I've posted a picture of my miner while it's mods were still in testing & development here:
https://bitcointalk.org/index.php?topic=7216.msg11340538#msg11340538I didn't want to go into details until I got everything done and tested.
I've tried several things with the miner to find the best solution for my case. The problem with S5 is that it has quite a bad cooling solution. A lot of air runs out of the heatsink cold or doesn't even go into it, so Bitmain compensates that with a lot of CFM and a lot of noise.
The fan that comes with the miner seems to be the
Delta 120 x 25mm Extreme High-Speed Fan, or an exact copy of it.
Before I even got the miner I searched for the best CFM vs. sound ratio fan and what I found was
Scythe Ultra Kaze, which I'm now using on both of my miners. Push configuration is enough when it's not too hot in the ambient (up to 35°C), push-pull when it's hot, to still be able to run miners overclocked.
I'm from Croatia and it tends to get really hot in the summer, so I had to get the miner temperature vs. ambient temperature difference as low as I could.
To do so I've:
- Repasted the miner with a much better termal paste,
- Added mini heatsinks on the external side of the hashboards with adhesive termal paste (to the first miner only, as second came with them),
- Closed the miner's heatsink with 3D printed plates so no air can run out on the top or bottom sides,
- Added fan ducts between fans and miners which direct most of the air through the main heatsink and blow just a little bit of air to external heatsinks, just to drive some airflow on the sides.
One of the Bitmain's design flaws worth mentioning is the fact that thermal sensors for the hash boards are on the outer side (instead of heatsink side) and are very sensitive to airflow. When using fan ducts that completely block off the side airflow and direct all of the airflow through the miner, I was getting the actual temperatures, which were 20°C higher than regularly displayed. That's why Bitmain recommends that you keep your miner under 60°C even though the safety limit is 80°C. When reaching 80°C with stock fan, I'm quite certain the chips at the end of the heatsink are >100°C.
Here's the miner I'll be modifying for this thread:
http://www.pohrani.com/f/3o/oX/Ky40HfS/01.jpgThe first thing I did was repasting the chips, which wasn't too hard, just dull. Just unscrewed every screw the miner has and carefully separated the hash board from the heatsink. I've cleaned the heatsink and the chips with paper towel. Here's the chips before and after. I didn't care much about the paste on the sides.
http://www.pohrani.com/f/1q/4T/4oPq40nG/1/02.jpgI've put the new paste on and screwed the thing back together.
The next thing I added were the bottom plates. I've used the M3 x 10mm screws to screw them to the bottom. For some reason, this miner's heatsink's screw holes are so shallow I had to use nuts to tightly hold the plastic.
http://www.pohrani.com/f/2G/13F/2IMbltls/03.jpgThe bottom plates are flat on one side, but feature a bulge on the other side, to prevent air running in the gap between them and the heatsink. Here's what it looks like on both of my miners, when one of 2 plates is removed. Wherever I felt cold air coming out of the miner I've tried my best to close that part off and force the most air through the main heatsink.
http://www.pohrani.com/f/h/4u/ieyKXBU/17.jpgThen come the top covers. These covers were a bit difficult to design as they also have to replace the metal plate which holds the main board. Here it is on the miner:
http://www.pohrani.com/f/3h/v6/4OBRtnGf/05.jpgThis way air is forced through the whole heatsink before allowed to go out, allowing you to use lower CFM fan and achieve the same temperatures.
Here are both of my miners with the main boards screwed onto the top plates. The screws screw in into the plastic perfectly. I prefer having my ethernet cable running out of the miner at the top. It's also easier to see status lights and ethernet activity. It is just as easy to have it all on the bottom.
http://www.pohrani.com/f/w/D1/2R4Niqjv/06.jpgNow we're going to have a look at fan ducts and legs that hold the miner vertically. Legs took me some time to get the height properly so that the fan can take in enough air.
http://www.pohrani.com/f/47/VE/lGbxdUF/14.jpgLegs are not necessary and your miners can be horizontal, if you wish. I was following the natural motion of the hot air so I prefer having them vertical. The legs are designed to match the Scythe Ultra Kaze fan's housing and they can be screwed onto it with the screws that come with the fan. Gluing them on is also an option if you don't plan to take them off.
