Hi Fellow Electricians, I need some advice with an issue I've never encountered before.
The customer is building an addition to his out building requested that the sub db have it's own earth leakage and taken off from the earth leakage in the main db at the house. So we did this. This sub db has 5 plugs and 3 lights and a swimming pool db. the lights are not on earth leakage. so this is where it gets interesting. When we switched the power on the lights, plugs and pool was working fine until a couple minutes later, the earth leakage in the sub db tripped. The time it takes to trip varies and when I Meggered each circuit between live/neutral/earth, I did not pick up any fault. It sometimes trippes after 2 minutes and sometimes after 20minutes. It seems to happen when the pool is running as nothing else is plugged in. But when I bypassed the earth leakage in the sub db and put the supply cable to the sub db back on to earth leakage at the main db and funny enough, it never tripped out again. the house earth leakage trippes on 20mA with the plug tester and the one I had in the Sub DB tripped at 30mA and I also changed the earth leakage twice. Any Advice on why it trippes at the sub db's earth leakage and not on the earth leakage at the main db in the house?