AC doesn't/shouldn't draw air from outside the room it's trying to cool. Just think about it.
Bringing in hot air from outside and trying to cool it is far less efficient than just trying to cool the air that's already inside, along with the fact that it would be creating positive pressure which would force cooled air outside. Instead, it recycles the air inside.
That depends on the temperature of the air outside and the power of your A/C unit. 16 S3's generate roughly 16x the wattage of a single unit, say 350 Watts per unit. This is roughly 5.5kW (plus the power the PSUs take just for running, these generate some heat as well). Does you A/C unit have enough power to take this much load?
If not, they will fry - assuming you have them enclosed in that room. Done that with much larger server room, fortunately the devices survived.
If you don't have them enclosed, i.e. you let the outside air in and exhaust the "used air", having the A/C unit cool the intake air is actually more efficient than keeping it up in an enclosed cabin. Again, it depends on the power of the A/C unit.
By having your miners blowing air outside of the room, it's creating negative pressure inside the building. Less air crossing the heatsinks, less air to absorb heat, they'll hang out and get toasty.
Fully agree. If you are blowing the air outside the room, you have to blow some air in as well. In the winter it might be actually a good idea to have them cooled with the outside air - depends on your winter temperatures though.
Note that in terms of electricity bill - S3 takes X Watts of power, this converts to mostly heat (mostly being like 99% here). To cool the S3 you need an A/C unit that cools the X Watts produced, so the A/C unit should be able to take at least the same amount of electricity as the S3's combined. Ergo you electricity bill for the mining operation will simply double.
The point being here - you either
- seal the whole room, do not let the air in or out, cool it with a sufficient A/C unit, worry about it failing (fire hazard!) and pay double the electricity S3's take;
- let the air into the room, cool it down before it reaches the S3's, then let the S3 exhaust the air out - this would actually be the recommended solution for you since
a) you don't have to worry about fire hazard in case the A/C fails (it is a wooden room, isn't it?),
b) you don't need to have the A/C large enough (heat-wise) to take all the heat S3's produce (it will only cool the outside air a little) and
c) you can leave the A/C off when the outside air temperature is relatively low (say below room temperature), during the cooler part of the year (again, depends where you live, though). This is not necessarily a cheaper solution (you still pay for the A/C working, but it does not have to be as powerful as in the sealed room conditions), but much safer, in case the A/C fails you do not give away the S3 produced heat in an enclosed compartment (an oven sould ring a bell) but rather blow the heat out cooling the units with (worst case scenario) outside temperature air.
Hope this helps...
