it trips the mcb as part of the NEIEIC test? All the paperwork was there clearly showing it was a 10.8kw unit. Dont fancy replacing shower, whole point was to get a decent temp/flow in the winter...

Steve · 9 Nov 2005

Perhaps it would be easier to get him to change the cu for one that will take a 45amp mcb?

why? can you not run the cable in self-adhesive trunking if it is so difficult to get at the route of the 6mm²? Certainly cheaper this way.

the instructions from Mira do say 6mm is ok for a run of that length.

never pay much attention to what that says - they make their tables based on cables clipped to a wall with ventilation - cables can carry less current in insulation or plaster and over long distances.

multidrop · 9 Nov 2005

The point is - new loft conversion - new 10.8 kW shower fitted and the idiot/s have f****d it up! I don't want a less powerful shower, or trunking all over the walls. There seems to be a fair bit of debate among spark's on this and other message boards about the right cable/mcb for a 10.8kw shower. As I understand it 6-mm cable and 45 amp mcb are ok (if on the limit) as long as the cable is not insulated or bundled along the route or too long a run (in this case 9 meters). Back to the same problem, 45 amp mcb wont fit in a newlec CU. Presumably a 40 amp mcb would keep tripping, and a 50 amp could allow the cable to overheat.

Is that about it?

pdcelec · 9 Nov 2005

Get the idiots to put it right at their cost. Since this is a Part P job, there is a warranty involved

BenStiller · 10 Nov 2005

Talking about recommendations, one of the shower manufacturers on an install the other day recommended an extractor fan to be fitted.....Honest, cant remember which one but it might have been bristan
PSPSPS
As an installer I leave documentation with the customer advising them to never ever turn the shower on, think about it, it makes sense

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10.8 kw Shower & MCB in Newlec Consumer Unit

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