MCB keeps tripping

[nesty1760]

Hi

I have a Wylex circuit breaker box in my house. Recently my number 1 MCB keeps tripping. On my board number 1 soley is used for the electric shower in the ensuite room.

I had the shower replaced with a Mira Sport, think something like 9.8 ka? Anyway the MCB doesn't trip straight away, but at varouis intervals trips off. The MCB is 30amps one, but I thought surely the shower can't be consuming more power then that?

Any ideas anyone?

Many thanks

 

[securespark]

9.8ka??

You mean 9.8 kw = 9800W = 42.61 Amps @ 230V.

Yes, more than 30A, I'm afraid.

And you'll need to check that the rest of the circuit is up to the job, not just change the CPD.

 

[nesty1760]

Hi

Sorry meant 9.8kw. I just found the instructions this morning, in back of cupboard. It states the Mira is either a 7.5kw or 9.5 model. Anyway recomends a 40 amp MCB. The wiring should be ok to handle it as the wiring was done especailly for the shower. Though wil get a qualified electrican to test and upgrade the MCB.

Many thanks for your advice.

 

[davelx]

The wiring is not necessarily up to the job - it depends on the cable size used and where it runs - in conduit, buried in plaster, in an insulated wall etc. as these all effect the current capacity of the cable.

It is possible that the cable used was OK for a 30A breaker but not sufficient for a 40A circuit - the cable may need to be replaced.

 

[nesty1760]

OK many thanks. From what I can remember the 30A MCB was already in the wylex box, so the bloke that fitted it the cable just used the spare breaker. I'l get someone in to have a look.
Thanks again

 

[dingbat]

OK many thanks. From what I can remember the 30A MCB was already in the wylex box, so the bloke that fitted it the cable just used the spare breaker.

Ah... that'll be one of them there 'electricians', who also do a bit of plastering, cut wood on occasions and are handy with pipework. Good luck.

 

[sm1thson]

The wiring should be ok to handle it as the wiring was done especailly for the shower.

dont assume so its a lot easier to pick the right mcb than cable, and they got that wrong! can you see the cable size on the cable?

Though wil get a qualified electrican to test and upgrade the MCB.

so not the person you used before then!?! note the fitting of showers now comes under art p of the building regs, so you have to either pay building control before you start or use an electrician that is registered to do the work (different to been qualified). Im just telling you so you know what to look for in electricians and electrical work in future.

 

[Softus]

The wiring should be ok to handle it as the wiring was done especailly for the shower.

How can you be in the situation where the wiring was especially done, but the MCB wasn't?

 

[nesty1760]

The house was totally gutted. The then sparky who done the fuse box put the breakers in, but knew as the house in vast development after that time he put spare breakers in for future use, as when required.

The person who installed the shower hooked it up to a spare MCB on the panel.

 

[plugwash]

The person who installed the shower hooked it up to a spare MCB on the panel.

sure and he did that without checking if the breaker he hooked it up to was suitable. Anyone who uses an existing breaker without checking its suitability is either incompetant or a cowboy. As such you cannot trust that the rest of what they did was up to scratch.

did he claim to be a member of any part P self certification scheme? did he give you any paperwork for the installation? if yes then does the paperwork mention anything about membership of a self cert scheme and his ID status within that scheme?

 

[Softus]

The house was totally gutted. The then sparky who done the fuse box put the breakers in, but knew as the house in vast development after that time he put spare breakers in for future use, as when required.

The person who installed the shower hooked it up to a spare MCB on the panel.

Frankly, you're either too trusting, or you know perfectly well that you engaged someone incompetent.

Without wishing to tar the "person" with a paintbrush soiled by what might just be your poor choice of words, if a professional electrician described to me what he/she did as "hooked it up to a spare MCB", then I'd be pushing him/her out of the door and immediately 'unhooking' everything they'd just done.

Lke what plugwash said, basically.

 

[nesty1760]

Thee bloke that done it was a complete idiot, that I know that now. Which is why I am asking that something is not quite right? Though afterwards i did uprate the shower, so hence wanting to know if circuit can be volt tested.

 

[Softus]

Thee bloke that done it was a complete idiot, that I know that now. Which is why I am asking that something is not quite right? Though afterwards i did uprate the shower, so hence wanting to know if circuit can be volt tested.

So, to summarise:

1. Someone you call an electrician installed a consumer unit.

2. Someone you once called an electrician installed a shower with cable of unknown capacity, and performed an unknown amount of testing.

3. You later changed the shower without checking the current carrying capacity of the cable or CPD.

4. You now have an appliance consuming more current then the CPD is designed for, over a cable of unknown capacity.

In your opinion, which of the above people are idiots, or incompetent, or reckless, or perhaps even downright criminally negligent?

 

[nesty1760]

Well obvouisly this has all come to light now. The orignal person was supposedly qualified at the time, but now come to light but maybe he wasn't. I wouldn't say I was an idiot, conned maybe yes.

When the 2nd shower was installed, (I didn't install it). A quailfied person did and said the wiring was ok. It worked ok for 2 years now and now starts tripping. Hence my question about further testing maybe required.

 

[sm1thson]

It worked ok for 2 years now and now starts tripping.

you forgot to mention the 2 years bit in your original post! -reread it it sounds as though the problem started when the new shower was installed!

Or is the 2 years ago the classic part p style 2 years ago nudge nudge wink wink!?!