Nice job on your breakout box.  I do have a few suggestions for you.

1. All metal boxes MUST be grounded.  That means the lead from the dryer plug must be tied to the metal box as well as the two lines to the outlets.  It's not a big deal, just screw a ground wire into the box and tie it into the other three grounds with a wingnut.
2. Always use strain release.  Never have unsecured wires in the middle of a hole where they can wear on the edge of a hole.
3. The 12 gauge wire and 20 amp plugs are only rated at 20 amps.  The dryer outlet is rated at 30.  You can burn out the wire between your breakout box and the outlet box or the power cable from the outlet box to your equipment without the 30 amp breaker tripping.  This may or may not exceed your tolerance for risk.
4. You can do everything in a single box if you get a deep one.
5. You will want to have 20 amp breakers protecting each of the 12 gauge wires if you build this for sale or your insurance company will disown you.

If I were to do this project, I would probably buy something like http://www.ebay.com/itm/DELL-AP6031-5T439-4-Outlet-Rackmount-Server-220-240V-Power-Distribution-Unit-PDU-/371098052990?pt=US_Power_Distribution_Units&hash=item56672ae97e , cut off the plug and buy a dryer plug to replace the twisty plug.  Disclaimer, I don't' know who that seller is, it is the cheapest "220v pdu" I found on ebay that looked like it would do the job.

Good work on your project.  It looks like you did a good job.  Just please don't try to sell it without fixing a few safety issues.

If you want to go the PDU route, consider something cheap like http://www.ebay.com/itm/APC-basic-rack-PDU-AP9566-12-PORT-3004-USED-SEE-PHOTOS-/201052628656 and either change out the wall outlet or cut the plug off the PDU cable and replace it with an appropriate plug.  That would be less expensive than buying or making an adapter.

That is unless you really want the features of that expensive PDU.

As long as you are sure your power supply will handle it, all you need to do is buy the proper cable.  Do the images on https://www.google.com/search?q=20p+to+c15 look right?

I have not tried the main branch cgminer yet but I can confirm that bfgminer has issues with r-box.  It may only happen with multiple pools.

I switched back to the custom cgminer fork and all my problems went away.

1 - please do not try to make your own cable without a volt meter to verify your work.
2 - please do not cut the cables out of your power supply.  The power supply has a much longer useful life than any mining hardware you buy today.
3 - please do not try to make your own cables without a volt meter to verify your work.
4 - see #3

You are not going to get 7 R-Box connected via molex adapters.  They have PCI-E to barrel adapters for sale but they generally won't work on R-Box.

A 20 dollar break out board is probably your best choice at this time, but please, pretty please, find your volt meter before you plug anything into a miner.

Have you tried cleaning it?

Mine got its knickers in a knot last month and refused to work until I took it apart and blew all the cat hair and dust bunnies out of it.

Do you have multiple pools configured in fallback mode?

If so, bfgminer doesn't handle that well.

I have the same issue and it is frustrating.   I use ghash.io as my primary and btcguild as my secondary.  bfgminer survives one, maybe two failovers before it whacks your rock miner.

You could install 4 220 circuits or 8 120 circuits.  You may be able to convert some of your existing circuits to doubles and get even more.

220 has less wire loss which is of little value here.

220 has a slightly better power curve in PC power supplies.  A couple of percent is a couple of percent.

As long as the sum of what you are running now is the same is what you plan on running once you get rid of the fire hazards ... do it.

Oh, and while there technically IS a 220v 40A socket, I haven't seen one and it is not common in computer equipment.  220v20a and 220v30a are common.

Are you looking for a short and sweet answer?

Oik.  Install a l6-30 outlet and plug a 30 amp 220v PDU into it.  Plug anything that will run off 220 v into that pdu and you will be happy.

Don't run extension cords.  I am sure you already know they are fire hazards.

Or were you looking for a long, detailed explanation?

40000 w * 3.4 btu/w = 136,000 btu heat generation.
Rough, general, sometimes/often wrong is to spend half again as much on cooling.
136,000 / 2 = 68,000 BTU cooling
1 Ton is 12,000 BTU/Hr
So, if you believe all the rough generalities, you need a 6 ton AC unit.   Even if it is wrong, it gets you into the right ballpark.

They don't list middlecoin on that comparison page.  It is a good chart but the pools it tracks change often and rarely include the ones I have used.

FWIW, I started with middlecoin 8 months ago.  I ran my own charts comparing them with hash cows.  There were daily differences but on average they were similar.  That is until middlecon jumped on doge before anyone else and hash cows ran off with my coins

I don't have any side by side comparison of middlecoin vs other pools any more, but to the people who claim middlecoin is dead I can certify that they are not.  They may or may not be competitive in their coin selection.  That I do not know.

