Weird electrical problem!

[Grusa]

Ok, you gurus out there, explain this one!

I have an outside utility area, fully covered and wired by myself, with a substantial grounding rod in damp ground and its own distribution box. Running off it is a pump, a water heater, two fridges, a washing machine, a RO filter, fans and lighting. All are grounded where appropriate or possible, including the roof structure.

Yesterday, going to draw water, I touched the stainless steel sink, and I got a shock - more than a tingle and less than a belt.

Using a multimeter, I measured the voltage between myself and the sink, at 200volts! I then checked against everything else in the area - same result. Even the brass non-return valve in the blue plastic water supply line showed 200v.

Inside the main house, the kitchen sink showed 150v, as did everything electrical in the kitchen with exposed Metalwork - but no shock from any of these.

My first thought was an electrical fault in one of the appliances, so disconnected them all - no difference. Switched off the power - no difference.

It was getting too late to do anything useful, so I deferred the job until this morning.

 

Today I got my meter and tools, ready to open up the distribution boxes and check everything. Imagine my surprise that the fault is gone....... zero volts anywhere. No detectable earth leakage whatsoever.

 

Does anyone have any idea how this could happen? 

[ubonjoe]

Moved to the Electrical Forum.

[bankruatsteve]

Critters getting into an outside box can put a fault between L and E.  Sometimes large enough to energize the ground system.  After frying, the fault can go away.  In my case, I had geckos in the box and anything connected to ground gave me a zing until I found and cleaned.

[Crossy]

Is your system MEN (N-E link in the box)? If not sure post a photo of the box with the lid off (care please).

 

An open neutral between you and the transformer could lead to this kind of issue, PEA then fixed the fault.

 

[Grusa]

18 hours ago, Crossy said:

Is your system MEN (N-E link in the box)? If not sure post a photo of the box with the lid off (care please).

 

An open neutral between you and the transformer could lead to this kind of issue, PEA then fixed the fault.

 

Not linked. I know it should be, but fear the potential (55) consequences of attempting to do it myself.

 

No way is any local Chan getting anywhere near it!

[carlyai]

19 minutes ago, Grusa said:

Not linked. I know it should be, but fear the potential (55) consequences of attempting to do it myself.

 

No way is any local Chan getting anywhere near it!

So you had 200 v where it shouldn't be, it cleared, but you don't want to listen to advice of a possible fix. 

So why post?

[Grusa]

1 minute ago, carlyai said:

So you had 200 v where it shouldn't be, it cleared, but you don't want to listen to advice of a possible fix. 

So why post?

I am waiting for someone to advise me how to ensure it is safely done, without causing a blackout to the entire nation, or killing myself!

[carlyai]

5 minutes ago, Grusa said:

I am waiting for someone to advise me how to ensure it is safely done, without causing a blackout to the entire nation, or killing myself!

Ok, sorry I misread your post.

I suppose the next step is to take the cover of as suggested (post pic back here) and ask someone how to do it.

I did it and I'm still alive. 

While you're waiting there could be a pinned thread that has a diagram of the wiring setup.

[Grusa]

4 minutes ago, carlyai said:

Ok, sorry I misread your post.

I suppose the next step is to take the cover of as suggested (post pic back here) and ask someone how to do it.

I did it and I'm still alive. 

While you're waiting there could be a pinned thread that has a diagram of the wiring setup.

Thank you, I have the diagrams and the theoretical knowledge. What I don't have, and don't want, is the experience of the big bang if it all goes wrong. So, were you lucky and all went well? Does anyone out there bear the scars, mental or physical, of it going wrong? Just asking!

[carlyai]

3 minutes ago, Grusa said:

Thank you, I have the diagrams and the theoretical knowledge. What I don't have, and don't want, is the experience of the big bang if it all goes wrong. So, were you lucky and all went well? Does anyone out there bear the scars, mental or physical, of it going wrong? Just asking!

Well I suppose I was lucky and all went well. I am not an electrician and I know your fears.

[MrJ2U]

1 hour ago, Grusa said:

Not linked. I know it should be, but fear the potential (55) consequences of attempting to do it myself.

