Got the responsibility for a 100 yrs old building, The elctric systerms was rewired at lo cost 15 yrs ago. When I com in the morning at least one, sometimes 15 FFCI had don their job... but all measuring shows nothing wrong.
We have a 230V 3 phase supply quite equal to US 208V delta systems. (I'm in Norway) All this is wired for 230V single phase.
All hints to find and make documented reports are welcome.
One thing I learned as an inspector is installers seldom make one mistake if they are making mistakes. It is worth inspecting each circuit you are having trouble with paying particular attention to the neutrals. Folks tend to get sloppy with them assuming they are grounded conductors, what could go wrong but if they get grounded or share current with another circuit on the load side of a GFCI/AFCI it will trip. You may find multiple problems once you start looking but you have to start somewhere..
No risk that anybody will bypass it, the weakness is the combination of an early version of the units and the old-fashioned system together with great capacitive "feedback" from the wires in steel tubing in the walls.
A less than 100 mA fault made around 15 of these elements to trip at the same time. Those are rated to trip at max 30 mA we have tested (all of) them to trip between 12 and 15 mA.
Only units of this make are tripping in these cases. I have been told that thees are lo-cost but approved.
I have been told that this supply-system was abandoned in the UK in 1948.
