Low Earth Voltage in bathroom from bonded fittings

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Kris Dor

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I have a hot/cold feed power shower in bathroom, shower frame and a radiator near by.
I'm measuring the voltage difference between the three things and getting the following and wondered if anyone could help. Had two sparky's out who have not thrown any light on it so far.
Shower hose (metal) to radiator 0.2v
Radiator to Shower frame 2v

When I run the shower for 2-5 mins I get these readings
Shower hose (metal) to radiator 5v
Radiator to Shower frame 12v

This voltage then very slowly drops back down to earlier figures over the course of mins/hours rather than seconds (in 5-10 mins it would drop from 12v to 10v)

I have this: Bonding from rad to both inlet pipes of shower
I was advised to do this which is now done: Bonding from earth in shower unit to the pipework feeds and supplementary bonding from pipework to two upstairs light rings which was advice sparky got from NIC

The shower is hot/cold so just a pump from a spur on ring main protected with switched fused 3a and RCCB on ring main circuit

If I switch off the bathroom lights the first 0.2v reading prior to running shower might drop from 0.2v to 0.1v

Nothing on the CU has tripped but there is a tiny spark when sparky took off an Earth from the (rail?) in the CU while he was looking at it.

No single circuit seems to be the cause of the low voltage readings but if everything is off on the CU the reading is 0v.

Any help ideas would be appreciated .
Cheers
Kris
 
Hi spinlondon,
Cheers - no one has mentioned this.

Could the shower motor be faulty?

If the shower is completely disconnected physically apart from the bonding the radiator to shower frame is still 0.2 - 0.4v
I measured it without the shower running at about 2am and radiator to shower frame showed 12v

There is another cable in the wall to a burglar alarm which may be close to the run for the shower. I could disconnect this quite easily but when I turn this circuit off on the CU it doesn't affect the earlier situation.

Cheers
Kris
 
Hi Kris and Welcome to the Forum !
My first dumb question (of many, sorry) is why are you standing in your shower with a multimeter? Did you get a tingle?
 
If the shower pump was faulty, I would expect a greater voltage and for the RCD to trip.
Some PLC controlled equipment will have Earth leakage under normal operation, but I doubt your shower pump is PLC controlled.
 
I'm wondering why 'we' are bothered about bonding shower frames and radiators?
 
fit a usb socket between shower and radiator. free charger.
 
Thanks so far for the interest,
Cheers spinlondon re the pump.
Wilko I got a tingle from the shower head in the shower and began investigating as I'm allergic to electricity :eek:)
Midwest I don't want to bond the shower frame - I'm using it as a 0v to measure the others in the absence of 100m of earth cable and a spade in the garden - I appreciate this is haphazard but I can feel a tingle from the showerhose and sometimes the rad too, never anything from the shower frame.
Rob - it's a LAP MAS830B digital multimeter from Screwfix
Murdoch - how can I check continuity back to the CU? Although if the voltage is registering on an earth cable at the CU I guess the voltage on the Earth is getting back to the CU somehow... (?)
 
^ you need a competent spark, with a proper tester and knowledge to use it and finally a wander lead.
 
Cheers Murdoch, my sparky has tested from the earth bond under the sink in kitchen back to CU and it was fine with wander lead and megger
 
Hi Kris, thought you might've felt a tingle. How often do you feel them? Sometimes the earth provided by the electricity supplier may have a few volts on it relative to the local general mass of the Earth. But some external faults may increase it. Are you able to confirm the type of earthing used at your house?
 
my sparky says Im TNS. I'm told that the setup will be that the earth is taken from the Neutral and in my box I have a 100amp fuse and the earth cable goes into a box and comes back out of it.

I have got solar panels linked into the supply but sparky checked it and said it wasn't that.

There was a cable (single core copper with steel armouring) I removed in the garden a couple of months ago, don't suppose Earth to the house would be via a separate cable? I showed sparky but he said this had nothing to do with it.
 
Cheers Murdoch - Im sure this will be next on the list when my sparky comes back. If not I'll mention it to him. I don't suppose there is anything I can do to check this? I'm not going to mess around in the CU so I guess I'll have to leave that idea until he comes back.
 
