What RCD or RCBO Does a Heat Pump Need? Type A, F & B Explained

What Type of RCD Does a Heat Pump Need?

The correct RCD type depends on the residual-current characteristics of the heat pump.

Modern heat pumps commonly contain equipment such as:

• Inverter-driven compressors
• Variable-speed fans and pumps
• Electronic motor controls
• Rectifiers and power-conversion electronics
• EMC filters
• Electronic control boards

These components can produce residual currents that differ from the simple sinusoidal AC leakage associated with traditional electrical loads.

That is why heat-pump protection should be selected from the manufacturer’s requirements rather than assuming one RCD type suits every unit.

A manufacturer may specify:

• Type A
• Type F
• Type B
• A particular residual-current sensitivity
• A particular MCB or RCBO curve
• A maximum protective-device rating
• Specific upstream or dedicated circuit protection

When Can a Heat Pump Use a Type A RCD or RCBO?

Type A RCDs are designed to operate with sinusoidal AC and pulsating DC residual currents.

A Type A device may be appropriate where:

• The heat pump manufacturer specifies Type A protection.
• The equipment’s residual-current characteristics remain within Type A capability.
• No smooth DC residual current outside the device’s permitted characteristics can occur.
• The upstream RCD arrangement is compatible with the heat pump.

Type A is widely encountered on modern electronically controlled equipment, but it should not simply be regarded as the minimum acceptable heat-pump RCD.

The manufacturer may require Type F or Type B instead.

👉 Browse Type A RCBOs and Type A RCDs.

When Does a Heat Pump Need a Type F RCD?

Type F RCDs are designed for certain single-phase circuits containing frequency-controlled equipment.

They provide the residual-current detection characteristics of Type A together with additional capability for defined mixed-frequency residual currents.

This can make Type F appropriate for some:

• Single-phase inverter-driven heat pumps
• Air-conditioning systems
• Variable-speed compressors
• Single-phase motor drives

Whether Type F is required depends on the heat pump manufacturer and the electronic design of the unit.

It should not automatically be substituted with Type A simply because Type A is easier to source, nor should Type B automatically be fitted without establishing what the equipment actually requires.

When Does a Heat Pump Need a Type B RCD?

Type B provides wider residual-current detection than Type A or Type F, including smooth DC residual current and other waveform characteristics within the device specification.

A Type B device may be required where:

• The heat pump manufacturer specifically specifies Type B.
• The inverter topology can produce smooth DC residual current.
• The equipment can produce residual currents outside Type A or Type F capability.
• The installation contains three-phase power-conversion equipment requiring Type B characteristics.

Type B is commonly associated with inverter and drive applications, but that does not make it a universal heat-pump requirement.

Some inverter heat pumps are specifically designed for Type A or Type F protection.

Installing Type B simply because manufacturer information has not been checked is not a substitute for correct circuit design.

👉 Where the equipment specifically requires it, compare Type B RCDs.

Type A vs Type F vs Type B for Heat Pumps

The correct progression is therefore not:

Type A → Type B if you want better protection.

Instead, ask:

What residual-current characteristics can this exact heat pump produce, and what protective device does its manufacturer specify?

Can You Use a Type AC RCD for a Heat Pump?

Type AC RCDs are designed for sinusoidal AC residual currents.

Modern heat pumps commonly contain electronic power-conversion and inverter equipment capable of producing other residual-current waveforms.

For that reason, Type AC should not be selected for a heat-pump circuit unless the equipment characteristics and manufacturer’s requirements specifically support its use.

In practice, modern inverter-driven heat pumps will commonly call for a more appropriate RCD type such as Type A, Type F or Type B.

Related guide: Are Type AC RCDs Still Allowed?

Can You Use an RCBO for a Heat Pump?

Yes. A dedicated RCBO is often a practical way to protect a heat-pump circuit because it combines:

• Residual-current protection
• Overload protection
• Short-circuit protection

However, saying “use an RCBO” does not complete the specification.

The installer still needs to confirm:

• Type A, Type F or Type B residual-current characteristic
• Rated residual operating current
• Current rating
• B, C or another overcurrent curve
• Breaking capacity
• Number of poles
• Neutral switching requirements
• Consumer-unit or distribution-board compatibility

A heat pump manufacturer may specify a particular RCD together with an MCB rather than an RCBO, so the manufacturer's circuit arrangement should still be followed.

