Electrical Shower issue

[JB8888]

Quick update. Shower has been replaced. Electrician cut back the wire but the end is still a bit damaged as he said not enough slack. Offered to replace for another separate call out fee.

He also checked the shower RCD as I mentioned the small shock we've had when pressing the power button. The RCD tripped every time he tested it, even when it was just a small amount being put through it. He said it was over sensitive and seemed surprised it hadn't previously flipped when using the shower. He said this made it very unlikely that we were getting shocks from the shower as any leakage should have caused the breaker to trip.

It seems the switches on the fuse board have also been replaced with a different model to the board itself which apparently is less than ideal. He's recommended an EICR.

 

[James]

Did you get a minor works certificate?
You should have.

 

[JB8888]

Did you get a minor works certificate?
You should have.

I did not..

 

[James]

In my opinion, you should have.
What do others think? Am I being pedantic?

 

[DPG]

In my opinion, you should have.
What do others think? Am I being pedantic?

Like for like change - I suppose some will issue one and some won't.

 

[James]

I don’t want to derail this thread but,

If I was changing a Shower (especially one that gave the user a shock)
I would not leave site until I had a certificate prepared that was a record of my test results, if nothing else, to cover myself.

But also to provide the customer with a written record of the safety tests.

 

[DPG]

I don’t want to derail this thread but,

If I was changing a Shower (especially one that gave the user a shock)
I would not leave site until I had a certificate prepared that was a record of my test results, if nothing else, to cover myself.

But also to provide the customer with a written record of the safety tests.

Good point bearing in mind the issue. Agreed.

 

[Dartlec]

Quick update. Shower has been replaced. Electrician cut back the wire but the end is still a bit damaged as he said not enough slack. Offered to replace for another separate call out fee.

He also checked the shower RCD as I mentioned the small shock we've had when pressing the power button. The RCD tripped every time he tested it, even when it was just a small amount being put through it. He said it was over sensitive and seemed surprised it hadn't previously flipped when using the shower. He said this made it very unlikely that we were getting shocks from the shower as any leakage should have caused the breaker to trip.

It seems the switches on the fuse board have also been replaced with a different model to the board itself which apparently is less than ideal. He's recommended an EICR.

Thanks for letting us know. Always good to see problems resolved

Did he mention any figures? A usual RCD is rated at 30mA and a sensitive one will often trip at 21-23mA, but even 1mA is in theory detectable - and wet skin is the 'ideal' condition for detecting it.

It is unfortunately common to see other makes of 'switch' in the fuse board, which as he said is less than ideal - though can be perfectly safe if installed properly.

An EICR sounds like a sensible idea if one hasn't been done for some time and will check things like that.
[automerge]1601489125[/automerge]

I don’t want to derail this thread but,

If I was changing a Shower (especially one that gave the user a shock)
I would not leave site until I had a certificate prepared that was a record of my test results, if nothing else, to cover myself.

But also to provide the customer with a written record of the safety tests.

I thnk I'd do the same, even if one is not necessarily "required". Though because I use certificate software I don't hand one over on the day. These days it usually goes via email with the invoice/receipt.

The most important thing is that the tests have been done of course, and a MWC is the only recognised way of doing that.

 

[JB8888]

Thanks for letting us know. Always good to see problems resolved

Did he mention any figures? A usual RCD is rated at 30mA and a sensitive one will often trip at 21-23mA, but even 1mA is in theory detectable - and wet skin is the 'ideal' condition for detecting it.

It is unfortunately common to see other makes of 'switch' in the fuse board, which as he said is less than ideal - though can be perfectly safe if installed properly.

An EICR sounds like a sensible idea if one hasn't been done for some time and will check things like that.
[automerge]1601489125[/automerge]

I thnk I'd do the same, even if one is not necessarily "required". Though because I use certificate software I don't hand one over on the day. These days it usually goes via email with the invoice/receipt.

The most important thing is that the tests have been done of course, and a MWC is the only recognised way of doing that.

I think he said 40 which he said was on the low side as the shower unit was technically capable of higher (42). But only a problem if turned up. He said it was tripping at about 5 I think? Basically everything he tried tripped it which is why he was surmised it had never tripped before.

I will make sure I get a certificate next time. Thanks again for your help and advice

 

[LastManOnline]

Quick update. Shower has been replaced. Electrician cut back the wire but the end is still a bit damaged as he said not enough slack. Offered to replace for another separate call out fee.

