RCD keeps tripping for no apparent reason.

[MikeyDay]

Hello guys, 

Before I call in an electrician, I want to see if I can do anything (As a DIYer).

So basically, I have a RCD in the kitchen, where all the switches are, all my sockets randomly stopped working (all light switches are still working), so I check my RCD and its turned off, so I switch it back on and continue what I'm doing, after about a minute the RCD turns itself off again, so I unscrew all my plug sockets and check the wires, everything seems correct, no loose wires or anything of the sort, so I try and test a few things out, and it seems using my microwave, toaster, oven and kettle (even using them separately) will cause the RCD to trip.

So I decided to keep on testing, I figured out, if I turn all my upstairs sockets off (using 1 of the socket switches in my fuse box) then all the downstairs sockets will work flawlessly, but if I then turn the sockets back on that are upstairs, the problem will start again.

I've got a feeling I'll need to call in an electrician, but I hope that maybe, just maybe, I could even fix it.

Thanks.

 

[sparkytim]

Hi try unplugging ALL appliances upstairs and see what happens

 

[Andy™]

most likely  a neutral to earth fault

 

[Doc Hudson]

Quite probably just a faulty appliance connected to one of the circuits that the RCD also protects. If the RCD supplies more than one circuit then a fault cannot be isolated by simply turning one of the MCB's off. As all of the neutral and earths are still connected together at the fuse box. RCD's detect leakage to earth in very, very, very, small amounts of current, (in the range of miiamps). Your big problem is that a circuit with a Neutral to Earth fault that is turned off, can still cause an RCD to trip from power flowing to any other circuit that shares the same RCD. You have no easy means of isolating the neutrals from each circuit, by just using the switches on the front of the fuse box. Dedicated RCD's per circuit, (items called RCBO's), are the only way to be sure which circuit has the genuine fault that has tripped the device. So its not impossible, but it can be a bit tricky trying to trace the genuine cause.

Doc H. 

 

[MikeyDay]

Hi try unplugging ALL appliances upstairs and see what happens

Hmm, well, I did just what you said, I unplugged every appliance upstairs and turned the socket switch back on, I tried using the appliances in the kitchen, the toaster, oven, microwave and kettle, and the RCD did not trip.

Kinda feel like a ***** now, seems like an easy fix I was hoping for, hopefully this fixes it, if it happens again and the method I just used stops working, I'll report back and let you guys know.

Thank you so much guys, you may have saved me a bit of money calling in an electrician.

 

[MikeyDay]

most likely  a neutral to earth fault

Quite probably just a faulty appliance connected to one of the circuits that the RCD also protects. If the RCD supplies more than one circuit then a fault cannot be isolated by simply turning one of the MCB's off. As all of the neutral and earths are still connected together at the fuse box. RCD's detect leakage to earth in very, very, very, small amounts of current, (in the range of miiamps). Your big problem is that a circuit with a Neutral to Earth fault that is turned off, can still cause an RCD to trip from power flowing to any other circuit that shares the same RCD. You have no easy means of isolating the neutrals from each circuit, by just using the switches on the front of the fuse box. Dedicated RCD's per circuit, (items called RCBO's), are the only way to be sure which circuit has the genuine fault that has tripped the device. So its not impossible, but it can be a bit tricky trying to trace the genuine cause.

Doc H. 

Thanks for both of your replies, much appreciated.

I just hope this fixes it for awhile, and sorry if i wasted your time, you've all been a great help, i'll report back if this continues.

 

[Geoff1946]

I became involved in tracing a random RCD trip fault whilst visiting a relative in France. It was a single phase two RCD panel, similar in most ways to many of ours, though bigger to accommodate  lots of radials, BUT all their MCBs were double pole.

This made fault finding SO much easier. 

Is there any good reason why we don't use double pole MCBs?  

 

[Evans Electric]

Is there any good reason why we don't use double pole MCBs?  

Must be tradition  from the fuse in the live  I'd guess  .     Plus doubling the board sizes.  Plus expense. 

 

[Geoff1946]

Must be tradition  from the fuse in the live  I'd guess  .     Plus doubling the board sizes.  Plus expense. 

The French MCBs were no bigger than ours. I can't recall exactly how the busbars were arranged, but the only reason the panel was bigger was to accommodate more (radial) circuits.

Must be similar (busbar spacing) for RCBOs, but they are too recent for me.

 

[Evans Electric]

Are they marked up as DP   Geoff  or could it be just a loop in terminal ? 

 

[Geoff1946]

Are they marked up as DP   Geoff  or could it be just a loop in terminal ? 

Its a few years ago now, but I'm fairly sure they were Dp.

 

[Geoff1946]

Are they marked up as DP   Geoff  or could it be just a loop in terminal ? 

They were definitely double pole but I think my memory is playing tricks on their size. They must have been double width as well. (At least google can't find the ones I was visualising)

However, my main point was how much easier fault finding was.

 

[Phoenix]

The ones I've seen available in this country were SPSN. (Single Pole Swicthed Neutral). I.E They break both conductors, but only the current on the live side flows through the coils and bimetalic strip that can trigger the tripping. I have a feeling in france they might be true DP as they are less concerned about us on the importance of polarity!

Hager were trying to market SPNSN to housing associations around the time the 17th edition came in, on the premise that faced with a tripping issue, the tennant could phone up the property help desk, who would follow a script to advise them to switch off all mcbs, reset and bring in one by one, etc. Following them to be without only one cirucit and the electrician to be sent out doing normal working hours, instead of out of hours. It appears that they were not sucessful in their marketing!

 

[roys]

Slightly different but SBS Daves RCBO’s are DP with a dual bus bar running along the bottom, very neat and as stated fault finding is a lot easier.