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Topic Title: VOLTAGE IN SHOWER!
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Created On: 23 October 2013 09:47 PM
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 24 October 2013 06:25 PM
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purplemaf

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Joined: 23 October 2013

The answer to all those point's is yes. Apologies yes the 0.26 is ze.
 24 October 2013 06:52 PM
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Legh

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It must be a faulted circuit somewhere in your property or possibly next door, as previously stated, such as a trapped cable - otherwise, its 'Mercury in Retrograde'........

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 24 October 2013 06:58 PM
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WiredScience

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Has the IR testing been performed with all cpcs connected to main earth, and if so what results did you get?
 24 October 2013 10:52 PM
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OldSparky

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if its any help i too had a similar problem, its on this forum some where.

the house holder was getting tingles stepping out of the shower, long story so wont bore you, but it turned out there was a fault on a property up the lane which was TT but it had no rcd so the fuse didnt blow,

voltage was traveling to the earth stake on the DNO pole which was in this womens garden and was picked up by the waste pipe from her bath, which was a copper one..

maybe look for a fault on the neighbors house as previously said.

it is a worry now your involved...

oh and the NICEIC .. that dosent surprise me in the least, anything thats out the norm they are useless with..
 25 October 2013 04:23 PM
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purplemaf

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Ok gents here is todays update. Only had a short while at property so I chose to record some IR readings directly to waste water at one of the showers. Also I have double checked and I do definately have 3 seperate stacks that meet in the ground outside.

The following IR readings were taken with each circuit completely disconnected on 500v - 20mohm. I literally had a lead poked into the waste with he water running.

Live to water
Lights Down - 0.62
Lights Up - Clear
Skts Down - 3.07
Skts Up - 0.63
Smokes - Clear
Cooker - 13.55

Earth to water
Lights Down - 0.45
Lights Up - 0.3
Skts Down - 0.07
Skts Up - 0.07
Smokes - Clear
Cooker - 0.08

Water to Met - 0.07
Water to Neutral Bar - 2.45
Water to Bond - 0.08
 25 October 2013 04:34 PM
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OldSparky

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i think you need to look next door...

is it detached or a semi.. is next door TT supply

do the supplies loop from one house to the next,
 25 October 2013 04:47 PM
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Parsley

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Originally posted by: purplemaf

Ok gents here is todays update. Only had a short while at property so I chose to record some IR readings directly to waste water at one of the showers. Also I have double checked and I do definately have 3 seperate stacks that meet in the ground outside.



The following IR readings were taken with each circuit completely disconnected on 500v - 20mohm. I literally had a lead poked into the waste with he water running.



Live to water

Lights Down - 0.62

Lights Up - Clear

Skts Down - 3.07

Skts Up - 0.63

Smokes - Clear

Cooker - 13.55



Earth to water

Lights Down - 0.45

Lights Up - 0.3

Skts Down - 0.07

Skts Up - 0.07

Smokes - Clear

Cooker - 0.08



Water to Met - 0.07

Water to Neutral Bar - 2.45

Water to Bond - 0.08


Sorry but 'm struggling to understand how you obtained your readings, where the CPC disconnected from the earth bar?
What voltage have you measured between the MET/other parts connected to the installations earthing/bonding and the temporary garden rod that has been suggested by many.

Regards
 25 October 2013 04:53 PM
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rocknroll

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The sole purpose of the IR test is to determine a close proximity leakage to earth, connecting L + N together and testing to earth will lessen the stress on electronic components, there is very little point in testing between L + N as in T&E as they are not in close proximity and any form of leakage between live conductors will show up beforehand as a short circuit taking out the CPD.

Lets look at the definition of Insulation Resistance:
Insulation resistance is the resistance to the passage of direct current through the dielectric between two electrodes. In the case of an electric cable it is the value of the resistance between the conductor and the earthed core screen, metallic sheath, armour etc;.