 

No way is any local Chan getting anywhere near it!

If there's an electrician available from the nearest City?

 

Worth it to pay a lot extra to have them come out for a day or two.

 

 

Good luck.

[Crossy]

23 hours ago, Grusa said:

Switched off the power - no difference.

 

I missed this on the first reading.

 

Definitely odd and an open neutral somewhere would definitely be a candidate, do you have close neighbours who might have a MEN link?

 

It is worth checking if your poles are MEN enabled (neutral grounded every third pole) as adding MEN would improve safety.

 

[bluejets]

22 hours ago, Crossy said:

An open neutral between you and the transformer could lead to this kind of issue, PEA then fixed the fault.

Yes, kind of problem that turned a teenager into a vegetable in Aus a couple of years back.

Sadly every protection device known is not enough to detect or isolate.

Aside from visual or the usual testing.

[Crossy]

Yeah, it blew up a row of cottages in Wales a few years back too.

 

An open supply neutral meant that the return current was going via a very convenient pipe. 

 

Unfortunately for the cottages it was the gas pipe!! 

 

Amazingly nobody was killed.

 

[Rookiescot]

I dont understand the voltages.

Your supply will be 220v.

As for 150v thats got me scratching my head. You would need to put the supply through a step down transformer to get that.

Then the whole thing disappears?

Honestly mate I got no idea right now but I will keep thinking about it.

[Crossy]

@Grusa It would still be useful if you could post a photo of your distribution board with the lid off, if for no reason other than interest to work out what you were seeing.

 

@Rookiescot Imagine an open neutral which is being somewhat bypassed by all those (not perfect) earth rods, it's quite easy to imagine the "earth" getting to somewhere rather less than the supply potential.

[Rookiescot]

8 minutes ago, Crossy said:

@Grusa It would still be useful if you could post a photo of your distribution board with the lid off, if for no reason other than interest to work out what you were seeing.

 

@Rookiescot Imagine an open neutral which is being somewhat bypassed by all those (not perfect) earth rods, it's quite easy to imagine the "earth" getting to somewhere rather less than the supply potential.

Aye I'm still struggling to think where the cause could be located. 

OP where is your neutral point located?

[Rookiescot]

2 minutes ago, Rookiescot said:

Aye I'm still struggling to think where the cause could be located. 

OP where is your neutral point located?

Just wondering if the earth spikes could be the source of the voltage?

With heavy rain and a raised water table those "earths" might be conducting between each other.

[Grusa]

Ok, update. My property is a 30-ish year old townhouse, with mostly original wiring, modified some 10 years ago, and added to by myself. The mains feed is underground from the mubaans' transformer and through their meter. I have no access to check all that out. There is no original earthing, as expected.

I have installed a new box with ELB for the back yard, with live and neutral feed from the original main switch downstream side, and a new ground from a spike and linked back to the original box, where it is bonded to neutral. As it is some two years since I did it, I could not remember making that link.

Interestingly when the incident occurred the ELB did not trip. To me this suggests a fault in the main house.

Thanks for all interest, and constructive comments.

I will open up and photograph asap.

[Rookiescot]

10 minutes ago, Grusa said:

Ok, update. My property is a 30-ish year old townhouse, with mostly original wiring, modified some 10 years ago, and added to by myself. The mains feed is underground from the mubaans' transformer and through their meter. I have no access to check all that out. There is no original earthing, as expected.

I have installed a new box with ELB for the back yard, with live and neutral feed from the original main switch downstream side, and a new ground from a spike and linked back to the original box, where it is bonded to neutral. As it is some two years since I did it, I could not remember making that link.

Interestingly when the incident occurred the ELB did not trip. To me this suggests a fault in the main house.

Thanks for all interest, and constructive comments.

I will open up and photograph asap.

If the supply is underground and the insultation was broken then with heavy rain you could find the earth spikes are picking up a voltage?

[Crossy]

18 minutes ago, Grusa said:

As it is some two years since I did it, I could not remember making that link.

Interestingly when the incident occurred the ELB did not trip.

