Joeman Posted May 14, 2015 Posted May 14, 2015 I was measuring the width of my kitchen tonight with a metal tap measure. I hooked the tape measure over a metal faced plug socket. As the tape touched the spout of my metal kettle, sparks appeared! Thinking the kettle or the plug socket might be live, i very cautiously touched each one in turn to see which one would give me a shock.. but both were fine - no shocks So, whats going on? The kettle is on the main kitchen ring circuit, and the plug socket is the main switch for the oven on the oven circuit. So it seems i have a potential difference between the earthed kettle and the earthed socket face on different circuits.I have a recent consumer unit with everything connected to RCD's but non of the RCDs tripped out when the sparks appeared.Any sparkies on the forum? is it normal to have a potential difference between earths on different circuits in a domestic installation?Tomorrow i'll be getting the multimeter out... Quote
Tankbag Posted May 14, 2015 Posted May 14, 2015 I'm not a sparky but my mate had a similar thing between sockets I vaguely remember it traced to a fault within his kitchen wiring, I know thats not much help but it was deffo a fault. Quote
Joeman Posted May 14, 2015 Author Posted May 14, 2015 I'm not a sparky but my mate had a similar thing between sockets I vaguely remember it traced to a fault within his kitchen wiring, I know thats not much help but it was deffo a fault. cheers. so im not the first!IVe got a tester plug with three lights on that tests the connections. i'll dig that out tomorrow and test all my sockets.its strange that i get sparks, but cant feel any shocks, and dont trip the circuit breakers...I must admit, in not brave enough to touch one hand on the kettle and the other to the socket though - not until ive got my meter on there and know what to expect! Quote
Tankbag Posted May 14, 2015 Posted May 14, 2015 I'm not a sparky but my mate had a similar thing between sockets I vaguely remember it traced to a fault within his kitchen wiring, I know thats not much help but it was deffo a fault. cheers. so im not the first!IVe got a tester plug with three lights on that tests the connections. i'll dig that out tomorrow and test all my sockets.its strange that i get sparks, but cant feel any shocks, and dont trip the circuit breakers...I must admit, in not brave enough to touch one hand on the kettle and the other to the socket though - not until ive got my meter on there and know what to expect! Up the life insurance on her & get the missus to do it Quote
Joeman Posted May 14, 2015 Author Posted May 14, 2015 curiosity got the better of me. I just braved the rain to get the multimeter from the garage. Im reading 55volts between the oven socket and the socket on the kitchen ring. when i Isolate the oven, the voltage drops from 55v down to 2v.So tomorrow i'll take the socket apart and have a look for anything obvious. hoping its not one of the applianced (oven or hobs) putting power back down the earth, but if it was, surely that should trip the RCD? Quote
rennie Posted May 14, 2015 Posted May 14, 2015 I'm a sparky (sort of) I haven't got a clue without being there!But something is wrong! can you disconnect the cooker/appliance easilyand see if fault disappears?edit I've read it properly now,Neutral fault on the cooker? Quote
Joeman Posted May 14, 2015 Author Posted May 14, 2015 I'm a sparky (sort of) I haven't got a clue without being there!But something is wrong! can you disconnect the cooker/appliance easilyand see if fault disappears?edit I've read it properly now,Neutral fault on the cooker? There is only the cooker and hobs attached to the switch. The cooker is integrated, so i'll need to lift it out of the cabinet - a heavy lifting job for tomorrow.i'm hoping its not a faulty appliance, as thats gonna cost me money! weird that the RCD is not tripping though... Quote
rennie Posted May 14, 2015 Posted May 14, 2015 The breaker may only trip if it's an earth fault! depending on it's type.Hence me suggesting a neutral fault.It has to be the oven or the hob because the fault is going awaywhen disconnected. Quote
Fozzie Posted May 15, 2015 Posted May 15, 2015 I'm a sparky This situation sounds pretty weird. Could you upload a picture of the kitchen area where it happened, and maybe of the inside of that metal faced socket?If the two circuits are earthed properly there shouldn't be a potential difference, unless somehow mid-circuit the connection to the kettle interrupted the earth going from that socket and it earthed into the kettle. But that is still a short circuit and an MCB should have popped its clogs over it. Unless of course the kettle being earthed properly meant that it couldn't find a path through the kettle, which will have sent the casing live, but was still earthed by the kitchen ring circuit. But that's just speculation.You'd need to do some tests to see if there is an earth of neutral line fault. Sparks can fly and MCB's not trip, but usually only when they make a solid connection to something. So it sounds like you managed to make the kettle part of the circuit without it being detected as a short circuit... Impressive Quote
Joeman Posted May 15, 2015 Author Posted May 15, 2015 Yep, its weird!! And if I touch either the socket or the kettle I feel no shock, so neither are at full 240vIts only if I touch both the kettle and socket together, completing the circuit do I get a shock (tried it this morning). The multimeter reads 55volts between the kettle and the socket, so I guess its enough to feel a tingle but not enough to trip the breaker.More investigation needed.. Quote
Stu Posted May 15, 2015 Posted May 15, 2015 Is it just that one socket? Or is it the same if you move the kettle to another socket say upstairs? It could be a fault with the kettle and your just earthing it with the metal socket Quote
Fozzie Posted May 15, 2015 Posted May 15, 2015 Yep, its weird!! And if I touch either the socket or the kettle I feel no shock, so neither are at full 240vIts only if I touch both the kettle and socket together, completing the circuit do I get a shock (tried it this morning). The multimeter reads 55volts between the kettle and the socket, so I guess its enough to feel a tingle but not enough to trip the breaker.More investigation needed.. Stu mentions above, just try crossing it against other metal items, and then use the kettle to do it with other circuits.You will narrow down if the kettle is faulty. But if the kettle was acting as an earth, it should be tripping the MCB. But then again, at 55v the current is probably tiny. Quote
Joeman Posted May 15, 2015 Author Posted May 15, 2015 Problem solved chaps!So I took off the cooker switch and the terminals inside were corroded. Where its located it gets a lot of steam from the kettle.I replaced the cooker switch but before connecting the earths from the hob and oven i measured the voltage between their earth leads and the supply cable's earth. The oven's earth cable seems to be at abouy 50v and the hob's earth is about 20v.So I think the metal socket wasn't correctly earthed to the supply cable earth, but it was earthed to the oven and hobs. So the metal face plate of the cooker switch was at 50v that was leaking from the oven.The kettle socket is correctly earthed so when the metal tape went between the cooker switch face (at 50v) and the correctly earthed kettle, 50v sparks flew!!Ive got a socket testing plug so I'm testing them all now.. Quote
RantMachine Posted May 15, 2015 Posted May 15, 2015 ...and that was the last that they ever heard from Joe.http://www.crnc.org/wp-content/uploads/2015/03/obama7.jpgShotgun the KTM Quote
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