Studio mains surge fried motherboard. TWICE. Why?

[sonicowl]

So, I managed to have motherboard on one studio PC destroyed by mains surge. Replaced it, and second one in the same PC got destroyed again after 2 days.

I need to figure out why this happened, before I install third motherboard. I have idea why this could happen, but must understand it better to prevent it. Please help with troubleshoot.

Setup is like this. Mains power is EU, 220V. All my studio equipment is on mains phase1, including this PC. But in the back of the room I have printer, internet modem and large TV on mains phase2. AND, on phase2 in the back of the room I also have portable room halogen quartz heater.

Both times that motherboard was fried, situation was the same. I turned on heater, and mains circuit breaker on phase2 tripped. And TV, printer and internet modem went out.

My thinking is like this. All three backroom PC peripherals on phase2 are connected to that PC on phase1. TV via HDMI, internet box via ethernet and printer via USB. I turned on quartz heater, and phase2 mains breaker tripped. That caused phase-to-phase load surge to travel through HDMI or USB or ethernet and destroy motherboard. Twice.

Am I thinking properly?

What to do to not burn more motherboards like this? If I connect all PC peripherals to same mains phase as PC, and keep heater on different mains phase, would that save me from burning more motherboards?

[Softsynth]

I think your best bet is to get out an electrician to look at your dodgy mains wiring.

I don't think we can diagnose your problem online here without being in full possession of the facts.

It seems obvious in the meantime not to operate the mains heater at the same time as using sensitive electronics!

Look to see if you are overloading the circuits with lots of different things plugged in and switched on.

As for the "modern large TV" if it is truly modern it probably doesn't use much power. If on the other hand it's an old model from say 15 years ago they used a lot more power back then - especially plasma screens.

Anyway:
https://www.heat-outdoors.co.uk/help...e-circuit.html

[sonicowl]

I'm not looking for solution to heater tripping breaker. Circuit breaker was overloaded, it is clear. Still, this shouldn't burn PC motherboard on another mains phase. I doubt it has to do with wiring itself. It is more of a pulse/surge situation.

My query is about the situation, where fuse tripping on one mains phase repeatedly burned motherboard on another mains phase. I'm hoping for ideas/confirmations about how that could happen in theory.

I suspect that usb/hdmi connection between pc on phase1 and printer/TV on phase2 could be the reason. Because two other PCs were fine, just the one connected to peripherals on heater's phase got fried motherboard.

I'm hoping that someone with more knowledge of mains surge protection can explain a bit how such thing can happen, and possibly how to prevent it in future.

[ajaym]

I would be concerned about neutral bonding in this scenario. If you are running different outlets on different phases it's possible that there is a significant neutral current being introduced especially in a transient fault scenario. This could introduce significant transient voltages across equipment that supposedly shares a common ground. As has already been mentioned, you need a good electrician to take a very careful look at your current wiring and switchboard and if there are issues, they need to be addressed as there could be safety-critical problems here.