[LandoCalrissian]

'If you google “plugging a PC into multiple outlets”, you get lots of warnings that if you even consider such a setup you will instantly burst into flames. So I hired a professional PC builder make sure it was safe.'

Not really sure how that makes it safe but OK!

[mrandish]

I guess it was supposed to be a humorous aside, but it wasn't actually helpful because the relevant issue is when you pull more total amps from a single circuit than it's fused for (usually 15 or 20 amps in U.S. residences). The failure mode is usually tripping the circuit breaker.

That issue can often be addressed fairly easily by splitting the power draw between two adjacent circuits. You can have an electrician do it permanently or temporarily DIY it with an appropriately rated extension cord. The real issue was OP was in an apartment at the time so an electrician would have been difficult. I assume they decided to just have a system integrator build it because they didn't want to figure out how to segment and route the power rails in a dual power supply system, but it's not exactly rocket science. Problems are often more due to choosing power supplies that aren't up to their claimed spec, not pre-testing them under load or using incorrect or under-spec cables.

[ttshaw1]

I think the relevant issue is you could conceivably have a house with two outlets with opposite phases. Bussing them together in the PSU will then create a short

[dheera]

> two outlets with opposite phases

This is actually THE standard in the US, which is actually fundamentally a 240V power grid but with an electrode stuck halfway down the secondary winding on every pole transformer, which becomes your "neutral". The two ends become L1 and L2, so that L1-N is 120Vrms, L2-N is 120Vrms, and L1-L2 is 240Vrms, and this is what goes into every home.

The power outlets connected to L1 are all opposite phase to all the ones connected to L2.

Rather than bussing the two outlets together, what you can safely do is get an electrician to just wire up an outlet with L1 and L2 and voila you have a 240V outlet. This is how you get all your dryer outlets, EV charging outlets, electric stove outlets, etc.

[IshKebab]

I used to work for a company where we made test rigs and their safety guys were strictly against having a single machine with multiple power inputs. It wasn't about power draw. Once you have two plugs:

1. You no longer have the nice property that unplugging it guarantees (more or less) that it isn't electrified.

2. You open up the possibility of mains voltage from one plug appearing on the unplugged prongs of the other plug.

3. It possibly messes with RCDs, depending on what you do exactly.

Although in this case it's probably fine because he's just plugging totally separate power supplies in and they're already fully enclosed.

[kccqzy]

Probably means hiring someone who has more knowledge about PSUs and especially about having two simultaneous PSUs. There are questions like: when you press the power button how do the two PSUs turn up and in what sequence? How do you deal with the PWR_OK signal? What if there are voltage differences between the two PSUs? What about power backfeeding?

[niobe]

Agreed, if anything an electrician was needed, not a professional PC builder.

The picture shows two power supplies. Powering what is effectively one appliance from different circuits is a definite no-no, and I can't think of any circumstance where it wouldn't be in a home.

If his mains supply was sufficient to run the server and the house in the first place then the simplest solution would be to simply upgrade one of the MCBs/RCBOs on one of the circuits to the required capacity. I am not sure a landlord would even notice something like that, and if the house is wired correctly in the first place, it's unlikely to be dangerous. So going from say, 6A to 12A, on a 20A mains supply is generally fine if the gauge of wiring is correct.

[4chandaily]

I read this as; the "professional PC builder" would carry some sort of insurance. So it isn't really "safer", but if something goes wrong, the investment is (potentially) still safe.

Just an assumption, though!