Electric fence causing problems

[Rockingit]

Had a really odd problem out on a job the other day and wondered if others have encountered the same and what they did!

Large rural plot with house, outbuildings and lots of land. TT, but on a dedicated pole which is PME so not sure what happened there!

When doing some ground works and digging up some old oil pipes (I was there to wire in a sewage system...nice.....) we noticed that the underground copper was all 'live', ie if you touched it you got a shock. Got my meter on it and couldn't find anything, though, very odd. Defo a 'throb tingle' there when you put your hand to it but not strong enough to be a danger and definitely not mains voltage or frequency. This continued INSIDE the house and you could feel it through the stainless kitchen sink. I checked all the bonding, metered the place right through and couldn't find an installation fault anywhere.

Eventually, after 2 hours......

They have an enormous big duck pond, various animal pens etc all protected by one very long electric fence. And it turned out it was feeding back via the actual ground itself where it was touching (as it's meant to...) and therefore creating a loop via the TT earthstakes back into the main installation. So.... in a reverse of the normal situation the more rods you bang into the ground, the worse it gets!! The fence controller itself was fine (double insulated) and everything was working 'as designed and intended'. I think it's just the extremely conductive soil we get around here in Somerset (very wet and peaty). I eventually made the problem go away by banging a whole load of earth rods in all around the perimeter of the fence and then installing a great long return loop back to the fence controller, but that's not really how they're meant to work!!

Thoughts, anyone?

 

[truckster]

Have a peek at this

Troubleshooting guide

 

[Rockingit]

Cheers for that, step 3 pretty much sums it up - what they had before (poor installation) and what I ended up doing (good installation), with a slight twist to suit the location.

 

[pushrod]

Did the fence have its own rod connected to the fence energiser and was it making good contact with the earth?

 

[Rockingit]

Did the fence have its own rod connected to the fence energiser and was it making good contact with the earth?

Initially no, it had been wired back to the installation earth, but logically speaking, as it is a TT installation, then it makes no difference, surely? If it had been on it's on single rod then that rod would geographically been the same distance from the fence as the main installation rod so either way the 'common' ground is just that, the Terra ground. It's a shame I don't have any pictures of it because what this thread lacks is the ability for me to express exactly how BIG this fence is - must be at least 500m around the perimeter so the ground area is enormous (and testament to the energiser!) The TT Ze at source is really low as well (something like 25 from memory) so it's the good with the bad! We banged in a dozen rods at strategic points only inches from the fence and then linked them back to the energiser earth return which solved it (as per Trucksters post). I also advised the client to put some PVC guttering along the bottom of the fence so that the wire sits in it insulated from the soil.

The big picture is that it's all due to be redone and rebuilt so when that happens I'll get the supplier to change to TNCS (not sure why it isn't in the first place) so that should eradicate the problem as there'd be no bare copper or steel in the ground as part of the equi bonding.

But all in all, it was a new one on me!

 

[truckster]

"Initially no, it had been wired back to the installation earth, but logically speaking, as it is a TT installation, then it makes no difference, surely?"

Yes!

The problem is that it is connected to the system earth which is making it all pulse. The controller is essentially a safety source, juice comes out and heads back to the source via the ground. You need to get the controller rod away from the system earth rod and any other metalwork that is connected to it or you are effectively making the installation earth a part of the electric fence.

 

[pushrod]

Initially no, it had been wired back to the installation earth, but logically speaking, as it is a TT installation, then it makes no difference, surely? !

Yes , they should have their own rod connected to the energiser, or at least mine does and when you buy them as kits the ones that i have seen, will provide a rod that you knock in near the fence. It would also reduce the effectiveness of the fence. Unless it is the type that works on an animal bridging across wires. Otherwise, as you have seen, the current will try and get to the nearest earth, in your case all the metal work between it and the main earth rod.
The advantages of keeping chickens eh -you get fresh eggs and learn about electric fences

Edit : you type quicker than me truckster lol

 

[Rockingit]

Cheers gents, I understand all the physics, it was just a damn infuriating problem when I realised what was happening. And as you've both said, the theory is backed up by how I solved the problem on site. It's a good job the energiser was sited in an out-building otherwise I'd still be there now knocking in rods!!

As for the chickens (and ducks)....omelettes have never tasted so good!! (and Mrs Rockingit is now buying eggs off the client!! ) The benefits of having a rural round

 

[truckster]

As for the chickens (and ducks)....omelettes have never tasted so good!! (and Mrs Rockingit is now buying eggs off the client!! ) The benefits of having a rural round

Must be tight down your way, I have a beef farmer who regularly gives me a joint or two and some eggs as a tip!
(Nearly said he slips me some meat)