Tripping RCD nightly

[davidjpowell]

Hello I have a frustrating problem, that I am hoping that you may help me with.

I bought a new computer before Christmas. It has since that time developed a fault that used to be taking place every 6 weeks. It's now down to anytime the PC is plugged in.

The fault typically occurs in the early morning - Can't be sure when as I am normally asleep when the RCD in the main consumer box trips. The RCD will not reset until I unplug the PC.

I have tried several different PSU's, I have moved it onto a different socket, and it has been back to the retailer where it ran for 5 days with no problems.

I don't think it is related, as I have tried from a different socket, but the PC is normally located in my home office which is run off the ringmain in the house and has a consumer box which never seems to trip.

If I leave the PC unplugged the RCB will not trip.

The RCB is rated at 80A 30mA

I would be very grateful for an help on this..

 

[Chri5]

A single PC should not cause anything like enough leakage to trip a rcd- my initial thought was of a carp psu, but you have covered that.

Is the PC plugged in direct or via a 4 gang extension socket ?

A quick solution would be to stop wasting 30w ph and turn the PC off at night

Have you tried turning everything off on the circuit other than the PC and seeing if it still happens ?

Have you any test paper work for the current system ?

 

[davidjpowell]

Forgot to say this will occur even if the PC is switched off.

PC is plugged in with a new surge protected adapter. But it has also happened when in the house and plugged directly into a socket.

No test paperwork for the current system.

It's weird as it seems entirely linked to the combination of the supply in the house and the PC. Remove either and there is no problem

Have not tried turning everything off - will do on sat eve as it means powering down my work server

 

[Chri5]

What IT kit have you got on the same ring ?

You mention a PC, now a server, next a media unit, a large switch, cisco hub and ?????

Could you confirm what you have on the circuit by way of high leakage equipment ( kit with psu's ).

A long shot would be too much, and that you need to consider high integrity earthing or a dedicated 20 amp radial just for the IT items.

 

[JACKC]

A pc as mentioned above should not have enough earth leakage to cause a trip. I would suspect you have lots of circuits with leakage and the pc is what is breaking the camels back. This is difficult to locate without the correct test equipment. I would start with conducting a ramp test on your rcd and seeing what is wrong with your whole installation as you have ruled out the pc as faulty. Not much help I know but it will need a sparky's help.

 

[davidjpowell]

Hmm let me see. I don't think I am going to like the way this is headed.

In the office there is a Server, monitor (off most of the time) laptop (should be off but usually is not), Monitor, unmanaged switch, bt hub and printer.

 

[JACKC]

each piece of IT equipment has a functional earth leakage current. May be that with all of that IT a high integrity circuit needs installing.

 

[davidjpowell]

sounds expensive?

 

[JACKC]

get a sparky in and discuss the options, he will be able to advise on what you tell him and more importantly what he can see. could be a simple task to convert circuit to high integrity, could be a rcd fault. Either way it will involve more than just advise on here.
Sorry

 

[ColJack]

is it only the sockets that trip out ( you say it's an 80A and that sounds like a split load board rather than one with rcbo's.. )

do you have any electric heating? immersion heater?

we need to see the layout of the fuseboard to identify any potential causes.

any new installs recently? outside lights perhaps?

 

[davidjpowell]

There is a single electric heater.

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[ban-all-sheds]

each piece of IT equipment has a functional earth leakage current. May be that with all of that IT a high integrity circuit needs installing.

It will still leak - will do nothing for the RCD tripping.

Needs a separate circuit, or maybe two.

 

[ColJack]

pics no use we need to clearly see the lables for the breaker.. do multiple shots if needs be.. and use macro mode on the camera..

 

[bongos]

Take a pic of the labeling on the RCD protected (green) circuits that are in the CU.

It's likely that the combined earth leakage of all those circuits on the RCD side is causing the RCD tripping. The additional earth leakage caused by the IT equipment may be pushing it over the edge.

Although that RCD is rated to trip at 30mA, I understand that the regs stipulate it can trip anywhere between 16-30mA to pass. If it is on the sensitive side then this would cause you more problems.

The other possibility is earth leakage due to an intermittent fault. Have you done any DIY recently? No nails through cables or anything like that?

Any outside circuits on the RCD protected side (outside sockets/light etc)?

Access to an insulation resistance tester and a RCD ramp tester would go a long way towards solving this problem but you'll probably need to call out an electrician for that.

 

[Chri5]

If the general consensus (after a site view) is that the circuit causing the leakage problem is the study, then there is a solution worth trying before going down the route of a dedicated radial or even a high integrity circuit.

It might be worth getting an RCBO, taking one of the existing circuits out the direct (non rcd) side and swapping them over. So you end up with the leaky circuit running on its own RCBO (which does the job of both a RCD and a MCB)- and the other circuit can then be shunted over to the now spare position on the RCD side.

High integrity circuits have connections for both the twin and earth cables earth wire / cpc and also for a earth loop cable that runs to extra terminals on the sockets.
Updating the whole existing circuit would be madness, since the 4mm earth cable (it might be 6mm- I can't remember ) would have to travel to all sockets on the ring and back.

There's a slight problem with providing a new dedicated radial circuit- there appears to be no room on the existing board


And a final thing, try ditching the mains protector for the weekend- some of them are very poorly made and it would be good to eliminate it completely.