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I try to set a small size mining farm. I try to understand 3 phase electricity, but it is difficult to understand. I asked many electricians but everyone has different answers and I am kind of confuse.

I want to know the capacity of my 400 amp panel. It is 3 phase. I believe it can make 240v with two lines. It has a wildleg(208v? delta system?).

How many s9 can run on this panel?

My simple head calculate like this...I feel like something missing...
---------------------
Each Machine operate
1440w/240v = 6 amp
400Amp panel
so 400amp / 6amp =66 S9s
 
Constant electricity so 80%
66.66*0.8 =53 S9s
----------------------
Is this a right way to calculate?

I'm running my whole shop off a 3-phase wye (so, 120V line-neutral and 208V line-line) through a 400A panel. Got 350A of sub-breaker handling the hosting room, drawing roughly 100KW for 80-odd machines (most S9 but not all). I'm comfortable at 100KW, will run 110KW peak which puts my breakers at 90% capacity so I'd rather not do it for long. I've got meters on every leg so I can monitor the power use on the fly.

Every electrician is telling you something different because there are a lot of different ways 3-phase can be run. Different line voltages, delta or wye, each one does something different.

The first thing you're going to want to know is exactly what kind of 3-phase configuration you have coming in the building. I have 120V (208V L-L) 3-phase wye, which is probably the easiest kind to figure out.

You mentioned that it is a wild-leg setup and for the most part utilities do NOT want a full load running from that leg as it is intended more for moderate 3-phase motor loads in the building like HVAC with the lions share of load coming from the 2 legs working as part of the 110v taps.Those 2 legs together is where most of the 208V load should be drawn. Look up wikipedia's Wild-leg explanation. Now if you are in a light industrial zone area the normal wild-leg load restriction may not be an issue, it mostly crops up in commercial/office areas where most of a buildings load are 110v

edit: also, it is bad form to make duplicate posts in different areas asking the same question. I requested the mods remove the dupe in Mining > Support.

I remember that few electricians told me that I can't use every third space in the panel because the wildleg, Delta.

Does it mean the delta system like my setup have less capacity than the wye system like the gentleman above has?

98 S9s On a 400 amp 240v 3 phase panel

400*240v*1.73=166,080 Watts

Each S9 1,350 watts
166,080*80=132,864 continuous watts

132,864/1,350=

98 S9s

The 'not use every 3rd space' refers to trying to use a single-pole breaker in that slot which is fed by the wild leg thinking that it will provide 110V referenced to Neutral -- it doesn't. Is more like around 180V as I recall...

That said, using a 2-pole breaker for 208V single-phase is fine same as using a 3-pole for 3-phase power: You are now drawing power phase-to-phase in either case so it does not matter what slots are used.

As for can you draw full 400A from the wild leg, probably but if possible try to find out how your utility feels about it. Some will tack on a surcharge because their local grid was not setup a lot of people doing that. True full delta or Wye incoming service does not have any phase-to-phase load limitations but in turn in the case of delta require a transformer to provide building 110V service. Wye service is 4-wire with 3-hot legs and a center referenced neutral but generally have limitations to how much unbalanced single-phase (hot leg-to neutral) current is allowed.

I believe it is safer to say to have another single phase distribution panel connected to that 400A 3-phase breaker for proper load balancing with smaller rated circuit breakers. With the computation above, 98 S9 miners divided in 3, so you will connect 32 S9s in line 1-2, 32 in line 2-3 and 32 in line 3-1.

We run our small farm off a 400amp 3-phase Wye configuration. We have 2 pole 30amp circuits so we are taking single phase 208v (leg to leg) off the 3 phase panel. You have to remember to balance the load across all three phases as much as possible on a Wye system. We currently run a bout 82 miners on it (mostly S9's, couple of 741's) and still have some room to spare in the panel. Here's what it looks like including the panel:

https://lib.store.yahoo.net/lib/animecorner/EchoBaseFarm.jpg (https://lib.store.yahoo.net/lib/animecorner/EchoBaseFarm.jpg)

We're pulling about 116KVa (it's a little more than the total wattage due to the 'power factor') through the panel and had the PoCo set a 150KVa 208v Wye distribution transformer to support it (it was only 75KVa originally and had to be upgraded). So even if you have a 400amp in the panel, make sure your transformer is large enough to support your load. Your total load should not draw more than 80% of your transformers total service rating, otherwise you'll reduce it's service life significantly. Datacenter operations like mining draw power much differently than typical commercial power usage. It's always on. You'll want to check with the PoCo that their facility to your building will support that load, and they may require you to submit a load letter describing how much you will be drawing and what it is for.

First off, I am NOT calling doubt into anything that experienced miners have said.

With that, I would HIGHLY recommend you get an extremely qualified electrician to have a sit down and explain everything to you.

A 240V 25 Amp circuit flashing will instantly fry you. A 400 amp circuit overloading and arching will literally make you explode.

You are right about the 80% continuous load, but man oh man please be careful.