He also checked the shower RCD as I mentioned the small shock we've had when pressing the power button. The RCD tripped every time he tested it, even when it was just a small amount being put through it. He said it was over sensitive and seemed surprised it hadn't previously flipped when using the shower. He said this made it very unlikely that we were getting shocks from the shower as any leakage should have caused the breaker to trip.

It seems the switches on the fuse board have also been replaced with a different model to the board itself which apparently is less than ideal. He's recommended an EICR.

Have you used your new shower? Has the "tingling sensation" disappeared? (hopefully yes). I find this a particularly interesting shower fault as normally shocks (mild ones) tend to be experienced from touching the metal hosing or other metallic parts. You however experienced it from the "on/off" button (I, m assuming it's, plastic). So as, previous posts have stated there may well be some build up of foreign matter in the shower itself.
You also mentioned that your wife felt it for some time so the fault has obviously been present for some time. This does, not sound like a failing heating element as once they start to go they rapidly deteriorate.
The most common cause however for these problems in modern showers has to do with the earthing of the installation. Many modern showers use the earthing system in a way older showers did, nt (functional earth). If the earthing is not low impedence than "shocks" will be experienced

 

[pc1966]

Even with a nominally safe shower that is correctly earthed to the supply but the bath metalwork is not properly bonded as well you can get ten-ish volts of a difference. When wet that is noticeable!

But far more worrying is under fault conditions (PME open, some scroat stealing the sub-station neutral, etc) that could even become fatal.
[automerge]1601498984[/automerge]
There was a time when supplementary bonding was the norm, in fact it became quite ridiculous at times (joking about standing still long enough and you would get some green/yellow wire attached to an ankle...).

But today there is a view, more of a slightly misplaced trust, that an RCD will save you no matter what. Sure RCD protection should be the norm, but it is not (in my mind) an excuse for not having extraneous parts properly bonded (i.e. metal gas & water pipes, possibly some other things as well), and in some cases supplementary bonding to be sure that no stray potential appears in wet conditions, etc.

 

[LastManOnline]

Even with a nominally safe shower that is correctly earthed to the supply but the bath metalwork is not properly bonded as well you can get ten-ish volts of a difference. When wet that is noticeable!

But far more worrying is under fault conditions (PME open, some scroat stealing the sub-station neutral, etc) that could even become fatal.

Correct. When wet every milli amp is felt.I should add that I have, nt seen a metal bath in a long, long time. Our problems with people experiencing "shocks" in showers here tend to be almost exclusively down to houses not been neutralised.
It does annoy me when appliance suppliers don't alert installers to the fact there will be some leakage due to the earth been used as a functional earth. Is, this an issue on TT systems in the UK?

 

[pc1966]

It would not normally be a problem here, even on TT, as the regulations require all extraneous parts to be bonded to the MET. So in effect they supplement your earth rod (but should never be considered a replacement as the water or gas utility can and do replace metal with plastic without informing you).

The problem in some cases (other than incompetent electric in the first place) is bonding that relied on metal pipework and over the years that gets replaced by plastic sections when stuff is repaired or kitchen/bathroom rooms upgraded. Usually that reduces the risk (taps etc not good conductors any more) but that is not always the case, hence the rules about bonding wires attached to external pipework as they enter the premisses before any T-joint, etc.

 

[Dartlec]

Even with a nominally safe shower that is correctly earthed to the supply but the bath metalwork is not properly bonded as well you can get ten-ish volts of a difference. When wet that is noticeable!

But far more worrying is under fault conditions (PME open, some scroat stealing the sub-station neutral, etc) that could even become fatal.
[automerge]1601498984[/automerge]
There was a time when supplementary bonding was the norm, in fact it became quite ridiculous at times (joking about standing still long enough and you would get some green/yellow wire attached to an ankle...).

But today there is a view, more of a slightly misplaced trust, that an RCD will save you no matter what. Sure RCD protection should be the norm, but it is not (in my mind) an excuse for not having extraneous parts properly bonded (i.e. metal gas & water pipes, possibly some other things as well), and in some cases supplementary bonding to be sure that no stray potential appears in wet conditions, etc.

Only yesterday the MK RCD I button tested while looking at an elderly couple's immersion failed on first effort and only 'unstuck' after several on/off cycles. in their case the CUs were at height in the main stairwell so not really accessible and of course they'd never pressed the button before. Of course it may have tripped in a fault condition, but RCDs failing is not exactly a rare occurence.

With CU with multiple RCBOs in now I imagine the chance of them being tested more than once every 5 years is slim to none.

There seems to be a growing number of PME neutral issues too, either theft or maintenance related, so maybe pushing for more self testing or audible warning on fail RCDs would be more beneficial to safety than pushing AFDDs on everyone.

