– Adding a Second Fan to an Antminer S1

I mine Bitcoins.  My favorite company (these days) is BitMain out of China.  They ship fast, the quality is great, and I’ve had zero problems with their miners.

If you own an Antminer S1 model, you’ll notice there’s another 4-pin connector at the rear of the unit, so I found a super quality fan and wired it up as a 2nd fan.  As you may or may not know, keeping your mining hardware cool is the name of the game.

Let’s get started.  You’ll need a few items:

  • (4) #8-32×2″ screws (Home Depot, Lowe’s, Ace, etc.)
  • Flush cutters (or razor blade, or Dremel, etc)
  • Rubber O-rings (to dampen vibration, found in sink/faucet repair)
  • A Henry F. Philips head screwdriver
  • A 120mm x 38mm PWM 4-Pin fan (I used Delta AFB1212VHE)    (a  2 or 3 wire non-PWM fan is OK, but will run at its full speed…)

NOTE:  If you opt for a 120mm x 25mm fan, the instructions are essentially the same, just use (4) #8-32×1 1/4″ screws.

I chose a fan capable of 4000rpm – a real bad-ass, the Delta AFB1212VHE.  It’s pin compatible with the S1 so you don’t have to do anything to it other than trim a little plastic so it will fit on the S1’s 4-pin connector.

#8-32x2 fan_flushorings

Using the cutters, trim away the tiny ridge on your fan connector (closest to the blue wire).


The O-rings go between the fan and the Antminer, here’s a shot of them installed on the screws:


Next, install the fan onto the Antminer S1.  It will have holes in place for the fan, but it will take a little effort to get the screws in as the holes in my S1s have not been pre-threaded.

To make it look nice, leave the bolt nearest the 4-pin connector for last and use it to hold the cable for the fan.  When you’re done you’ll have a nice clean installation.  Make sure the BLACK wire is closest to the top of the S1:


I e-mailed the guys over at Bitmain to see if they would let me know how to enable the tachometer in their WebUI, and if they get back to me I’ll update the post.

If you want to “hot-rod” your fan to the full 4000rpms (approx. 50dB!) then find a 4-pin PC Molex to case-fan connector like these:4pinmolex

If you end up with the style with the white shroud around the pins, use those trusty cutters to trim that away until you have something that looks like this:


Now, connect that to a PC-style power supply’s 4-pin Molex power connector and that fan will run full steam ahead at 4000rpm.  Make ABSOLUTELY sure that the BLACK and RED wires line up!


On my Antminers using the onboard connector is more than sufficient to run overclocked without any overheating issues.  Both sensors usually stay around 42C (107F).  The “hot-rod” mod will drop both temps by around 4 degrees C (usually around 38C/100F) on my Antminer S1s.


Update:  Check out the new Antminer S3 – looks to be based on the S1 chassis, and … there’s the 2nd fan and an actual enclosure, which mimicked the ‘shroud’ I build around my miners.   Nice!


  11 comments for “ – Adding a Second Fan to an Antminer S1

  1. Martin
    June 8, 2014 at 9:41 PM


    Are you blowing air into the Ant miner or sucking to work together with original fan?

    • RevisionX
      June 8, 2014 at 11:36 PM

      Hi –

      Both fans are pulling the same direction. It’s also quite easy to put a small plexiglass ‘shroud’ over the open top of the miners (where power and network connections are) to help channel the airflow. I have those on all of my S1s, but never added images.

      • Ryan
        March 8, 2015 at 7:02 PM

        Hi there. I hate to sound stupid here but when you say both fans are pulling in the same direction do you mean that both fans are sucking the air out (blowing the air outwards so if you put your hand infront of the fans you feel the warm air blowing at you) or sucking the air in (blowing air onto the heat syncs and you wont feel the fans if you put your hand near them)?

        Thanks. Ryan.

        • RevisionX
          March 8, 2015 at 8:48 PM

          Both fans should blow in the same direction, regardless of orientation. Arrows indicate direction of air-flow.

          Air > Fan > Heat Sinks > Fan > Air
          Air < Fan < Heat Sinks < Fan < Air

  2. Anthony Jones
    June 24, 2014 at 1:12 PM

    Could you add details and pictures about plexiglass shroud. I followed you write up, and love it so far. I’m down from 50/49 to 41/42 not hotrodding them.

    • RevisionX
      June 24, 2014 at 2:05 PM

      Hi –

      The “shroud” can be plexi, cardboard, or plastic but you should know that I eventually removed them as I did not see a significant difference (my S1s sit directly in front of a 9k BTU mini-split AC). You are essentially making a “lid” that covers the entire top of the S1, but has small cut-outs for the NIC and PCIe connectors. My thinking was that this would help channel the air-flow of the dual fans, making them more efficient, but both fans are powerful enough that I did not see a significant temp drop (more than 1-2 degrees) with the plastic covers on.

  3. Anthony Jones
    June 26, 2014 at 9:09 AM

    Ok thank you! Did you ever hear anything back about the fan control for second fan from Bitmain? When I hotrod the fan the stock fan goes to 1k rpms. I figure they will work better if they were both around the same speed

    • RevisionX
      June 26, 2014 at 11:55 AM

      I actually did hear back from Bitmain – they basically just commented on the additional fan mod with a “nice!” The new fan is controlled by the hardware (as you noticed they will both spin up/down accordingly), but the code to reflect that in the Web UI just isn’t there. They did not respond to the request…I’m hesitant to post a code-hack here, mainly because the fan is behaving properly.

  4. Mitchell
    July 3, 2014 at 12:14 AM

    any idea why the antminer doesn’t show a fan speed for the second fan? This is the one I bought:


    • RevisionX
      July 3, 2014 at 1:03 AM

      Unknown. Didn’t hear anything back on my questions about the 2nd tach. It’s that way for all 2nd fans. They work as they should, but that sensor just isn’t being reflected in the UI.

    • RevisionX
      July 3, 2014 at 10:57 AM

      One very important thing to keep in mind, you want the CFM of these fans to be “balanced” or nearly equal. Worst case, you want the additional fan to move *more* air than the original. Think “server or industrial” ball-bearing fans, not PC case fans. The original fan is capable of a great deal more than 66CFM, so if the original fan spins up fast, it will be fighting to push air through the 2nd fan that can’t move the same quantity. Granted, the ‘open air’ S1 will allow that extra air to escape, but it will make the original fan work harder than it has to with a lower CFM fan on the opposite end.

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