Neutral-Earth voltage

[leep82]

Called to a property yesterday after the customer had been advised to call an electrician by an engineer who had done some work on there cooker. I arrived and was directed towards a socket in the kitchen. The lady couldnt really explain what the engineer had told her.

I plugged my multifunction tester in and immmediately realised there was a problem. The display wasnt showing a voltage between live and earth but was showing voltage between live-neutral and neutral-earth. I removed the socket front and saw that the live and neutral conductors had been connected into the wrong terminals. Once i had sorted this out i plugged my tester in again to try and do a Zs test, but i was unable to as there was still voltage showing between neutral and earth. I tried another socket in the kitchen on the same circuit and was able to perform the test, getting a reading of 500ohms. The system is a TT although a quick look at the mains suggests there might be PME available.

I went around various sockets on the circuit and was left a little bit baffled as some would let me perform a Zs test and others wouldnt as it was indicating a voltage between neutral and earth. When i initially removed the socket with reversed polarity i used my tester across neutral and earth and was getting a voltage of around 30v. I have advised the customer to have a EICR, which she is going ahead with. I wasnt able to spend any great deal of time there last night so sorry for any lack of other information. As already said i will be returning to carry out an EICR so will hopefully get to the bottom of the issue then, but in the meantime any suggestions, advice greatly welcomed.

 

[westward10]

Not uncommon on TT systems.

 

[DPG]

What voltages (L-E, L-N, N-E) were at the main incomer?

 

[leep82]

What voltages (L-E, L-N, N-E) were at the main incomer?

unfortunately didnt check at the main incomer as i was really pushed for time

 

[westward10]

It isn't uncommon to detect small voltages on TT systems but yours seems problematic.

 

[Wilko]

May I suggest to test the rod and means of earthing etc ?

 

[leep82]

May I suggest to test the rod and means of earthing etc ?

Once i can get back there this is somthing i will be doing.

 

[dmxtothemax]

could it not just be ghost voltage ?

 

[Octopus]

Sounds like no or poor earth to me.

Did you check the R1 + R2 on the cooker circuit?

 

[Dcesilo80]

I have no idea of it.

 

[leep82]

Hi guys finally got back to this property at the weekend to carry out the EICR. First thing i checked was the main earthing conductor, which had corroded within its enclosure and was providing no means if earthing. I put a new clamp on and took a Ze reading ( 41 ohms ). As i started to remove accesories for inspection it became clear that the installation was in quite a poor state.

A couple of things i picked up in was that a supply to the shed was wired in 1.5mm swa, and protected by a 32a mcb. I disconnnected this and informed the customer. Unfortunately there is no room inside the DB to install a smaller rating MCB. I have left this disconnected for the time being. I also noticed a 2.5mm T&E protected by a 32a MCB i again disconnected this as i couldnt identify what it was supplying. It has since become apparant that this was the supply to the boiler. What code would this warrant as far as my observations are concerned?

Although the installation is a mess there seems to be little reason to report it as unsatisfactory. Understanding that an EICR is not a means of quoting for remedial work i really feel that the installation would benefit from a new consumer unit given some of the C3's that i have raised. The existing consumer unit is not very accesible at all for inspection and maintenance, and poorly fixed, circuits have been doubled up into the same OCPD. And although PME is available the system as mentioned is still on a TT. Should i recommend a new consumer unit based on the report?

 

[SparkyChick]

Personally I'd C2 the oversized breaker for the boiler, advise replacement with a 16A on the cert.

When you say some circuits are doubled up, what? And how many? And what other reasons do you have for suggesting a replacement CU?

When you say PME is available, is that at the head or have you just confirmed with the DNO that PME is an option?

 

[Octopus]

A couple of things i picked up in was that a supply to the shed was wired in 1.5mm swa, and protected by a 32a mcb. I disconnnected this and informed the customer. Unfortunately there is no room inside the DB to install a smaller rating MCB. ?

So are you suggesting that the SWA was connected to a MCB with another circuit? Possibly a RFC? If so, this is no different to a spur at the CU!

I don't think you can justify disconnecting circuits from 32A breakers - they are C2 at worse, certainly not C1's

 

[Deleted member 72666]

What type of board is this, are the mcb's still available and can't you just swap out the two 32 amp breakers for 16 amp? A board change seems overkill to me.

 

[leep82]

So are you suggesting that the SWA was connected to a MCB with another circuit? Possibly a RFC? If so, this is no different to a spur at the CU!

I don't think you can justify disconnecting circuits from 32A breakers - they are C2 at worse, certainly not C1's

Yeah the swa was in with the ring final circuit, and it wasnt terminated correctly. No gland just stripped and taken in through a knockout in the board. There is absolutely no room whatsoever to make it off into an enclosure or even into the board itself. I will try to upload a pic. The DB is in a really poor location