Shower fuse reccomendations

[johnc1873]

Hi there, im new here and quite new to DIY to be honest!

My prob is- I had a new 9.5kw electric shower fitted about a year ago to replace an existing 8kw? one. the thing is at the time it had reccomended that I use a 45amp fuse, however I couldnt get one of these anywhere. I managed to find a store quite local who advised that the existing 30amp would be fine.

Now the shower's not working (well the power cord light doesnt go on and water doesn't heat up).

Is this just likely to be the fuse thats gone? And if so what amp should I replace it with? Also are there any web-sites that supply these as Ive tried to locate a supplier again with no luck!

Thanks for any advice!!

 

[ZenStalinist]

Yes, you require a 40 or 45 amp fuse or mcb. You should also check that suitable cable has been used.

 

[securespark]

We need more info.

How long is cable run, what size cable (if known) what type of board you have etc....

 

[johnc1873]

As I say- I don't know much but here goes:-

Cable- thick about 12mmm thick (casing- cant see inside).

Cable - Run about 6.5 to 7mts from shower to electric box.

Fuse box- white with on/off at left with screw-on casing for fuse.

Fuse- Brown 30amp 'Wylex'.


Does that help? Im really looking for a supplier of the right fuse as well if poss??

Thanks again.

 

[johnc1873]

So can anyone help??

 

[ban-all-sheds]

I managed to find a store quite local who advised that the existing 30amp would be fine.

Whoever gave you that advice is a bl00dy idiot - mad, bad, and dangerous to know. 9500W ÷ 230V = 41.3A

Is this just likely to be the fuse thats gone?

Yup.

And if so what amp should I replace it with?

Unfortunately it's not as simple as that.

Also are there any web-sites that supply these as Ive tried to locate a supplier again with no luck!

That's because you can't get rewirable fuses bigger than 30A.

Cable- thick about 12mmm thick (casing- cant see inside).

That sounds like 4mm cable to me - typical external dimensions of flat twin & earth cables are:

4mm - 11.9mm x 6.25mm
6mm - 13.5mm x 7mm
10mm - 17.1mm x 10mm

(when cable sizes are quoted, e.g. 4mm, 6mm etc, that actually means the cross-sectional area of the main conductors inside, in sq mm - should really be written 4mm², 6mm² etc, but people rarely bother...)

Anyway - even if it is 6mm² cable, that is still not enough for a 9.5kW shower.

You need to replace the cable with 10mm², you need to use a 45 or 50A MCB, not a fuse, to protect it, and you should (highly advisory) have RCD protection.

My guess, from what you have said, and from the questions you've been asking is that you'll need to get an electrician in to do all this for you.

 

[johnc1873]

As you've guessed I know nothing about this kind of stuff, forgive me if i sound daft, but whats an MCB?

Its worked okay for a year or so with the same cable and 30amp fuse, why not just replace the existing type? Or is that just asking for trouble?

Where can I get fuses or MCB's then? Tried all over the web and local stores but not knowing what i'm looking for doesn't really help!

Thanks again.

 

[plugwash]

sounds like a wylex standard

if *AND ONLY IF* the main switch on your CU is 100 you can fit a 45A cartridge fuse http://www.tlc-direct.co.uk/Products/WYC45.html (wylex standard plug in mcbs stop at 40A) and rewire your shower with 10mm cable

if not then you could henly in a shower CU (see my post in for referenace) but its probablly better to replace the whole CU with something like this

http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=25879&id=64020 (you will have to buy a 45A mcb seperately though http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=25878&id=75933

however fitting a CU involves pulling the service fuse and while i would be happy to do this myself it does require care and you must make sure connections of such high power are tight

 

[securespark]

I feel I should add this again, so that DIY'ers are aware:

If you need to add a consumer unit, or change the existing one, the best course of action would be to call the Regional Electricity Company (REC), and ask them to fit (or install one yourself and ask them to wire in) an isolator that is fitted inbetween the tails from the meter and the CU itself. This means that the tails to your CU are also isolated, thus making the CU safe to work on. If you want to, you can always fit a henley block inbetween the new isolator switch and the CU, allowing you to fit extra CU's in the future.

BUT PLEASE DON'T:

Tamper with the cut-out seal or cut out

Tamper with meter seal or tails

as this will render you liable to prosecution, and may even be lethal. One slip is all it takes - I'm not trying to scare anyone, but I've seen it done, and it's not pretty.

Leave the meter seals, cut out etc to the REC, and once you have installed your isolator, you can work on the system in complete safety without bothering the REC again.