Heat pump electrical protection: circuit breaker & RCD (2026 installation guide)

Understanding the electrical risks of a heat pump and the protection objectives

Why a heat pump is sensitive: compressor start-up, current draw and micro-outages

A heat pump is not a radiator. On start-up, the compressor can draw a high inrush current. Add the power electronics and fans, and you have equipment that reacts to voltage dips and micro-outages. Without suitable protection, you risk tripping, overheating and premature wear.

What circuit breaker, RCD and earthing protect: complementary roles

The circuit breaker mainly protects the cables and the machine against overload and short circuit. The RCD monitors current leakage linked to an insulation fault and trips to limit the risk of electric shock. Earthing provides a fault path and improves the RCD's effectiveness. Together, they reduce the risk of fire and accidents.

Identifying the heat pump type and its power supply: single-phase, three-phase, outdoor/indoor unit

Before sizing the protection, identify the type of power supply shown on the rating plate and in the manual. Single-phase and three-phase don't imply the same currents, nor the same cable cross-sections. On many split systems, the outdoor unit is powered, then the indoor unit is interconnected. When in doubt, follow the manufacturer's documentation. To go further on grid-side sizing, see the power and meter needed for a heat pump's electrical connection.

Choosing the right circuit breaker for your heat pump installation

Rating the circuit breaker based on the heat pump's power and nominal current

The circuit breaker's rating is chosen first from the nominal current shown on the heat pump's rating plate. A rating just above this current is selected, while staying compatible with the cable's capacity. If the outdoor and indoor units are powered together, rely on the values given in the manufacturer's manual.

Trip curve (C, D): avoiding start-up trips without under-protecting

On start-up, the compressor can draw a higher current. A C curve is often enough. If tripping occurs despite a correct rating, a D curve may help, provided the installation can handle this inrush and the protection stays effective in the event of a fault.

Dedicated line and upstream protection: cable cross-section, length, voltage drops

Plan a dedicated line from the panel. Adjust the cross-section based on current, installation method and length. Over long runs, voltage drop can cause overheating, extra consumption, or tripping. Measure, calculate, then validate on site before commissioning.

Selecting the RCD for a heat pump: type, sensitivity and compatibility

Type A, AC, F: which choice depending on the heat pump's technology (variable-speed drive, inverter)?

A heat pump with inverter technology carries power electronics on board. In this case, avoid type AC, which is more sensitive to "classic" faults only. Aim for at least a type A. If the manufacturer mentions leakage currents with high-frequency components, a type F can limit nuisance tripping.

30 mA sensitivity and selectivity: limiting nuisance outages in the home

In housing, personal protection is provided at 30 mA. To prevent a heat pump fault from cutting everything off, dedicate an RCD to it. Spread large appliances across several RCDs, keeping a good circuit distribution.

RCD at the panel: placement, coordination with other electrical circuits

At the panel, the RCD is placed upstream of the circuit breaker dedicated to the heat pump, on a specialised circuit sized to match the conductors. Also check compatibility with surge protection and load shedding. The goal is simple, readable coordination.

Implementing compliant, lasting electrical protection for the heat pump

Installation diagram: labelling, local isolation switch, connection and earthing

For a heat pump, start with a dedicated circuit from the panel. Clearly label the feeder, the circuit breaker, and the 30 mA RCD suited to the equipment (often type A, sometimes type F depending on manufacturer recommendations). Plan an accessible, lockable local isolation switch near the unit. Connect the protective conductor without interruption, with checked earthing and careful tightening.

Surge protection: SPD, risk zones and 2026 good practice

Heat pump circuit boards don't like surges. In 2026, the good baseline remains a type 2 SPD at the panel, coordinated with upstream protection. In exposed areas, with overhead supply, or if the building has lightning protection, a type 1 may be required. Keep earth connections short and avoid loops.

Sealing and cable routing to the outdoor unit: enclosure, cable glands, fixing

Outdoors, aim for a suitable IP rating. Use a sealed enclosure, correctly sized cable glands, and UV-resistant sheathing. Form a "drip loop" before the cable enters the enclosure, fix every 40 to 60 cm, and protect the wall penetration. Separate power and communication cables to limit interference.

Checks, tests and troubleshooting: securing commissioning and reducing callbacks

Commissioning is like closing the windows before winter. If the electrics are clean, the heat pump starts without a bad surprise, and your callbacks drop sharply.

Pre-commissioning checklist: tightening, insulation, earth continuity, polarity

Cut the power then check the tightness of connections at the panel and on the machine. Check phase-neutral polarity, earth continuity, and conductor insulation before the first heating cycle.

• Earth properly connected, no mixing of neutral and earth.
• Cross-section and protection consistent with the rating plate.
• Cable routing without crushing or moisture in the enclosures.

Heat pump tripping the breaker: diagnosing RCD vs circuit breaker (field method)

Identify which device trips. If it's the RCD, look for an earth leak (moisture, damaged cable, EMC filter, shared neutral). If it's the circuit breaker, look for an overcurrent (compressor start-up, insufficient cross-section, poorly tightened terminal).

Traceability and maintenance: readings, labelling, advice for the customer to preserve the protection

Record your measurements (earth, insulation, voltages) and label the heat pump circuit. On the customer side, remind them not to add sockets to the dedicated line, to keep the panel accessible, and to report any repeated tripping before it damages the protection. To go further on good practice and obligations, see also heat pump maintenance.