Just had the kitchen re-fitted and was getting electric shocks off the dishwasher when touching it and the sink. Measured at 150v, dropping immediately to 5-6v. The sink isn't earthed and has plastic pipes.
Found the socket wasn't earthed, the sleeve was pinched under the screw. Put this right and all is now OK.
What bothers me is it didn't trip the electrics. I didn't measure the current between the sink and d/w, but this voltage/current must now be grounding to earth and not tripping the electrics.
Can anyone explain?
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I'm not an electrician, but if you haven't got an earth it can't ground to it
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>> I'm not an electrician, but if you haven't got an earth it can't ground to
>> it
I think the point is that now there is an earth then voltages of the magnitude suggested in the OP should be sufficient to trip the CB?
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Having an earth wire at the plug does not necessarily mean there is an earth.
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It is current not volts which matter. A static shock (eg: from a carpet) could be several thousand volts. You may feel it - but it is not life threatening.
I understand that a current of as little as 1ma can be felt.
Electrical devices tend to have a trip current of 30ma.
So, it is entirely possible to feel an electric shock which is (presumably) not a lethal threat.
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I think I’d have the electrics checked by a qualified electrician
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It was definitely not a static shock, I get plenty of them. This was a voltage that could be measured with a cheap multimeter. Pity I didn't measure the current.
I presume it was earthing through the sink, water and then metal pipes.
I was just concerned the dishwasher body was connected to mains, but is this normal with modern 'touch' controls?
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If you think it was not static, you should definitely get a qualified electrician in.
Last edited by: maltrap on Wed 28 Sep 22 at 16:18
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Small earth leakage currents are pretty normal and an RCD won’t trip until you exceed 30mA, which in layman’s terms is “that b***** hurt”.
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Missed this before but:
As has already been said, a small earth leakage current is normal and is actually part of the design of most fitted appliances.
Where the power enters the appliance it is often filtered to reduce incoming mains spikes and also reduce outgoing mains noise caused by motors or internal switching. The filter is basically a couple of capacitors connected between live and earth and also neutral and earth. They present a high impedance to 50Hz but much lower impedance to higher frequency noise so the noise is dumped to earth.
The problem is that some filters use the chassis as an earthing point and if the mains socket earth is faulty the chassis will be at a voltage half way between live and neutral.
You can buy a socket tester that plugs into any 13A socket and indicates via leds whether it is wired correctly. Only cost a few quid.
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FF and Kevin. That seems to exactly explain what happened. The guy responsible for wiring the socket turned up with one of those testers that immediately showed the problem. I suppose it could have been a different matter if a fault had caused the case to go live.
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You can buy a socket tester that plugs into any 13A socket and indicates via leds whether it is wired correctly. Only cost a few quid.
You get what you pay for. A socket tester will only show that its connected - not that conductors are rated correctly, ring circuits are complete, or if high resistance joints (fire risk) exist. Earth cabling needs to be 'correct' for earth leakage (safety devices) devices to operate correctly.
Whilst any test is better than no test, you can get false reassurance. Particularly if moving into a 'new' property.
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Slight thread drift, but still on topic with regard to testing.
As a qualified PA Tester. I've recently come across quite a few IEC leads ( cdn.aws.toolstation.com/images/141020-UK/800/21431.jpg ) that are wired incorrectly.
Basically the live and neutral connections swapped, resulting in the live wire not going through the fuse. That's if the plug has a fuse at all, because I've also had instances of moulded 3 pin plugs without any fuse at all ( bs1363.fatallyflawed.org.uk/assets/images/Illegal_plug_2n.jpg ) or a metal bar fitted in place of a fuse.
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As a PA tester, how do you determine the current rating for the cable of an IEC socket to a 13A fused plug? ie whether the correct fuse is fitted for cable rating?
(without cutting the cable :)
I have tried to find where the 'polarity' is defined for the floating socket - cannot find it?
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>> As a PA tester, how do you determine the current rating for the cable of
>> an IEC socket to a 13A fused plug? ie whether the correct fuse is fitted
>> for cable rating?
