Power Flow in Both Directions

When Is a Bidirectional RCBO Needed?

Power Flow in Both Directions answers an important question facing UK electricians working with solar PV, battery storage and other sources of electrical energy: when is a bidirectional RCBO actually needed?

A bidirectional RCBO is needed when the intended circuit arrangement can place a source of supply at either terminal set and the manufacturer declares the exact device suitable for that connection.

It is not required simply because current may flow in both directions or because an installation includes solar panels or battery storage.

The difference is important. Current direction describes what is happening within the circuit. RCBO directionality describes where the manufa

cturer permits a source of supply to be connected.

What does this white paper explain?

This free technical white paper provides a clear and practical explanation of bidirectional and unidirectional RCBOs for UK electrical installations.

It explains how traditional installations were designed around power travelling from one supply towards the connected loads. It then explores how solar photovoltaic systems, battery storage, vehicle export equipment and backup supplies can change the source connections within a modern installation.

The paper will help you understand:

• What a bidirectional RCBO is

• The difference between current flow and device directionality

• When solar PV or battery storage may create a requirement for a bidirectional RCBO

• Why every RCBO in an installation does not automatically need to be bidirectional

• How to follow each source through every intended operating mode

• How line, load, in, out and directional markings should be interpreted

• Why manufacturer information for the exact product reference is essential

• What site testing can confirm and why testing alone cannot prove that an RCBO is bidirectional

• How existing installations and EICRs should be approached

• Which additional RCBO characteristics must still be considered

A practical selection process

The paper provides four questions to work through before selecting an RCBO:

What are all the possible sources of electrical energy?

Which circuit connects each source to the installation?

Could any intended operating mode energise the RCBO through terminals marked load or out?

Does the manufacturer declare the exact RCBO suitable for that connection?

This process helps electricians move away from assumptions and make the selection decision using the actual circuit arrangement and reliable product evidence.

Written for UK electrical professionals

This white paper is intended for electricians, electrical contractors, designers, inspectors, specifiers, wholesalers and anyone responsible for selecting circuit protection for modern UK electrical installations.

It supports a clearer understanding of bidirectional protective devices under BS 7671 while recognising that every installation must be assessed using its individual design, current manufacturer instructions and all applicable requirements.

About Navitas bidirectional RCBOs

The paper also introduces the Navitas Type A Bidirectional RCBO range.

Navitas bidirectional RCBOs provide overload, short circuit and residual current protection with switched neutral operation and bidirectional source capability in a compact one module device.

The range is rated at 30mA and 6kA, with B Curve and C Curve options available from 6A to 40A.

Every device is individually tested and passes through the Navitas 37 point quality control process.

Download Power Flow in Both Directions for a simple explanation of what a bidirectional RCBO is, when one may be needed and how to select the correct device with confidence.