Looks pretty damn nice.
In line with UL and insurance do not forget the power cords feeding the miners. Stayonline.com makes and sells Made-in-USA UL listed power cords.

Huh?
Assuming a person knows nothing about writing software much less a very specific type of software (firmware), just how does one develop something without hiring a developer? Ans: you don't.

Even if you are a programmer it takes a fair bit of time. Is your time free? No!
When -ck was hired to do the firmware for the Dragonmints it took him several months with over a dozen live releases and who knows how many tries between releases to get it right. Pretty damn safe bet he did not do the work for free.

Because with today's social media mindset it seems that folks would prefer to post such questions to get answers from random people vs actually 1st trying the support desk... 

Medically it is very useful dealing with chronic pain. I had a case of Shingles several years ago and am one of the 1-in-10 where it resulted in permanent and painful neurological damage. Medical cannabis works great for numbing that down (and yes, I have a Michigan 'Green' card based on that).

For general recreation (also legal in Michigan but is sold with reduced potency vs Medical grade) - it has far fewer adverse points than alcohol. Most folks are familiar with the phrase calling someone "a mean drunk". You will never hear the same about a stoner....

Yes.

Unless they are a factory authorized distributor - they don't. It is up to you to deal with the OEM. If they *are* a factory authorized distributor they usually will help you as long as the miner is fairly recent model. If it is more than a couple years old you may be screwed because not enough PSU's (and other parts) are built for use as replacements/spares.

Any reseller (someone who is not an authorized distributor) will most likely ignore your requests for spare parts.

Ever hear of software tools called decompilers?

Almost any closed source code can be reverse engineered to see (most) of what went into making it. While decompilers are not perfect and tend to also output a lot of assembler code they still will reveal much of the code used, more than enough to get a good idea how it works.

The power connections are not the problem. How the PSU's work is the problem: Modern miners do not use a fixed, universally available 12VDC input like older miners did.

In older miners 12VDC was fed to each hash board and each board had a second-stage regulator on them that lowered the 12V to a level suitable to feed the strings of chips. Those secondary regulators introduced an efficiency loss plus the low voltage limited the number of chips that can be in a string. Modern miners directly control the PSU to set voltage to the strings and that voltage will be variable to somewhere between 15 and 21VDC depending on the model of miner and the miner settings. So, now not only are there more chips in each string but the voltage fed to them is now directly adjustable by the miner controller talking to a custom PSU and because there are no secondary regulators that increases efficiency by several %.

Mikey brings up a good point talking about miners being resold possibly multiple times: You included the point of "free electricity" in the OP. The only reason that should matter is if you are getting used & older, less power efficient, hardware. Point being the question for you that should bring is, "the hardware is x years old, how much longer will it last?"

Are you looking at using/getting old to very old gear?

Why would you even care?
However, to answer:
  Using OEM firmware - no.
  Using 3rd party firmware, because they periodically mine to a special DEV fee pool -- maybe.

Any particular reason you are asking these security-related questions? Are you mining in a country where it is illegal? If you are - BAD idea!

Free electricity is irrelevant and by design miners are intended to run 24x7x365.

That said, it depends on the make and model. If kept reasonably clean and ran in reasonable temperatures the Avalons from Canaan can easily last many many years. I have over a dozen A841's from 2018 that are still running perfectly with zero maintenance (but in clean environment).

Miners from Bitmain are more of a crapshoot. I have a R4 from 2017 that still runs flawlessly and 2 others that died in about 2 years. Early s9's were near bullet-proof up to around batch-9, later ones up to a 15-20% failure rate within 2-3 years OR LESS.

That I do not know so you will most likely have to do a search for it. Most of what I've seen about VPN's suggests that you will need to setup a pc/laptop to act as a bridge running the VPN and connect the miners to that.

Don't you mean maximum power per-rack? As a max it would make more sense because as you said, 4.8kva in a full rack is a lot for just powering servers and switches. But, a 42U high rack could easily pull over 20kva if filled with miner hardware.

My guess is that the data centers were forced to not only look at distributing that kind of dense power but also how to get rid of the heat generated. Most were designed and built to be data centers -- not mining farms.

edit: Got a PM and yes it is a minimum power per-rack. In short, it seems many clients op-sec requirements are demanding that only the clients and providers hardware be in a rack with no other (different) clients hardware allowed. That led to unused rack space which folks were filling with miners.

Moving back to on-topic, I'm hoping for -5.69% as that is my guess in the .01BTC "who can guess the closest" giveaway Kano is running in his Discord channel for folks mining at his pool

If living in an area that gets cold during the winter an Avalon A841 works great as a space heater. Throttled down to 9THs and fan limited to 40% it's nice and quiet while pulling about 750w.

Of course there is also Sidehacks R606 which has threads here as well.

Bet the cable was a charger cable. They lack the wires used for data transfer. The USB cable MUST be one that supports both charging and data transfer.

Ran into this a couple times when running Avalons and using cables I have laying around.

The miners could care less about a brownout, they will run as normal until the PSU cuts off and will restart the the PSU comes back online.

The PSU's are a different story: Running at a very low line voltage (below their nominal rated minimum voltage, usually around 190VAC) puts a lot of stress on their input circuits and will no doubt shorten their life. When the line voltage drops below a certain minimum the PSU *should* shut off but that feature is up to whoever makes the PSU.

Please read the stickied post at the top of this area... Mainly point-3:For BTC, trying to mine with anything other than an ASIC-based miner is beyond useless even when using free or stolen power.

For some alt crapcoins - maybe, but that discussion would belong in the altcoin areas not here in the Bitcoin area.

That is why I suggested to try running through a VPN as a test. If the country is having the ISP's block mining why the Bitmain miners can connect is odd but it's possible something about the Avalons trips the barriers while the Bitmain ones do not.

Oh, instead of opening another new thread about it, you can just move this thread to the other area. At the bottom-left of the webpage for any topic create is a button "Move Topic" to do that.

HagssFIN went through Canaan's training a couple years ago. His A10 review/troubleshooting guide starts here.

Definitely weird. Again with all 12 going down it is highly unlikely something broke in all 12 of them at the same time. Something is hinky about their connection to the network.

Question: From the A10 on up the Avalons support running 1 network cable between the router/switch and then daisy-chaining more miners onto that 1 connection by using both LAN ports on the miner. eg, router > miner1 > miner2 > miner3 > etc. Are you doing that or does each miner have its own cable running to the router/switch? Folks have had issues with doing the daisy-chain configuration.

Is it possible for you to move 1 miner to a different location and try it from a different network connection?