Today I came across an interesting fault and I havnt figured out yet what it could be. Any advice or ideas greatly appreciated.
The main breaker from the poco is 63A. I have a panel monofase (1 fase+N). There are 2 RCDs. The main one is 300mA which covers the whole panel and the 2nd one is 30mA which covers bathrooms, washing machine and central heating boiler (which rund on gas).
The main breaker from the poco is on. When I measure between fase and Neutral I get 0 Volt, between fase and earth=224V, between Neutral and earth 224V! The Neutral is not broken.
If I push the test button on the main RCD 300mA, then it jumps.
When I disconnect the 2nd RCD 30mA, then all the other circuits work fine.
I measure between fase and Neutral I get 224 Volt, between fase and earth=224V, between Neutral and earth 0V (as it should be).
When I reconnect, the problem comes back.
After having reconnected I turn off all the breakers which are under RCD30mA, turn on the RCD and turn all the breakers back on and low and behold, everything works fine!
There are 2 things which maybe I should mention:
1, Both RCDs are 40A whereas the main breaker is 63A, so they should have been 63A as well.
2, There were different issues with the central heating boiler (which is under RCD 30mA).
Could it have to do with the boiler?
For me it's a riddle. If any of you has any logical clear explanation, please let me know.