RCBO Application Guidance
Hager Guidance
This guidance must be read in conjunction with the BEAMA attached technical bulletin.
Overview
This document provides guidance on the application of Residual Current Devices (RCDs) and Miniature Circuit-Breakers (MCBs), specifically RCBOs, for various power supply connections. These include battery storage, Photovoltaic (PV) systems, Electric Vehicles (EV), micro-generators, and the main grid supply.
Connection of Unidirectional and Bidirectional Residual Current Devices (RCDs) and Miniature Circuit-Breakers (MCBs) to power supplies e.g. battery storage, Photovoltaic (PV) systems, Electric Vehicles (EV) to home, a micro-generator, or grid (mains) supply.
The electrical inspector or installation duty holder is responsible for determining necessary actions and timelines. Based on potential safety issues highlighted in the BEAMA bulletin, Hager recommends replacing any incorrectly selected or installed RCBOs with a suitable alternative.
The following sections help identify incorrectly selected and installed Hager RCBOs and provide appropriate solutions.
Issue 1: Non-Neutral Switching RCBOs
Problem: RCBOs that do not switch the neutral conductor as required by BS 7671 Regulation 551.7.1.
Indicator: A solid neutral connection is indicated in the product instructions or on a diagram associated with the RCBO.
Solution 1: Utilize Bidirectional RCBOs
Description: Bidirectional RCBOs switch both the line and neutral conductors. They are designed to fit onto a standard Hager consumer unit busbar, occupying either one or two module ways.
Example Product: ADC920R 1 Mod RCBO
This is a 1 Module RCBO for 230V ~ 50Hz supplies. It features terminals marked LINE (LIN) and LOAD (LOUT), and NEUTRAL (N) and NEUTRAL OUT (NOUT). A specific terminal is identified as 'Out'. The device switches only the line conductor.
Diagram Description: A schematic shows a 230V ~ 50Hz supply connected to LINE and NEUTRAL inputs. The RCBO has internal components for switching the line conductor and for residual current detection. The neutral conductor bypasses these components.
Example Product: ADA920U 2 Mod RCBO
This is a 2 Module RCBO.
Note: The ADA920U is shown as an example of a bidirectional RCBO suitable for this application.
Issue 2: Unidirectional RCBOs Connected to Energy Source
Problem: Unidirectional RCBOs where their outgoing/load terminals are connected to a source of energy.
Identification: Unidirectional RCBOs can be identified by specific terminal markings on the device and its diagram, such as 'line/load' or 'in/out'.
Solution 2: Employ Bidirectional RCBOs
Description: For applications involving unidirectional RCBOs connected to a source of energy, the use of bidirectional RCBOs, as detailed in Solution 1, is recommended. These devices ensure correct switching of both line and neutral conductors.
