There are a lot of factors involved and it's too unpredictable. The calculator you linked does not seem to include coin price changes. Nobody knows what will happen but it's largely self regulating market, so if the difficulty goes up and it becomes more costly to mine, miners will raise the sale price. Things to worry about is if the current large amount holders flood the marked selling their coins but recent surveys indicate that sell off will only happen when BTC reaches $200k. Assuming that price does rise and you do not sell your all your coins they will be worth more in the future. Second is if the demand for BTC falls because most of the market shifts to something else and third if somebody releases much more efficient miner, the best currently seems to be Ebit E10.1 18Th at 1600W using 10nm chips so not much better than S9 http://miner.ebang.com.cn/goods-2.html. There is also worry that coin could fork to another algorithm but BTC developers seem pretty stubborn bunch so unlikely to happen.

I think it's important to diversify and spread your risks, I think LTC and L3+ have great potential in terms of usability, potential price rise and I think difficulty will rise slower than BTC at least until the price picks up. ETH and Dash also show great potential. It's too hard to say about other coin. I better end it here before I drift off in to many other coins.

First test in order of evening running S9 with just the intake fan, the second fan still connected to stop it freaking out but removed and running on the side of miner. Did I tell you those stock fans are powerful?? With just one intake fan connected I can feel air flow is better than Manrose fan if I put my hand at the back. It seems exhaust fan does not do much. 2 stock fans highest chip temp 80-82C, only intake fan 83-84C, only Manrose on intake 90-91C. This is only one S9 I am testing with Delta fan as intake and Yate Loon exhaust. Looking at different miners there are 4 or 5 different fans used in different configurations sometimes the same both ends, sometimes different. Max rpm are 4500-6400 between fans, current between 1.65-3.0A, different blade counts, different area taken by the motor in the middle, other specs are a bit hard to find as some of the part numbers seem to be exclusive to Bitmain and yield no hits on the web or return very different rpm and current specs than what it says on the fan.

Now on to test Manrose fan on L3+

So the initial testing results for L3+ with Manrose fan are in. Before I was running my overclocked L3+ at about 1000W with a fixed fan speed of 20% and the highest chip temps were aboout 77C with 70dB. Manrose fan without any adapters just put next to miner on intake with nothing on exhaust 64C max chip temp and 65dB.

I have not tested D3 with this fan but with a custom firmware and settings it's also running at 1000W so I guess results should be similar. S9 temps are higher but it can also tolerate higher temps so you could go for 6" fan or just accept that temps are higher and use 5" fan. Well they are not cheap @ £60-70 but they will have re-sale value as well if you need to sell them. Another conclusion is that exhaust fan does not do much on Antminer so you might as well ditch it for the 2C temperature difference and save up to 36W of power usage worth about £2.88 per month.

Interesting findings there with the fan experiments, I had a little play with my S9 today in regards to ducting cold air to it from outside. That dropped the fan speed down to almost pleasant levels.

Finding a reliable source of cold air but keeping it simple will be a challenge.

Was thinking about setting up in the loft but that gets hot in the summer so would mean ducting in air from outside and that will mean holes in roof :(

Ducting in air from under the house would be nice but that means the miners would be down stairs :tuttut:

Damn it I need a new house.

Same here but the miners have not earned for new house yet :ROFL:

I have 1x L3+ running on the loft but that's about it, 1st there is not enough power going up there even if I have 2 ethernet cables going to the loft so would need new power cables. And it would get very hot in the summer.

I have not tried ducting to go directly outside as that would mean noise going directly outside as well an it's about 70dB at the end of duct.

My guess would be that, while the inlet fan does most of the work, the purpose of the exhaust fan is to ensure that more of the air is drawn all the way through. Without it I would be concerned that a lot more air would escape through the hashing board power connector slots and the upper grille (on the L3/D3 miners), which could result in hot spots at the far end of the hashing boards. It's possible there may be only one temperature sensor per board too, so you may not be seeing the far-end temperature. Additionally, with the stock fans removed, the Antminer will not be able to ramp up the fan speeds should it detect that the temperature is too high. If the exhaust fan is relatively quiet, I think I'd be inclined to keep that one on, just in case.

Unless you have a 'converted' loft, shouldn't there be ventilation gaps/holes in the eaves?

I understand there is temp reader in every chip but it only displays the highest on each board, there are also several PCB temp readers and earlier firmwares were displaying up to 4 different PCB temp readings but later firmwares only show highest/exhaust side temp.

I have not converted any roofing arrangements but there are no holes and even if there was any I don't think they would be sufficient to vent what would be up to 9kW of heat.

If it was me, I’d not bother with a aerated block and go for a dense concrete block, almost certainly better at blocking noise +++. That said, also a lot heavier!

My house is 118 years old and the cross ventilation is what comes in under the roof tiles.

Wouldn't be a clean stream of air through that that I can imagine to be able to duct it into a miner.

Maybe you are right but these are marketed as having excellent acoustic performance, it's a plus that they are lighter to handle but more importantly they are also bigger in size making pretty much ideal size shelves for 2 miners. With the bigger size they will also be more stable if I just stack them up without mortar so that I can take it down it easily if it does not work out and re-use or sell them.