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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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live dish washer
I would be grateful for some advise regarding a fitted dish washer. I
was in the process of removing it from its kitchen cabinet when I had an electric shock on touching both the washer's metal interior and the stainless steel sink. I checked which was live and using one of those cicuit testing screw drivers it was the dishwasher. Neither the circuit breaker or the main RCD tripped. I have had a good look at the wiring in the dishwasher and can find no obvious fault. I have also tested the diswasher regularly and it has not been live again. I assume the shock was caused by me shorting the circuit between the then "live" dishwasher and the sink which I again assume is connected to earth via the cold water pipe. Can anybody offer any advice as to what could have caused the fault as I would have thought that if the dish washer was faulty it would be "live" on a regular basis. |
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live dish washer
if the dish washer was faulty it would be "live" on a regular
basis. Was it in a particular place in the cycle at the time ? -- Please add "[newsgroup]" in the subject of any personal replies via email --- My new email address has "ngspamtrap" & @btinternet.com in it ;-) --- |
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live dish washer
Geoff wrote:
I would be grateful for some advise regarding a fitted dish washer. I was in the process of removing it from its kitchen cabinet when I had an electric shock on touching both the washer's metal interior and the stainless steel sink. I checked which was live and using one of those cicuit testing screw drivers it was the dishwasher. Neither the circuit breaker or the main RCD tripped. I have had a good look at the wiring in the dishwasher and can find no obvious fault. I have also tested the diswasher regularly and it has not been live again. I assume the shock was caused by me shorting the circuit between the then "live" dishwasher and the sink which I again assume is connected to earth via the cold water pipe. Can anybody offer any advice as to what could have caused the fault as I would have thought that if the dish washer was faulty it would be "live" on a regular basis. Is the sink earthed ? Some sinks and tap combinations are insulated from each other by rubber washers sandwiched between the tap body and the sink itself. Is the socket that the dishwasher is connected to earthed properly ? TURN THE POWER OFF at the mains. Open the socket and check that all the wiring is in the correct places and fully tightened. Was there any other appliance plugged in or running while you got the shock ? It could be that another appliance has a fault or low resistance and it caused the earth to rise slightly and give you a tingle from the potential difference. Do you have any low voltage lighting or other type of light fitting that are connected to the ring circuit ? Where they switched on at the time ? --- http://www.basecuritysystems.no-ip.com Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.692 / Virus Database: 453 - Release Date: 28/05/04 |
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#9
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live dish washer
There is on an odd collection of circuits with one single
socket on its own circuit! It is normal to have a dedicated circuit without RCD protection for the fridge/freezer. This ensures that an earth RCD trip elsewhere in the house doesn't ruin all your food. Also, there is no earth in the lighting circuits and there appears to be no earth bonding for any of the metal objects in the house, including the sink next to the dish washer. The kitchen sink does not need to be bonded. Indeed, it is better to insulate it by using plastic supply pipes if possible. That way, it doesn't act as an earth, so you don't get a shock through it. This will have to be rectified as I have recently purchased an electric shower. Yes, you should install supplementary bonding in the bathroom. However, again it is safer to use plastic pipework. If all plastic pipework is used, then the baths and radiators don't need bonding either. The electric shower DOES need cross bonding. I thought there was a problem with the RCD as several times it has tripped when I was doing work to individual circuits. I had assumed that as I had popped the circuit breaker for the circuit then that ciruit was comletely "dead". Nope. The MCBs do not fully isolate the circuit, they just cut the power. Personally, I always isolate the whole thing at the main switch (unless it is an DP RCBO circuit, but these are rare). now understand that, if you short the earth and neutral then the RCD will trip. I stand to be corrected! Prepare to be corrected! Depending on the type of your earthing arrangements, a neutral/earth short is unlikely to draw enough current to blow the RCD. However, it may provide a sneaky backdoor for the neutral current from a different RCD protected circuit to bypass the RCD and set it off. Such an effect may be dependent on the current usage of that circuit and might only manifest when a beefy appliance is turned on. I can't recall whether there were any other appliances running at the time although I dont think there were. As to the "shock" it was more of a jolt. The machine was not actually on at the time. It could easily just be a faulty earth, rather than a more serious fault. Obviously, it must be fixed. Christian. |
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live dish washer
On Wed, 2 Jun 2004 12:10:50 +0100, "Christian McArdle"
wrote: The kitchen sink does not need to be bonded. Indeed, it is better to insulate it by using plastic supply pipes if possible. That way, it doesn't act as an earth, so you don't get a shock through it. Hmmm, I would have thought that if a kettle or radio lead fell into a metal kitchen sink it would be better off if it was earthed. cheers, Pete. |
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live dish washer
Hmmm, I would have thought that if a kettle or radio lead fell into a
metal kitchen sink it would be better off if it was earthed. I'd still prefer insulated and with all sockets on an RCD. Even if the non-earthed sink doesn't provide sufficient earth leakage to blow the RCD, it is easy enough to just turn off the appliance before retrieval. Besides, you should be using kettle leads. It is much safer to use a cordless kettle with a short lead to the base that won't even reach the sink. Christian. |
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