Alcazar Posted September 2, 2006 Share Posted September 2, 2006 Whilst over this time, wife complained that the dishwasher gave her a shock when she touched the inside. I put a multimeter across it and came up with 70V across earth and neutral, and the same at the socket. The cable was connecteed correctly at the nearest junction box, although the earth was NOT connected there, just cut short.Removing the cable connecting the socket to the nearest junction box, I tried all methods of continuity between live, neutral and earth wires, but got zero for all three, ie: no break in insulation, and all three are continuous along their length, no breaks.Replacing said wire with a fresh piece, removed the fault, but WHAT ON EARTH (sorry), CAUSED IT?Alcazar Link to comment Share on other sites More sharing options...
Dick Smith Posted September 3, 2006 Share Posted September 3, 2006 Had you moved the dishwasher recently? We once got shocks from ours, and it turned out that in moving it we had trapped the power cable and cut it. Link to comment Share on other sites More sharing options...
Nick Trollope Posted September 3, 2006 Share Posted September 3, 2006 [quote user="Alcazar"]Whilst over this time, wife complained that the dishwasher gave her a shock when she touched the inside. I put a multimeter across it and came up with 70V across earth and neutral, and the same at the socket. The cable was connecteed correctly at the nearest junction box, although the earth was NOT connected there, just cut short.Removing the cable connecting the socket to the nearest junction box, I tried all methods of continuity between live, neutral and earth wires, but got zero for all three, ie: no break in insulation, and all three are continuous along their length, no breaks.Replacing said wire with a fresh piece, removed the fault, but WHAT ON EARTH (sorry), CAUSED IT?Alcazar[/quote]UnIess I have misunderstood, the dishwasher. Most electrical appliances produce some residual voltage to the casing & hence earth. If your earth was disconnected ("just cut short") then 'er indoors provided the earth.Our tumble drier is the same - I really must rewire the utility room.... Link to comment Share on other sites More sharing options...
Alcazar Posted September 3, 2006 Author Share Posted September 3, 2006 [quote user="Dick Smith"]Had you moved the dishwasher recently? We once got shocks from ours, and it turned out that in moving it we had trapped the power cable and cut it.[/quote]Yes, it had been moved, but the power cable was intact, and the fault has now gone, wife no longer complains, (I couldn't feel the "buzz" anyway), and the multimeter registers zero Volts across neutral and earth.[8-)]Alcazar Link to comment Share on other sites More sharing options...
Alcazar Posted September 3, 2006 Author Share Posted September 3, 2006 [quote user="nicktrollope"][quote user="Alcazar"] Whilst over this time, wife complained that the dishwasher gave her a shock when she touched the inside. I put a multimeter across it and came up with 70V across earth and neutral, and the same at the socket. The cable was connecteed correctly at the nearest junction box, although the earth was NOT connected there, just cut short.Removing the cable connecting the socket to the nearest junction box, I tried all methods of continuity between live, neutral and earth wires, but got zero for all three, ie: no break in insulation, and all three are continuous along their length, no breaks.Replacing said wire with a fresh piece, removed the fault, but WHAT ON EARTH (sorry), CAUSED IT?Alcazar[/quote]UnIess I have misunderstood, the dishwasher. Most electrical appliances produce some residual voltage to the casing & hence earth. If your earth was disconnected ("just cut short") then 'er indoors provided the earth.Our tumble drier is the same - I really must rewire the utility room.... [/quote]OK, but if that's right, then...a) how did the 70V get into the neutral wire when the dishwasher was "off", although plugged in, and b) why didn't it trip the RCD protecting that mcb?, andc) why doesn't my multimeter STILL show 70V potential across neutral and earth, even now I'VE provided a decent earth path?Alcazar[8-)] Link to comment Share on other sites More sharing options...
Chancer Posted September 3, 2006 Share Posted September 3, 2006 It was probably caused by a motor interference capacitor (I cannot remember the exact technical term but have some of them in my box of electrical bits) the one I am thinking of has 3 wires to be connected between live neutral and earth and is probably a dual R/C (resistor capacitor) network.I used to use them as a last resort when older washing machines/dishwashers caused burglar alarm systems to false alarm, usually when system was set at night and machine was on timer.Never needed them on modern machines so I concur that they are now fitted for C.E. emissions compliance."The machine was switched off" - probably by a single pole interruptor so a 50/50 chance that it isolated the neutral return path leaving the internals live (remember French electrics are not polarised). So a potential of 240v was present on the machine case (via the R/C network)and the disconnected earth wire. If this voltage was passed to earth by your wife, or by the now reconnected earth wire the tiny current resulting from the resistor would be less than the 30Ma needed to trip the RCD but enough of a tingle to frighten your wife. You (dependant on your resistance or footwear) may not even have felt it. I bet your wife no longer feels it now the earth is connected but is reluctant to try!The 70v ) I believe is the result the impedance of the meter on the miniscule current.Incidentally I also have a similar fault on one circuit (my house has 80 year old wiring and very few earths) which shows 190v and lights a neon tester similar to another posting here.Answering this post has finally put my mind at rest as the the problem that I have, but just to be sure I am going to lick my finger and give it a swift prod! (maybe I should wear clean pants!) - don't try this at home!!!!! Link to comment Share on other sites More sharing options...
Alcazar Posted September 3, 2006 Author Share Posted September 3, 2006 Thanks for all replies, although I'm still not sure if the dishwasher is the cause, since the fault was also at the very old socket, even with the dishwasher unplugged.I was amused at your comment about my wife being "reluctant to try it", JR, since I told her she had to once I'd got it cured. She was NOT happy, but did so, and felt nothing.After all............I couldn't feel it in the first place, so how else was I to know if it was gone?................Tsk, tsk, women!Alcazar Link to comment Share on other sites More sharing options...
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