Possible Appliance fault tripping RCD

[AJshep]

Just come back from an interesting fault.
Typical RCD tripping randomly. The customer was not using anything in particular, at any time.

Anyway I carried out Insulation Resistance on every circuit, each circuit was above 200M L-E and N-E and the
RCD tests were good.
The place was rewired in 2010 by a Domestic installer who did quite a nice neat job !!
I also removed the cover of the boiler to check for moisture and also carried out Insulation Resistance tests at 250v between L-E and N-E the readings were above 1M

Went round the kitchen carring out Insulation Resistance tests between L-E and N-E (only 250v just incase ) on the plugs for the Toaster, Fridge, washing machine etc.
Everything was above 200M

I'm the second spark to look at this and was just about to leave with my tail between my legs when the elderly customer mentioned that the last time it went she was talking to a friend on her laptop.

The laptop has recently been moved from upstairs to downstairs and is plugged in to a socket constantly turnned on and charging all the time because the plug is a little hard to get to.

So I got my test kit out and tested the IEC type lead that plugs into the Power supply

L-E 0.17 Mohm
N-E 0.26 Mohm
Obviously not good, and ive told the customer to get a new one, and not constantly charge her computer.

it's been disconnected all day because another member of the family went round earlier to unplug stuff to see if they could help. Has anyone ever had this before ?

I'm thinking as the lead gets warmer the fault gets worse causing the RCD to trip.

 

[Wilko]

I've had boiler pumps causing havoc with RCDs before. But if it was that, it should trip when it tries to run. Does the boiler have an internal pump? If so, it's possible that it wasn't in circuit when you were IR testing perhaps.

 

[AJshep]

I've had boiler pumps causing havoc with RCDs before. But if it was that, it should trip when it tries to run. Does the boiler have an internal pump? If so, it's possible that it wasn't in circuit when you were IR testing perhaps.

The Boiler was a Combi boiler ( again less than 8 years old ) with an external potterton 1 channel time clock for the heating.
So when I carried out a Insulation Resistance test i doubt the pump would have been included in the circuit.

If the problem remains I'll stick the link back into the boiler.
To be honest there wasn't a great deal on effected side of the DB.

Upstairs Lights ( no outside lights)
Downstairs Ring ( no outside sockets)
Boiler ( 1 x twin socket in loft, with a TV amp also plugged in)
Smoke Alarms ( 3x Aico, interlinked )

But the boiler has been running pretty much all the time keeping the house at a constant 20 degrees.

By the way here's a pic of the damaged lead !