I recently spent Chinese New Year at my girlfriend's apartment (in China) and woke up one morning to find we'd lost power. I opened the breaker box in the apartment to find the main breaker (2P 40A) had tripped and the top screws looked blackened. I couldn't get the breaker to switch back on even with all the other breakers off, so I reasoned it was shot and needed to go to the local hardware store to get a replacement.
As I studied the wiring layout before heading over a couple of things caught my attention. As an American, I'm accustomed to a breaker bus that the breakers snap into to receive power from the main breaker. No such thing here. Obviously I'm also accustomed to 120v but not unfamiliar with 240v circuits both in the US and from time living in the UK.
I understand that in the UK, 240v to individual homes is carried on a single phase with hot, neutral and ground. My expectation is that China would follow Europe's lead as it's also 50hz and because it does so in most other areas. However the supply coming into this apartment has two hot legs, no neutral, and no grounding bus †. That makes it seem to me like it's split-phase center tap with the 240v being line to line.
If that's the case, I'm guessing the lack of neutral is not as concerning as I initially thought? However I also notice the two hot legs are not balanced: one feeds two 16A breakers while the other feeds three 16A breakers. Don't the two hot legs need to be balanced if it's line to line to compensate for the fact that there's no neutral?
The main 40A breaker also seems too small to supply three 16A subbreakers at 80% of their load, so I bump up to a 63A breaker. However, the house's breaker box is actually a subpanel, with the main panel being downstairs in the apartment block's stairwell with the meters. Everything is fed by the same kind of 2P 40A breaker that served as the main breaker in the house panel, rendering the 63A breaker redundant! I have no access to the interior of that panel as it's locked by the utility company.
I'm also concerned that the wire gauges aren't correct for the amount of amperage being carried both to the breakers and from the breakers to the individual circuits.
The blackening of the top screws of the old breaker is also concerning. Is too much resistance on the wire or screws/breaker a possible cause?
Being a little out of my depth here, my first inclination would be to call a licensed electrician were this the United States. I don't really trust the knowledge, workmanship, safety practices or ethics of Chinese tradesmen though (the first electrician to come out from the power company bypassed the breaker on one leg as a fix, you can see in the photos below!), so any advice would be appreciated. I've also reached out to electrical contractor friends in the US.
† There are however two ground wires from opposing directions spliced together, maybe one is tied into all the outlet boxes and the other goes to true ground, or a ground bus in the main panel? I didn't open the outlets to check because everything is concrete and there's no obvious way to get the faceplates off without breaking them.