The purpose of the IR test is to check for damaged insulation, this can be mechanical damage or damage by heat, (overloaded cables), readings less than 2 Mohm indicate damaged insulation, readings of 2-50 Mohm are indicative of long circuit lengths, moisture and contamination and do not indicate the insulation quality, therefore readings of 2-50 Mohm should not be specified as a fail value. The IR test is a stress test and note should be taken of the voltages applied, for cable <=0.6kV 500V dc and for flexible cords <= 0.3kv 250V dc, the use of the incorrect test voltages is not recommended as it overheats the cable and accelerates insulation breakdown also continous testing even with the correct voltage is not recommended unless a period of around 5 minutes has passed to enable the cable to return to its original state, ie; temperature.

Regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
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 25 October 2013 05:01 PM
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UKPN

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I agree with Parsley, and its about time this "problem" was sorted.
the time this investigation is taking it would be cheaper to rewire.
we will always check our system if a "shock" incident occours, and there seems to be a belief of "high" volts on the neutral. call us, eliminate the
DNO supply and put us out of our misery!!!

Regards
 25 October 2013 05:37 PM
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John Peckham

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It sounds like you have a combination of faults. The low IR needs sorting out and they may be a problem with the PME earthing having a different potential to the general mass of earth. However in the mean time for heavens sake tell the occupiers to stop using the shower as the consequences of the delay in finding the fault may result in a fatality.

You need to get in there ASAP and stay there until you find the fault or isolate the installation from the supply.

Before you have a re-run of This.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 25 October 2013 05:58 PM
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purplemaf

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With all due respect.....it obviously goes without saying that I have condemned the use of all showers AND basins/bath. I HAVE had SSE out to check their system....

Parsley, of course I have disconnected each earth from the bar to test. I have also checked the voltage in waste between Met, Temporary earth stake, bonding....everything. I have read 5-18v in the waste. At a given point in time with load on system constant the readings are the same wherever tested to.
 25 October 2013 06:03 PM
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purplemaf

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Originally posted by: OldSparky

i think you need to look next door...



is it detached or a semi.. is next door TT supply



do the supplies loop from one house to the next,


House is detached. Haven't got to next door yet. I believe most likely they are all pme as all built at the same time about 15 years ago tops.
 25 October 2013 06:43 PM
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Legh

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The following IR readings were taken with each circuit completely disconnected on 500v - 20mohm. I literally had a lead poked into the waste with he water running. Live to water Lights Down - 0.62 Lights Up - Clear Skts Down - 3.07 Skts Up - 0.63 Smokes - Clear Cooker - 13.55 Earth to water Lights Down - 0.45 Lights Up - 0.3 Skts Down - 0.07 Skts Up - 0.07 Smokes - Clear Cooker - 0.08 Water to Met - 0.07 Water to Neutral Bar - 2.45 Water to Bond - 0.08


Not consciously attempting to be obtuse or Friday pm belligerent or even thick.....
you have IR'd all your circuits that have been completely disconnected so I assume you disconnected the cpcs as well?

and what exactly do you mean by 'up' and 'down' ?

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 25 October 2013 06:44 PM
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OldSparky

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is it possible that the supply cable to the house has been damaged under ground? assuming it is under ground and not over head.

Does the house have a completion certificate? it is pretty new in house years. I would also assume there will be no bonding, just gas and water? am i correct..

Have they had a plumber on site? dont laugh, the problems i have come across with them doing their own wiring you wouldn't believe.

is there voltage on the neutral at the cutout?

completely off tac but i have had in the past on a house, the wire to the shed was so long it acted like a capacitor, once disconnected you had to discharge it or you got a belt

are they electric showers or just mixer type?
 25 October 2013 06:54 PM
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OldSparky

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oh and i cant understand th IR readings?

its only 15years old, should be fine you would have thought
 25 October 2013 07:09 PM
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daveparry1

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OS, if it's 15 years old there should be some supplementary bonding too unless it's been upgraded with a 17th. compliant c/unit?

Dave.
 25 October 2013 08:27 PM
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Zs

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Purple, So far I think what you have done is thorough and brilliant.

I've had two of these so far;

A little while back to the tune of 80Volts (wow) between the metal of the shower screen and the taps of a nearby basin. I changed the DB, added supplementary bonding and all the usual routine.

