SHOWER FUSING

[booner]

Hi, my redring expression chrome 8.5kw shower has been running fine on 6mm cable and 30 amp fuse for the past 6 years, replaced the phased shutdown relay a month ago(electrician not me , lo and behold the fuse has blown twice since, the last time it happened the fuse melted part of the carrier to it, its still usable but am reluctant to naturally, wife uses shower, never has it more that luke warm and never showers for more than 5 mins or 10 minutes.......any advice please, electrician suggested 40 amp fuse (given the type of usage), but there doesnt seem to be a replacement carrier available for a 40 amp fuse?

 

[EFLImpudence]

8.5kW is 35.4A, so...

However a 30A rewirable fuse will never blow at that amperage, although it may get too hot and wear out, eventullay giving up although luke warm for five minutes might be fine.
Who knows what fuse wire someone might have put in it?

Perhaps you now have an unrelated fault. Coincidences do happen.

40A is probably not available for your fuse box.
You could fit a stand-alone shower unit with 40A MCB and 30mA RCD.

You would be wise not to replace anything with higher ratings until you determine the cause.

 

[flameport]

electrician suggested 40 amp fuse

That is correct.

but there doesnt seem to be a replacement carrier available for a 40 amp fuse?

Make and model of fusebox?
Plenty could not accept devices over 30A, in which case the solution is a new consumer unit.
Is there an RCD for the shower or the installation as a whole?

 

[booner]

its a wylex, no, its running straight off a 30 amp fuse, house is 18 years old, i love the way 6mm was still being used when 7.5kw showers where being phased out not that long afterwards

 

[ban-all-sheds]

6mm² Method C will cope with the most powerful shower you can buy.

 

[EFLImpudence]

i love the way 6mm was still being used when 7.5kw showers where being phased out not that long afterwards

Not sure what you mean by was still being used.

It was used because BS3036 fuses (rewireables), because of their characteristics, require the Current Carrying Capacity of the cable to be derated by a factor of 0.725. Therefore 30/0.725 = 41.4A so 6mm² is required.

 

[booner]

you missed my point, or maybe you just wanted to show me how clever electricians are, the fact remains, a selection of showers that are compatible with standard 6mm cable (without any fancy add on rcd mcb blurbablurb) are noticeable by their absence, thanks for the repiles though

 

[EFLImpudence]

you missed my point, or maybe you just wanted to show me how clever electricians are,

That's an strange unnecessarily pompous comment.
I was telling you the reason for 6mm² cable. If you are not interested in learning anything, that is up to you.
There are plenty of ignorant electricians around; You'd better employ one of them.

the fact remains, a selection of showers that are compatible with standard 6mm cable (without any fancy add on rcd mcb blurbablurb) are noticeable by their absence,

Why would they state such things? It is not done that way round. The necessary cable is selected for the appliance.
However, in your case, with 6mm² cable, method C, you cannot have a rewireable fuse of more than 34A. As the nearest available to this is 30A, which you have, then the maximum shower you can have and be compliant is 7.2kW.

thanks for the repiles though

Really.

 

[ban-all-sheds]

you missed my point,

Your point was predicated on factual errors.

or maybe you just wanted to show me how clever electricians are

Or maybe he wanted to show you what the facts are.

the fact remains, a selection of showers that are compatible with standard 6mm cable (without any fancy add on rcd mcb blurbablurb) are noticeable by their absence

With which part of "6mm² Method C will cope with the most powerful shower you can buy" do you disagree, and why?

And what does "without any fancy add on rcd mcb blurbablurb" mean?

 

[booner]

i just want to put a 30 amp fuse in, nothing else, and be able to shower, it seems i need a 7.5 kw to do that without problems, am i wrong?

 

[ban-all-sheds]

No you aren't.

 

[booner]

and my point was, there isnt a selection of 7.5kw showers to choose from, which seems silly when modern houses with 6mm as standard in a standard unit that only takes 30 amp fuses, is only suitable for 7.5 kw showers, none of this is solving my problem however, but its nice to talk

 

[JohnW2]

and my point was, there isnt a selection of 7.5kw showers to choose from...

I don't think it's as bad as you seem to believe. I've done no searching, but I'm sure that, for starters, Triton, Mira and Redring do 7.5kW showers - how many do you need in your 'selection'?

In any event, as you've been told, 6mm² cable is going to be adequate for virtually any shower you can buy. The problem is your obsolete fuse box, which ceased to be 'current' decades ago.

Kind Regards, John

 

[ban-all-sheds]

and my point was, there isnt a selection of 7.5kw showers to choose from, which seems silly when modern houses with 6mm as standard in a standard unit that only takes 30 amp fuses, is only suitable for 7.5 kw showers,

The real culprit is your type of protective device, as this reduces the best case current carrying capacity of your cable from 47A to 34.

"Modern" houses use MCBs.