What Amp fuse for replacement shower and new bathroom light?

[WattsTheFrequency]

Hi, recently, after extended showers by family members the wylex box/ shower wire, which is outside bathroom in cupboard, started to heat up and set off the smoke alarm. We had it shut off and pulled the fuse. We decided to downgrade the gainsborough energy 2000x which, after taking off the cover appears to have 10.8 printed on the 'heat exchanger?'. We assume that is a 10.8kw, and that the wire to which it was connected is a 10mm wire, measures 4.1 ish on the calipers. We are downgrading to a redring 8.5kw. Question- Will the wylex 30A fuse, which didnt blow, still be suitable for protecting the circuit, and will the 'mcb?' at the consumer unit at the front door need upgrading/downgrading? Finally, old single light/heater unit coming out of bathroom, is the 5A fuse in the wylex box sufficient for a new 36w dimmable light, or do we need to downgrade it to a smaller amp? Thanks in advance. Photos provided.

 

[Geoff1946]

That needs replacing in total., not just the load reducing. Is there an RCD anywhere?

 

[Fleeting]

As above there has been a serious thermal issue lucky you had a smoke detector. That consumer unit now needs replacing.

 

[Murdoch]

I think you will find that the manufactures instructions will state RCD protection IS required so you need a competent spark to replace that fuseboard.

Also they need to check the earthing and bonding too.

 

[WattsTheFrequency]

That needs replacing in total., not just the load reducing. Is there an RCD anywhere?

Hi, thanks for the reply, I'm in the learning phase here, where would the RCD be likely to be found?

 

[WattsTheFrequency]

I think you will find that the manufactures instructions will state RCD protection IS required so you need a competent spark to replace that fuseboard.

Also they need to check the earthing and bonding too.

Cheers for the advice

 

[WattsTheFrequency]

As above there has been a serious thermal issue lucky you had a smoke detector. That consumer unit now needs replacing.

Thanks, any idea about the fuse rating required as posted in the question?

 

[Geoff1946]

Thanks, any idea about the fuse rating required as posted in the question?

No-one on here is likely to advise you to connect a shower through a fuse board which is already damaged as well as being long out of date and probably lacking RCD protection.
The 30amp fuse was well below the rating for the shower you mention; that's why the board almost set alight!
Get an electrician involved before you either burn down the house or electrocute one of your family.

 

[WattsTheFrequency]

Thanks. I hope I wasnt suggesting it wasnt going to be replaced, nor that I was going to carry out the repair, (I wouldnt risk anyones life) I am trying to find out from a technical standpoint what fuse rating for an 8.5kw shower, on this system as given, and whether a 36W light can run on a 5A fuse...it was an electrician that wired it first time around (apparently by your comment, incorrectly) I would like to find out for my own peace of mind. If any one has any technical advice based on my question, I am all ears..thanks again.

 

[BorisJ]

An 8500kW shower needs a 40 amp circuit on 6mm cable.
A 36w light can be run on a 5a fuse on 1.0mm cable. The fuse is to protect the cable not the light on the end of it.

 

[Fleeting]

An 8500kW shower needs a 40 amp circuit on 6mm cable.
A 36w light can be run on a 5a fuse on 1.0mm cable. The fuse is to protect the cable not the light on the end of it.

Depending on volt drop and installation method.

 

[Geoff1946]

The reason fuses have been superseded on domestic circuits is because they are no good at overload protection. They are good at short circuit protection, blowing quickly on the massive overload such a fault causes, but as you have demonstrated don't break on moderate overload, leaving the other circuit components to overheating, etc.
Miniature circuit breakers, (MCB), conversely. will break an overload current much more quickly than a fuse, but are vulnerable to permanent damage if repeatedly short circuited. They are the base standard for domestic boards for at least the past forty years.
RCDs, which I fear you may lack, detect small currents leaking to earth which if greater could harm, (kill!) a person. I personally would not use a shower which didn't have one. They can be combined with an MCB when they are designated an RCBO.
Please don't use the advice in this string to go and buy a 40 amp fuse for your antique Wylex board!

 

[WattsTheFrequency]

An 8500kW shower needs a 40 amp circuit on 6mm cable.
A 36w light can be run on a 5a fuse on 1.0mm cable. The fuse is to protect the cable not the light on the end of it.

Thankyou, and a 8500kW shower still 40 amp on 10mm cable?

 

[WattsTheFrequency]

The reason fuses have been superseded on domestic circuits is because they are no good at overload protection. They are good at short circuit protection, blowing quickly on the massive overload such a fault causes, but as you have demonstrated don't break on moderate overload, leaving the other circuit components to overheating, etc.
Miniature circuit breakers, (MCB), conversely. will break an overload current much more quickly than a fuse, but are vulnerable to permanent damage if repeatedly short circuited. They are the base standard for domestic boards for at least the past forty years.
RCDs, which I fear you may lack, detect small currents leaking to earth which if greater could harm, (kill!) a person. I personally would not use a shower which didn't have one. They can be combined with an MCB when they are designated an RCBO.
Please don't use the advice in this string to go and buy a 40 amp fuse for your antique Wylex board!

Thanks for the comprehensive advice, very thorough. In the light of all the advice given, we plan to have the box replaced with one that incorporates an RCD. PS, sleep easy guys, we wont be buying a fuse for the Wylex board..

 

[Fleeting]

The electrician who replaces that consumer will be better placed to advise.

 

[Murdoch]

Thanks for the comprehensive advice, very thorough. In the light of all the advice given, we plan to have the box replaced with one that incorporates an RCD. PS, sleep easy guys, we wont be buying a fuse for the Wylex board..

A unit with a single rcd isn’t a good idea. Ask for quotes for RCBO fuseboards

 

[Murdoch]

Thankyou, and a 8500kW shower still 40 amp on 10mm cable?

get the spark to advise you on such matters

and if you are in England or Wales, you need to make sure that the sparks provide and EIC and part p compliance too