Old wiring question

[JDLDIY]

Hi there.
We have an old fashioned fuse box - MEM, with cartridge fuses. Can't replace it yet as it would be a waste of money, big project to do at some point which will mean replacing all the electrics.
Problem is the 30A fuse for the 9kw shower keeps going. From my maths it's not a big enough fuse, but obviously the circuit will need checking to see if it's safe to put a bigger one on.
Question is, is this even possible? I'll get a sparky in, but just wanted to know what you think might be the best option, assuming the circuit is good enough. Can you get the parts? Is it possible to replace it with some sort of MCB?

Many thanks for any advice.

 

[PrenticeBoyofDerry]

It is possible to replace the cartridge fuse holder and fuse.
As you say the cable size and any de-rating factors must first be established before increasing the fuse size.
But who was the ignorant person that installed a 9kW shower on a 30A device?
If the circuit cable does not meet the criteria of an increase of current, then you must downsize the rating of the shower!
As I doubt by what you have so far mentioned, that there is RCD protection on the shower circuit, I would recommend having this circuit RCD protected also!

 

[JDLDIY]

Certainly no RCD protection, how would this be done then, just put one in line outside of the fuse box?
Where would you get the parts - they're not universal these things are they?

 

[deadshort]

I would advise you have the installation checked over, it maybe electrically sound and you could replace the fusebox with a consumer unit with mcb's and RCD protection. This is what most people who do not want to rewire but want the additional protection opt for.You could faff around adding an additional CU for the shower which you will rip out later when you do replace the fuse box.

Regards,

DS

 

[JDLDIY]

Thanks for your advice, but no I don't want to go to the expense of replacing the fusebox now when we are potentially going to knock the house down in the not too distant future. I could do with a temporary but safe fix if it's at all possible.

 

[seasickstevie]

Replacing the CU with an RCD board won't be a "waste of money".
There's no reason why your 'new' board couldn't be reused following your big project anyway, particularly if you know in advance how many ways you're going to need for the end result.

If the budget allows, go for a non-RDC CU, and use an RCBO for your shower, then it's future-proof with (RCBO) options for your later arrangements.

 

[endecotp]

"Temporary but safe fix" is to replace the shower with a lower-power one.

 

[PrenticeBoyofDerry]

As above putting correct sized shower for the circuit would be a improvement.
But RCD protection was/will be very likely recommended on the manufacturers instructions of the shower (I know in some circumstances that the MIs do no longer have to be followed but as the location is a shower/bathroom, it is advised to)
It would be possible to install a standalone external of the board inline RCD isolator or shower control unit for this circuit.
These items can be obtained from most electrical wholesaler and I would expect the big sheds to have them.

http://www.screwfix.com/search?search=shower+rcd+unit

 

[deadshort]

Thanks for your advice, but no I don't want to go to the expense of replacing the fusebox now when we are potentially going to knock the house down in the not too distant future. I could do with a temporary but safe fix if it's at all possible.

Ah, that's a "big project" the separate cu for the shower is the way to go then.

DS