Sorry Wilko - in answer to your question it seems to be pretty constant 0.2v and 2v unless I run the shower when it increases. If I run it then stop it then run it again it is cumulative but the subsequent rises are not as high as the first which goes from 2 to 12v, the second might get it from 12-14v the third 1v extra then it seems to top out.
 
Kris Dor said:
Thanks so far for the interest,

Midwest I don't want to bond the shower frame - I'm using it as a 0v to measure the others in the absence of 100m of earth cable and a spade in the garden - I appreciate this is haphazard but I can feel a tingle from the showerhose and sometimes the rad too, never anything from the shower frame.
Click to expand...

Your shower frame, it is just a piece of metal, it is not connected to the general mass of earth, unless the fixings screws are really long!

Same goes for the radiator. Some things may require bonding, such as the pipes feeding the radiator. You will need to have a logical approach to this problem, and rule out the obvious to start with, best done by an electrician.

And I'm not suggesting your imaging things, but checking 'voltage' with a multi meter is meaningless, but that's not to say there isn't a fault.

As an example, whilst doing a bathroom refurbishment a few years back, the plumber was a getting a shock when he was touched the walls and pipes. It transpired, the previous owner had put up some dado rail on the landing, and nailed a cable for the landing light, making the wall nice & live.
 
Good call Risteard - yes, the earth is going into and out of the box with the 100A rather than tagged onto the cable before the fuse.
 
Cheers for the reply Midwest - I'll have a think about nails, I did put a piece of chipboard down in the loft, I'll make sure I haven't nipped or crushed a cable up there.
 
Don't be offended Kris, but if you are experiencing 'tingles', think its time you asked a competent electrician to carry out some tests on your installation, perhaps even an electrical installation condition report (EICR), don't know what the other members think about that suggestion?
 
I had to investigate something like this a couple of years ago. I found that that shower cubicle was live
 
I've had two Part P registered sparkies round already and booked in for next week hopefully to do some more testing. Unfortunately it's not something I can instantly achieve - seems to be a busy time round here - there is a massive amount of housing being built so I'm just waiting in line - I appreciate your sentiment though Midwest - I'm just seeing what i can do on the home owner front while I'm waiting.
 
Kris Dor said:
I've had two Part P registered sparkies round already and booked in for next week hopefully to do some more testing. Unfortunately it's not something I can instantly achieve - seems to be a busy time round here - there is a massive amount of housing being built so I'm just waiting in line - I appreciate your sentiment though Midwest - I'm just seeing what i can do on the home owner front while I'm waiting.
Click to expand...
Kris
You mentioned that you have had 3 "Part P Electricians" (quite what a Part P electrician is I'm not sure) around already, what did they actually do? and did the find anything wrong with your electrical installation?
 
I've had two Part P registered sparkies round already and booked in for next week hopefully to do some more testing

Checking on a individuals testing and fault finding competence, perhaps via qualification,it would be a better precaution than gauging someones testing abilities by them being on that Part P register
 
The water outlet from the pump to the shower will be in plastic, therefore the shower not extraneous conductive. Is the radiator extraneous and conductive or is there any plastic plumbing? If you are connecting non extraneous parts via some form of bond, any voltage on the earth cable will be introduced to these parts. You already implied that there is something on the earth as there was a little spark when it was disconnected from cu.
Are you not making non extraneous conductive parts into extraneous ones and then wondering why there is a voltage on them?
Clamp the earth, find the earth leakage and go from there
 
mhar said:
The water outlet from the pump to the shower will be in plastic, therefore the shower not extraneous conductive. Is the radiator extraneous and conductive or is there any plastic plumbing? If you are connecting non extraneous parts via some form of bond, any voltage on the earth cable will be introduced to these parts. You already implied that there is something on the earth as there was a little spark when it was disconnected from cu.
Are you not making non extraneous conductive parts into extraneous ones and then wondering why there is a voltage on them?
Clamp the earth, find the earth leakage and go from there
Click to expand...
Don't think the OP is an Electrician or any Electrical knowledge
 
When you do get a tingle (sorry not meant to sound funny) what are you standing on ?
 
I get the odd tingle , wince these days .
Nothing electrical , just my body telling me off for an unusual stance/position ( and my not being 25 any more)
..Nerve impulses going for a wander..
(common in the bathroom -Plenty of hard suraces)
 
static zap said:
I get the odd tingle , wince these days .
Nothing electrical , just my body telling me off for an unusual stance/position ( and my not being 25 any more)
..Nerve impulses going for a wander..
(common in the bathroom -Plenty of hard suraces)
Click to expand...
You as well Zap?
 
