New Shower old wylex consumer unit question

[Valcor]

Hi noob here

Old shower (9.5kW) is kaput Have bought new shower, same - 9.5kW. Have been told I need a new consumer unit, (old one is cream 6 way cartridge fuse version with 60A label by switch) and subsequent testing etc. I am presently unable to afford this but am saving to do it next year. (Been quoted £400 min!)

The old shower, has the correct 10mm cable, isolator switch etc and another chap said he would just swap my old shower for the new one but he say a 40A cartridge fuse should replace the current 30A one. Is this OK, will the unit be able to take a 40A fuse??

thanks in anticipation....

(Currently have 1x5A for lights 1x30A for downst plugs, 1x30A for upstairs plugs and 1 30A for old shower, that is all)

 

[ericmark]

Unlikely you will find a 40A fuse for the Wylex unit. 9.5kW = 41.3A and if you look at the charts it will take around 2000 seconds before it will rupture at that current. So around 1/2 an hour. Most people do not shower for 1/2 an hour so likely it will not rupture in spite of overload. So as far as will it work then the answer is likely it will. Is it safe wall as far as fuse goes yes the fuse will fail before cable over heats so it will fail safe.

However the real question has to be what RCD if any is fitted? RCD's have been required for a in bathroom shower for many years. Some countries will not allow one to have the shower inside the cubical and clearly when it is outside the cubical then the dangers of power tracking due to water ingress are much reduced. But we tend to mount the shower unit in an area where it will get wet. We of course hope water will not get in. But from time to time it does happen. Some using a RCD which will trip at 30ma in 40ms is required in the UK.

So if you have a RCD fitted then no real problem. If you don't have a RCD then it will need an enclosure to fit it in. This enclosure can include a overload device. (MCB or RCBO) and could be powered from before the consumer unit although it is not a DIY job. However it will be cheaper than changing whole consumer unit. Personally I don't like the idea of loads of little boxes and would like to see a consumer unit with RCD or RCBO covering whole house. But it is an option.

In fact my house has two old Wylex consumer units both supplied from 30ma at 40ms RCD's with all the re-wireable fuses swapped for MCB's. Been like that for years. But I don't have an electric shower, they are too much like standing under warm drips. I use my domestic hot water instant boiler and at 27kW that's a reasonable shower.

 

[chivers67]

http://www.fastlec.co.uk/wylex-b40-40a-plug-in-mcb-p-3675.html

Is this what he's asked you to get?

You could get a seperate shower suppply independant of your consumer unit just depends if you've a henley block to "split the supply"

http://www.tlc-direct.co.uk/Products/CPSP1.html

Best get a 45 amp though as per post above

(at 240 volts just under 40amps - 39.58 . )

 

[Valcor]

Thanks for replies This is what he had in mind-

http://www.discount-electrical.co.u...-fuse-holder-assembly-with-contact-shield-40a

Not sure about this but, we only have 10 minute showers max?!

Chivers67- would your first linked item be ok?

 

[flameport]

(old one is cream 6 way cartridge fuse version with 60A label by switch)

That fusebox cannot have a 40A fuse or MCB fitted, since they were designed for 30A per way maximum.

There is no RCD, so the installation won't comply with BS7671 or the manufacturers instructions.

As you already have a 40A load connected incorrectly via a 30A fuse, it is very likely the fusebox has already been damaged by overheating.

 

[Valcor]

As you already have a 40A load connected incorrectly via a 30A fuse, it is very likely the fusebox has already been damaged by overheating.

Thanks for that advice flameport, (old shower been there 10 years and no visible sign of damage to fusebox!!?)

 

[RMS]

Thanks for that advice flameport, (old shower been there 10 years and no visible sign of damage to fusebox!!?)

That doesn't surprise me. The chances are it never will but that said the design of the fuse box does not permit >30A per way. Failure to adhere to this is failure to comply with BS7671.

I know you said you can't afford to have a new consumer unit fitted, you should consider this as any money spent now will most likely be a waste as you will only have to spend more to upgrade the whole consumer unit in the future.