Hydro miner on the heating circuit – setup, temperatures, heat exchanger

A hydro miner is not connected directly to the heating system. A heat exchanger sits between the two, and the setup consists of two separate circuits.

The setup

1. Miner circuit. A closed circuit with coolant: miner, pump, expansion vessel, filter, primary side of the heat exchanger.
2. Plate heat exchanger. It transfers the heat without the liquids mixing.
3. House circuit. Secondary side of the heat exchanger, buffer tank, and from there radiators, underfloor heating and hot water.

Why two circuits

• The heating water in the house contains dirt, oxygen and metals from old pipes. None of that may flow through the miner's cold plates.
• The miner requires a specific coolant within tight limits. In the small miner circuit that can be maintained, in an entire house system it cannot.
• A leak or work on one side does not affect the other.

Temperatures

The manufacturers specify different parameters:

• Bitmain states the permitted inlet temperature: 20 to 40 °C for the S19 XP Hyd, 20 to 50 °C for the S21 XP Hyd. At the outlet the water is a few degrees warmer. Below an inlet temperature of 20 °C the unit does not start.
• MicroBT states the outlet temperature: up to 70 °C for the Whatsminer M63S+, up to 80 °C for the M64. There too, it is the inlet that is controlled: 25 to 55 °C for the M63S+, 35 to 70 °C for the M64.

This gives the following match: for underfloor heating and low-temperature radiators, the temperatures of all units are sufficient. For hot water and old radiators with a high flow temperature you need a model that allows high outlet temperatures, or auxiliary heating.

Flow rate

For the S21 XP Hyd, Bitmain requires 8 to 10 litres per minute at a maximum of 3.5 bar. The pump in the miner circuit is sized for this value, not for the demand of the heating system. Install a flow switch that shuts the miner down if the pump fails.

The buffer tank

The miner delivers its heat evenly, the house draws it unevenly. The buffer tank balances this out. 500 to 1,000 litres are common; the rule of thumb is 50 to 100 litres per kilowatt. The larger it is, the longer the miner keeps running when nobody needs heat at the moment.

Where the heat goes in summer

This question decides the whole system. Three options:

• Dry cooler outdoors, which releases the heat to the air. A diverter valve sends the water there as soon as the tank is full.
• Summer consumers such as a pool or hot water, if their demand is large enough.
• Throttling or switching off, controlled via firmware according to the tank temperature.

Control

The simplest rule: the tank temperature determines the miner's power. If the tank is cold, it runs at full power. As it approaches the target temperature, it is throttled. For this, Whatsminers come from the factory with three power modes and a power limit in watts. You control Antminers with third-party firmware that accepts a power target in watts.

Who builds it

A heating engineer builds the house circuit, an electrician the electrical connection. The miner circuit is small, but it must be built exactly to the manufacturer's specification.

Sources

• Bitmain, specifications: S21 XP Hyd, S19 XP Hyd
• Bitmain: notes on hydro miners, no start below 20 °C
• MicroBT, manuals (PDF): Whatsminer M63S+, Whatsminer M64
• MicroBT: power modes and power limit
• Buffer tanks: Bosch, Buderus

As of October 2026. This article does not replace planning by a specialist contractor; your model's manual is what counts.