different sized cable for electric shower

[bb76]

Hi, I currently have a 7.5 kw shower connected via a 6mm cable on a 32a MCB. I would like to have this uprated (before the cold weather comes) to a 9.5 or even 10.5 kw unit. Replacing the cable with a 10mm cable between the consumer unit and double pole switch shouldn't cause to many issues, however the cable run(approx 2m) from the switch to the shower is chased into the plaster and behind the tiles and would make a mess of what is currently a nicely decorated bathroom. My question is would it be acceptable to keep this section of cable as 6mm while replacing the main cable run (about 11-12m) with 10 mm cable along with fitting the appropriate MCB. I would be getting a qualified electrician in to do this but am looking for a heads up on what the options are. Thanks.

 

[oharaf]

The 6mm is not suitable for the current to be drawn by the new shower you are intending to install.

Your electrician should tell you the same, so the entire run will require replacing

 

[pompeygit]

IF...................
The existing cable is undamaged and is buried in plaster, runs in voids, and is not covered enclosed on its run with any insulation(ie rockwool or similar) why change any of it? Use a 40amp mcb and an 8.5kw shower which is adequate. They give a good flow rate and you are saving both money and water. Running costs over a year will be substantially cheaper. Most of the water from 9.5kw is straight down the drain and it costs. What is it in this country that people want to be hurt by the power of a shower.....personally I,ve never enjoyed a shower where I am being blasted

 

[ericmark]

Most likely because of cooling effect of plaster and the fact that showers don’t run for long it would be OK but if I was the electrician doing the job I would not want to take the chance and would insist on renewing all the cable. Changing the isolator for a pull switch type may help but at the end of the day it is the guy signing the paperwork who must make up his mind as to what he can accept. It is a Part P job so all the inspection and testing paperwork is sent to the local authority building control either direct or via clearing agent. So not as if it can be hidden and he could be caught out when the next inspection and test is conducted so 9 years later he could still get in trouble.
Not sure how routed with the new Guardian and Flexishield cables to BS 8436 then 6mm² cable will take 58 amp which would be well within requirements so when on site the electrician may see a way to replace cable without removing plaster not want you want to hear a know but seems likely you will need to re-plaster.
Eric

 

[bb76]

Thanks for your quick replies! The 6mm cable was only installed 6 years ago and should be in decent nick so I may well go for the 8.5kw option, it's just that the 'funkier' electric showers available on the market seem to start at 9.5kw. The ultimate choice may well depend on how keen I'm feeling over the next couple of months!

 

[TopTrumper]

Most likely because of cooling effect of plaster and the fact that showers don’t run for long it would be OK but if I was the electrician doing the job I would not want to take the chance and would insist on renewing all the cable. Changing the isolator for a pull switch type may help but at the end of the day it is the guy signing the paperwork who must make up his mind as to what he can accept. It is a Part P job so all the inspection and testing paperwork is sent to the local authority building control either direct or via clearing agent. So not as if it can be hidden and he could be caught out when the next inspection and test is conducted so 9 years later he could still get in trouble.
Not sure how routed with the new Guardian and Flexishield cables to BS 8436 then 6mm² cable will take 58 amp which would be well within requirements so when on site the electrician may see a way to replace cable without removing plaster not want you want to hear a know but seems likely you will need to re-plaster.
Eric

Eric, whats this type of cable?
58 amps for 6mm? not a condescending question, i really am intrigued.

 

[Pensdown]

http://tpwcc.com/technical.html

I'm still waiting to speak to someone thats tried it. Also, there have been many posts on the IET on whether it meets BS8436.

 

[ban-all-sheds]

58A at 90°.

Chances of being able to run it at 90°: slim - stick to the figures in 4D2A.

I'm still waiting to speak to someone thats tried it.

They offered me a free sample - never turned up....

Also, there have been many posts on the IET on whether it meets BS8436.

Would the maker falsely claim it did?

 

[ericmark]

Some links I am sure there are many more and it seems looking at it to be very similar to FP100 in fact some also has that ratting as well but to begin with I didn’t realise it was all to BS 8436 as in many places it quotes the BS numbers for insulation and cores rather than whole cable. But never been able to find a price since did not need to use it yet never tried. I down loaded speck sheet and was surprised at current carrying cap but I suppose ali shield is good at getting rid of heat and it is a 90 deg C cable. Up to 4mm seems many options but 6mm version in some makes only in 3 core.
http://www.batt.co.uk/products/index.asp?area=2&p1=20&p2=140&p3=394
http://www.eland.co.uk/cable-genius/
http://www.buildingtalk.com/news/baz/baz107.html
http://www.voltimum.co.uk/news/10695/infopro.whatsnew.latest/basec-approval-for-unique-cable.html
http://tpwcc.com/flexishield.html
http://www.clevelandcable.com/products.asp?id=1798&step=2
I would be interested to hear from anyone who has used the cable.
Missed one Pirelli do Earth Shield see http://www.voltimum.co.uk/news/4174...s8436/Pirelli-Earthshield-and-LSX-cables.html
With 2.5mm rated at 33 amp radials look more promising.
Eric