Blown Shower and incorrect MCB

[Kempydiy17]

Good evening.

Yesterday, my electric shower blew (all sorts of melted wires in there!!) so I'm installing a new one. I've just checked the consumer unit as to fit a 10.5kw unit it is suggested I connect it via a 45a MCB. As it turns out, I have a 32a MCB (MEM 321QEB). Is this directly replaceable by an MEM 451QEB 45a MCB?

Are there any others that will fit straight in or do I need to stick to the MEM variety?

Cheers in advance for any advice offered.

Chris.

 

[westie101]

You need to absolutely ensure that the cable is big enough for the shower load and the MCB rating before going any further

 

[Kempydiy17]

It looks to be a 10mm2 cable.

 

[Taylortwocities]

Westie is absolutely correct.

To expand. The purpose of the fuse in the consumer unit is to protect the cable that runs to the shower.
You do not just buy a fuse to match the load!

At the time of installation the electrician will have decided what the maximum current is that the cable can safely carry.
That decision was 32amps.
If there is an overload then the MCB/fuse will interrupt the electricity before that cable heats up and sets fire to the house.

So, before any MCB/fuse can be increased the following must be checked:

the size of the cable
the installation method
what route the cable takes (e.g., does it pass through insulation material, etc)
Is the EFLI low enough for the MCB to trip under earth fault conditions.

only then can a decision be taken to increase the MCB size.

 

[Taylortwocities]

It looks to be a 10mm2 cable.

How did you measure the cable?? The 10mm² refers to the cross sectional area of the copper of the live conductors.

 

[deadshort]

Hm, and do you have RCD protection ?

Kind Regards,

DS

 

[Kempydiy17]

So, will a 10.5kw shower run on a 32a MCB and be safe if that breaker matches the cable load rating (which is what the original installer went for)?

All the instruction manuals for all three power ratings recommend a minimum of 40a and replacing the cable at the moment is a bigger job than we have time or money for.

 

[Kempydiy17]

Nope, got it wrong... is a 6mm cable. (compared 6mm & 10mm cable reels I have in the loft). definitely 6mm.

 

[Kempydiy17]

And there is a 'Residual Current Operated Circuit Breaker' on the consumer unit.

 

[RF Lighting]

No. 10.5kW is over 45A. It will trip your 32A breaker.

 

[deadshort]

If you need to install a 50a mcb, you may struggle to get a mem QEB range mcb as they are discontinued.

You may be lucky on eBay.


DS

 

[Taylortwocities]

50A??? His cable is only 6mm²

 

[deadshort]

TTC, catch up the OP knows he has to change the cable.

Regards,

DS

 

[ban-all-sheds]

Deadshort, catch up the OP has said he isn't going to change the cable.

 

[Kempydiy17]

Thanks for all the replies chaps.

So... If I have this straight... EITHER, I have no shower, OR I need to replace the cable with 10mm2 AND replace the breaker with a 50a MCB to run a 10.5kw shower.

Is there a safe option for fitting a new shower on the current setup? (6mm2 and 32a MCB)

Chris.