Hydro cooling bitcoin mining: from cold plate to dry cooler

It is liquid cooling through cold plates, with no fans on the machine. Sellers list the same build as a water cooled ASIC miner or a hydro cooling ASIC miner. Coolant runs through metal plates pressed against the chips and carries their heat out of the chassis to equipment that sheds it elsewhere.

That is different from immersion, where whole machines sit in tanks of dielectric fluid. In hydro cooling the coolant stays inside sealed plates and hoses and never touches the electronics. The machine is built for it at the factory: a hydro model ships with its plates fitted and its fans left out, so it cannot be run on room air if the loop stops.

For the wider picture of what a host does around the machine (power, network, monitoring, payouts), start with how bitcoin mining hosting works. This page stays with the coolant.

Through the plates and out of two ports. The S21+ Hyd. has three hashboards standing on edge, each with a cold plate clamped down over its chips where an air machine would carry fins. Coolant enters through one OD10 port, runs along the boards, and leaves through the other. Both ports sit on one sealed plate at the end of the chassis.

Bitmain's manual sets the conditions at that inlet:

• Inlet temperature: 20 to 50 °C.
• Flow: 8.0 to 10.0 litres per minute, per machine.
• Pressure: 3.5 bar or less.
• Fitting: an OD10 coolant pipe connector.

The same manual rates the 395 TH/s version at 5,925 W and 15 J/TH, measured with coolant entering at 35 °C, on a three-phase supply of 380 to 415 V. So one machine puts close to six kilowatts of heat into its coolant, continuously, through a pair of small fittings. Everything downstream exists to carry that away at the flow and pressure the machine expects.

Because the coolant that touches the machines and the fluid that meets the weather have different jobs, and keeping them apart lets each be looked after on its own terms.

1. The machine loop. Supply and return manifolds run along the racks. A hose and coupling join each machine's two ports to them, so coolant arrives from the supply side and leaves on the return side. This loop holds the coolant whose chemistry the machine's manual specifies, and it stays indoors.
2. The coolant distribution unit (CDU). Pumps push the machine loop around, and they have to deliver the rated flow to every machine on the manifold at once, not to one. The CDU is also where filters, gauges and the fill point usually sit.
3. The plate exchanger. A stack of thin plates where the warm machine-loop coolant passes the cooler outdoor-loop fluid on the other side of a metal wall. Heat crosses the wall; the fluids stay apart.
4. The outdoor loop. It carries the heat from the exchanger up to the cooler and back. This is the side that sees summer heat, winter cold and whatever the site's air carries.

In Proton's planned container the CDU, with its pumps and plate exchanger, sits between the two loops, and the heat leaves through a dry cooler on the roof. You can rotate the cutaway on the hosting page and hover each of those parts.

It is the point where the loop finally meets air. A dry cooler is a large finned coil with fans blowing outdoor air across it. The fluid stays sealed inside the coil and nothing evaporates, so it uses no water to reject the heat. The fans a hydro miner gave up have, in effect, moved to the roof and grown much larger.

It also has a hard limit: a dry cooler cannot bring the fluid below the temperature of the outdoor air, and in practice it returns it somewhat above that. On the hottest afternoon of the year, the coolant reaching the machines is at its warmest. That is why a hydro system is sized for the local summer, not the annual average, and why the machine's inlet range matters.

Bitmain's own curve for the S21+ Hyd. shows what warm coolant costs. Efficiency holds at 15 J/TH through the lower part of the inlet range, then slips as the inlet climbs, reaching between 16.8 and 17.3 J/TH at 50 °C depending on the coolant. On the same chart the hashrate stays flat across the range; the machine just spends more power per terahash.

Winter brings the opposite problem. Any fluid that sits in an outdoor coil can freeze if it stops moving, so a site in a cold climate needs freeze protection on the outdoor side. Evaporative towers and hybrid coolers can cool below the outdoor air temperature in dry weather, at the cost of using water. Each site makes that choice for its own climate.

One of three, according to Bitmain: antifreeze, pure water or deionized water. Each has its own pH band, and the coolant in the machine loop should stay inside it:

• Antifreeze: pH 7.0 to 9.0.
• Pure water: pH 6.5 to 7.5.
• Deionized water: pH 8.5 to 9.5.

Tap water is not on the list. It carries minerals that can leave scale inside narrow cold-plate channels, and dissolved salts make it more conductive if it ever escapes onto electronics. Bitmain sends readers to the coolant maintenance section of its container manual, so the maker expects coolant to be looked after like any other part.

Which coolant a hosted loop runs, and the temperature range it is held to, belong in writing for the specific site. At Proton both are confirmed per site, in writing.

More than air cooling, and of a different kind. An air fleet's upkeep is dust and fans. A hydro fleet's upkeep is the coolant, the joints and the readings.

• Coolant quality. Test pH against the band for the coolant in use, look for cloudiness or particles, and keep the loop's filters clean. Top up with the same coolant the loop already holds, not whatever water is at hand, because mixing changes the chemistry.
• Couplings. Every machine joins the manifolds through couplings that are connected and disconnected each time it is swapped. Seals wear. A coupling swap is routine work, and couplings are among the spares worth keeping on site.
• Leaks. A wet fitting or a falling fill level is the early sign. Isolate the machine's power before touching it. Fix the joint, then check that no coolant reached the electronics before the machine runs again.
• Air and flow. A machine fitted back into the loop can trap air, which cuts its flow. If a machine's outlet runs hotter than its neighbours' at the same inlet temperature, it is likely getting less coolant than they are.
• Readings. Coolant inlet and outlet temperature per machine show the loop's health directly, before it shows up as lost hashrate.

When you compare hosts for hydro machines, ask who does each of these jobs, from which spares, and how the work is charged. The checklist in how to choose a bitcoin mining host covers the rest of that conversation.

It depends on what you are cooling and where. Hydro suits machines designed for it, packed densely, at a site built around a loop. Air cooling is simpler: fewer parts, no plumbing, no coolant chemistry, and a machine that runs wherever there is power and airflow.

What hydro gives you: no fans on the machine, so far less noise and dust at the rack; dense racks, because heat leaves by pipe rather than by moving huge volumes of air; and heat in a liquid, which is easier to send somewhere useful than hot exhaust air. What it costs you: pumps, manifolds, an exchanger and a cooler to buy and maintain, coolant to manage, and leaks to watch for.

A hydro machine is also hard to run at home. The S21+ Hyd. needs a three-phase supply and a loop with a pump and a cooler before it can hash at all. If you are weighing a garage setup against a host, read home mining vs hosted mining. If you already know you want hydro machines hosted, hydro miner hosting covers what to ask a host and where Proton's planned sites are.

Proton's planned containers are hydro-cooled on a closed water loop, with no air crossing your machines, and the coolant temperature range is confirmed per site, in writing. Hosting is for hydro-capable machines bought through Proton. Capacity, timing, rate and terms are confirmed per site and set out in writing before anything ships.

A good fit if

• You are buying hydro machines such as the S21+ Hyd. from the Proton catalogue and would rather the loop, the cooler and the coolant upkeep were someone else's job.
• You want coolant inlet and outlet temperature monitored per machine, alongside hashrate, board temperature and power draw, with automated alerts.
• You want coupling, PSU and hashboard swaps done from on-site spares, with how labour and parts are charged set out in your hosting agreement.

Not a fit if

• You want to build and run your own loop: this guide is your reading, and hosting is not needed.
• Your machines are air-cooled: hosting is for hydro-capable models only.
• Your machines were bought elsewhere: hosting is only for machines bought through Proton.
• You need a start date now at a proposed location: proposed locations have no confirmed hosting start date.