Leg, screw and the fan are shown in the picture:
http://www.pohrani.com/f/1u/gz/4w8FzGYO/12.jpgOn the top image you can also see how I screwed in the fan to the miner, having the fan duct stuck in the middle. I've deliberately used these screws because, as you can see on the following image, I don't have to take the legs off if I want to unscrew the fan to clean the dust. Screws are screwed in by hand and then just tightened a little bit with the tool on the picture:
http://www.pohrani.com/f/1m/r9/j9UpoaM/13.jpgScrews are M4x40mm.
This is the bottom fan duct:
http://www.pohrani.com/f/r/bn/1THljCgs/15.jpgIt is designed to force the most air into the main heatsink, with little gaps letting the air through to side heatsinks and thermistors. The only reason for this is to force the air to move around external heatsinks and affect the thermistor. If there were no gaps at all, the temperature readout would equal pretty close to ASIC's core temperature. The fan duct perfectly fits the miner on one side and a 120mm fan on the other.
http://www.pohrani.com/f/2d/ig/37MxWcUI/16.jpgI have also replaced the default screws that hold the miner's front side to heatsink. They were sticking out too much and fan duct would have 2mm gap from the miner. I've used some flat top M3x5mm screws I got from China a while back.
The top fan duct is different, featuring no side gaps:
http://www.pohrani.com/f/22/oE/4dDH479U/09.jpgIt also perfectly fits the miner.
http://www.pohrani.com/f/1V/13A/1PYuZnuD/10.jpgThe fan screws on top just as easy as it is with the bottom duct:
http://www.pohrani.com/f/3K/Hk/45VN3smK/11.jpgSince the screws are 40mm and fans are ~30mm thick, getting them in so that they would not fall too short when the fan duct is in between is important. You want the screws to be positioned like this:
http://www.pohrani.com/f/3F/ru/tvWUFvX/01.jpgTo do so, put the screw you're adding like this:
http://www.pohrani.com/f/2x/N7/nMhpvui/02.jpgTake your screwdriver and start screwing it in. The plastic will be dragging it in as you're screwing.
http://www.pohrani.com/f/41/9Q/4yi79XqT/03.jpgIn the end it will just fall in.
http://www.pohrani.com/f/3c/cg/2t6rfdZa/04.jpgYou will probably damage a tiny bit of plastic, but not enough to void warranty or anything like that. I had one of the fans going back under warranty because of excessive vibration. Got a new one back without a problem.
The end result is something like this:
http://www.pohrani.com/f/7/10x/4V3Rcu04/result.jpgMy PSU of choice is the Super Flower Leadex Titanium 1600W, because of it's extremely high efficiency.
Here are the results for both of the miners after running for 24h at 400MHz, ambient temperature was ~25°C during the night and maxed around ~35°C during the day.
The older miner with bigger gap between heatsinks and custom external heatsinks:
http://www.pohrani.com/f/3r/Mk/1cPJ9Z27/24h-400mhz-black.pngThe newer (green plastic) miner:
http://www.pohrani.com/f/26/cZ/4tSzdgfu/24h-400mhz-green.pngVery, very low number of hardware errors, so I'm calling this a success and am planning to keep them running like this, as ambient temperatures will probably reach 40°C during the day sooner rather than later.
Here you can download all of the STLs for the 3D printed parts:
https://dl.dropboxusercontent.com/u/22363327/S5%203D%20printed%20mods.7zIf you want to tip me for the designs, here's my address: 1F7itYL4vDh4BfHy8m4KnVx1UqgS462Ej6
You may use my designs for your own miners, please do post photos if you mod some!
If you have any questions, do not hesitate.
