Topic: Power Configuration [BOUNTY 5BTC] (Read 5705 times)

Honestly, I wouldn't bother with an expensive PDU and an electrician and stuff.
That $900 basically pays for an entire low-end (4 x HD 5830) rig.

Why don't you wire some kind of adapter cable that routes one 110V circuit to a $5 power strip A and the other 110V circuit to a $5 power strip B. Then, you start by plugging in two rigs to power strip A and two rigs to power strip B. This will definitely work. So far, so good.

The elephant in the room is what your circuit breakers actually are.
20A each?  This is what I had in Palo Alto, and I maxed them out.
35A each? 30A each? 40A each?
Check the circuit breaker panel. The circuit breakers should be labeled with the office suite #.

If you cannot clearly identify the circuit breakers, buy a $29.99, 1000 W electrical space heater at Walmart.
Plug it into power strip A, while all miners are mining, and turn it on.
Then repeat for power strip B.
If the circuit breaker doesn't fall, you're good to go for another 2 rigs (one goes into strip A and one goes into strip B).
Now you got 6 rigs.

Rinse and repeat this simple test to get to 8 rigs.

I'd stop at 8 rigs, 4 on each side, for a symmetrical load.

Edit: In case a $5 power strip is only rated for 10 A, you'd want more than one for each of the 110 V circuits. But the principle remains: No need to spend $900 on this.

Yes (and it is a single phase outlet). The problem is that at 208V it will take more higher amperage to get the same amount of power.

Yep. In any case, the electrician might be a good idea, since he will have to convert it to a 4-wire system. Right now you have 2 phases and a ground, but that is grandfathered in. Need 2 phases, a neutral, and a ground. At 208v, the rigs will pull a lot more amps than at 240v, but the only way to fix that would be to install a buck/boost transformer in boost mode. http://en.wikipedia.org/wiki/Buck%E2%80%93boost_transformer

Like TWO 110V single phase outlets.
Or like ONE 208V single phase outlet.

Does that mean I treat it like a singe phase outlet then?

The other legs of the 3 phase prob go to other offices.  You have 2 legs of 208 3 phase in that outlet.

Ahha! I probably only understood 5% of article. Now you've got me wondering if my circuit is three-phase. From what I could understand about the article the only way to get 208V is from the difference between two phases in a three phase system. The difference between a phase and neutral would be 120V. That seems to be what I'm measure on my outlet. But why would anyone hookup a three phase socket  for office use?

I've tot a Leviton -


What I get when I measured the points you referenced -
X -> Y = Ranges between 208V and 210V
X -> W = 120V Solid
Y -> W = 120V Solid

Is it possible that it's wired incorrectly or am I just doing something incredibly stupid?

This might provide some insight on 208 vs 240: http://www.phaseconverterinfo.com/phaseconverter_deltawye.htm

Like I said, wye vs. Delta - they are different.

It should look like this:



W = neutral
X = one 115V leg
Y = one 115V leg
There is no ground on this outlet which is why it is obsolete.

X -> Y should be ~230V (220V-240V)
X -> W should be ~115V (110V-120V)
Y -> W should be ~115V (110V-120V)

I've already got 3 rigs running without any issues. I'm expanding to 9 after the power issues are addressed. Regarding AC from what I could learn on the net it's clear what I need to plan for -
   1200 Watts per Rig * 9 Rigs = 10,800 Watts of power  (45 Amps)
   To convert that to BTU I've read you multiply by 3.413 giving me 36,860 BTU
   And then to convert that to AC Tonnage divide by 12000 bringing my requirement to a 3 Ton AC Unit
 
The office I'm in has a dedicate 4 ton AC Unit. So if i'm to trust my knowledge I gained from googling this crap I should be okay...


 

So I didn't measure hot-hot.. Didn't think that was a wise idea at the time.. So after you mentioned it I decided I'd go measure it and found it's reading only 208V?!?!?! I double checked the Hot to Neutral and it's 120V. Show does 120V + 120V = 208V???

I would suggest that you don't purchase all nine rigs immediately, but start with, say, three and find out whether the A/C can actually get rid of the heat of 3 rigs nicely, leaving the room at 72 or 74 maybe even 78 degrees Fahrenheit.
Because chances are, the A/C (and/or the air duct system) is not designed to get rid of 10,000 W - maybe it is only designed  for two or three humans at 250W each and a single desktop PC at 250W.

I had an office in Palo Alto with 8 rigs drawing a total of 4,000 W and the only way I could avoid thermal meltdown was opening the window and putting the rigs on the windowsill, their rear facing outwards. Eventually they kicked me out for using excessive electricity ("breach of contract").

Currently I have an office in Santa Clara with 3 rigs drawing 2,000 W, but the window cannot be opened and thus I cannot turn on more rigs. Even so, it gets hot like in a sauna and when I spend any extended period of time there, I have to take off my shirt and sit there in my undershirt...

It you measure it hot to hot it should read 240V.  I assume you were measuring it hot to neutral which would should read 120V.


