Consumer Unit Tripping From The Shower

[neilmurray]

Hi

I have a 8.5w shower, the electrician i used installed a 30amp fuse. To the best of my knowledge this is to small in terms of amp. I understand that you work the amps out by [amps x 240v = xxx[, thus 30amps x 240v = 7200w so the fuse i am using is to weak i need a 40amp fuse.

There is a 6mm thick cable running from the shower to the consumer box which is suitable, is it possiable to just install a 40amp fuse? or do i have to replace the fuseblock as well.

Thanks

 

[1john]

Have you got a wylex fuse box with plug in fuses? What is tripping, if it is an RCD then it is possible that your fault is not with the shower.

 

[Beelzebub666]

6mm is fine so long as the run is under 18 metres, but it would have been better to use 10mm to keep your new shower options open. There's no problem just swapping the fuse on a modern CU for the right one, provided there is no fault on the circuit. Your electrician cocked it up (technical term) and should pop round and swap the fuse for free, and retest the circuit while he's about it. Or you might want to get a better one anyway.

Did he have the proper test equipment? Did he put in earth bonding?

 

[1john]

Except if it is an old Wylex board, there should be no protective device greater than 30A

 

[riveralt]

There's no problem just swapping the fuse on a modern CU for the right one, provided there is no fault on the circuit.

Some may argue that doing so will need require Building Control to become involved because you will be changing the characteristics of the circuit. As Beelzebub666 said get the electrician back to replace the existing fuse but get him to complete the paperwork for Building Control as well.

 

[riveralt]

Except if it is an old Wylex board, there should be no protective device greater than 30A

1John, doesn't that depend on the age of the board? Cause if what you say is right then why do Wylex sell 45Amp HRC plug in fuse carriers and 40Amp plug in MCB's.

 

[Beelzebub666]

Except if it is an old Wylex board, there should be no protective device greater than 30A

Good point, but in that case he'll be wanting a different electrician to put in at the least a seperate RCD box serving the shower.

 

[RF Lighting]

Except if it is an old Wylex board, there should be no protective device greater than 30A

1John, doesn't that depend on the age of the board? Cause if what you say is right then why do Wylex sell 45Amp HRC plug in fuse carriers and 40Amp plug in MCB's.

It depends on the board, but the majority of standard wylex CUs will only take upto a 30A OCPD.

It's only the newer ones with a 100A rated main switch, and the ones with a single fuseway to the right of the main switch (with the normal circuits on the left) which can take ONE >30A load.

Slapping a 40A fuse into a wylex designed for 30A circuits never ends well.

These are the type that can take a >30A OCPD

Untitled

• RF Lighting
• 19 Jul 2008
• 2

 

[ban-all-sheds]

6mm is fine so long as the run is under 18 metres

Yeah, but....

There is a 6mm thick cable running from the shower to the consumer box

What odds would you like to offer on it being a 6mm² cable?

And you have no idea how the cable is installed, so you can't say that it'd be OK on a 40A fuse even if you did know it was 6mm².

 

[Beelzebub666]

6mm is fine so long as the run is under 18 metres

Yeah, but....

There is a 6mm thick cable running from the shower to the consumer box

What odds would you like to offer on it being a 6mm² cable?

And you have no idea how the cable is installed, so you can't say that it'd be OK on a 40A fuse even if you did know it was 6mm².

I didn't tell him the whole cable was suitable, he has stated it is. My advice is based on the information received. If you have any currently baseless concerns about his ability to recognise what size a cable is and suspicions that it has been badly laid, you need to address them to the original poster, who is the proper person to ignore them rather than me.

 

[ban-all-sheds]

I didn't tell him the whole cable was suitable, he has stated it is.

1) YOU said "6mm is fine so long as the run is under 18 metres".

2) YOU don't know what size the cable is.

3) YOU did not use the proper terminology for cable sizes.

4) YOU don't know how the cable has been installed.

My advice is based on the information received.

You have been told that the cable is "6mm thick".

You have not been told how it's been installed.

You do not have enough information to advise that it's suitable for a 40A fuse.

If you have any currently baseless concerns about his ability to recognise what size a cable is

It's not baseless:

There is a 6mm thick cable running from the shower to the consumer box

and suspicions that it has been badly laid,

Where did I say, or suggest, that the cable had been "badly laid"?

you need to address them to the original poster, who is the proper person to ignore them rather than me.

