Weird Earth Fault

[ThrownRazor25]

Had a weird one today. Doing an EICR and the lady says yeah we dont touch the screws at the switches or sockets as we get a shock from them. I said yeah?? Went to unscrew a light switch and sure enough zap.

Touched it again and nothing so i was thinking static.

Tested the house ze 0.14 tncs system lighting circuit r1r2 0.34 zs 0.56 rcbo x1 21.8 everything fantastic went to screw back the switch zap again. Then nothing. No voltage between earth connection and neutral but 8-10 ohm between live and earth. Is it just static?

 

[static zap]

( No electrical theories , but was house baking hot , recent rain humidity should make static unlikely - New carpets ? )

 

[DPG]

If you have 10 Ohms between live and earth, then it isn't a static electricity problem . And if it was static, it wouldn't occur every time you touched the switch plate - it would have to build up again.

 

[James]

Sounds like static to me, if you get a shock from a well earthed thing, then immediately after all is fine when you touch it.

A resistance between live and earth when all is dead is normal, earth and neutral are connected together at source, live to neutral are connected by the loads on circuits.

 

[ThrownRazor25]

It is not happening all the time. It will happen then i can touch it and there is nothing. Strange thing is though i can touch the earth connection with the probes of my meeger and you can see and hear the zap, i can instantly touch it afterwards though. The probes are obviously metal but they are rubber insulated so if it was static how could that pass through me onto insulated holders to the metal tips? Very confused.

 

[DPG]

I not convinced this is static. The occasional static zap maybe, but this sounds far too often.

Unless they have nylon carpets, or a Vaan de Graaf generator in the kitchen.

 

[James]

If you have a good earth
And a good connection from device to earth, then the potential at that point is 0V
You can’t get a shock from something that is well earthed unless you have potential yourself.
But I agree with your point @DPG it sounds far more often than I would expect.

 

[Strima]

Had this in an office with nylon carpet tiles and when the panel heaters were on the air would dry out.

Staff would often get static shocks so as an experiment I placed a bowl of water out of harms way and within a couple of hours the static shocks had reduced.

They now have a small humidifier and this works a treat.

 

[PEG]

Hi,what have you got,between the screws in the switchbox,and the fabric of the building or ground outside?

 

[westward10]

How have you measured 8-10 ohm between line and earth, that would result in 20 odd amps flowing.

 

[derek]

What are your insulation resistance values on the circuit with all loads disconnected?

 

[ThrownRazor25]

With rcbo off but main switch on 8 - 10 ohm between l and e on continuity tester. Ir test is greater than 299 on every circuit
[automerge]1570137908[/automerge]
With main switch off, the 8-10 ohm disappears but the tester just clicks on off on off on off for continuity

 

[westward10]

Turn the main switch off you are getting continuity because neutral and earth are connected external to the installation.

 

[Strima]

With rcbo off but main switch on 8 - 10 ohm between l and e on continuity tester. Ir test is greater than 299 on every circuit
[automerge]1570137908[/automerge]
With main switch off, the 8-10 ohm disappears but the tester just clicks on off on off on off for continuity

Sounds like your picking up the circuitry within the RCBO. What continuity do you get with the RCBO disconnected?

 

[ThrownRazor25]

It disappears when disconeccted from rcbo so changed rcbo but new rcbo has same ptoblem

 

[westward10]

What disappears. Randomly changing components is only guesswork you need to find the actual problem causing the issue.

 

[ThrownRazor25]

I never randomly changed anything. As i said the 8 ohm disappears when the live and neutral disconnected from rcbo so i suspected a faulty rcbo. I changed it to see if a new one had tbe same result. It did.

 

[westward10]

If you have 8ohm between line and earth you would have 20 + odd amps flowing.

 

[ThrownRazor25]

How can i touch it randomly then?

 

[PEG]

How can i touch it randomly then?

.....it's easily done....i have the restraining order,to prove it...

 

[ThrownRazor25]

dunno what to do with this one.

 

[static zap]

... Strange thing is though i can touch the earth connection with the probes of my meeger and you can see and hear the zap,

If you can get 6mm of spark , that's aprox 10kV of static .

(was it pretty toasty there ? (mid winter also works when ground frozen))
Moving around -from shoes , sliding over a carpet / getting up from seating - will also re-charge you.
(If they are having computer problems - Ionisers /van der graaf !)

 

[Deleted account]

Sounds like it’s a build up of charge in the person rather than the switch screws.

When coming into contact with the well grounded/ earthed screws the charge is released.

 

[DPG]

Just to confirm, do you mean 10 Ohm live to earth, or 10MOhm when you test IR?

 

[ThrownRazor25]

10 ohm live to earth. Been reading a lot about loss of neutral on a tncs system. Could this be the cause?