Electrical Shower issue

[JB8888]

Hello all,

We have an electric shower in our bathroom. Since we have moved in I've noticed that when turning it on sometimes the lights in the flat (which are all on dimmers) reduce their output very slightly. My understanding is that this isnt completely abnormal but over the last few days I've noticed the slightest tingle in my finger when turning the shower on and off. Almost like a hardly noticeable pins and needles which lasts for a split second. Obviously this is a very mild electric shock.

No more showers until I get a professional out obviously but I just wondered if anyone could shed any light on what the issue might be and also just how dangerous is? Could it just be a static shock for example or it it definitely some kind of defect in the unit? I asked my wife and amazingly she said she's noticed it for ages but hasn't bothered mentioning it!

Any help or advice would be appreciated.

Thanks

 

[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.

 

[Dartlec]

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

Far be it for me to suggest that RCDs were getting cheaper so less profit to be made from them by the manufacturers, and here was a technology that they could slap higher margins on...

The US has had them for ages, but I believe that they are more beneficial there with their voltage and wiring setup.

 

[pc1966]

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

As you say it is not always obvious. But for me it is the bath/shower setup that is the greatest risk. A towel rail out of reach from the bath less so, but if in hand's reach (which is what most would want after all!) it would be the same and I would like to see some supplementary bonding:

• shower - bath fittings - railing

Just in case!

 

[LastManOnline]

As you say it is not always obvious. But for me it is the bath/shower setup that is the greatest risk. A towel rail out of reach from the bath less so, but if in hand's reach (which is what most would want after all!) it would be the same and I would like to see some supplementary bonding:

• shower - bath fittings - railing

Just in case!

Am a big fan of supplementary bonding. If all else fails its a, great backup and usually very economical to install

 

[pc1966]

Often it was installed but some plumber in their infinite wisdom decided to cut/disconnect it

 

[Dartlec]

As you say it is not always obvious. But for me it is the bath/shower setup that is the greatest risk. A towel rail out of reach from the bath less so, but if in hand's reach (which is what most would want after all!) it would be the same and I would like to see some supplementary bonding:

• shower - bath fittings - railing

Just in case!

I did find a kitchen sink bonded a week or so ago - definitely done after 1984 or whenever it was that they dropped it. Usually no way to (neatly) bond a fancy towel rail though, even if you wanted to, so has to rely on access outside the bathroom or under the floor.

 

[LastManOnline]

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.

Yes. I should have been clearer in describing what I said. Electric showers appear to be using the CPC as a functional earth (which they are entitled to do here). It creates problems here on TT systems (very few of these, left here) especially TT systems with a high res electrode. Just wondered if you experience that much in the UK. I should add that the problem is more usual to an older installation with a shower tray lying on concrete. In a modern house this leakage would not be noticed due to wooden floors etc

 

[pc1966]

I should add that the problem is more usual to an older installation with a shower tray lying on concrete. In a modern house this leakage would not be noticed due to wooden floors etc

OK that makes sense.

I can't say I have heard much about that sort of an issue, I guess it is just not so common to have a shower on concrete so it has its own leakage path to Earth to notice the difference on the supply MET potential.

If planned that way I would try and get some rebar in it and bonded to that! Alas, it never is planned...

 

[LastManOnline]

OK that makes sense.

I can't say I have heard much about that sort of an issue, I guess it is just not so common to have a shower on concrete so it has its own leakage path to Earth to notice the difference on the supply MET potential.

If planned that way I would try and get some rebar in it and bonded to that! Alas, it never is planned...

What's interesting is I have dealt with

OK that makes sense.

I can't say I have heard much about that sort of an issue, I guess it is just not so common to have a shower on concrete so it has its own leakage path to Earth to notice the difference on the supply MET potential.

If planned that way I would try and get some rebar in it and bonded to that! Alas, it never is planned...

What's I find interesting is that this situation doesn't occur more often in the UK,especially in TT installations. Here's my reasoning on it. When we investigate a call from someone who has suddenly started getting a "tittle" (or something a little stronger) we always find it's the same cause. An older home that is un-neutralised , basically a TT installation where overnight a low impedence earth has become a high impedence earth either by a plumber replacing a copper service with a plastic one or the Water services upgrading their pipes to plastic.This leaves only the rod as the main earth which is never more than a 4 ft rod and is untested. The shower tray is either is either on a concrete floor or is in contact with metalwork.
The solution is provided by arranging to get the DNO to provide a, Neutralising link.
I think that in the UK your TT Installations are likely to have lower impedence earth rods because from what I read you guys are not happy with anything over 200 ohms. I think that may be a major factor in these "shower shocks" been less common. I am open to correction here.

I have contacted both Triton and Mira for confirmation that they use the CPC as a functional earth as well as a protective one. I need to do that as as I have to write a report for one landlord. They have so far been a little reticent to respond. In fact according to the regs here they are entitled to do that. I just want to nail it down so I can put it in writing

 

[Mike Johnson]

TT installations are becoming rarer in the UK, but are the norm in France where the regulations require a reading under 200Ω and is generally wanted below 150Ω trouble is this would only be checked on a new installation or on the sale of the property, and even then a Ω check is not done, just a visual check that an earth rod is in place.

 

[LastManOnline]

TT installations are becoming rarer in the UK, but are the norm in France where the regulations require a reading under 200Ω and is generally wanted below 150Ω trouble is this would only be checked on a new installation or on the sale of the property, and even then a Ω check is not done, just a visual check that an earth rod is in place.

They must have a lot of confidence in the conductivity of their soil?

 

[Mike Johnson]

They must have a lot of confidence in the conductivity of their soil?

The majority of new builds in France are supplied with a mesh/grid system of Earthing surrounding the house, becoming rare to have rods now except on older properties, which is the majority in rural France.