Would that not be determined by the appliance connected eg PC, screen etc?
The last Civil Service office I worked in had a power rail on the desk connected to a mains socket in the floor.
Each socket was fused at 2.5 amps. OK for a PC etc but we'd a constant battle with staff plugging in fans or auxiliary heating or the cleaners using them for Henry the vac. Any of those fused the socket.
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I spent best part of a year working in a chemical plant in the North East (ex-ICI) - they had really stringent H&S rules. The PAT testing one seemed the most bizarre to me. We were installing new desktop computers and screens. The old electrician chappie determined that all cables had to be tested, at the build area inside the plant. That was a weekend job as he was so busy during the week...
Then when we deployed the machines the cables had to be tested again, in the actual socket they were going to work in. He actually allowed us to get the test equipment and some training so we could do it, otherwise the project would have never ended.
There's no doubt they were working with very volatile products but the H&S did seem to me to be a little OTT, and a little inconsistent - you had to have three points of contact when using stairs (so carrying a box upstairs was a no-no) - and you weren't allowed to be wearing high heels on stairs, which didn't bother many of my engineers :-) - but there was nothing stopping you walking the length of the entre office block from the coffee room to your desk carrying boiling water in a mug...
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>> I spent best part of a year working in a chemical plant in the North East (ex-ICI) ...
...Wilton?
I did a University session of power-station evaluation there in the early 70's (It was either there or Windscale, but the reputation of free-flowing liquid entertainment at Wilton tipped the balance).
A fairly conventional steam-turbine power station, but it took much of the burnable chemical-production by-products as fuel. (It supplied the site, but even in those days sold excess capacity to the grid).
The whole site smelt pungently of chemicals, and we were regaled with one story about a diesel powered vehicle which, once the engine was nominally turned off, continued to run on the fumes ingested from an adjacent leaky pipe, raced it's engine until it backfired, and blew up part of the plant.
I suspect the story was embellished somewhat, but we were certainly shown the on-site vehicle workshops where compression-ignition vehicles were being fitted with additional speed-governers.
Working in the turbine-hall the day after a bender and with a raging hangover wasn't the greatest day of my life.
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Nah, proper chemicals place at Billington, though ISTR there was a research bit at Wilton.
From what I recall there was (amongst other things) cyanide running through the outdoor pipes all over the site. If you saw anything which might indicate a leak you hit the alarm. If you were outdoors and inside the plant perimeter and the alarm went off you had to strip off completely and get under one of the cold water shower which were, among other places, on the bottom of the pipes running round the site. The cold water apparently closes your pores and lessens the risk (of death, I suppose).
There was an H&S film describing how to behave, and there was a bloke from the plant who couldn't wait for his 5 minutes of fame by stripping off and doing the shower bit -probably a bit of an exhibitionist really!
There was an annual shutdown for some weeks when a specialist team from Texas came over a d cleaned the pipes.
They had quite an ongoing problem with theft of some of the live high voltage (= very thick) copper cabling
But to be fair, they had a great safety record with no significant incidents for over a year, as far as I recall.
Last edited by: smokie on Wed 5 Oct 22 at 16:18
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>> Nah, proper chemicals place at Billington, though ISTR there was a research bit at Wilton.
>>
Billingham?
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>> Nah, proper chemicals place at Billington
...Billingham, I suspect ;-)
Wilton was (and still is) a massive, proper chemicals site.
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>> There's no doubt they were working with very volatile products but the H&S did seem
>> to me to be a little OTT, and a little inconsistent -
I was working on a contract at a BP data centre for their dealing room, They gave me a desk, and the H&S woman had to sign me off in proper posture, keyboard, and screen use. I was supplied with a new multifunctional ergonomic office chair.
A month later Deepwater Horizon exploded killed loads and destroyed the local environment due to appalling safety management.
Last edited by: Zero on Wed 5 Oct 22 at 15:15
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>> As a PA tester, how do you determine the current rating for the cable of
>> an IEC socket to a 13A fused plug? ie whether the correct fuse is fitted
>> for cable rating?