Are you saying that the OP should ignore factors such as cable size and installation method when determining what load it can carry and what protective device it can be on?

 

[ban-all-sheds]

There is a 6mm thick cable running from the shower to the consumer box

//www.diynot.com/wiki/electrics:flatpvccables

• 
  

 

[Beelzebub666]

I didn't tell him the whole cable was suitable, he has stated it is.

1) YOU said "6mm is fine so long as the run is under 18 metres".

2) YOU don't know what size the cable is.

3) YOU did not use the proper terminology for cable sizes.

4) YOU don't know how the cable has been installed.

My advice is based on the information received.

You have been told that the cable is "6mm thick".

You have not been told how it's been installed.

You do not have enough information to advise that it's suitable for a 40A fuse.

If you have any currently baseless concerns about his ability to recognise what size a cable is

It's not baseless:

There is a 6mm thick cable running from the shower to the consumer box

and suspicions that it has been badly laid,

Where did I say, or suggest, that the cable had been "badly laid"?

you need to address them to the original poster, who is the proper person to ignore them rather than me.

Are you saying that the OP should ignore factors such as cable size and installation method when determining what load it can carry and what protective device it can be on?

6mm is fine so long as the run is under 18 metres. Obviously if he wraps it fifty times round the gas pipe and nails it to the wall with carpet tacks it won't be, but such things really don't need saying.

Again, he has stated it is 6mm and run from the CU to the shower. This is what my advice is based on. If you have reason (which you don't) to doubt what he has said, why tell me about it? If you think he has overlooked a badly laid cable or doesn't know how to recognise what size it is, address your sanctimonious lectures to the OP. I'm advising what he can do with a 6mm cable run from the CU to the shower on the wrong fuse, which is what he as asked.

"There's no problem just swapping the fuse on a modern CU for the right one, provided there is no fault on the circuit. Your electrician cocked it up (technical term) and should pop round and swap the fuse for free, and retest the circuit while he's about it. Or you might want to get a better one anyway. "

And only extremely anal people bother with a superscript 2.

 

[ban-all-sheds]

You really don't seem to have a clue what's going on, do you.

6mm is fine so long as the run is under 18 metres.

How many times does it have to be pointed out that we have no way of knowing whether the cable is 6mm², and that given the OP's description it probably isn't, before it sinks in?

How many times does it have to be pointed out that we don't know how the cable has been installed and therefore we don't know what de-rating factors apply before it sinks in?

Obviously if he wraps it fifty times round the gas pipe and nails it to the wall with carpet tacks it won't be, but such things really don't need saying.

What on earth are you on about?

Again, he has stated it is 6mm and run from the CU to the shower. This is what my advice is based on.

He has said that it is 6mm thick, not that it is a 6mm² cable!

He has not said what installation method applies!

Your advice is flawed, and could be fatal!

If you have reason (which you don't) to doubt what he has said, why tell me about it?

I'm telling you because you are the one giving incompetent advice.

And I have every reason to doubt that the cable is 6mm².

If you think he has overlooked a badly laid cable

Will you please explain why you keep going on about a "badly laid cable"?

Will you please show me where I have said, or implied, that the cable has been badly laid?

You don't actually understand what is meant by installation method, or its relevance to the current that cables can carry, do you?

or doesn't know how to recognise what size it is, address your sanctimonious lectures to the OP.

I'm sorry that you think it is sanctimonious to point out that it is wrong to give advice on how big a load a cable can take when you don't know what size the cable is and you don't know how it's been installed.

Maybe you should stop giving advice - it's beyond you.

I'm advising what he can do with a 6mm cable run from the CU to the shower on the wrong fuse, which is what he as asked.

You're giving him advice which could cause the house to burn down.

Do you want to know what you might have told him to do?

You might have told him that it's OK to put a cable rated at 17.5A on a 40A fuse. You don't have enough information to know that you haven't.

"There's no problem just swapping the fuse on a modern CU for the right one, provided there is no fault on the circuit.

Err... what about "and provided the cable is adequately rated"?

And only extremely anal people bother with a superscript 2.

No - people who realise that "6mm²" is not the same as "6mm thick" do that.

People who realise that the csa of cables is what matters do that.

People who realise that a cable which is "6mm thick" could well not be a 6mm² cable do that.

i.e. not people like you.

Please go away.