Four days later I was still looking and the voltage remained. Socket circuit was dodgy on the IR testing though, so I went after it. I took up the floorboards on the landing and found a floorboard nail through a connector block (connector block added when a spur had been put into the spare room a few years ago). It was pretty badly melted. As soon as that was changed the problem vanished.

The previous one was enough to make one of those old fashioned Drummond style test lamps light up to a vague glimmer but I don't remember the voltage. Fat husband, thin wife. She was getting the shocks and he wasn't.

IR on the cooker circuit was ok ish at about 20M, but I'm used to cooker circuits coming in at >999 even when they are about 40 years old, so I went after it..

I found a floorboard nail through the cooker cable under the study floor, on day three.

Edit. Neither of these were new floorboard work. I assume the nails had gradually been working their way deeper as people walked an them. Both were under areas of carpet where the occupants step regularly. One just outside of the bathroom and one just under the desk chair. End of edit.

So, These days I look for nails through cables. I really hope that helps.

Please please let us know how you sort this one out.

And good luck.

Zs

Edited: 25 October 2013 at 08:47 PM by Zs
 25 October 2013 09:12 PM
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OMS

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Right - forget IR testing - as you are adding load, you are seeing the voltage increase - now that should be screaming to you that you need to go and put a screwdriver in the flower beds and measure that to the building MET - from there, you can quickly deduce that either the voltage from the installation is raising the potential or its the system neutral doing so - my money is still on the latter.

You may need to lift off existing bonding to explore further - so be bloody careful

I'm still not convinced your TT succeeded in breaking the N-E bond - it may well be still made from adjoining properties.

Keep in mind also that the voltages you are talking about are pretty imperceptible to most people even if they are barefoot and soaking wet - so you may well find a much higher voltage sitting around somewhere

You want mains on, bonding off, consumer unit off and a spike in the flowerbeds - start from there,then add the bonding and see what that does

Regards

OMS

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Failure is always an option
 25 October 2013 11:00 PM
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John Peckham

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You are wasting your time IR testing to the water.

Do a thorough periodic I&T doing all the appropriate tests in sequence as if it were an initial verification. Make sure the installation CPCs are connected to the earth bar, and the earth bar is connected to the supply earth for the IR test. Correct any defects as you go.

Make sure there is a sound bond to gas , water and soil pipes.Are the bathrooms bonded and is there a nice low impedance to all the extraneous metal work in the bathrooms? Hopefully you already have 30mA RCD protection on all circuits?

If all is Ok with the installation, then an only then, isolate the supply from the installation and disconnect the earthing and bonding from the supply neutral/suppliers earth. Use insulated tools to do this just in case. Then do a line to neutral loop test on the incoming supply using a high current loop tester. Hopefully you should get a nice low loop figure (<0.35 ohms). An old fashioned Drummond test lamp is also good for finding lost neutrals. Re-connect the earthing and bonding. This test will prove if you have a good neutral present.

Then stick and earth electrode ( Alcapons long screwdriver) in the soil outside connect this to a long lead and a voltmeter connect the voltmeter to your supply earth. Then checking the voltmeter as you go load up the installation with as much load as you can, ovens, kettle, immersion heaters all the lights etc. If the voltage between the supply earth and the general mass of earth is more than a couple of volts you probably have a long run on the concentric cable from the transformer/ not to many PME earths along the cable/ a heavily loaded supply cable or a combination of all 3. A supplementary earth electrode ( the longer the better) connected to the supply earth but reduce the potential difference. If not you are looking at ditching the supply earth and TTing the whole installation and maybe installing lengths of insulated pipe in the water service pipe and asking the gas board to put an insulated joint in their service pipe.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 26 October 2013 12:58 AM
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Legh

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Originally posted by: Legh

Not consciously attempting to be obtuse or Friday pm belligerent or even thick.....

and what exactly do you mean by 'up' and 'down' ?

Legh


Sorry guys it may actually be true........

However, back to the problem....

We are now looking at a possible damaged PME cable or damaged / faulty circuit/s cabling

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
IET » Wiring and the regulations » VOLTAGE IN SHOWER!

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