How many miners, how big of a miner, can I fit on a circuit?

More and more I’ve seen questions from folks about how many, or how big, of a miner can I fit on a circuit. This is a question that has many unknown variables that I plan on diving into below. Disclaimer – Please keep in mind this is my opinion and not an actual consultation for your mining business, so before you do any wiring or make any changes to your electrical system please consult a licensed electrician.

Now on to the good stuff. In order to answer the question how how many/how much we need to know a little more information; the basics of your panel, the basics of your circuits, the basics of the miner, and anything else you plan to operate. 

RESIDENTIAL/INDUSTRIAL CIRCUITS

For starters, each location in question needs to have a load calculation done to insure that you aren’t going to draw more than 80% of the maximum panel rating. As an example, if you have a dedicated 100A panel you can’t draw more than 80A continuous at any time. Since the mining world is in watts, let’s use Ohms law to break that down.

100A Panel @ 80% rule = 80A

Ohms Law tells us that Power = Current x Voltage

80A x 240V = 19,200W

So the key thing to keep in mind before planning out circuits is that you can’t have a continuous load more than 19,200W on this panel.

CIRCUIT/LOAD PLANNING

Now that we know the maximum wattage of our panel, we can use a little math to plan out what our circuits need to be. I’ll make the assumption that whatever miner we are using operates on 240V since that’s the industry standard at the power level they operate on.

There are 2 main amperage ratings for 240V breakers that are used in the mining world (yes I know there are more but these are the most common), 20A and 30A. There are several reasons for choosing one over the other, ranging from length of wire run, number of units per circuit, cost of wiring, and available breaker space. The most important thing to remember about each circuit is that they also have a maximum wattage rating:

20A Circuit @ 80% rule = 16A

16A x 240V = 3840W

30A Circuit @ 80% rule = 24A

24A x 240V = 5760W

MINING EQUIPMENT

So we know the maximum wattage our panel will hold, and we know the maximum wattage different types of circuits hold, only thing we are missing is what type of miner we’re running and what its power requirements are. 

Since this is February 2022 I’ll choose two scenarios, the first is using a newly released miner, the second is using a couple generations old miner. I’m partial to Bitmain products so I’ll look at the S19 or L7 for one scenario (~3250W) and the L3++ for the other (~900W, don’t hate on my S9 people!)

We know that our maximum panel wattage is 19,200W, so how many of each miner could we theoretically operate (I say theoretical since we have to split this up in to several circuits and the math may not work out perfect.)

S19/L7 = 3250W

19,200W / 3250W = 5.9

5 S19/L7 = 16,250W

So that leaves us with 2950W available in the panel for other electronics, fans, network equipment, etc.

L3++ = 900W

19,200W / 900W = 21.33

21 L3++ = 18,900W

So this leaves us with only 300W available in the panel for other electronics, fans, network equipment, etc. Of course this is only relevant if you plan on running everything for your operation off this one panel. 

FINAL CIRCUIT PLAN

Now that we know what our options are it’s more simple at this point, with a little math for the L3++ scenario.

For the S19/L7 scenario it’s clear that we need 5 – 20A circuits, one circuit for each unit. This allows us to dedicate one circuit per unit and keeps us under the 80% rule for the full panel load (we are only using 16,250W which is only 68%.) Unfortunately you can’t fit two of them per 30A circuit like some other units (you’d need to be closer to 2800W to do this) but we have plenty of space in the 100A panel for 5 20A breakers. Keep in mind that 20A breakers will use 12ga wiring whereas stepping up to a 30A breaker requires 10ga wiring.

For the L3++ scenario we use a little math. We can put 4 units per 20A circuit (3600W) or 6 units per 30A circuit (5400W). To maximize the number of units, and keep it simple, we can also go with 5 – 20A breakers, 4 units for each circuit. This keeps us under the 80% rule for the full panel load (we are only using 18,000W which is only 75%.) Once again we will use 12ga wiring for this.

This was a quick down and dirty calculation and please know that there is more in depth planning that would go into an actual circuit design (like run lengths, ventilation, other equipment draw, main panel draw, etc.)

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