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The key to doing this is simple.
1) dec 2018 bitmain firmware set to LPM
2) 1 hash board in the center.
3) proper fans -----
The Delta fans I used were purchased from China source at about 9 dollars each
https://www.ebay.com/itm/for-Delta-AFB1212SH-12cm-Ball-Bearing-12V-0-8A-4pin-PWM-cooling-Fan/182961677356? cost was about 32 dollars for 4 fans
4) proper spacers. ----- got these on amazon
https://www.amazon.com/gp/product/B0103MXYA2/cost was 4 per spacer you only need 1 spacer for the push intake fan
You are building a space heater that mines.
Not a miner that space heats
net cost is 8+8+4 = 20 bucks to make a 1 board 3.3th 335 watt heater.
This assumes you have a psu and a miner.
I have lots of s-9's and will be retiring them from Clifton farm this fall but they can do space heating for me in my house and buysolar's house
hard to read but it is 335
lastly the psu is a 1000 watt gold I think I could drop to 310 watts if I used a titanium
You may need run on Low Power Enhanced Mode as it may not cool at Low power mode
On my test model I do 4700gh and 480 watts and temps go too high 105 since the fans max at 2800 rpm.
So I simply do Low Power Enhanced Mode get 3300gh at 335 with temps at 88 since fans max at 2800 rpm.
No real need to sound proof since sound is in the 41-45db range which is fairly quiet.
Since I have 20+ s-9s my guess is I will build quite a few of these units.
That fan I use pushes 115 cfm but it is quiet at 2800 rpm.
There is another model delta that pushes 150 cfm but goes up to 3600 rpm it may be too loud for a space heater.