👉 Browse the full RCBO range.

Should a Heat Pump Use a B Curve or C Curve RCBO?

The B or C curve describes the overcurrent characteristic of the RCBO. It is separate from whether the residual-current element is Type A, Type F or Type B.

A heat pump may have startup or inrush characteristics associated with compressors, motors and power electronics, but that does not automatically mean it requires a C curve.

Use the curve specified by the equipment manufacturer.

If no curve is explicitly stated, assess:

• Starting and inrush current
• Maximum running current
• Compressor characteristics
• Cable current-carrying capacity
• Maximum Zs
• Required disconnection time
• Prospective fault current

Changing from B curve to C curve purely to stop an unexplained trip can mask another circuit or equipment problem.

Related guide: B Curve vs C Curve RCBOs

Does a Heat Pump Need a Dedicated Consumer Unit?

A separate heat-pump consumer unit is not automatically required simply because a heat pump is being installed.

However, a dedicated board can be useful where:

• The existing consumer unit has insufficient space.
• The required RCD or RCBO is not compatible with the existing board.
• The heat pump requires its own dedicated protective arrangement.
• Local surge protection is required.
• The circuit needs to be separated from existing RCD-protected groups.
• A higher-current or specialist protective device is required.
• The installation needs a clear standalone point of isolation and distribution.

A pre-built heat-pump board can package the required devices neatly, but the installer still needs to verify that every component matches the exact heat-pump specification.

👉 Compare dedicated heat pump consumer units and boards.

Related guide: What Consumer Unit Do You Need for a Heat Pump?

Does a Heat Pump Need Surge Protection?

Surge protection is a separate consideration from RCD selection.

An RCD protects against residual-current faults. An SPD protects equipment against transient overvoltages.

When designing the heat-pump circuit, check:

• Existing SPD protection at the origin
• The distance between the heat pump and upstream SPD
• The heat pump manufacturer's requirements
• Equipment impulse withstand
• Whether supplementary protection is required locally

A Type B RCD does not replace an SPD, and an SPD does not replace the heat pump RCD or RCBO.

Related guide: Does a Heat Pump Need Surge Protection?

Check the Upstream RCD as Well

The protective device directly supplying the heat pump is not the only RCD that matters.

If the heat pump circuit sits downstream of another RCD, the upstream device also needs to be compatible with the residual-current characteristics that can occur.

For example, installing a suitable downstream device does not automatically resolve an unsuitable upstream RCD that could be affected by DC residual current from the heat pump.

Review:

• The heat-pump protective device
• Any upstream RCCB
• Any main or sub-board RCD
• Time-delay and selectivity requirements
• The manufacturer's residual-current guidance

Where possible, a dedicated RCBO arrangement can reduce the number of RCDs in series and limit disruption to unrelated circuits.

How to Choose the Correct RCD or RCBO for a Heat Pump

1. Identify the exact heat pump model. Do not select protection from the heat output alone.
2. Read the current electrical installation manual. Look for RCD type, MCB or RCBO rating, curve and maximum protective-device requirements.
3. Identify the supply. Confirm whether the unit is single-phase or three-phase.
4. Check the inverter topology. Establish the residual-current characteristics where manufacturer information provides them.
5. Select Type A, F or B. Follow the equipment requirement rather than assuming Type B is safer.
6. Confirm the residual-current sensitivity. Do not assume every heat pump requires the same mA rating.
7. Select the current rating. Coordinate the design current, protective device and cable.
8. Check the B or C curve requirement. Review inrush and manufacturer data.
9. Verify Zs and disconnection time. Ensure the selected overcurrent characteristic suits the circuit.
10. Check breaking capacity. Confirm the device can interrupt the available prospective fault current.
11. Review upstream RCDs. Prevent incompatible devices being placed in series.
12. Check surge protection separately. RCD and SPD requirements perform different functions.
13. Confirm board compatibility. Use an approved device or dedicated heat-pump board.

