Connecting a heat pump – Electrical requirements and installation
The heat pump is the heating system of the future. However, connecting it places special demands on the electrical installation: three-phase connection, high fuse protection, special tariffs, and, increasingly, coupling with photovoltaics. This guide explains the electrical engineering requirements.
Quick info on heat pumps
- A three-phase connection (400V) is required for power consumption of 5 kW or more.
- Separate circuit with its own residual current device
- Register with the energy supplier and, if applicable, apply for a heat pump tariff.
Electrical basics – power and connection
Depending on the type and heating capacity, heat pumps have an electrical power consumption of 3 to 15 kW. The compressor capacity is decisive for the connection.
| Heat pump type | power consumption | connection type | hedging |
|---|---|---|---|
| Air-water (small) | 3–5 kW | 230V, single-phase | 16–25 A |
| Air-water (medium-large) | 5–12 kW | 400V, 3-phase | 16–20 A |
| Brine-water / Water-water | 6–15 kW | 400V, 3-phase | 16–25 A |
Protection and cabling
Circuit breaker (LS)
Heat pumps generally require an LS switch with characteristic C due to the high starting currents of the compressor. Typical: C16 or C20 for three-phase current.
Residual current device (RCD)
A separate residual current device (30 mA, type A or F) is mandatory. For heat pumps with frequency converters, a type F or B residual current device may be required, as DC fault currents may occur.
cable cross-section
A NYM-J 5×2.5 mm² cable is required for a typical air-to-water heat pump (8–12 kW). For cable lengths exceeding 20 m or higher power ratings, 5×4 mm² is recommended.
Grid connection, tariffs, and smart grid
Grid registration with the energy supplier
Heat pumps must be registered with the energy supplier. Above a certain output (3.5–5 kW, depending on the energy supplier), a permit is required.
heat pump tariff
Many energy suppliers offer a cheaper heat pump tariff (approx. 20–25 ct/kWh instead of 30+ ct/kWh). Prerequisite: separate meter and acceptance of restricted periods.
SG Ready interface
The SG-Ready interface enables communication between the heat pump and energy management system. When there is surplus PV energy, the heat pump can increase its heating output and charge the buffer storage tank.
Combination with PV system
Combining a heat pump with PV maximizes self-consumption. On sunny days, free solar power is used for heating—particularly effective with battery storage.
Practical tips for connecting heat pumps
1. Always prepare the three-phase current connection
Even if the current heat pump runs on single-phase power, install a 5-core cable. This will allow you to switch to a more powerful model later on without any problems.
2. Using SG-Ready for PV self-consumption
Activate the SG-Ready interface and connect it to your inverter or energy manager. This allows you to automatically use surplus PV energy for heating.
3. Separate meter for heat pump tariff
A separate meter for the heat pump electricity enables a cheaper tariff. The savings often amount to €200–400 per year.
4. Select a generous cable cross-section
Heat pumps can be replaced with more powerful models over the years. A larger cable cross-section (5×4 mm² instead of 5×2.5 mm²) provides a safety reserve.
Conclusion: Heat pumps require professional electrical installation
The electrical connection of a heat pump requires expertise in fuse protection, grid registration, and, increasingly, energy management. Forward planning saves costs in the long term.
Important: Heat pumps must only be installed by certified specialists! The electrical connection must be carried out by a registered electrician.