Is what I've done any good/safe?

[Tibbyltd]

Hi everyone,

I've come here as a DIYer asking for professional advice/opinion.

I have an 8.5KW shower on a 6mm cable and a 40amp MCB.

The shower works fine........for about 8 minutes! It invariably trips out. Sometimes it lasts 6 minutes, sometimes it lasts 10. I was considering changing the cable to 10mm (I actually changed a partial section of it to the switch) but I'm under the impression this shouldn't be necessary.

Could it be a faulty MCB or shower? It's been doing this for years and I just periodically reset the MCB.

Anyway. I've just put in a new 45a MCB hoping it will fix it. Off the finish the partial shower I got earlier!

FYI its only a short, maybe 4-5 meter run.

 

[Pete999]

Hi everyone,

I've come here as a DIYer asking for professional advice/opinion.

I have an 8.5KW shower on a 6mm cable and a 40amp MCB.

The shower works fine........for about 8 minutes! It invariably trips out. Sometimes it lasts 6 minutes, sometimes it lasts 10. I was considering changing the cable to 10mm (I actually changed a partial section of it to the switch) but I'm under the impression this shouldn't be necessary.

Could it be a faulty MCB or shower? It's been doing this for years and I just periodically reset the MCB.

Anyway. I've just put in a new 45a MCB hoping it will fix it. Off the finish the partial shower I got earlier!

FYI its only a short, maybe 4-5 meter run.

Is it an RCD, RCBO or an MCB that is tripping? there are things to take into consideration when sizing the cable, length of cable run, installation method etc.

 

[telectrix]

it could just be that the MCB having run close to it's rating for years has just got tired. your 45A MCB will be OK on the 6mm cable providing that said cable is not derated due to insulation.

are you sure it's MCB trip and not RCD/RCBO?

 

[Pete999]

it could just be that the MCB having run close to it's rating for years has just got tired. your 45A MCB will be OK on the 6mm cable providing that said cable is not derated due to insulation.

are you sure it's MCB trip and not RCD/RCBO?

Agree to the question

 

[JK-Electrical]

I encountered the very same problem a couple of years ago and the cause turned-out to be an overheating MCB that had not been properly connected to the busbar thus creating a 'hot spot'.

 

[Tibbyltd]

Is it an RCD, RCBO or an MCB that is tripping? there are things to take into consideration when sizing the cable, length of cable run, installation method etc.

Just the MCB. Although as I say I'm not an electrician.

 

[littlespark]

An rcd or an rcbo has a test button and also a rating in mA. Normally 30.
An mcb does not

 

[Tibbyltd]

An rcd or an rcbo has a test button and also a rating in mA. Normally 30.
An mcb does not

It's an MCB. I've attached a photo of what I fitted.

Update: I took a shower for at least 12 minutes without problem!
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I encountered the very same problem a couple of years ago and the cause turned-out to be an overheating MCB that had not been properly connected to the busbar thus creating a 'hot spot'.

Well I fitted a new higher rated MCB. It didn't work at first because I didn't even attempt to tighten the busbar screw (as I say, amateur).

What you describe could have been the issue I was experiencing. I didn't want to go poking around things I know nothing about without having the part to replace.

The problem seems to now be fixed. Not bad for a 49p job. Although I should have tried your potential solution first.
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it could just be that the MCB having run close to it's rating for years has just got tired. your 45A MCB will be OK on the 6mm cable providing that said cable is not derated due to insulation.

are you sure it's MCB trip and not RCD/RCBO?

Do they get tired?

The cable is clipped straight to the shower. No insulation.

So I'm all good?

Thanks ?

 

[ipf]

It's an MCB. I've attached a photo of what I fitted.

Do they get tired?

The cable is clipped straight to the shower. No insulation.

So I'm all good?

Thanks ?

I'm sorry, but I get tired of people putting themselves in danger.
The number of times I've come across 'tired' or just loose terminals on domestic 6mm or 10mm cable joints is frightening.
You may think it's sound but IS IT??
Get someone qualified.... at least to check it.

An example of a shower 'joint', found last year.

 

[Micktw68]

Well the problem was sorted quickly and painlessly and almost for free.

It's like 5 minutes a 4 screws, hardly brain surgery. The supply was isolated so who's getting the Darwin award? Do you even know who Darwin is you snarky ----?

You leave school with no GCSEs and expect me to pay you £50 for 5 minutes to tell me a job which I know is probably better than the original install is OK? The 'qualified' person who fitted it didn't do a very good job in the first place.

I guess I'll use less pretentious forums in future.
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Explain why then. Because their screwdriver has a better lubricated muffler bearing?

My question was;

Is what I've done any good/safe?

The answer from all available sources seems to be yes.

The MCB is correct, the cable is of satisfactory diameter and the shower now works without fault. So why do I need an electrician again? Oh, so I can pay them money for nothing ?

The fact that you refer to the cable size as diameter tells us all we need to know about how safe your installation is. It’s not about pretentiousness, most of us here have spent a lifetime putting right amateur lash ups in domestic installations and know the dangers of amateurs having a go. Did you torque up your new mcb to the manufacturers recommend settings, do a CPC continuity test or any of the other tests our years of experience tells us to do to qualify something as safe.

 

[Dustydazzler]

£50 for five minutes , that is too cheap...

standard call-0ut is £65

 

[Bigshow84]

Just read this through and there is no mention of 30ma rcd protection for a shower so maybe not that safe.

 

[richy3333]

@Tibbyltd I hold 2 degrees one of which has a biological aspect and also involved me having to study Darwin. So yes I know quite a lot about him. What would you like to know? I also have several professional qualifications including being a full member of the IET.

I’m sorry my words touched a nerve there and upset you so much. Good news that you have resolved your issue ?

 

[HappyHippyDad]

Well the problem was sorted quickly and painlessly and almost for free.

It's like 5 minutes a 4 screws, hardly brain surgery. The supply was isolated so who's getting the Darwin award? Do you even know who Darwin is you snarky ----?

You leave school with no GCSEs and expect me to pay you £50 for 5 minutes to tell me a job which I know is probably better than the original install is OK? The 'qualified' person who fitted it didn't do a very good job in the first place.

I guess I'll use less pretentious forums in future.
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Explain why then. Because their screwdriver has a better lubricated muffler bearing?

My question was;

Is what I've done any good/safe?

The answer from all available sources seems to be yes.

The MCB is correct, the cable is of satisfactory diameter and the shower now works without fault. So why do I need an electrician again? Oh, so I can pay them money for nothing ?

The problem wasn't sorted Tibby, you just got it working. It's easy to get electrics to work, you could have even just twisted the wires together and it would have worked but it would be dangerous. There is a 50/50 chance that the 6mm cable is not suitable for a 45A MCB and at some point the switch or MCB will overheat and possible cause a fire. I have seen so many burnt connections for showers as they have not been done properly.

I kind of get the impression though that you just want it working and are not too worried about how that is obtained. I guess if you live by yourself in a detached house you could take the risk, but if there are others living with you then you might want to check with them if they are happy to live with possible dangerous electrics.

This post really isn't designed to wind you up it's just straight talking and hoping that you will get someone to at least check it over.

 

[westward10]

I suggest @Tibbyltd you get an electrician in to check this circuit for piece of mind as suggested. Thread closed.