I see what you're saying, but the draw is coming from the single breaker in the main box, so it has no effect on your service limit. From that point, a 220 40a will provide enough power for 2x20a @220 or 4x20a @110. It's the same amount of energy.
I'm pretty sure that's not right, if you use 120V you will be using 1 Hot leg + 1 Neutral. You won't be using both hot legs. So if you have 4 * 20A 120V breaker you have 80A available, 80% = 64A@120V = 7680Watts available. If you have 80A on 240V you have 64A@240V = 15360Watts available.
This is why you want to use 240V for mining, as you halve your amount of AMP use, effectively having access to twice as much Watts on the same electrical entrance.
Maybe a certified Electrician can comment...
Your power consumption isn't based on amperage, it's based on wattage.
And I am talking about a sub box, not a single outlet (which your math makes sense for). Your neutral is in the box and you have a separate ground. You can run whatever you want out of it up to the max wattage supplied by the breaker supplying the box (and space in the box, 220s take up twice the space, remember). So in your example, if you have 80A on 240 feeding the box, you indeed have 15,360W available (for constant draw, but since we're both working that into the math already, let's leave it as assumed for the rest of this example). How that gets broken up is up to you, you can have, say, 4x 20a 240v breakers (4*20=80*240*.8=15360), or 8x 20a 120v (8*20=160*120*.8=15360), or you can have, say, 2x 20a 240v and 4x 20a 110v, or any combination that adds up to 15360 (or less).
That is correct. I've measured it on a rig running on 120V and I've measured it on a rig running 240V. If your rig on 120 is drawing 8A, it's only drawing 4A on 240V.
Wattage divided by Voltage = Amp ... 900W Rig/120V = 7.5A ... 900W Rig/240V = 3.75A.
That's correct. But the draw is wattage, not amperage. Both those examples are using the same amount of energy.
I never said it was using less energy. They use equal amounts of energy. I'm saying that your service limit is what it is ... 100A, 200A, ect (should be labeled on the breaker box) ... So I would rather be using up less of that limit by running off of a 240V outlet, as opposed to 120V.