Here's a strange one for you geniuses.
My brother has a house near the shoreline. Some people have complained they get a shock from the kitchen sink, especially when they've come in from the beach in wet flip-flops or bare feet.
I put a sensitive voltmeter between the sink and a damp cloth on the quarry-tiled floor. It revealed a PD of anything up to 4.2 volts - surely enough to produce a tingle on damp skin (which of course is reported as a "jolt" or "shock" when you're not expecting it).
Time to call in sparky. The guy couldn't find anything wrong with the wiring, even though it's quite old, but said he could cure it with an earthing rod. He drove a four foot (so I'm told) rod into the ground right beside the sink and strapped it directly to the stainless steel.
(The house is built on what we believe is heavily compacted sand and clay. The rod went straight down into it.)
Some cure! People are still complaining of shocks and a subsequent check shows typically 3.5 volts on the same test.
What goes on here? In theory we have a dead short between sink and ground yet it's still producing a voltage. At first I thought there might be some electrolytic action from the salty "earth" below but it seems unlikely this could generate enough current to cause a noticeable jolt, especially through quarry tiles.
I'm beginning to wonder if there is something up with the mains supply itself. Oddly enough, the guy next door has complained that he gets a "tingle" off an outside tap (house is fed by a separate overhead cable from a shared pole).
Any clues, gents? Incidentally, I'm well acquainted with microelectronics but less familiar with the black art of mains power supply.
My brother has a house near the shoreline. Some people have complained they get a shock from the kitchen sink, especially when they've come in from the beach in wet flip-flops or bare feet.
I put a sensitive voltmeter between the sink and a damp cloth on the quarry-tiled floor. It revealed a PD of anything up to 4.2 volts - surely enough to produce a tingle on damp skin (which of course is reported as a "jolt" or "shock" when you're not expecting it).
Time to call in sparky. The guy couldn't find anything wrong with the wiring, even though it's quite old, but said he could cure it with an earthing rod. He drove a four foot (so I'm told) rod into the ground right beside the sink and strapped it directly to the stainless steel.
(The house is built on what we believe is heavily compacted sand and clay. The rod went straight down into it.)
Some cure! People are still complaining of shocks and a subsequent check shows typically 3.5 volts on the same test.
What goes on here? In theory we have a dead short between sink and ground yet it's still producing a voltage. At first I thought there might be some electrolytic action from the salty "earth" below but it seems unlikely this could generate enough current to cause a noticeable jolt, especially through quarry tiles.
I'm beginning to wonder if there is something up with the mains supply itself. Oddly enough, the guy next door has complained that he gets a "tingle" off an outside tap (house is fed by a separate overhead cable from a shared pole).
Any clues, gents? Incidentally, I'm well acquainted with microelectronics but less familiar with the black art of mains power supply.