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ChiliTom

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I have a dual board consumer unit. Both sides have a RCD. The left hand side of the board has all the MCBs for all the 6 ring mains for the property. The right side of the board has the lighting and hob and cooker for the house.

Whenever a current is drawn from a socket the right side RCD trips, but not the left side. So my lights trip but sockets stay on. It happens on any of the 6 ring mains. And seems to be any appliance that draws a large current such as a hoover, kettle, immersion heater etc.

I do have a alarm system but I have totally isolated it by unwiring it front the spur it was connected to. Still the same issue.

I do also have under cabinet lights that are ran from a ring main... I have yet to investigate these.

The MCBs switched off were because they were just straight up tripping the right side RCD. Probably because they all had stuff like a fridge, boiler etc drawing current. The right hand side lighting circuit that is turned off also automatically trips the right RCD.
[ElectriciansForums.net] RCD issue baffling me


Electrician has tested each circuit and can't find a fault. The board has been wired correctly with no crossed over neutrals.

Anyone got any clue where to start some more fault finding? I am a ex Army Electrician, that was 17th ed trained... But that was about a decade ago but I know enough to be safe.

Cheers
 
Is it the same electrician who installed the CU that's doing the testing now? Not exactly impressed with the distribution of circuits between the two RCDs in that CU.
It'll be an earth to neutral fault in one of the RH bank circuits, and things with ceramic, metal enclosed elements don't always show poor IR when cold.
 
The MCBs switched off were because they were just straight up tripping the right side RCD. Probably because they all had stuff like a fridge, boiler etc drawing current. The right hand side lighting circuit that is turned off also automatically trips the right RCD.
Turning off single pole mcbs won't disconnect the N to Earth fault, best to disconnect individual circuits entirely.
If it trips instantly with all circuits energised, then it shouldn't take long to isolate the faulty circuit.
 
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