>>
>> (without cutting the cable :)
As Brompt says, the fuse rating is determined by what appliance the IEC lead is connected to. Trouble is, as they are interchangeable between a kettle, PC monitor, Desktop PC, and many other electrical items, the unwise never bother to check the fuse rating if they unplug it from one appliance and plug it into another appliance. Something like a kettle should have a 13 amp fuse, but a PC monitor only 2 amps. Most people just leave a 13 amp fuse in the plug.
The latest advice from the IET Code of Practice says to only use two different fuse ratings. i.e. a 3A fuse should be fitted where the appliance is rated at 700W or less, and a 13A fuse when the appliance is rated at more than 700W.
However, I'm old school and still work on the principle of fitting the correct rated fuse for the appliance it's connected to at the time of testing.
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The fuse is mainly to safeguard the wiring upstream of the socket back to the fuse board.
The risk is that a fault or short circuit in an appliance would otherwise create a fire and electrocution risk if the current carried exceeds the capacity of the cable.
Whether a 2 or 13 amp fuse is fitted makes little difference to lethality - a current in the low milliamp range will kill.
The main reason for the choice of fuse has more to do with the plug to appliance cable - a desk light or PC is likely to be 3amp not 13amp as would often be used for a kettle or washing machine,
Last edited by: Terry on Wed 5 Oct 22 at 15:01
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Some of the cables supplied with low current kit have very thin conductors and a 3A fuse, very easy for them to be repurposed for kettle use and a 13A fuse fitted. The article below shows a marking that should be on a UK moulded 13A plug - just checked several and none have that marking!
That article also answers one o my questions - about using a 10A rated cable with a 13A fuse - allowed if less thaan 2m long!
www.pat-testing-training.net/articles/fuse-ratings.php
Terry -""The fuse is mainly to safeguard the wiring upstream of the socket back to the fuse board."
NO the fuse in plug is to protect cable downstream! The fixed wiring is protected by the consumer unit. Fuses DO NOT protect against electrocution risk!
and if you want a laugh look at
www.touchstone2c.co.uk/products/connected-fidelity/c-f13a-220-240vac-uk-plug-fuse-13a/
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Never understood the British fixation with fuses. The continental plugs don't seem to need them but maybe the consumer units are more reliable.
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I always thought it was historical. The UK adopted the ring main as a standard after the war, to save copper, I believe, and as a result fused plugs were necessary to protect the circuit. Pre war 15 amp and 5 amp plugs were unfused.
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>> Pre war 15 amp and 5 amp plugs were unfused.
As were 2 amp plugs. I've still one of those universal plugs, where you can use it for 5, 15 and 13 sockets by slipping out different pins.
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I had 15 amp wall sockets AND 13 amp sockets in ye olde cottage.
I used the 15 amp unfused jobbies for the table lamps.
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We had Wylex when we moved in 50 yrs ago. Remember them ? Two flat pins and a round centre one !
Local elec trade place still sells 5amp round pin. I bought some for use on the model railway 12V DC system.
Ted
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The electricians put me some 5A round pin plugs in for bedside and floor lamps. I never thought to ask about the fuse aspect
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The whole of Nottingham University was wired with Wylex sockets when I was there.
The hall porters made a fortune selling replacement plugs to the unfortunate temporary residents.
Last edited by: tyrednemotional on Thu 6 Oct 22 at 15:07
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>>I've still one of those universal plugs, where you can
>> use it for 5, 15 and 13 sockets by slipping out different pins.
I'd forgotten those. My Mother used to have a peripatetic hairdresser do a 'shampoo and set' on a regular basis. He had a universal plug on the space helmet type hair dryer he kept in his car.
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30+ years ago IBM fitted 13 amp fuses to pc mains cables.
The reason was that the cable could support 13 amp for a kettle or 3 amp for a light/PC etc etc
The fuses in the PC were there to protect the PC.
The cable from the socket to the PC was looked after by the 13 amp fuse.
Some customer H&S people insisted on the fuses being changed before the end user was allowed to switch it on.
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Dodgy mains earth - maltrap
