RCBO keeps tripping without reason

[pads69]

The wiring in the house is split into separate circuits each with their own RCBO for
3 for lighting (separate for ground floor; upper floor; and basement)
3 for power (again as above)
1 for cooker
1 for shower
2 for fridge/freezers

The problem exists only on the ground floor power circuit.
Whenever the vacuum (two core) is switched on in any socket, the RCBO trips. It's not the vacuum as it dos not happen on the upper floor.

Occasionally the circuit trips on its own, or if the computer is switched on.

I've checked al the sockets for damaged or tapped wiring, but nothing found.

Does anyone have any suggestions please.

Thanks
Peter

 

[ricicle]

What about when any other large-ish load appliances are switched on ?

 

[pads69]

That's the really funny thing.

It always happens with vacuum (1320W). But remember not on upstairs circuit.
Kettle (2000W) plus microwave (1000w) no effect.
But sometimes the microwave on its own causes problem.
Sometimes computer (600w) switched on at socket but not powered up causes problem.
Then sometimes it just flips without any noticeable appliance change - say noticeable as the boiler may have fired up.

Baffling.

Peter

 

[nickjb]

I'd swap two of the power RCBOs over and see if it is the circuit or the RCBO.

 

[pads69]

Forgot to say that I had already tried that - problem stay with the wiring not with the RCBO.

!!!

Peter

 

[Robin0577]

Do you have one of those surge protector socket strips attached to the computer by any chance?

They are quite prone to tripping RCDs or RCBOs because they have capacitors connected from live to earth and from neutral to earth.

 

[ericmark]

I will guess on an earth - neutral fault it could be in any class I item using the same RCD or in wiring but step one is unplug all items and switch off any FCU then retry and see if still trips.

 

[ericmark]

I have found a bit of bread stuck in a toaster has caused the RCD to trip when kettle is switched on the bread is the fault but it needs kettle load before it trips the RCD.

Likely the start load of vacuum cleaner is enough current draw for neutral - earth fault to show up.

 

[ericmark]

Do you have one of those surge protector socket strips attached to the computer by any chance?

They are quite prone to tripping RCDs or RCBOs because they have capacitors connected from live to earth and from neutral to earth.

Very likely I agree but first make sure everything unplugged not just switched off as often no switch on neutral so needs to be unplugged.

Also any supply to shed, pond etc we hope through a double pole switch.

 

[pads69]

Firstly - all outside circuits are on a separate CU entirely.

I have unplugged or switched off (where via switched spur outlet - DP).

And the RCBO stays on for about 2 mins or more then trips.

This is now getting silly.

Peter

(writing this with computer & modem plugged in via extension to basement socket)

 

[JohnW2]

I have unplugged or switched off (where via switched spur outlet - DP). And the RCBO stays on for about 2 mins or more then trips.

If you really have unplugged (or DP isolated) everything from the sockets circuit in question, and since you have already demonstrated that the RCBO itself is not the problem, that doesn't leave much to point a finger at other than the fixed wiring of the circuit and its accessories (sockets etc.). I think you probably need an electrician with some test equipment.

Kind Regards, John

 

[PrenticeBoyofDerry]

I agree with John, if you have taken everything off load and as you have said the RCBO behaves when on other circuit, it can only be part of the hardwiring of the installation.
I this socket circuit a ring final or radial circuit?

 

[pads69]

Its a ring circuit.

 

[AdrianUK]

I agree with Eric..... my money is on a neutral-earth fault on the ring.

It only happens with the vacuum cleaner because it pulls such a large current (for a short time) as the motor speeds up. This current could easily be 40-50A for a few 10's of milliseconds ... something which you just cant match with the kettle. The microwave might be drawing large pulses as the magnetrons transformer energizes which could also make it trip.

Since you have eliminated the RCBO by transposition it must be down to a fault on this circuit..... you just haven't located it yet!

What is the route of the ring? Under the downstairs floor? Any hidden junction boxes? Any evidence of poor DIY work? Maybe a chco-block buried in the plaster which is now damp?

 

[PrenticeBoyofDerry]

First thing to do would be remove all loads then do an insulation resistance test on all conductors of the circuit, those readings could help diagnose the fault, then it would be a case of breaking down the circuit.
Has this circuit ever been sound to your knowledge?
If so has any recent work been carried out in the property, after which this fault started?