I think the OP needs to get some strips of copper and zinc,and sort through the fruit bowl,for lemons...;)
 
Murdoch said:
I had to investigate something like this a couple of years ago. I found that that shower cubicle was live
Click to expand...
I foolishly drilled one of my own cables (for under cabinet lights) when fitting my kitchen last year, although I realised it was very close to where I'd drilled, I tested the cable and it appeared to be undamaged, however it turned out the screw I put in was touching the live and the metal capping, so when the lights were on, the wall was live....now this only came to light (pun intended) whilst grouting at night (lights on)...kept getting zaps when sponging the grout in and resting other hand on the cooker....had 100 or so volts between wall and earthed cooker!
Maybe you have a similar problem?
 
Hi Mhar, Thanks for your reply, no, the rad is copper all the way so part of the earth, the shower hose is Extraneous as you said the connector is plastic. since the unit is earthed and the rad is earthed and bonded to each other I guess the difference is because the voltage is making the hose conductive through the water. Since water is a bad conductor this would account for only 0.2v on the hose and 2v on the rad (or 2v and 12v after shower is run) I haven't and wouldn't be so mad as to connect an earth from the unit to the hose given that the unit is contained and earthed thus giving the current a path to something metal I can touch in the shower.

Hi Wilko, The tingle is when I'm standing on a tiled floor near the shower.

Midwest, cheers again good advice of course but when I isolate the shower it's still giving this reading, also when I flick the switches in the CU no single circuit seems to be responsible for the voltage, as my sparky turned them of the voltage just slowly decreased.
It seems to be a few circuits combined that make a difference though, the three light circuits and one ring main although it isn't 100% clear.
If I turn off two of the lights on one lighting circuit the 2v goes to 1.9 but if I isolate that lighting circuit it stays on 1.9v
 
Are you saying, that with other circuits switched off the voltage goes away?
 
Yes for some, for instance if I just have the cooker and appliance ring on there seems to be no voltage on rad.

The 3 lighting circuits and Smoke detectors that seem to affect the reading are next to each other on the board but no single circuit kills the voltage.

If I turn off:
Lighting Upstairs
Lighting Upstairs
Smoke Detectors
Lighting Downstairs
Ring Main 1 (this has the spur for the shower)
The voltage reads 0.0v

the main ring circuit that seems to have an effect is not physically close on the board as it's RCCB protected (CU is Contactum split with some circuits not on the RCCB)

(Having said that I can only measure tenths of a volt on the multimeter so it could be 0.02v and my multimeter would read 0.0v)
 
Kris Dor said:
Hi Mhar, Thanks for your reply, no, the rad is copper all the way so part of the earth, the shower hose is Extraneous as you said the connector is plastic. since the unit is earthed and the rad is earthed and bonded to each other I guess the difference is because the voltage is making the hose conductive through the water. Since water is a bad conductor this would account for only 0.2v on the hose and 2v on the rad (or 2v and 12v after shower is run) I haven't and wouldn't be so mad as to connect an earth from the unit to the hose given that the unit is contained and earthed thus giving the current a path to something metal I can touch in the shower.

Hi Wilko, The tingle is when I'm standing on a tiled floor near the shower.

Midwest, cheers again good advice of course but when I isolate the shower it's still giving this reading, also when I flick the switches in the CU no single circuit seems to be responsible for the voltage, as my sparky turned them of the voltage just slowly decreased.
It seems to be a few circuits combined that make a difference though, the three light circuits and one ring main although it isn't 100% clear.
If I turn off two of the lights on one lighting circuit the 2v goes to 1.9 but if I isolate that lighting circuit it stays on 1.9v
Click to expand...

I don't why I'm doing this, because your electrician should have an understanding of these phrases your using, but you may care to watch this video, and perhaps think again about your issue;

 
Induced voltage is caused when cables from different circuits are run close together.
The current on one circuit creates a magnetic field, and that field if it intersects a cable from another circuit can cause voltage on the other circuit.
If you turn off the first circuit, the voltage on the other circuit goes away.
This can also happen with copper pipe work.
 
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