 

This definitely says "open (or high resistance) neutral" somewhere upstream of your main switch.

 

For those interested, try drawing out a TNC-S system with local rods, give those rods a non-zero resistance to ground. Then do the sums with the neutral open at some point.

 

By the way some time in the past I posted "lost neutral detector" using a regular RCD as the sense element, I'll see if I can find details.

 

 

[Rookiescot]

5 minutes ago, Crossy said:

 

This definitely says "open (or high resistance) neutral" somewhere upstream of your main switch.

 

For those interested, try drawing out a TNC-S system with local rods, give those rods a non-zero resistance to ground. Then do the sums with the neutral open at some point.

 

Crossy you are a hard task master. You know how long its been since I dealt with this stuff?

Even back then I was an electronics technician not an actual electrician but had to occasionally try my hand at it because the Royal Signals had no electricians ????

[Crossy]

I could do it for you of course, but it's finding the time to be honest, I do actually have a life and a job ????

 

Maybe if the cricket gets rained off again ...

 

[rwill]

5 hours ago, Grusa said:

Not linked. I know it should be, but fear the potential (55) consequences of attempting to do it myself.

 

No way is any local Chan getting anywhere near it!

There are some knowledgeable electricians here.  But of course there are lots of pretenders too.  Sometimes you can find PEA guys that moonlight.

[Rookiescot]

14 minutes ago, Crossy said:

I could do it for you of course, but it's finding the time to be honest, I do actually have a life and a job ????

 

Maybe if the cricket gets rained off again ...

 

Cricket would be rained off here in Nong Khai thats for sure.

Even Yorkshire wouldnt play in this.

[Crossy]

2 minutes ago, Rookiescot said:

Cricket would be rained off here in Nong Khai thats for sure.

Even Yorkshire wouldnt play in this.

 

There's going to be a glut of matches:-

 

England - NZ women ODIs in the UK (the ladies have come on leaps and bounds very good watching).

Pakistan - NZ ODIs in Pakstan.

 

Then the IPL gets going.

 

Too much cricket, not enough hours ???? 

[Rookiescot]

Just now, Crossy said:

 

There's going to be a glut of matches:-

 

England - NZ women ODIs in the UK (the ladies have come on leaps and bounds very good watching).

Pakistan - NZ ODIs in Pakstan.

 

Then the IPL gets going.

 

Too much cricket, not enough hours ???? 

IPL is excellent. Really enjoy that.

Although it is a complete anathema to some who regard it as some kind of sacrilege. 

[FNQ]

On 9/14/2021 at 4:15 PM, Crossy said:

Is your system MEN (N-E link in the box)? If not sure post a photo of the box with the lid off (care please).

 

An open neutral between you and the transformer could lead to this kind of issue, PEA then fixed the fault.

 

Get PEA ? To check there unearthing connection on the wire running past your house. (Fixed a similar prob I had.)

[xtrnuno41]

I measured the voltage between myself and the sink, at 200volts! I

 

You put one lead of the meter on the sink and the other you hold in your hand?

you were on bare foots then? Amazing measuring.

You switched off power (live?) and still measure it in same way. Even on a return valve in plastic pipe water supply.

My best guess then would be, the water is conducting electricity. Maybe even built up static electricity in the water system.

Water in Thailand is not Ph 7. More like Ph 4 (acid) or so and then it can conduct electricity.

As you grounded all, as you said, it should flow away but doesnt. Ground properly working then? 

The electricity can then come from another device in another group and has a fault in it. The group protection in it doesnt work, you have differential circuit breaker's in your box? But has to be a device connected with the water, your shower? 

Next day you go back and all gone, so fault erased, maybe for a short or longer time.

[Grusa]

Hello @Crossy here are the photos.

 

Numbered items: original box,  1&2 feed to secondary box, 3 grounding from secondary box, 4 N-E link. It looks messy but it's safe.

Grounding rod is 6' buried immediately under a roof drain pipe.

 

Checked again today, 0v at sinks etc. One fridge shows 15 v, it has a 2-pin plug and no earth, coffee machine 5v again not earthed.