a 220 volt 20 amp circuit should be good for over 3500 watts constant load in North America. Why is it requiring two circuits?
This server has two IEC C20 connectors, rated for ~16 amps, each feeding a PSU rated for 1600W (i.e. 16A @ 100v)
If you're plugging in to 110v you shouldn't plug them both into the same outlet, as a 20A circuit can't supply 32A.
As each PSU is rated for 1600W you'll have to plug both in to get 3200W even if you're running on 220v - although they'd only draw ~7.2A each in that case.
US Residential 220v dryer outlets are usually wired one-circuit-to-one-outlet, and multi-way adaptors are discouraged. So although plugging two 7.2A loads into a single 20A feed would work from a current perspective (and indeed it's common in Europe), I don't know how easy it is to do legally.
If you're in a data centre with a 3-phase 220v power you probably know what you're doing. Your UPS guy will probably thank you if you split your load over two phases instead of putting the whole load onto one phase.
As for the datacenter (I’ve racked many things with A/B power) the entire point is redundancy which this defeats the purpose of since each PSU is not properly rated. Seems incredibly bizarre to me in so many ways.
Yes - often for the data centre you'd end up with something like [1] with 4x 2700W power supplies, providing redundancy and ample power at the same time. It does mean you need four 220v power feeds though.
[1] https://www.supermicro.com/en/products/system/gpu/4u/sys-421...
It used to be done in kitchens in the US, back when appliances were power hungry. I have done so in my workshop for the same reason.
Houses are wired in split phase 240V, with the neutral in the middle. That is, you have two opposite 120V phases, around the same neutral.
This is a clever way to double the power, while adding a single wire.
In the US the standard outlet receptacle has two outlets. Bring the same neutral to the two outlets, and assign one phase per outlet (outlets have metals tabs you can break off, you don't need any extra wiring).
At the panel, you have a dual breaker. One breaker per phase, with a physical linkage forcing them to trip and arm together at once.
As a benefit; but very unsafe; you can make up a Y that plugs into the two 120V outlets, and gives you a single 240V receptacle. This is unsafe because if you plug only one of the 120V plug, the other one has now 120V on its exposed phase prong! On the other hand, I have both 240V@20A and 2×120V@20A anywhere in the shop ;)
https://store.leviton.com/products/duplex-receptacle-outlet-...
With my setup I have 2×120@20 always available, and 240@20 for the occasional welding.
I could assign a different 120 phase to every other outlet but then I would need some clear identification.
The two phases are assigned to the top and bottom outlets the same way all around the shop. If I need to run two high amperage machines, I only have to remember to use one bottom and one top outlet.
- $20
- GFCI, $115
- GFCI + AFCI, $115
A 1-pole GFCI breaker, a 2-pole GFCI breaker, and an ordinary GFCI outlet all have the same clever pair of coils, the same IC, and rather similar trip mechanisms. Yet the costs are quite different, and the costs get _really_ absurd if you want a breaker that trips at a level other than ~5mA.
And yes, they’re all very much worth using. I do wish that electrical codes would at least start encouraging the use of GFCIs for 240V outlets, which might encourage manufacturers to start making them, and those would actually be able to compete with each other.
I've been looking for a proper answer to this for a while, because I want to build a similar machine with 8 GPUs (~4500W max load) which would need to be split between two 16A 230V circuits.
Are you planning to build such a machine for your personal home use? If so you should be aware that (a) you might find server hardware hasn't thoroughly tested compatibility with things like suspend; (b) you might find games haven't thoroughly tested compatibility with multi-GPU setups; and (c) you might find the idle power consumption is 200W or more, even while doing nothing.
That is good to know multiple phases can work. Perhaps there would still be a fire risk in case of a short? Like somehow bridging the circuits > breakers don't trip?
Something to keep in mind though is that (at least with consumer-grade PSUs) it is not safe to simply tie the outputs together, even if both PSUs produce 5V, 12V, 3.3V, etc. The voltages will be slightly different and connecting them together will cause current to flow back into one of the PSUs.
You can still use this setup though, the key is that the GPUs do not (or should not) connect the motherboard voltage provided via the card slot to the voltage provided via the power connector. This detail allows you to safely power the motherboard from one PSU and power the GPU from another one, you just have to be careful not to mix connectors on the same card between different PSUs (if it has multiple). Additionally the motherboard should be entirely powered from a single PSU.
Most folks aren’t going to unplug their water heater to turn on their AI.
If I was serious about this I'd have an electrician and HVAC installer on the way first. A mini split in the computer room with a dedicated 50A/220v circuit.
But yes, a power supply can draw around 240V times 20A = 4800VA, which is nearly 4800W if the power factor is close to 1. An office in an office building is more likely to have 208V.
Water heater, heat pumps, stove, dryer, hot tub, etc are all 220.
So if you want to plug in a device like this "tinybox" at home, it's going to be a lot easier to find two separate 110v outlets on different circuits than to have a new 220v circuit added, or to unplug your stove every time you want to use it.
It's common for EVs, clothes dryers, ovens, and hot water heaters to use 240V while most other appliances are 120V.
There is nothing in US power system that is 220V.