That will work but $900 for a PDU plus $400 for electrician is highway robbery.  Even if you want an electrician I would ask him if he can check on upgrading the circuit.   If the wiring can handle 60A then upgrading the breaker and installing 2x L6-30 is going to give you more power and cheaper wiring options ($100 vs $900).

Ah the ole 208V/220V/230V/240V/250V question.

So what is 208V?

In the US the only place 208V exists is when tapping between two phases of a 3 phase circuit.   Datacenters and industrial buildings will be supplied power using 3 phases where each line is 120V potential with the ground.  Each line is out of phase from the other two.   Tapping from one phase to another results in a 208V circuit.  It allows more circuits to be installed on one wiring run (among other reasons).  

All the rest of the power in the US is 120V/240V split phase where two 120V mains are supplied.  Tapping between them gets you 240V.  Tapping either of the 120V mains to the neutral gets you 120V.  That is how homes in US can have both 120V and 240V using only 3 wires (leg1, leg2, and neutral) from the street.

If all that was confusing don't worry about it.  The important part is that 208V circuits only exist in buildings wired for 3phase power.
The good news a PDU designed for 208V should work fine at 220V-240V.  Some brands will even write it like that (208V/230V).

The APC 30A models I listed above are designed for 208V circuits but work fine with 240V.  The only thing to worry about would be a 3 phase 208V PDU.  A PDU listed as 3 phase 208V is designed to take the ENTIRE 3 phase circuit (rather than split 3 phase circuit into 3x 1 phase circuits).  Connecting that to non 3phase wiring would be very very bad.  Good news is they use completely different plugs so you would have to try hard to get it connected.

So why do some things say 220V, some 230V, some say 240V?  
Stupidity?  Voltage in the US is often called 110V/220V but it isn't.  It is actually 115V/230V however it can vary from location to location and even on time of day.  

Generally speaking:
220V/230V/240V all refer to the same thing.
110V/115V/120V all refer to the same thing.

You can't change your voltage (well not in any way that is useful).  Your voltage depends not only on the building but the mains supplied by the power company.  You got what you got.

So what is 250V?
Nothing runs @ 250V the connectors are simply rated @ 250V.  Which means it can safely handle 0V to 250V which covers 208V and 230V.

I just purchased a multimeter and measured the voltage at the NEMA 10-50 Socket. Each of the two lines is 120V. So that makes it a 240V circuit.

So if I power only 8 rigs through the PDU i'll pull only 40 Amps and will be within code. I can then place everything else on the 110V line.

When I'm ready to expand I'll go the route that DeathAndTaxes suggested and install new 30Amp lines using NEMA 6 sockets.

250 Volts is just the maximum tested and allowed voltage for the plug/receptacle itself, the actual voltage will need to be measured with a meter. Common voltages are 208, 220, and 240 volts, depending on where you are.

I'm not 100% sure why they are different, but I believe it is due to whether the service is wye or delta phasing.

Great information much appreciated even though it's not what I wanted to hear. It's clear from what your saying that I can't use a 50Amp /  208 Volt supply for my farm and it got me thinking. What determines if the line is 208/240/250 Volts. I looked at the NEMA 10-50 Socket again and noticed it says 250V. I assumed it was 208V since that seems to be what most PDUs reference. How do I know what voltage my line actually is? Should I go with what's written on the socket? Can the voltage be changed at the circuit breaker or do you need to have the building wired for different voltages?

If the line is 250V as the socket says then the farm will pull 41.4 amps and wouldn't that put it within tolerance of the code requirements??? I do have several 110V Lines that I can use to make sure the circuit stays at/under 40amps.


 

Well pulling 50A continual load on a circuit reated for 50A is a code violation anyways so if you want to violate code then I would go with:
NEMA 6-50 outlet (or CA connector but they are much more expensive)
custom Y adapter (L6-50P -> 2x L6-30R)
2x $50 used 30A PDU
Just make sure to keep wattage down below 40A (maybe put 1 of 9 rigs on a seperate circuit).

Are there any other 230V outlets (50A or otherwise)?

On edit: one last option would be to determine if the wire can handle 60A (it may). You (or electrician) will need to see is part of insulation is visible to get type, gauge, and temp rating of the wire.

http://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

If the wire is rated for 60A (my guess would be it is 6 gauge 70C) then you could replace the 50A breaker w/ 60A breaker ($25 part) and install a pair of NEMA L6-30 outlets ($40 in parts plus labor).  A pair of used (ebay) 30A PDU ($50 ea) would give you 48A usable and you wouldn't violate the 20% derate requirement for continual loads.

Note: the derate requirement is important.  With variable loads the conductor will get a chance to "cool off" between duty cycles.  With a continual load you are pushing the wire closer to max rating 24/7.  Any defect or failure could cause an ignition event behind the wall.  Now do I think 50A continual on a 50A circuit is going to cause a fire?  Probably not but the electrical code is intentionally conservative.

I looked at these solutions but unfortunately 30Amps will not power all 9 machines. I need a minimum of 50Amps. I don't want to pay the electrician to run new lines if I can get it to work off the existing 50Amp Line.