Meter box RCD tripping

[MickC67]

The meter box RCD for my power outlets in my home trips at random times, approximately every 13 hours. Have used a portable RCD box to test every appliance plugged into outlets but the portable RCD doesn’t trip. Any ideas? Faulty outlet? Faulty RCD ( it’s 25-30 years old)?
No other circuit trips, (oven, pumps etc.) only the power outlets.
Driving me nuts.

 

[Avo Mk8]

The meter box RCD for my power outlets in my home trips at random times, approximately every 13 hours. Have used a portable RCD box to test every appliance plugged into outlets but the portable RCD doesn’t trip. Any ideas? Faulty outlet? Faulty RCD ( it’s 25-30 years old)?
No other circuit trips, (oven, pumps etc.) only the power outlets.
Driving me nuts.

I believe you're in Australia? Could you clarify the distribution arrangements - is this RCD for one particular circuit, or is it protecting a number of MCB's feeding different circuits? A pic of the board would be useful.

Do you have an electric water heater or other equipment wired directly on that circuit, that you haven't disconnected in your tests? It sounds like the sort of time frame a self defrosting fridge or immersion heater could be responsible for!

If practical, you could try disconnecting all household appliances on the circuit for say 24 hours to see if the tripping stops, and if possible narrow down which is responsible. You need to disconnect both live and neutral, ie pull out the plug etc. to verify that's not the faulty appliance (as a neutral to earth fault can cause tripping)

Apart from home experimentation, you could get an electrician to check leakage currents of appliances and for any insulation resistance issues in the property. Also to check the RCD. I suspect it's more likely to be a fault than the RCD, but the latter can be tested with appropriate equipment.