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It appears I might be heading into renting fairly big warehouse at 30k$ a year lease can not find any cheaper one as they are snatched right away. So I still decided to go for it because almost half of my GPUs are sitting and collecting dust at home unable to use. Now agent said it is my responsibillity to bring your own electrician to test electrical output, but with EE degree I thought to do myself (bit apprehensive about bringing outsider because wanna keep mining operation and location under a sleeve due to high cost of equipment being used) but I was wondering what I can will be appropriate. Will it be a simple job and what do they test?
My EE degree is 15 years old and I am all software now but still remember basic electrical stuff like P=IV, V=IR and stuff like that. :)

Should be able to determine the setup based on fusing if accessible. No reason aside from certification that you couldnt do it yourself. In my state you can wire up your own domicile without certification as long as it passes code.
Those laws are basically all you would need. And the codebook for proper wiring laws. Its easy peasy, at least for home wiring, but shouldnt differ for commercial really.

I mean, look at the damn breaker panel that you will have access to. That will spell out pretty plainly the power availability of the facility.

yes for home i do sort of familiar with it, i was thinking some special equpment to initiate some current to see circuit breaker will activate etc.,

if you do the wiring from zero, you can choose a good brand of cable/wiring parts.
1 MCB group can be use for several mining rig but no more than 4.
less is better but cost you a lot of cable running down to rigs.
use branded PDU or build it your self. dont use the max capacity. always spare at about 20%

if you want to use existing wiring than you should test them with insulation tester and current leakage tester.
those equipments is also costly.

rgds,

No need to test anything, just look at what kind of service is installed and it's amperage. You can bring an electrician and not reveal that it's for a mining operation, you know? He doesn't give a fuck why he's there, as long as he's getting paid.

Agreed - I would have one come out to inspect the panel / mains for aged breakers or crappy wiring before anything was brought to the warehouse.
  Run all the circuits/outlets yourself for whatever racking setup you do and take head of your amperage per circuit and you should be fine...
but, that's just my 2 cents... meh

the reason for "jumpiness" is reasonable as cryptomining, you are keeping tens of thousands of dollars of equipment in the warehouse and one theft or burglary is all it takes to ruin your business, also i am already having difficulty finding an insurance at least my farmer's agent pretty much ruled out insuring the crpyto equipments. Compared to that, most smaller size business would keep at most several PC and few equipments at their warehouse which is far less costlier than mining equipment. So keeping under sleeve I believe is justified.  ;D

First thing i would have done it open the Main Breaker box and check what gauge the main wires were coming into from the outside wire
connection from the pole.   You could easy calculate what amperage you have coming in and calculate how many rigs you can run without
changing anything major from the pole.

Invest in a semi-decent security system (door mag locks/card key access/cctv) and tell the Insurance company that you are a data storage center for the cloud... ha  ;D

Best answer ever!

Well i decided to declare as cryptomining and software development :D. Indeed I am actually coming up with sw platform to manage the rigs. Hopefully i can put it on market either as open source, subscription, or donation or whatever. I think hiding crypto nature will almost be impossible shoud audit comes by. Insurance scams are costly (prison term)  ;D

I will be getting surge protectors literally, good ones, little bit research shows there are good and bad ones. from the wall to the equipment including camera, temperature sensors all remotely connected, i am going to make sure of all the safety precautions however most concern is the what is behind wall is outside my control :)

Most building in consideration were built around 1970-1980, not sure of the electrical system quality of those buildings. Some of them says it has been renovated however wheher electrical system has been updated or not, not sure. Will have to ask.

Say what? "You could easily calculate what amperage you have coming in"?   The amount of current coming is totally dependent on what the load is.  In this case the load would be rigs, lights, fans, etc.  You cant have any current flow without a load.

A cheap harbor freight infrared thermometer is your friend.  Check all connection with the IR Thermometer.  If one is loose then its temperature will be 5-10 degrees plus higher than the rest.  This check can only be performed when there are loads connected to the breaker panel. (AKA branch circuits connected to your (branch) circuit breakers.  Use proper electrical safety when working in an electrical panel at all times!

OP....You just call the power company that feeds power to the building and ask them what the service entrance feed from the pole is rated for.  Goto your main panel and check the main breaker rating and take that number and multiply that by your service voltage and that answer will be your total watts. Your main panel will tell you what your voltage is most likely if all the stickers are still there.  Then multiply total watts by .80 (80%) which is the 20% derating amount for constant duty cycle.  

Heres an example for a typical U.S. household.

200amp main breaker  240vac service entrance feed.

200 x 240 = 48000 watts.

48000 x .80 = 38400 watts Total Watts available for constant Duty Cycle.

Do not think you will use a power cable to feed equipment that is rated for say 20amps and think it will be ok to run 18Amps continuously 24/7. Remember the 80% rule of derating for constant duty cycle.

Basic electrical math formulas

Power (w) =  E (volts) x I (Amps)    P=ExI

E (volts) = Power (w) / I (Amps)     E=P/I

I (amps) = Power (w) / E (volts)     I=P/E

I=Current   P=Power  E=Voltage

Now there is also a possibility that this warehouse has 3 phase power and thats a whole different ballgame.  Could be 208 3 phase, 480 3 phase and even bigger depending on what the building was used for over the years.  You should have checked to see what the power input to the building was before you leased it.  If its 3 phase then you are screwed because you will need alot of step down transformers and your efficiency will be down in the weeds.  208 3 phase is 120v to ground from each leg to ground. You cannot get 240v from 208 3 phase without very expensive step up transformers.

