RCD on my Consumer Unit Tripping

[JtB]

Thank you everyone for all your comments and suggestions.

Update: For each MCB except one I’ve now seen the RCD trip (at one time or another) with that MCB switched off. I’ve not seen the RCD trip though with the MCB that protects the central heating circuit switched off. So unless the problem is due to the sum of the residual currents from multiple circuits then hopefully I’ve narrowed it down to the central heating circuit.

Note 1: The central heating consists of a gas boiler heated hot water cylinder and radiators.
Note 2: The RCD has tripped while neither the hot water cylinder nor the radiators are switched on.

 

[raleighnut]

Thank you everyone for all your comments and suggestions.

Update: For each MCB except one I’ve now seen the RCD trip (at one time or another) with that MCB switched off. I’ve not seen the RCD trip though with the MCB that protects the central heating circuit switched off. So unless the problem is due to the sum of the residual currents from multiple circuits then hopefully I’ve narrowed it down to the central heating circuit.

Note 1: The central heating consists of a gas boiler heated hot water cylinder and radiators.
Note 2: The RCD has tripped while neither the hot water cylinder nor the radiators are switched on.

That doesn't mean there isn't an electrical fault in the boiler, get the boiler checked over would be my advice

 

[Tom B]

The fridge / freezer are the usual suspect for random RCD drops.

Usually the start up "capacitor" on the motor.

 

[Gwylan]

Inductive devices are candidates. Kettle, iron or toaster. Assume the cooker is on its own circuit.

 

[raleighnut]

The pump on a central heating system probably has a Capacitor

 

[CXRAndy]

These days there is a common issue with multiple electronic equipment having earth leakage which can randomly trip the RCD.

Cumulative leakage. It doesn't need to exceed 30mA to trip, anything from 20mA upwards can do it.

I experienced this our last house. Random tripping. I bought a meter which could read down to 1mA with a clamp. My house totalled 25mA leakage. I then tested each circuit and all the affected circuits were very low less than 7mA-added upto nearly 25mA.

I paid my electrician to change all the MCBs in the consumer unit to RCBO breakers. These have their own RCD in each one. After that no more random tripping.

Came in handy, when we sold the house the following year having latest consumer unit design and electricians sign off

 

[JtB]

In the end the culprit was the fridge-freezer.

 

[raleighnut]

In the end the culprit was the fridge-freezer.

Bet there is a capacitor on the compressor motor.