I can also certify that they DO pay once you get to 0.01 coins and they always have.  I have 8 months of history that confirms it.  Whether they pay out dust after a week is a completely different story.

If the worst people can say about a pool is it doesn't automatically pay out balances so low that it won't even buy a cup of coffee ..  Well, that's pretty high praise.

Excellent decision.  That should work well for you.

I suppose it is all in how you look at things.

To me, they are identical.  I do both as an excuse to play with new toys.  It is fun to build your epeen stuffing as many GPU's as you can in one system or optimizing your ppd/$ err, ghash/$.  It doesn't make much difference to me whether I am folding proteins or making bitcoins.  Though, making bitcoins allows me to exchange the results of my work for more toys which is something you can't do by folding proteins.

So, if you are an outsider who doesn't know a bitcoin from a protein?  Well, yeah, they are pretty much the same

But, if you are into mining bitcoins to make a profit, or you are a biologist trying to find a cure for cancer?  Yeah, then they are very, very different.

One other thought comes to mind ... how far are the miners from your service panel?

It might be less expensive to install a sub panel where you are installing your miners than run multiple small circuits if the distance is long.

It is true that a PDU costs more than a duplex outlet but you will be able to reuse them as you grow.  I am not sure you got 200 dollars.  http://www.ebay.com/itm/30-56051-01-Compaq-220-240V-Single-Phase-PDU-Power-Distribution-Unit-24Amps-/390707938184?pt=US_Power_Distribution_Units&hash=item5af8020388 are 50 bucks each, http://www.ebay.com/itm/Lot-of-3-HP-E7674-63001-100-240V-50-60Hz-16A-Power-Distribution-Unit-PDU-/251276014756?pt=US_Power_Distribution_Units&hash=item3a8137b4a4 are 75 for the three.  Not sure if they are any good but that's what ebay found.

How far from your panel are you going to put your miners?  How many slots do you have in your panel?

I would make a little spreadsheet comparing 6 x 120v20a, 3 x 240v20a and 2x240v30a.

The 6 x 120v20a circuits would require 6 runs of 12awg wire, 6 single pole breakers or 3 of the 2 in 1s, 6 duplex boxes and 6 duplex outlets.  No power strips needed.
The 3 x 240v20a circuits would require 3 runs of 12awg wire, 3 double pole breakers, 3 duplex boxes, 3 outlets and 3 16A PDUs
The 2 x 240v30a circuits would require 2 runs of 10awg wire, 2 double pole breakers, 2 duplex boxes, 2 outlets and 2 24A PDUs

Of course, a more important question is how long you plan on keeping this up and do you ever expect your power consumption to go DOWN.  History shows it rarely does

2 x 220v 30 amp circuits with 2 x 220v 24 amp PDU's would be my initial design for that sort of setup.

The evolution from using general purpose computing to specific purpose computing is a natural evolution.  Your statement suggests you can not adopt to evolution so I suggest you invest your time and money in an endeavor you are more comfortable.  USB miners are fun.  I have a few of as many as I can just for run.  But you are never ever, ever gonna make money with usb miners.

Do you want the ultimate answer?

Ok, here it is.

Dunno.

Lotsa folk bought when BTC was at 1500 USD.  They lost their shirts.

Lotsa folk bought when BTC was at 5 USD.  They have, on paper, made a fortune.

So, is buying at 500 USD gonna make you money or loose you money?

Dunno.

Is buying mining hardware gonna make you money or loose you money?

Probably gonna loose you money unless you have really cheep electricity.

Do you think BTC is gonna go up?  Are you willing to gamble that it does?  If so, buy BTC.

Do you have cheap electricity?  Do you think there are going to be no major changes in the mining market over the next half year?  If so, buy hardware.

Otherwise, go to Vegas if you feel risky, buy stock if you feel kinda risky or buy a CD if you want to slowly loose your money to inflation.

According to the man page, the rules are loaded in sort order.  01 is loaded before 99.  Other than that, anything goes.  I picked 77 because ... well ... just because.  I looked at the other files in the folder and guessed a number.

Are you running as root?

I had a heck of a time getting nano fury's to work with bfgminer without being root.

I had to create

pi@pi2 /etc/udev/rules.d $ cat 77-hidraw.rules
ATTRS{idVendor}=="04d8", ATTRS{idProduct}=="00de", SUBSYSTEM=="hidraw", ACTION=="add", MODE="0666", GROUP="plugdev"

To let my miner user get at the device.