RCD tripping out caused by Dishwasher


Postby sophie » Tue Oct 20, 2009 6:01 pm

Hi There,

I dont know if anyone can offer any advice but would be much appreicited
We brought our house just under three years ago and have until recently a few minor electrical problems i had noticed in the past that if a light bulb went in the lounge it would trip the RCD in the fuse box and we have had trouble with the extractor light every time i replaced the bulb it would blow either straight away or after a few days i dont bother any more.
Last week the RCD tripped out again for no reason so i swiched it back on again then a few days later i went to put the dishwaser on and it wouldnt come on so i presumed that there was a fault with the dishwasher the next day the RCD tripped out again this time it wouldnt come back on again so all the sockets in the house wouldnt work i unplugged the dishwasher from the main socket and tried the RCD again this time it went back on.

We had a friend pop up to take a look he is an electrician he put a prob in the dishwasher socket and this caused the RCD to trip out again so looks like an instalation problem somewhere rather than the dishwasher he has advised us to contact the house builder but i was wondering would we be covered for anything now we have lived in the house for 2 years, 10 months not sure what to do next, or should i contact insurance company dont want to have to pay out a fortune if it was the house builders fault has anyone any advice or help they could give. Thanks Zoe
sophie
Rank: Labourer
Progress to next rank:
25%
Posts: 2
Joined: Tue Oct 20, 2009 5:31 pm

Sponsor

Simply Build It

Postby ericmark » Wed Oct 21, 2009 12:18 pm

Unfortunately when a RCD trips it can be very hard to isolate why.

First a little to how an RCD works. It measures the amount of electricity out on one wire and makes A comparison with the electricity going back on the other.

If the two amounts are within 15ma of each other it assumes no electric is going to earth.

When a fault allows a connection between the line wire and earth this very quickly trips the RCD.

But when the fault is between neutral and earth the resistance needs to be very low before it trips and tripping is also very dependent on the power being used.

So for example a faulty hair drier with a neutral earth fault left plugged in may not trip the RCD. But as the dish washer is used and the power used goes up then and only then the hair drier will trip the RCD.

Of course the first impression is that the dish washer is at fault.

So step one is to ensure everything is unplugged before blaming the installation as a whole as being faulty.

Immersion heaters and other permanently connected equipment can really throw a spanner in the works as when they become faulty it can blow the fuse but the fuse is only on the line wire so unless switched off it can cause the RCD to trip as other items are used.

The RCD marked as 30ma has to maintain power with a 15ma drain to earth and to trip at 30ma but exactly at what point between 15 and 30 is not stipulated so in theory it may trip at 16ma.

This is not very much and every piece of IT equipment tends to have some electronics to stop interference and these allow a little leakage of power to earth. Although one item will not trip a RCD when you add together maybe 20 items all with a little bit then the combination may cause the RCD to trip.

314.1 regulation says the power must be split into separate circuits to reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation.

In theory this means that if all your equipment is sound and due to the adding up of all the little stray currents the RCD trips the installer would be at fault for not using enough RCD's in the installation and where just 2 RCD's are used it could be argued that the builder is at fault.

But in reality you would be very unlikely to win the case. Since builders do like to keep customers sweet if he still has an electrician on site he may agree a half way with you and if you provide the RCBO's his electrician may fit them but I would not hold your breath.

The likely hood of the fault being in the building is very slim and really only by using expensive meters can you be certain it is in the building and not in the equipment. The test set normally used costs around £750 so if you can't find the faulty unit then really you will need an electrician to isolate exactly where the fault is.

There is also a device called a PAT tester which can be used to test each item of equipment to see it it's faulty but again around £750 for tester.

So first unplug everything not in use and only plug in when required and that way you may with a bit of luck find what is causing the fault without calling an electrician.

As to bulbs with extractor fans the back EMF can cause the bulb to blow sometimes when the extractor switches off especially when using small size bulbs so try a bigger bulb.

Does this help?
ericmark
Rank: Project Manager
Posts: 1796
Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.

Postby sophie » Wed Oct 21, 2009 4:07 pm

Hi,

Thanks for the help and advice i have told my husband to see if he can take the plug of the dishwasher and check the fuse and to see if there are any loose wires in the plug also he did get an extension lead plugged the dishwasher into the extension and plugged the extension into another socket in the Kitchen and this caused the RCD to trip again which would suggest a fault with the dishwasher electrics or plug.
sophie
Rank: Labourer
Progress to next rank:
25%
Posts: 2
Joined: Tue Oct 20, 2009 5:31 pm

Postby ericmark » Fri Oct 23, 2009 1:23 pm

Seems I have not explained very well.
Because a dish washer uses a lot of power it can high light a problem with some other item when it is not faulty it's self.
This is due to a neutral earth fault normally.

So unplug every other item in the house then try dish washer.

If when only item plugged in it still trips then either the dish washer is faulty or the house power is faulty.

Try a large item like a kettle in the same socket. If it only trips with dish washer likely dish washer faulty.

If also trips with kettle then likely house wiring faulty. Or you missed something and there is still something switched on or plugged in.
ericmark
Rank: Project Manager
Posts: 1796
Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.

Display posts from previous
Sort by
Order by



  • DIY How to Project Guides

  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!



 


  • Related Topics