Bitmain PSU does not switch modes, it runs continuously from 100-270V. Since it is current limited at the input, more input voltage will naturally give more output power.
In other words, it's automatic, rather than requiring a manual switch. Doesn't seem to make a difference overall.
The short version is that you want 240V (or 220 if you want to call it that).
Well of course I want that. Regardless of safety, I can use twice as many miners if I use all 240v outlets because I'd use less amps per miner at higher volts. As an aside, my breaker box is actual 110v/220v (I'm not just calling 240v a 220v line - there's an actual difference, although a small one) so I'd need a new fuse box anyway.
And from your description, I might suggest that it does not seem like a good idea to mine on antique wiring in the main house.
My service technically allows for up to 320 amps of total service standardized to 120/240v (although, interestingly, there is a 480v option in my area, not that it would seem to mean anything here), while my breaker box is currently rated up to 125 amps at 110/220v.
The plan remains to switch everything over to 240v eventually with a new 325 amp fuse box. What I'd like to shoot for is building an entire room in the basement myself - wooden framed, with some EM and sound shielding (not perfect of course) so it doesn't disrupt the rest of the house. It would be a good location to pump cold air in and then use the heated air for the house and greenhouse, although I'm unsure what to do about summer.
I was thinking I could disconnect the water heater and then have a plumber run pipes back and forth inside a hollow space in the wall where air from the outside can be cooled before going into the room and then continuing the pipes on the wall where the miners will be, with their fans plugged directly into a hollow space behind the wall, so the pipe would continue to be heated before going to the water heater (thus removing heat, and saving energy) but the problem with that idea is that if I draw air into that space in the winter it would instead freeze and burst those pipes so I'm still thinking of a possible work around to that. There's also the obvious problem where, although the water coming in from the city would be cold, it would heat up fast and unless I turn the hot water on frequently enough it could reduce the performance so I'd still have to rely on large enough fans to move the air quickly.
However, I can't afford to do that right now with the money I already spent on miners. That's why I'm asking about safe wiring in the event that there is any delay in upgrading electrical. At the very least I will try to have 6 outlets added in one section of my basement where it can get access to cool outside area, which should use a max of 35 - 39 amps depending on if the electrician can get it to work at 240 volts or not, and also leave the other area clear for building, new wiring, and new plumbing. My intention is to do that as quickly as possible and then take my time having the new room built. Then, when it's ready, I'd upgrade to the 325 amp fuse at most 15 feet from any outlet I'd be mining from. However, there is still the possibility that I will have to run on 110v outlets at least initially so I want to plan for that possibility.
Consider having your electrician install a new circuit breaker panel with a few 30A, 240V circuits. It should be separate from the old wiring and hopefully separate in terms of code since it splits right at the feed. Only the feed to the panel to outlet should need to be permitted, and your other panel and old wiring should be outside that. At least that's how the code would work in my state, which is also pretty onerous about bringing everything up to code if you touch anything in the string. Also, if your code is strict don't do it yourself - you will get bit if you ever sell the place and they find unpermitted work
That's sort of what I was thinking I could do with the temporary area for now. The breaker panel has 8 extra circuits that are unused, so I could even use a whole circuit for each miner if it was necessary without having to replace the panel or touch the house wiring. That should keep costs down and minimize the amount of time I would have to spent on 110v.
Last, a new panel will be new wiring so it should not flicker in voltage like the rest of the house wiring, UNLESS your problem is an old connection to the mains out at the pole.
Actually, even if it is the drop line (which very well could be the problem - lights do dim briefly whenever a space heater clicks on and are prone to blowing - but I'm assuming that if I upgrade to a 325 amp breaker box I will need a new drop line anyway.
In that case, you'll easily know on the day you power up the rig because all your lights will dim considerably.
But then it's on the utility company to come and grind the corrosion off your feed so your connection doesn't suck anymore. In fact, you may want to call them and tell them you already get flicker and are about to throw another 10kW on their feed and you want it checked out. My colleague had flicker, and they found the connection was not watertight underground and nearly corroded through - fixed in a day at no cost to him as it was outside the meter.
Way ahead of you there, although was a bit more cryptic. I basically told them in an email that I was planning some renovations and wanted to upgrade my wiring and fuse boxes and wanted to future proof so asked about upgrading to a 325 amp service and how much it would cost. I don't want to tip them off yet that I will expect my electric bill to skyrocket by $500 practically overnight and remain there permanently and then jump again by another $500 a few months later. I'm on budget billing and I am actually hoping that if I time things right it will take 3 months before the energy bill actually goes up which should speed up my ability to afford the upgrades . Additionally, while there doesn't appear to be a maximum power draw (we actually pay less when we go over 800 kwh) there is a clause that we are subject to energy audits if we hit a high threshold of usage so don't want to tip them off to that either. Not before I am ready anyway.
I wasn't aware that it could be free though, so when I hear back from them I will mention the flicker and power supplies erupting in flames and ask if the line can be checked at no cost earlier.
While I am doing all the upgrades though, would a whole house battery backup make any meaningful difference? Not that I expect one to run up to 50 miners, but if the power can last long enough to deal with a power flicker or a brown out that would be nice. Additionally, I wonder if a whole house voltage regulator and surge protector would help to protect them more than putting one on each miner.
