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Planning the electrical connection for miners – continuous load, the 80% rule and Schuko
A miner draws its full power around the clock. A household socket is not built for that. What continuous load means, why Schuko ends at 10 A and which connection suits which unit.
A kettle draws 2 kW for three minutes. A miner draws 3.5 kW without a break, for years. This difference is called continuous load, and it determines the entire connection.
Why Schuko is not enough
A Schuko socket is labelled 16 A. Under the product standard DIN VDE 0620-1, however, it can carry 16 A only for limited periods. The temperature-rise test lasts one hour and is not continuous operation. In practice, 10 A counts as the continuous load, which is around 2.3 kW at 230 V. For the same reason, the ADAC recommends limiting electric car charging from a household socket to 10 A.
A current air-cooled miner with 3.5 kW draws about 15 A at 230 V. That is permanently too high for a Schuko connection.
Where the fire risk arises
Not in the cable, but at the contacts. Every junction has a small resistance: plug pin in the spring contact, screw terminal in the socket, contact in the power strip. Under continuous current this point gets warm. Heat fatigues the spring, the contact gets worse, the resistance rises, the spot gets hotter. In the end, plastic melts.
The breaker does not trip, because the current is not too high. That is why miners do not belong on power strips, cable reels or adapters.
The 80% rule
It comes from the US electrical code NEC: for loads that run for three hours or longer, the overcurrent protection must be rated at 125% of the continuous current. Put the other way round: a circuit is loaded with continuous load only up to 80% of its rated current. The German DIN VDE 0100 has no blanket 80% rule. As a planning rule it still makes sense, because it leaves a reserve for heating.
- 16 A circuit: 12.8 A, around 2.9 kW single-phase
- 32 A circuit: 25.6 A, around 5.9 kW single-phase
- 16 A three-phase: around 8.8 kW
- 32 A three-phase: around 17.7 kW
Which connection for which unit
- Air-cooled, around 3.5 kW: a dedicated circuit per unit with a CEE socket (blue, 32 A) or a hard-wired PDU. A 16 A circuit is too tight under the 80% rule.
- Hydro, 4 to 11 kW: three-phase 400 V via CEE (red). Up to about 8.8 kW, 16 A is enough; above that, 32 A.
- Several units: sub-distribution board with one breaker per unit and a PDU rated for the continuous load.
CEE connectors are built for continuous current, Schuko is not.
What the electrician needs to check
- Conductor cross-section matched to the breaker rating, length and installation method.
- Service connection: Is the reserve enough for the additional continuous load?
- Phase distribution: Spread single-phase units evenly across the three phases.
- Terminals: Retighten after a few weeks of operation and check with a thermal imaging camera.
In short
No miner on Schuko. Every circuit loaded to 80% at most. Fixed connections or CEE, and an electrician who knows that the load never switches off.
Sources
- DKE, VDE, ZVEH et al.: Technischer Leitfaden Ladeinfrastruktur Elektromobilität, load capacity of Schuko sockets (PDF)
- ADAC: charging an electric car from a household socket
- Initiative ELEKTRO+: technical requirements, continuous operation on household sockets
- Cummins: continuous load and the NEC's 125% rule (PDF)
- Mennekes: CEE connectors and continuous current
As of October 2026. Planning and connection belong in the hands of a qualified electrician; this article does not replace one.