Managing heat exhaustion from bitcoin mining machines, or ASICs, is a key part of miner operations maintenance. Miners typically choose between an air cooling or immersion cooling setup. Immersion cooling setups are more efficient at moving heat away from miners than air cooled systems, especially at scale.
This piece offers an overview of immersion cooling and breaks down terminology, cooling methods (single and double phase), and setup components.
Why bother with immersion cooling?
Immersion cooling is more efficient than air cooling. Engineered Fluids even claims that air cooling consumes 40% to 50% of total setup energy usage; 5% or less of the total power consumption is used by the device's onboard fans alone (by my calculations, based on the max amp rating of 3.8amps on the fan, at 12v DC, all four fans would consume 152 watts of power max, which would be a maximum of 5%, with fans not usually running at max power, it would likely be less). Miners who opt for an immersion cooling setup may be able to run their machines at higher hashrate per machine. Immersion cooling also does not require miners to clean their machines regularly for dust, dirt, and natural buildup, the immersion fluid takes care of this.
Immersion mining also handles mining machine heat and noise more effectively than air cooled setups. Unlike fluids, air is not a good conductor of heat and while it is very possible to build a low noise or even noise free ASIC container in an air cooled setup, immersion setups are, on average, much quieter.
Who should build an immersion cooling setup?
Miners should note that building an immersion cooling system is more expensive than building a standard air cooling set-up. Immersion cooling can also extend the lifespan of these machines. Economically, building an immersion setup makes sense for miners who want longevity, noise reduction, and the ability to move heat further distances away from the source.
Immersion cooling setups can range from a few hundred dollars to thousands of dollars. This investment should be chosen wisely as it is much more complex than air cooled setups. At the most basic level, a single S9 in a small tank with a small radiator is the simplest place to start if you are interested in learning immersion cooling at the lowest risk and price point. The price and complexity increases significantly once you go beyond a single setup.
Immersion cooling basics
Understanding key terminology is critical before pursuing an immersion cooling setup. Here are the most common terms simplified:
Dielectric coolant - an engineered fluid that has zero electrical conductivity, but reasonable thermal conductivity. There are many products to choose from with varying properties such as corrosive properties to materials such as rubber. This is a significant expense of an immersion setup.
ASIC tank - a container or enclosure that holds ASICs and dielectric coolant. These can be made of steel, aluminium, glass (such as fish tanks), or wood coated in fiberglass.
Brazed Plate Heat exchanger - used to transfer heat from a fluid on one side of a barrier to a fluid on the other side without bringing the fluids into direct contact.
Water to Air Heat Exchanger - This is used to remove heat from the liquid and vent it into air.
Pump - circulates the dielectric coolant and ensures that it flows continuously throughout the system.
Single loop - the dielectric coolant is pumped directly through a radiator, the radiator cools this fluid and then feeds it back into the ASIC reservoir.
Double loop - the coolant is first pumped to a heat exchanger. The heat from the exchanger is then transferred to a water line. The heated water is then pumped from its own loop to a cooling tower or dry cooler and cooled down. This second loop usually contains a water/glycol mix as glycol is a better conductor of heat than simple water.
Immersion coolant types:
Single-phase coolant - cooling oil remains in liquid state, never boiling or freezing. The oil is pumped to an external heat exchanger where it is cooled. This is the most simple solution and is very forgiving for errors or mistakes. Even in a catastrophic pump failure, the miner will shut down when it reaches a thermal limit. When the entire setup cools, it is likely the miner will return to normal operation. Note: Not all ASICs support this and it is not a guarantee.
Two-phase coolant - electronic components are submerged in dielectric liquid. This fluid boils on the surface of ASIC chips and/or heat sinks and rising vapor facilitates heat transfer. Circulation happens passively through evaporation. Gas is captured and cooled then condenses back into the liquid.This setup is extremely difficult and has a very high risk of severe damage to hardware if not done 100% correctly.
Single Loop and Double Loop cooling:
Single loop is where the entire system is comprised of dielectric oil. The heat from the oil is exchanged to air. This is the most easy to setup, but is the least scalable. Also, in the event of a leak in the system, you risk losing some or all of your expensive dielectric coolant.
Double loop is where there is an oil loop that goes through a brazed plate heat exchanger (or similar) and transfers its heat to another liquid, such as water or glycol. The benefit of a double loop system is less total oil is used. This becomes a much bigger factor when going beyond a single miner or two. But it could add expense depending on the setup
Key considerations for immersion cooling builds
Before building out their setup and submerging their ASICs in dielectric coolant, miners need to prep their machines and make sure all the setup components that they purchased are compatible with the dielectric coolant. Miners can reference this guide for details on material compatibility. Removing the thermal paste on ASICs can be done before submerging them, however, there is no clear evidence that shows this step is necessary or helpful.
In order to prep their machines, miners will need fan spoofers or special firmware installed. This is necessary because ASIC fans are not meant to be submerged. Submerging them in oil will change the fan’s speed and impact how the ASIC functions. Removing the fans will also cause the ASICs to malfunction. Fan spoofers can simply be plugged in in place of the fans but there must then be a means to have flow of oil over the ASIC, make sure to check if the ASIC needs a spoofer with 4 pins or 6 pins. A better solution to fan spoofers is to install immersion specific firmware on their machines such as Braiins OS+. Whatsminer does offer its own immersion-ready firmware, but it does void the warranty. But all immersion activities effectively void the manufacturer’s warranty anyway. At the time of writing, Braiins OS+ is not available for Whatsminer machines but development is nearly complete and is expected to be released soon
Miners should also follow these general guidelines:
- Miners should not exceed 80% capacity of their home’s electrical circuit in order to avoid fires and potential electrical issues.
- Mineral oil should be avoided except in experimental builds, or with the knowledge that it may cause damage over prolonged use. Mineral oil does function from a technical standpoint of being not conductive and safe to immerse electrical equipment into.
Immersion cooling shopping list
Basic immersion cooling builds will include the following:
- Immersion Liquid (dielectric coolant)
- Container/ASIC tank
- Heat exchanger
- Dielectric fluid (oil) pump
- Fan (to be paired with radiator)
- Fan spoofer or immersion firmware
For a low-cost economic build with shopping links, check out this page.
Immersion cooling setups are ideal for miners who wish to extend the lifetime of their machinery and control noise/heat as efficiently as possible, or push the miner beyond its original power rating, known as overclocking. Single loop works well for small setups. Miners operating larger scale setups should use a double loop setup. Miners who do not have an engineering background can use an S9, mineral oil, a fish tank, low cost pump and radiator, and install BraiinsOS+ and experiment before investing in a more expensive build or submerging their more expensive machines.