 

[LastManOnline]

It would not normally be a problem here, even on TT, as the regulations require all extraneous parts to be bonded to the MET. So in effect they supplement your earth rod (but should never be considered a replacement as the water or gas utility can and do replace metal with plastic without informing you).

The problem in some cases (other than incompetent electric in the first place) is bonding that relied on metal pipework and over the years that gets replaced by plastic sections when stuff is repaired or kitchen/bathroom rooms upgraded. Usually that reduces the risk (taps etc not good conductors any more) but that is not always the case, hence the rules about bonding wires attached to external pipework as they enter the premisses before any T-joint, etc.

But what about a TT installation in a rural area where there is unlikely to be any metallic services. So for argument sake, between your rod and other extraneous parts you have a total resistance of 75 ohms. Perfectly acceptable. But do you experience any issues with appliances requiring a functional earth?

 

[Vortigern]

I have often heard about these kinds of "experiences" where people have felt a tingle or even a shock, and even smelt burning from the consumer unit or accessory, or even hear crackling from an accessory. It flummoxes me that they never seem to take any action when something like this happens! For your information, if you ever smell burning or get a teensy weensy little tingle or hear crackling noises from electrical things, do something about it, isolate it or switch it off and don't use it and get it checked out!

 

[pc1966]

So for argument sake, between your rod and other extraneous parts you have a total resistance of 75 ohms. Perfectly acceptable. But do you experience any issues with appliances requiring a functional earth?

I think we might be talking at crossed purposes.

For electrical installations "extraneous parts" are defined as things that are present within the installation, but are able to introduce a potential (which thankfully is usually 0V true Earth). All of them should be bonded to the supply MET so within the installation you would see resistances of the order of 0.05 ohm or so.

Now outside, where you might be in contact with the Earth via feet in mud or hand railings, etc, those parts could well be raised under fault conditions to a point you would notice due to, for example, the 75 ohms resistance to Earth and some fault current.

But for anyone inside they should not see this.

I have seen 'functional earths' on some RCBO (Hager commercial 10kA range) which I believe was intended to trip them on L-N reversal (or open N fault) but I don't see a great benefit from this if the earth arrangement is sound. Certainly the majority of RCBO do not have this. I my case I terminated to N so N-E IR testing would be safe and as expected.

 

[LastManOnline]

Only yesterday the MK RCD I button tested while looking at an elderly couple's immersion failed on first effort and only 'unstuck' after several on/off cycles. in their case the CUs were at height in the main stairwell so not really accessible and of course they'd never pressed the button before. Of course it may have tripped in a fault condition, but RCDs failing is not exactly a rare occurence.

With CU with multiple RCBOs in now I imagine the chance of them being tested more than once every 5 years is slim to none.

There seems to be a growing number of PME neutral issues too, either theft or maintenance related, so maybe pushing for more self testing or audible warning on fail RCDs would be more beneficial to safety than pushing AFDDs on everyone.

Don't mention AFDD, s. Bad for my blood pressure. Watched a seminar on it yesterday. Despite having a "recommended status" only it's being made clear that REC,s are expected to really work hard to emphasize this product to customers. The one question I keep asking about AFDD, s is, how did they just suddenly appear out of nowhere and so quickly become vital to have. All feels a, bit rushed

 

[Dartlec]

It would not normally be a problem here, even on TT, as the regulations require all extraneous parts to be bonded to the MET. So in effect they supplement your earth rod (but should never be considered a replacement as the water or gas utility can and do replace metal with plastic without informing you).

The problem in some cases (other than incompetent electric in the first place) is bonding that relied on metal pipework and over the years that gets replaced by plastic sections when stuff is repaired or kitchen/bathroom rooms upgraded. Usually that reduces the risk (taps etc not good conductors any more) but that is not always the case, hence the rules about bonding wires attached to external pipework as they enter the premisses before any T-joint, etc.

I'll admit to not always having been so aware of this, but I think there is/was a common view that RCD protection automatically meant not worrying about supp bonding, even though the BBB makes clear that it also requires all extraneous-conductive parts to be effectively bonded.

I'm not sure there's enough information out there from the schemes on how to judge or test that in every situation, especially with fancy chrome towel rails, etc.

I know that I had to search it out myself and still end up not 100% clear where there is a mixture of stuff.

 

[pc1966]

AFDD appeared in the USA a decade or two ago to deal with a large number of fires. In most cases that was due to rubbish design in terms of fault-clearing (no requirement on Zs, etc) and the lack of appropriate OCPD for the flex connected to the unfused outlets they use.