I calculated my air needs based on a combined total of 300 cfm/s9.  So far, so good (at least as far as air flow is concerned).  I'm running about 120 S9s using that calc.

It should be noted that 841s draw less air.

I remember the "good ole days" where I would occassionaly be able to buy miners with a 100 days straight line ROI (cost/day 1 profit <= 100 days).  Always figured those would really ROI within a year, since difficulty was going up.

Now an S9 is clearing less than $1/day (or there abouts, depending on your power cost), and the units are still around $900 with shipping and power supplies.  900 day ROI?  That is insane.

Only good news is it looks like hashrate is FINALLY starting to fall.

I use APW3++s for S9s and 841s, Sorcerers for 821s and 841s.

Highly recommended kano.is as a pool, or if you insist on a fancier UI/Higher fee/lower variance - slushpool.

Presuming your running using 220V power, you likely just have a flaky hash card.  I've lost at least one hash card in 11 of my ~150 S9s, and I'm told I'm doing better than most.

Happen to know what the relative difficulty was this time last year?  e.g.  1/3rd of what it is today?  I'm just curious what the difficulty-adjusted price was this time last year vs. today.

I would feel better if you locked into that 220 solution - as would everyone else if you ever need help.  The first question always asked is "Are you running on 220?".

I'd also feel better if you cancelled and ordered directly from Bitmain.  You have no idea what you might be getting from Amazon, and you won't get a warranty.  However doing so would likely result in a several week delay.

OK, lets see: 

Amazon - hope that works out for you.  Unless you buy directly from Bitmain you don't get a warranty.

Would you know 12 gauge vs. 15 gauge wire if you saw it?  If so, pull a wall receptical and see how its wired...  or better yet, pull both the receptical and the breaker and see if they appear to use the same wire.   The stuff you got looks OLD - who knows how many patch jobs were done to it over the years.   Still a bit concerned about pulling that much current at 110V, but the receptical should handle it - only breakers have the 80% rule.  So yeah, if the wire is good, you should be good.  Of course, I'd suggest having a qualified electrician check it out.

220V:  Meant buy the plug, some wire, a rig something.  Of course, do so only if your comfortable doing so.  That doesn't sound like the case, so perhaps ask a friend who is?

1 makes it easier.  Its a cheat, but only for the 6 weeks... just buy the plug and wire it to a regular 110V receptical (putting that in a box of course).  Test it, and watch it, but running 220V through it will cut the amperage in half.  Rather suspect the receptical would handle the extra voltage without any problem.  You could even get away with using 15 gauge wire - which is both cheaper and easier to work with.  Do keep it as short as practical - under 20 feet would be good.  Note that wiring would be simple presuming you can identify the ground lead in the plug.  That one gets the bare copper, after that, it doesn't matter which terminal gets the black and which gets the white, since both will be hot (e.g. no neutral).  Again, probably best to get a friend that is comfortable building this for you.

Google NEMA standards chart images.  For all the common voltages and amperages there is a NEMA specified code - one for the plug, one for the receptical.  C13 is what goes into the PSU, other end goes into your receptical.

Actually, using (2) PSUs is not a bad idea, if you happen to have a few laying around - just make sure each is plugged into a different breaker.  One PSU powers 1 hash board and the controller (4 PCI-E plugs), the other powers the other two hash boards (6 PCI-E plugs).  Do not mix PSUs across hash cards.

No "dorm fridge" or similar setup has the BTU requirements to cool a S9.  Sounds like you need to rig ventilation outside - plenty of post showing 6" dryer duct for that purpose.  The S9 was designed to be used in an industrial setting, your either going to have to deal with the noise one way or another, there is no easy way to quiet it.

Guessing you didn't buy this directly from Bitmain... since they don't ship power cords.

Bad news:  Although some get away with powering an S9 on a dedicated 110V 15Amp circuit, doing so is dangereous.   Circuit breakers are rated at 80% continuous load, so a 15 amp breaker running at 110V can safely handle 12amps full time.  Your going to be pulling 1372W+10% ~-= 1509 W/110V = 13.72 amps, presuming you don't run it faster than 14 TH.  Some of my 14TH S9s run at 14.5TH, so draw 14.21 amps.

Good news:  Looks like you have all 20 amp breakers.  Big question is if you have 12 gauge wire running between the breakers and those outlets, which are 15 amp only.  That is a bit of a weird combination.  If you do, I'd just watch the temp at the power outlet.  If you don't, you may start a fire by melting the wires in your wall.

Safest thing to do is to wire up a 220V socket off that stove connection.  Your local Home Depot (or equivalent) should have the plug.

How many miners do you plan on running long term?  That 50 amp socket should be able to safely handle 5 of them.

Give us more details on your plan and we might be able to get a bit more specific.

You will, of course, have to buy matching C13 to NEMA 6-something power cords, depending on what sockets you select.  Easily found via Google.  I bought mine from Volex.

Remeber these things are load, like vacuum cleaners, and hot, like space heaters running on full 7x24.  You will need to plan for ventilation.

Is it line-of-sight by any chance?  I use radio bridges to go between my buildings and they work fine (about $69 each and you need a pair (disclosure:  price from memory a year ago)).

I wonder how many of those little guys are running older equipment and have shutdown due to higher diff and lower price?

S7s are barely worth running today unless you have free power (which few actually do - SOMEBODY is paying for that power!).  I hate to say it but (5) S3s is wha? ~2.5TH? - you could save power by replacing those with a single S9 and be running 5+ times faster.

Also, the line in the dust (sorry, couldn't resist) is somewhere around an S7 or V9 mining - hardly "big boys".  Unless my info is dated, a single S9 should be fine.

First: if an S9 doesn't sense both fans during startup, it will shutdown or just go into an endless test loop.

Obviously not all fans are created equal.  If its not sensing the speed there is likely an incompatibility.  The S&H is high, but Bitmain sells replacement fans for a reasonable price.

Be cautious folks... this guy is asking for 30 coupons and has a bit of an attitude when asked basic questions like if they have enough power and cooling to support that many S9s.

I have some I can spare.

PM me your Bitmain receiver ID (I think that is your bitmain account e-mail). 

Same holds for anyone else looking for $100 coupons.  First group expires on 6/30, after which I'll have fewer.

I've sent to the California location.  Zero communication but received replacement equipment directly from China 2-3 weeks later.

Thanks.

Do the Used 841s on your site come with the balance of the warranty?

Based on my last reward and a price of $6441, I'm at 19.24 blocks for break-even.  Yeah, I'm starting to get concerned.

Or buy a new control board from Bitmain if its out of warranty.