120V or 240V, what’s right look like?

I’ve seen a lot of posts about crypto miners (all types and brands) where people are having issues such as no hashing, low hash rates, or errors connecting to pools. One thing you should be prepared for, if you ask the Internet what’s wrong, is that you’ll get no shortage of answers. We are in a community that’s more than willing to help, give an idea or two, but sometimes the good ideas and willingness to help aren’t always in line with what the data is telling us.

I’ll stick with some more specific problems I’ve seen over the last few months, and that’s dealing with the power supply for the miners. First and foremost, a 240V supply is superior to a 120V supply (for mining) as it allows us to fit more miners/larger miners per circuit. A standard 120V residential outlet can safely output 1440W, which is enough to carry just a few types of miners. About the largest 120V residential outlet you’ll find is 20A (30A is far less common but exists.) This is by design as wire size increases with amperage. So once you get above 20A you’re having to get much larger wire sizes (10 gauge or larger) which makes for a much harder (and more expensive) run of cable. 


Now let’s take your standard electric over, water heater, or a couple S17 Pro miners. Each of these situations require around ~4500W. If we tried to run this on a 120V system (not saying they would, but stick with me here) we would need at least a 50A breaker and 6 gauge wiring. That’s because 50A gives us 4800W after taking the 80% rule into account.

Two problems here, first is if we have a 100A service panel in our home, that’s half your power (roughly speaking.) Second, I can run the same (actually more) power over just a 30A 240V circuit (5760W) and only need 10 gauge wire (commonly available in Romex style.) Now let’s see the cost savings as well, 10 gauge Romex runs about $1.50 a foot whereas the equivalent 6 gauge wiring runs about $3.50 a foot and is a bear to work with. 

Conclusion on this, you can run twice the power over the same size wire by going 240V, essentially doubling the amount of miners you can use on that line.


OK, back to the problem at hand. Why is my miner not hashing and why are people telling me it’s my 120V power supply. That’s a great question, and probably not the right answer you’re getting from everyone.

A power supply is generally rated in the power (watts) it outputs. This varies slightly with input voltage in the case of power supplies that allow 100-240V, however the output rating is generally close whether it’s 120V or 240V unless otherwise specified. In the case of the APW3++, it’s significantly different. Its rated for 1600W @ 240V but only 1200W @ 120V, more than enough to run an L3+ @120V but not enough for most S9’s (most common problem I hear about.)

Now the question, will that affect my hash rate. Short answer is yes, but it’s more likely to overload your power supply and cause a thermal shut down, which will shut down the entire supply and your unit won’t work at all.

The long answer is that you probably won’t have a situation where your unit isn’t hashing at all. Start looking at the other posts and suggestions folks are giving. But make sure that whatever you are running is supported properly by the power supply you are using.

In the case of the APW3++, it can pump out 133A @ 12V (1596W) when using a 240V input, however with a 120V input it only pumps out 100A @ 12V (1200W.) If you’re using an S9 (14TH) you need ~1370W to run, therefore if you run the supply at 120V it will “most likely” shutdown due to the lack of available power.

Power supplies are meant to pump out amperage at their voltage rating, up until they can’t pump out anymore. At that tipping point there is (or should be in any UL rated power supply) an overcurrent protection that shuts it down completely, it’s not a taper, it’s a hard shut down.

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