Mining farm cooling: air, hydro or immersion

A mining farm produces exactly as much heat as it consumes electricity – ten machines at 3.5 kW each are 35 kW of heat non-stop. Smaller farms are cooled with air: cool air in, warm air out, and the two streams strictly separated. A water loop (hydro) pays off with a higher machine density, where quiet matters or where you want to reuse the heat. Immersion, i.e. submerging the machines in liquid, is the solution for quiet, dust-free operation and overclocking.

Summary

• For each machine with a power draw of 3.5 kW, you need roughly 700 m³ of fresh air per hour if the air heats up by 15 °C.
• Bitmain specifies an operating temperature of 0–45 °C and humidity of 10–90% non-condensing for air-cooled machines.
• Air conditioning is the last resort: every kilowatt of heat removed costs roughly another third of a kilowatt of electricity.
• Hydro and immersion need a heat exchanger and a way to dissipate heat outside (radiator, dry cooler), but the heat is easy to use for heating.

How much heat you need to remove

A mining machine has no “useful” output that would carry the energy away. Everything it takes from the socket, it blows out as heat. An Antminer S21 with a power draw of 3,500 W is therefore a 3.5 kW heater that runs 24 hours a day, 365 days a year.

A small farm with ten such machines produces 35 kW of heat – roughly like the heating of a larger family house in the coldest frost. That is why cooling is decided before buying the machines.

Air cooling: how much air you need

You can calculate the required airflow from the power draw and how much the air in the room heats up. The rule: airflow (m³/h) ≈ power draw (W) × 3 ÷ air temperature rise (°C).

The warmer the outside air, the less it can heat up in the room, and the more of it you need. In summer, at 30 °C outside, only 15 °C remain before the 45 °C limit – and that is borderline operation. So design fans and openings for summer temperatures, not the average.

How to lay out the room

1. Turn all machines in the same direction. Intake into one “cold” zone, exhaust into another “hot” zone.
2. Take the warm air outside by the shortest route – through ducting or an opening in the wall directly behind the machines. Warm air must not return to the intake.
3. Put the fresh air inlet on the opposite side and fit it with a filter. Dust settled in heatsinks and fans worsens cooling just as much as hot air.
4. Add an extractor fan with an airflow according to the table. The machines' own fans are not enough to remove heat from the whole room.
5. Monitor the intake temperature, not the room in general. What counts is the air the machine actually draws in.

What to do in summer and winter

In summer, the problem is the outside air temperature. A higher airflow, shading the room and intake from the north side help. Consider air conditioning only for short heatwaves – with a coefficient of performance of around 3, it adds about a third of a kilowatt of consumption for every kilowatt of heat removed.

In winter, it depends on the room. In a heated living space, the air overheats because both the radiators and the machines are running – ventilating and turning down the radiators is enough. In an unheated space, on the other hand, it can be too cold. Then return part of the warm air back to the machines (with a mixing damper) and make sure moisture doesn't condense. Condensation is worse for electronics than frost.

Hydro: water loop

Hydro machines (for example the Antminer S21 Hyd or S23 Hyd series) have water blocks instead of fans. The liquid carries heat from them to a heat exchanger and from there outside – to a dry cooler, radiator or heating system.

• Advantages: quiet at around 50 dB, high power density, stable chip temperature, heat is easy to use for space or water heating.
• Disadvantages: higher upfront investment, three-phase power for powerful models, coolant maintenance and leak protection.

For the loop you need a cooler and pipework: you will find them in our radiators for hydro miners and water loops collections.

Immersion: submerging in liquid

With immersion cooling, the hashboards are submerged in a special non-conductive liquid (dielectric oil). The liquid draws heat directly from the components and passes it via a heat exchanger to water or outside air. Fans are no longer needed.

• Advantages: almost zero noise, no dust, even temperature, room for overclocking, easy heat reuse.
• Disadvantages: the tank and liquid cost money, servicing is more laborious (the machine is covered in oil), machines designed for immersion are best suited.

Tanks, liquids and accessories can be found in our immersion cooling collection.

Comparison: air, hydro, immersion

Where exactly air has its physical ceiling and why hydro machines achieve better efficiency is discussed in our article Where air cooling ends.

If you don't want to deal with cooling at all

A data centre will take care of ventilation, ducting, loops and summer heatwaves for you. In hosting, air-cooled and hydro machines run in an environment built for them, with monitoring and technical supervision. You will find the conditions and locations on our ASIC miner hosting page.

What next

• Building a hydro farm? Start by choosing a cooler in our radiators collection.
• Deciding between air and water? You will find the figures and limits in our article Where air cooling ends.

Sources

• Bitmain: Antminer S21 specification (operating temperature, humidity, power draw)