Jasey

Thanks, Jay-Dee. The EL's are not in series. I have 3 phase power and the main house's EL (2.5 kA) is on its own phase and when it is off, only the main house's power (plugs) are off. The new house's power does come from the main house's DB on a different phase and the EL is 3kA (the main switch of the DB of the main house cuts all power on the property. Now, the new house's DB wiring has the EL connected to the geyser, stove and lights, which, as I understand isn't strictly necessary (but safer?). Had a electrician tell me that the EL was overloaded, but that doesn't explain the problem, since the EL ONLY trips with a ligthning strike in the area.

I've searched the internet and forums for a solution to no avail. It seems for some people, who had exactly the same problem with lightning, the replacement didn't even work. But I guess I will have to replace it and hope for the best. And add the surge arrester for good measure. Thanks for your reply.

Thanks for the reply. Yes, they seem to be the same make (CBi), but the one in the main house is a much older version (HY-MAG CBi, 60A, with test button separate for the switches) while the newer ELCB (which is tripping) is the standard CBi 63A. So what I gather is that replacing the ELCB could solve the problem, but not necessarily, since the replacement might be just as sensitive?

Since having built a stand alone building next to the main house, every single time lightning strikes in the area, the earth leakage trips at the new building's DB (the new DB is fed from the main house, which is unaffected by any lighting strikes). This has been ongoing for the past 8 years and happens ONLY when lightning strikes. Is there a possible solution for this? I'm considering installing a double pole surge arrester in the DB, but not sure if this will solve the problem. Any ideas?