After some advice: Mild tingle from shower when in use

[JohnW2]

Two electricians have confirmed that the earth bond between the pipes and the rest of the house is good (but in my case who knows, I'm losing faith that they're even testing the right things!!).

Fair enough, but I'm not sure that we know exactly how they did that 'confirming', and how convinced we are!

My pipework is pretty much exclusively copper, except for waste pipes of course, currently there are no plastic supply pipes anywhere I can see...

OK. The cold water supply pipe to the shower could be electrically isolated from the cold supply pipe if it originates from a plastic cold water tank, but one would normally expect the hot supply pipe to have a good path to earth, via boiler/cylinder, immersion heaters, cold supply pipes or whatever - and presumably the hot and cold feeds are electrically connected at the shower (unless its 'works' are all plastic-bodied). One would therefore expect the shower mixer/plumbing to have a reasonable path to earth.

Kind Regards, John

 

[TheGovernor]

Fair enough, but I'm not sure that we know exactly how they did that 'confirming', and how convinced we are!

Agreed 100%

OK. The cold water supply pipe to the shower could be electrically isolated from the cold supply pipe if it originates from a plastic cold water tank, but one would normally expect the hot supply pipe to have a good path to earth, via boiler/cylinder, immersion heaters, cold supply pipes or whatever - and presumably the hot and cold feeds are electrically connected at the shower (unless its 'works' are all plastic-bodied). One would therefore expect the shower mixer/plumbing to have a reasonable path to earth.

Kind Regards, John

Yes, that's my thinking too, if we trust the earth checks thus far, and they are borne out by my own meter readings between shower and radiator, then the shower has a good earth to the rads, which in turn have a good earth to the ring main, which also appears to have a good earth to true earth (phew!)

No signs of water leaking anywhere on any surface, and the issue happens in at least two showers.

Let's hope the IR test tomorrow shows something, not sure where I go if it shows nothing mind you...

 

[JohnW2]

Yes, that's my thinking too, if we trust the earth checks thus far, and they are borne out by my own meter readings between shower and radiator, then the shower has a good earth to the rads, which in turn have a good earth to the ring main, which also appears to have a good earth to true earth (phew!) ... No signs of water leaking anywhere on any surface, and the issue happens in at least two showers. ... Let's hope the IR test tomorrow shows something, not sure where I go if it shows nothing mind you...

I know it's not what you really want to hear, but none of my money is going on the IR tests showing anything useful. Maybe it's time for me to return to a (now somewhat extendable) variant of what I wrote back on Page 7, namely:

Thinking aloud ... I'm starting to wonder whether all the OP's investigations and experiments are telling us about little other than the idiosyncracies, unpredicability/variability and 'unreliability' of these various 'voltage detecting' gizmos and that maybe the truth is that there is no real 'problem' - i.e. that any true potential differences between anything and anything else are extremely small.
As I understand it, the tingling the OP has experienced has been mainly/always experienced in broken skin. Once the highly protective (and quite insulating) skin is broken, the exposed tissues can be very sensitive to even very low voltages, particular if wet - as many/most people know if they have tried a battery on their tongue (although, admittedly, a lot of that is due to electrolysis)!

Kind Regards, John

 

[TheGovernor]

I know it's not what you really want to hear, but none of my money is going on the IR tests showing anything useful. Maybe it's time for me to return to a (now somewhat extendable) variant of what I wrote back on Page 7

Kind Regards, John

If the IR doesn't show anything, at least I should be reassured that a reasonable suite of tests have been done to establish the house is safe.

I think if the IR shows nothing I'll go ahead and get the replacement CU installed as that increases the protection available compared to what I have now, and then, unless something rears it's head will be where we end up leaving it

I won't be completely surprised if I was to have RCBO's fitted I may then start to get "phantom" upstairs light tripping...

 

[JohnW2]

If the IR doesn't show anything, at least I should be reassured that a reasonable suite of tests have been done to establish the house is safe.

That's true.

I think if the IR shows nothing I'll go ahead and get the replacement CU installed as that increases the protection available compared to what I have now, and then, unless something rears it's head will be where we end up leaving it

Although you have talked about having it changed for a dual-RCD or all-RCBO CU, I don't recall your having told us what you actually currently have. Is there currently no RCD protection (at all, or on the circuits of potential interest to us)?

I won't be completely surprised if I was to have RCBO's fitted I may then start to get "phantom" upstairs light tripping...

Who knows? If you do eventually change to a situation in which all circuits have 30mA RCD or RCBO protection, then you could at least be reassured that there were devices in place which would reduce the risk of any electric shocks [should the present situation (whatever is causing it) get much worse] having serious outcomes. However, that doesn't alter the fact that it is desirable, and would be satisfying, to get to the bottom of what (if 'anything significant') is currently going on.

Kind Regards, John

 

[TheGovernor]

Although you have talked about having it changed for a dual-RCD or all-RCBO CU, I don't recall your having told us what you actually currently have. Is there currently no RCD protection (at all, or on the circuits of potential interest to us)?


Kind Regards, John

I currently have a split load CU, I don't know all the industry lingo for the type one half, mains, kitchen etc is RCD protected, but the other half lights smoke alarms, immersion, isn't...

 

[JohnW2]

I currently have a split load CU, I don't know all the industry lingo for the type one half, mains, kitchen etc is RCD protected, but the other half lights smoke alarms, immersion, isn't...

That's the right lingo! OK, so the crucial thing is, I suppose, that the 'most suspected circuit' (the lighting one) is not currently RCD-protected.