I guess this is the good old US of A right? In Europe, bigger buildings are normally fused with the incomming connection with something called a Blade fuse, normally for 63ampere for each phase. in my tiny appartment ive got 3x 32 ampere, 400v. Makes things a whole lot easier mining!

I doubt your incoming power to your apt is 400v. 

havent leased yet, at least two of them were 3-phase and one of the 3-phase were 480v. So step down to 120v to standard household voltage may be needed unless power supply units can handle other voltage. I'd probably prefer 120v at the PSU unit. 3-phase is opposite of single phase (power+neutral) right? How much efficiency am I expecting to lose?
Say if I plugin power consumption meter at the 120v side of step down transformer and recorded using 10KWh than I am billed for 10KWh/efficiency?

Update: looking at spect of PSU (thermaltake 1200w units I am buying) it can handle 100v-240v so it appears it can handle 24v voltage.
Thanks.,

At least two articles on the internet says 3-phase is in general more efficient, of course there are lot of technicals but I am just covering the high level stuff can not read all of 'em but at least one of the article says it is expensive to convert 3-phase to a single phase. Now I am looking what really expensive means, is it just one time cost of step down transformer in which case i can shoulder or is it lowered efficiency in power throughout the usage, oh god there are so many things to consider, in the end, I hope lord will be watching me lol.  :D

https://blog.tripplite.com/single-phase-vs-three-phase-power-explained/

3 phase is more efficient....on 3 phase equipment. With a 3 phase building you will end up with a substantial amount of available power because there are 3 legs of power coming in instead of just 2 like in a home.  ANYTIME you step down or up power you end up with less efficiency...that loss is in the form of heat at the transformer. This is why no power supply is 100% efficient.  208 3 phase is what you want over a 480 3 phase power input.  208 3 phase has 120v to ground from each leg OR 208v across any two legs.  480 3 phase is 277v from each of 3 legs to ground or 480v across any 2 legs.  You wouldnt need a stepdown transformer for a 208v 3 phase building. You would be good to go just know that you CANNOT use anything that an electrical motor rated for 240vac (marked 220/230/240) in that building that has 208 3 phase.  They will burn up in very short order.  Now your power supplies will be fat dumb and happy in a 208 3 phase building.  You can run each power feed off of one leg to ground OR you could run them off of 2 phases which would yield 208v.

That is what i thought. The eddy current and all sorts of stuff happening in the transformer, used to study while I was doing EE but that was more than 10 years ago, so does not click much. I am looking at 480 to 240 or 480 to 120 transformer, and if efficiency is not too low I may get one, this is added expense, and who knows transformer will not blow up after constant use, another risk element to put into.

If you have to get a warehouse with 480v 3 phase and are buying 480 to 240 step down transformers you (A) Better have some serious cashola ready and (B) Better hope Bitcoin goes to $100k soon or you will never recoup your investment unless your rigs/farm is already paid for itself.  Id hate to see what a 480v 3 phase power bill looks like!  I know 208 3 phase aint pretty for one of the radar station I take of (power distribution and backup emergency power). 3 phase is more efficient when you dont have to step it down (this is where 208 3 phase comes in handy) but the up front costs along with monthly whether or not you use it can be high.  Me personally if I ever surpass my homes 200a supply then I will just put a shed or small garage on my 5 acres that is dedicated just for that and have another service entrance brought in to that building.

Yes, renting a commercial space  is increasingly looking unnattractive as i presume majority of them are equipped with 480v. I Am thinking a land or buhva far out house at cheap and just do the minkng there. It is more peace since u got 100pct control over your property.

I understand that  by how much? power in at 480v side and power out at 120v side and you will get some ratio right?

It would be a 4:1 stepdown going from 480 to 120v.   The current would end up being 4 times higher on the 120 side vs the 480 side though not including losses.  Price one....they aint cheap at all.  How big of area do you need?  How much land do you already own? Theres peace of mind having better security at your own place instead of having to worry about someone breaking into your warehouse across town. The gas back and forth will to the warehouse will more than enough pay for a couple German Shepherds to roam your own land around your own building.  There are options.  Prefab outbuildings, sheds, garages and even custom builds along with DIY. FYI Bring in a prefab shed and they put it where you want it, there are many places that will build to your spec and most places dont charge you property tax on the sq footage since its not considered a permanent structure like a garage. Sit the shed on cinder blocks, crushed rock or even on its own skids.  I have enough room to to put many of those on my house lot before Id have to start getting into my woods and start clearing.  The startup costs for a prefab shed, its own electrical (internal and the power feed) and ventilation/air conditioning are quite attractive.

How many Gpu's are you talking about here that need to be put to work? What kind are they?

Certainly there are i2r losses but I dont expect pathway between 120v side to PC-s will be longer than normal household wire length. Sent inquiry to one of the transformer manufacturer and said to me at least heat loss should not be a problem but i have to account for any possible negativity. I dont expect big area probably 10-15 miners 1st year but where live in CA the cost of electricity+tax is so much, i dont own house but condo so no land, so traveling to closes state NV for rental, with 20 gpus running in my condo, the electricity actually now costs more than if i do a small warehouse rent in NV. so that is what i am doing, at the same time, i am looking at cheap isolated small houses across state border to see if i can. If i manage to get something working NV just beyong the state line, then travel is reasonably 3-4hrs drive, i'd consider it manageable.