Hi,
I'm interested in views on an Earthing problem and my solution.
We're in a rural property, with about 10 houses spread out over an area, some (including our own) up to about 100m from a pole mounted transformer.
All were built around 1999, and have PME supplies.
When we replaced the ceramic tiles in our kitchen with natural stone (both on a concrete slab floor), we started to notice a very distinct tingling if you touched the kitchen tap and had bare feet.
Taking some measurements, I could see that over the course of the day, the neutral/PME voltage can vary from about 250mV up to about 3V relative to "true earth" (as measured to a 12ft earth rod I've now installed). With all the metal work in the house including the copper water pipes correctly bonded, this voltage obviously becomes visible between the tap and the kitchen floor (natural stone having a much lower resistance than ceramic).
Note that as a recent build, our water feed is PE and being rural we are off the gas grid, so unlike many urban properties the equipotential bonding to the other utilities provided no additional earth connection.
As far as I can see, this voltage difference is an unavoidable result of neutral currents resulting in our own relatively long, neutral feed, and neutral imbalance between all the properties. The problem is definitely worse during the winter when various electric heating loads (our own and neighbours) periodically switch on and off.
We have therefore disconnected the PME connection (on our side of the supply not the electricity company's) and moved to a TT system with a 100mA time delay RCD in an insulated enclosure on the incoming supply in front of the CU, reference to the aforementioned 12ft earth rod.
Relative to the PME connection we have measured an "earth rod terminal to transformer earth" resistance of 14ohms, which has been absolutely stable for the entirety of the last three years.
The tingling has entirely disappeared and everyone is now happy.
What prompted the question was that I recently discussed the change with a new friend of mine who is an electrician and he said I was much better sticking with the original PME earth. I said I wasn't a fan of electric shocks when making the tea. I also quoted back the bit in the regs which disallows PME from farm building where animals feed unless a ground mesh is present (which it isn't here) and said if it wasn't safe for cattle I didn't see why it was safe for my family.
However I wonder whether others have a view on the wisdom or otherwise of this move (subject obviously to it having been executed in a regs compliant manner, Part P approval being obtained, and regular testing being done on the resistance of the earthing system)?
I'm interested in views on an Earthing problem and my solution.
We're in a rural property, with about 10 houses spread out over an area, some (including our own) up to about 100m from a pole mounted transformer.
All were built around 1999, and have PME supplies.
When we replaced the ceramic tiles in our kitchen with natural stone (both on a concrete slab floor), we started to notice a very distinct tingling if you touched the kitchen tap and had bare feet.
Taking some measurements, I could see that over the course of the day, the neutral/PME voltage can vary from about 250mV up to about 3V relative to "true earth" (as measured to a 12ft earth rod I've now installed). With all the metal work in the house including the copper water pipes correctly bonded, this voltage obviously becomes visible between the tap and the kitchen floor (natural stone having a much lower resistance than ceramic).
Note that as a recent build, our water feed is PE and being rural we are off the gas grid, so unlike many urban properties the equipotential bonding to the other utilities provided no additional earth connection.
As far as I can see, this voltage difference is an unavoidable result of neutral currents resulting in our own relatively long, neutral feed, and neutral imbalance between all the properties. The problem is definitely worse during the winter when various electric heating loads (our own and neighbours) periodically switch on and off.
We have therefore disconnected the PME connection (on our side of the supply not the electricity company's) and moved to a TT system with a 100mA time delay RCD in an insulated enclosure on the incoming supply in front of the CU, reference to the aforementioned 12ft earth rod.
Relative to the PME connection we have measured an "earth rod terminal to transformer earth" resistance of 14ohms, which has been absolutely stable for the entirety of the last three years.
The tingling has entirely disappeared and everyone is now happy.
What prompted the question was that I recently discussed the change with a new friend of mine who is an electrician and he said I was much better sticking with the original PME earth. I said I wasn't a fan of electric shocks when making the tea. I also quoted back the bit in the regs which disallows PME from farm building where animals feed unless a ground mesh is present (which it isn't here) and said if it wasn't safe for cattle I didn't see why it was safe for my family.
However I wonder whether others have a view on the wisdom or otherwise of this move (subject obviously to it having been executed in a regs compliant manner, Part P approval being obtained, and regular testing being done on the resistance of the earthing system)?
