Type A RCBOs Explained: What They Are, Why You Need Them & How They Compare
Type A RCBOs (Residual Current Circuit Breakers with Overcurrent Protection) are widely used in modern electrical installations. They combine protection against residual earth fault currents, overloads and short circuits in one device, making them suitable for many domestic and commercial circuits.
In this comprehensive guide, you’ll learn:
- What a Type A RCBO does
- Why Type A is generally preferred over Type AC
- Where Type B residual current protection may be needed
- How to distinguish Type B protection from B Curve tripping
- What to consider for EV charging, solar PV and heat pumps
- Where to buy compatible RCBOs and consumer units
What Is a Type A RCBO?
A Type A RCBO combines the protective functions of an RCD and an MCB in one device.
- Provides residual current protection against sinusoidal AC and pulsating DC fault currents within its specified characteristics
- Protects against circuit overloads and short circuits
- Provides individual circuit protection, helping limit the disruption caused by a fault on one circuit
Type A RCBOs are commonly suitable for:
- Circuits supplying electronic equipment, chargers and LED drivers
- Socket outlet circuits
- Domestic and commercial lighting circuits
- Washing machines and other household appliances
- Suitable shower and cooker circuits
The correct device must be selected according to the circuit design, equipment characteristics, breaking capacity and consumer unit compatibility.
Is There Any Situation Where Type AC Must Be Used Instead of Type A?
No. Type AC is not specifically required in preference to Type A for modern electrical installations.
Type A provides additional residual current detection capability compared with Type AC. Under BS 7671, Type AC RCDs are restricted to suitable fixed equipment where it is known that the load current contains no DC components.
Type AC devices are therefore not universally banned, but their permitted applications are limited. Type A is generally the more appropriate choice for circuits containing modern electronic equipment, subject to the connected equipment’s requirements.
Type A vs Type AC vs Type B RCBOs
| Type | Residual Current Detection | Typical Applications |
|---|---|---|
| Type AC | Sinusoidal AC residual currents | Restricted applications involving suitable fixed equipment without DC components |
| Type A | Sinusoidal AC and pulsating DC residual currents | Suitable domestic and commercial circuits with electronic loads |
| Type B | AC, pulsating DC and smooth DC residual currents within specified characteristics | Selected EV charging, inverter-driven, industrial and renewable energy applications |
Type A devices are widely used in modern electrical installations. Type B protection offers additional residual current detection capabilities where smooth DC fault currents may occur and the installation requires them.
Clearing Up the Confusion: Type B RCBO vs B Curve RCBO
Many people confuse Type B residual current protection with B Curve overcurrent tripping characteristics. These are not the same.
- Type B RCBO (RCD type) – Provides residual current detection including smooth DC residual currents within its specified characteristics.
- B Curve RCBO (MCB tripping curve) – Has instantaneous magnetic tripping characteristics typically between 3 and 5 times the rated current.
For example, a 16A B Curve Type A RCBO provides Type A residual current protection with a B Curve overcurrent characteristic. It is not a Type B residual current device.
Always check the manufacturer’s datasheet before purchasing.
Example of Confusing Type B Product Descriptions
The following screenshot illustrates how product descriptions can confuse B Curve tripping characteristics with Type B residual current protection.
EV Chargers and Solar PV: When Is Type B Protection Necessary?
EV charging equipment, solar PV inverters and other electronically controlled systems can produce residual fault currents with DC components.
However, Type B protection is not automatically necessary for every installation. The correct RCD or RCBO type depends on the equipment design, manufacturer’s instructions and applicable electrical installation requirements.
EV Charging Installations
EV charging equipment requires appropriate residual current protection, including consideration of smooth DC fault currents.
Depending on the charger and installation design, a suitable Type A or Type F arrangement incorporating compliant DC residual current detection may be permitted. Alternatively, Type B residual current protection may be required.
Many modern EV chargers incorporate 6mA DC residual current detection, but this should always be confirmed against the manufacturer’s documentation.
Solar PV and Battery Storage
Solar PV inverters and battery storage systems may produce residual fault currents with DC components.
Some installations require Type B protection, while others may permit Type A protection according to the equipment manufacturer’s design and instructions.
Always verify the applicable requirements before selecting protective devices.
Type B RCBOs and Specialist Protection Now Available
Electrical4Less supplies specialist residual current protection products for installations where additional DC residual current detection is required.
Depending on the model and application, Type B protection may be suitable for:
- Selected EV charging circuits
- Solar PV and battery storage systems
- Variable-speed drives and inverter-driven equipment
- Specialist commercial and industrial installations
We also supply Type B and Type B-HP residual current protection products for suitable heat pump installations. These include RCDs as well as other protective arrangements; not every specialist Type B product is an RCBO.
Browse our RCBO Circuit Breakers and Heat Pump Consumer Units for available options.
Frequently Asked Questions
Section 1: General & Technical RCBO Questions
Section 2: Installation, Use & Safety Questions
Shop Type A RCBOs and Compatible Consumer Units
Electrical4Less supplies a wide range of RCBO circuit breakers for professional electricians and electrical contractors.
- RCBO Circuit Breakers – Explore Type A, specialist Type B, compact and bi-directional protective devices.
- FuseBox RCBOs – Browse compatible FuseBox protective devices.
- Hager RCBOs – Explore suitable Hager RCBO ranges.
- Consumer Units – Find compatible consumer units and electrical distribution equipment.
For installations requiring specialist protection, browse our Heat Pump Consumer Units.
Always confirm manufacturer compatibility before purchasing or installing protective devices.
References
- BS 7671 – Requirements for Electrical Installations, including relevant amendments
- IET Wiring Matters – Technical guidance on RCD selection and electrical protection
- BEAMA – Guidance on residual current devices and their selection
- Electrical Safety First – Electrical safety and RCD information
- Individual equipment manufacturer technical datasheets and installation instructions
Why Buy from Electrical4Less?
Electrical4Less is an independent electrical wholesaler based in Fulham, London. We supply protective devices, consumer units and electrical accessories at competitive trade prices.
We are members of the Independent Buying Association (IBA) and the Electrical Distributors’ Association (EDA).
Order online for UK delivery or collect from our Fulham electrical trade counter. Bulk orders and project quotations are welcome.
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