Ouch - belt off a neutral!

[Cirrus]

Working on an immersion cct today. Plumber been in loft for 2 days doing all pipework. Just bending over the Neutral on the supply and ....Zing - a belt. Thought I was going mad then 5 mins later I got a belt off the pipework I was leaning against. Made me jump out of the airing cupboard. Then, plumb says that he just got a belt off a pipe in the bathroom. Spoke to occupier and she says that whenever she turns on the outside tap she also gets a belt. WTF!!!??? Put meter across conductors on immersion feed to find 7 volts L-E but 80 Volts N-E but no RCD tripping! Turned off each cct on the C/U and the voltage dropped to 65 Volts at the lowest.

Oil fired boiler has 10mm main Eq bond, as does water. This is a TT system with a 10mm main earth. Confused! headbang

 

[binky]

Have the neighbours got PME?

 

[Cirrus]

Not sure - prob not as it's an old cottage

 

[Apache]

When using a neon screwdriver to test the terminals on an immersion heater you feel noting until your bare elbow touches a copper pipe!

Ouch

 

[Cirrus]

Haha - only use Irazola. Best for me!

 

[Apache]

Haha - only use Irazola. Best for me!

was a decent CK one

 

[Andy™]

sounds like a dodgy neutral somewhere. does the RCD work correctly if you test it?

 

[Mark2spark]

Do you get any V on N - E if the Imm circuit is switched off at the mcb?

 

[Apache]

Do you get any V on N - E if the Imm circuit is switched off at the mcb?

yes - MCB only breaks live/phase/line

 

[Evans Electric]

Live pipework is often down to a faulty immerson heater but yours was disconnected so not so simple. Why didn't the RCD trip ? Is it faulty ? What is the Ze on the rod ? Have you tried switching off each circuit to see if that 80 volts disapears ?

 

[Mark2spark]

Turned off each cct on the C/U and the voltage dropped to 65 Volts at the lowest.

Let's get this right.

With every circuit switched off you can still get 65 volts across N - E?

Pray

 

[Evans Electric]

Sorry , missed that bit. It sounds like a potentially dangerous fault TBH . Is polarity correct? If bonding and rod are connected , that RCD should be tripping out IMO . Needs a serious looking at , customer needs to be warned . I'm afraid it is now your problem Cirrus as the last spark on site , assuming they will pay you , of course. Suggest you tread carefully.

Forum would be interested in the result.

 

[Adrian]

you may have voltage but no current

as for the rcd not tripping check to see if you have not got a neutral to earth fault as this sometimes stops the rcd from tripping

also check your Ra if this is to high it could be the cause for the rcd not to trip

also a very good Zs on a tt system could mean that you have a neutral earth fault

 

[Mark2spark]

Plumber been in loft for 2 days doing all pipework.

I think i've spotted the likely cause of the fault!! ROTFWLROTFWLROTFWL

 

[wozz]

seen a fault that sounds similar before, was extremely strange never really got to the bottom of it. as each circuit was turned off voltage across pipework got lower. the electrician (i was a apprentice at the time) spent ages on the phone to the NIC about it,they couldnt come up with much more than something along the lines of the voltage was entering the house via the rod or main bonds and using the house as a earth path or something along those lines. all the surrounding houses were tt. problem was 'solved' as such by cross bonding all pipework to bring voltage down to zero.

 

[SPECIAL LOCATION]

Working on an immersion cct today. Plumber been in loft for 2 days doing all pipework. Just bending over the Neutral on the supply and ....Zing - a belt. Thought I was going mad then 5 mins later I got a belt off the pipework I was leaning against. Made me jump out of the airing cupboard. Then, plumb says that he just got a belt off a pipe in the bathroom. Spoke to occupier and she says that whenever she turns on the outside tap she also gets a belt. WTF!!!??? Put meter across conductors on immersion feed to find 7 volts L-E but 80 Volts N-E but no RCD tripping! Turned off each cct on the C/U and the voltage dropped to 65 Volts at the lowest.Oil fired boiler has 10mm main Eq bond, as does water. This is a TT system with a 10mm main earth. Confused! headbang

You are only giving us half the facts Cirrus.. as Evans has pointed out...

Sorry , missed that bit. It sounds like a potentially dangerous fault TBH . Is polarity correct? ......

What is the Ze on the rod.

Is Polarity verified at all points..

Incoming supply, Outgoing MCBS, connections at accessories.

What is the supply external earth loop readings... Ra on Rod!?

What voltage readings do you get between L-N, L-E, N-E at the incoming main switch?

When was the last Periodic Inspection done?

Is there any central heating wiring?

 

[M107]

Had a fault recently just like this.

Initial call from customer

" The electrician we have here at the moment cant solve the problem & has given up"

They had voltage present on pipework & when each circuit turned off the voltage dropped.

Finaly found burnt up neutral on shower switch was causing the problem.

 

[Cirrus]

You are only giving us half the facts Cirrus.. as Evans has pointed out...Is Polarity verified at all points..

Incoming supply, Outgoing MCBS, connections at accessories.

What is the supply external earth loop readings... Ra on Rod!?

What voltage readings do you get between L-N, L-E, N-E at the incoming main switch?

When was the last Periodic Inspection done?

Is there any central heating wiring?

Not able to do any testing on the installation yesterday due to time constraints but this morning I cross bonded all new pipework that I could see. Will be going back next week to conduct a thorough inspection and will test everything then. Last periodic was 2 years ago.