Heat Pump Circuit Protection

• Heat Pump Consumer Units
• Type A RCBOs
• High-Immunity RCBOs
• Type A RCDs
• Type B RCDs
• All RCBOs
• All RCDs
• Surge Protection Devices

Before ordering, check the current heat-pump installation manual and confirm the required RCD type, residual-current sensitivity, overcurrent rating, trip curve and number of poles.

Heat Pump RCD and RCBO FAQs

What RCD does a heat pump need?

There is no single RCD type for every heat pump. Depending on the manufacturer's specification and inverter design, the unit may require Type A, Type F or Type B protection.

Does a heat pump need a Type B RCD?

Only where the manufacturer specifies Type B or the equipment can produce residual currents that require Type B characteristics. Not every inverter heat pump requires one.

Can a heat pump use a Type A RCD?

Yes, where Type A is compatible with the heat pump's residual-current characteristics and the manufacturer permits it.

Can a heat pump need a Type F RCD?

Yes. Type F may be required for certain single-phase frequency-controlled or inverter-driven heat pumps. Check the manufacturer's electrical installation requirements.

What is the difference between Type A and Type B for a heat pump?

Type A covers sinusoidal AC and pulsating DC residual-current characteristics. Type B additionally covers smooth DC and wider residual-current characteristics within its specification.

Is Type B safer than Type A?

Type B has wider detection capability, but the correct protective device is the one specified for the equipment and coordinated with the installation. Wider detection does not remove the need for correct circuit design.

What RCBO should I use for a heat pump?

Use an RCBO whose residual-current type, current rating, curve, breaking capacity and pole configuration match the heat-pump manufacturer's requirements and the circuit design.

Can I use a Type B RCBO for a heat pump?

Yes, where a suitable Type B RCBO is available and the heat pump requires Type B residual-current protection. Check board compatibility and the full device specification.

Does a heat pump need a 30 mA RCBO?

Do not assume every heat pump requires the same residual-current sensitivity. Follow the relevant BS 7671 requirements and the manufacturer's instructions for the exact installation.

Does a heat pump need a C curve RCBO?

Not automatically. Use the curve specified by the manufacturer or supported by the unit's starting-current characteristics and circuit calculations.

Why does my heat-pump RCBO keep tripping?

Possible causes include genuine earth leakage, cumulative leakage, compressor or inverter faults, excessive startup current, an unsuitable RCD type, incorrect curve selection or another circuit fault. Identify which part of the RCBO is operating before changing the device.

Can Type AC be used for a heat pump?

Only where the equipment characteristics make Type AC suitable. Modern inverter-driven heat pumps commonly contain electronics that lead installers towards Type A, Type F or Type B instead.

Does a heat pump need its own consumer unit?

Not necessarily. A dedicated heat-pump board can be useful where the existing board lacks space or cannot accommodate the required specialist protection.

Does a heat pump need surge protection?

Surge protection should be assessed separately from RCD protection. Existing protection at the origin, circuit distance and manufacturer requirements all need to be considered.

Is an RCD the same as an RCBO?

RCD is the wider residual-current-device category. An RCBO combines residual-current protection with overload and short-circuit protection.

Can the upstream RCD affect the heat-pump circuit?

Yes. Every RCD in the supply path should be compatible with the residual currents produced by the heat pump and coordinated with downstream protection.

Should You Use Type A, Type F or Type B for a Heat Pump?

There is no universal answer based solely on the fact that the equipment is a heat pump or contains an inverter.

Use:

• Type A where the manufacturer permits it and the equipment remains within Type A residual-current characteristics.
• Type F where specified for suitable single-phase frequency-controlled equipment.
• Type B where smooth DC or wider residual-current characteristics require it.

Before selecting the RCD or RCBO, confirm:

• Exact heat pump make and model
• Manufacturer's RCD requirement
• Single-phase or three-phase supply
• Residual-current characteristics
• Required mA sensitivity
• Current rating
• B or C overcurrent curve
• Breaking capacity
• Zs and disconnection time
• Upstream RCD compatibility
• Surge-protection requirements
• Consumer-unit compatibility

👉 Ready to spec the circuit? Compare our heat pump consumer units, Type A RCBOs and Type B RCDs.