If you changed to a dual-RCD or all-RCBO CU, one of those devices might trip if (I personally think pretty unlikely) there was some underlying ('permanent') 'leak' (and, if it were all-RCBOs, that would identify what circuit was the culprit) but, unless things get much worse, would not trip in response to the 'tingle current' you are feeling - since that current would be far too little to trip the device.

Kind Regards, John

 

[TheGovernor]

Yes, in fact in an odd sort of way, an all RCBO solution becomes part of the diagnostic process!!

BG are doing a quote for a split load and an all RCBO unit, for me it's just a comparator as I know they will always charge twice as much as the job should actually cost!

 

[JohnW2]

Yes, in fact in an odd sort of way, an all RCBO solution becomes part of the diagnostic process!!

Indeed, that's one of the attractions of all-RCBO setups - it avoids all the 'hunt for the culprit circuit' exercises when an RCD trips! It also, of course, means that a fault on one circuit does not kill any others.

BG are doing a quote for a split load and an all RCBO unit, for me it's just a comparator as I know they will always charge twice as much as the job should actually cost!

Fair enough. To give you a very rough idea, based n TLC prices for Wylex components, in terms of component costs (if bought separately), what you would be comparing would be:
Dual-RCD: 2 x RCDs at about £28 each PLUS one MCB per circuit at about £3 each.
All-RCBO: one RCBO per circuit at about £28 each.
So, if there were, say, 8 circuits, the difference would be about £144 (£80 for dual-RCD vs £224 for all-RCBO). However, when 'whole CUs', rather than individual components, were purchased, figures could be very different (probably appreciably lower).

Kind Regards, John

 

[TheGovernor]

Thanks John

As I gather quotes, are there any manufacturers I should look out for that are better quality than others?

I'm thinking I might get a 10-way CU to allow for expansion, not that I have any plans but saves hassle later if I do, I don't think it makes a lot of difference ot the cost for the unit with the extra ports (is that the right word?).

I do have 8 circuits at the moment so your maths isn't far off

 

[JohnW2]

Thanks John As I gather quotes, are there any manufacturers I should look out for that are better quality than others?

Opinions will vary, so, although I have my own opinion, I'll leave it t the experts who are dealing with these things all the time to answer. Things have changed over time - for example, MK was once very highly regarded, now less so.

I'm thinking I might get a 10-way CU to allow for expansion, not that I have any plans but saves hassle later if I do, I don't think it makes a lot of difference ot the cost for the unit with the extra ports (is that the right word?).

They're usually called 'ways' - but be careful to ascertain how many 'available ways' (for final circuits) there are, since some manufacturers will include space for the main switch and RCDs (which could add up to 6 ways for a dual-RCD CU) in their quoted 'total ways'! As you surmise, the marginal cost difference of getting a larger CU is small, so it's best to think about 'future-proofing'.

I do have 8 circuits at the moment so your maths isn't far off

Ah well - my guesses aren't always wrong, then TBH, 8 is a pretty common number of circuits, so I don't deserve that much credit!

Kind Regards, John

 

[securespark]

BG used to do Hager or Wylex as standard, but they have since introduced their own brand consumer unit: not sure which manufacturer they have chosen.

When quoting, they should choose a board that leaves at least 20% free ways for future expansion.

When the guy comes tomorrow, ask him to confirm continuity on the pipework from the main bond to the local pipework in the bathroom. If you can access the shower pipes without ripping up the floor, that'd be good.

0.05 Ohms or less.

I would then suggest global IR on the board, linking out L&N and testing that to earth initially as a quick check to see if IR is acceptable.

Before doing this test, it is wise to remove appliance plugs from the sockets and switch off any appliances that are hard-wired or have hard to access sockets: ie switches for...

Boiler
Cooker
Oven
Hob
Shower
Immersion
Aerial amp
Security lighting
Fridge
Freezer
Dishwasher
Washer
Dryer
Microwave

This list is not exhaustive!!!

Minimum reading is 2 MegOhm, but really a healthy circuit should read higher.

In the case of lighting circuits, he should not forget to measure IR with switches on and lamps out (unless doing the global test with a temporary link between L&N at the CU, in which case lamps can stay in).

In the case of 2 (or more) way switches, he should do the test with the switches in both positions, to eliminate any potential damage to switch drops, eg cables crossing joists in the loft that have been crushed or screwed through, nails for pictures in the wall penetrating cables, and such-like.

 

[TheGovernor]

The mystery remains, BG guy just did an IR test on the lighting circuit 66 & 62 mega ohms (he tested live and neutral).

He wouldn't do a full IR test on all the sockets etc because he said there's nothing there to find and he wasn't getting any voltage at the shower.

So, plan B is get the CU replaced with an all RCBO unit and see where that takes me.

 

[deadshort]

I would think about £350-400 lighter and still having a tingly shower!

DS

 

[JohnW2]

I would think about £350-400 lighter and still having a tingly shower!

I fear so. Just changing the CU, per se, obviously could not get rid of the tingling. RCD/RCBO protection of the currently non-protected circuits (such as the lighting ones) would mean that the relevant device would trip if there were a fault on any of those circuits - but there pretty clearly are not any such faults. In the context of the present issues, a little bit of peace of mind for the OP, should anything change/progress to the stage of potentially serious shocks in the future (I would say incredibly unlikely) is probably all that Gov would be likely to gain - and I suppose it's for him to decide whether, for him, that is worth the cost.

Kind Regards, John