This article describes how the key functional characteristics of the various elements within protective devices can be recorded.
Jonathan Elliott | Principal Electrotechnical Engineer (Technical Publishing)
A number of protective devices are now available which perform more than one function, such as Residual Current operated Circuit-Breakers with integral Overcurrent protection (RCBO), and combination RCBO and arc fault detection devices (AFDD). The model 'Schedule of Circuit Details' in Appendix 6 of BS 7671 asks for a number of key functional characteristics of the various elements within the device to be recorded. This article describes how these details can be recorded.
However, enquiries received by the NICEIC field and helpline teams indicate that the use of such combination protective devices is causing some confusion in respect of the information that must be recorded on the Schedule of Circuit Details which form part of both an Electrical Installation Certificate (EIC) and Electrical Installation Condition Report (EICR).
As can be seen in the extract reproduced in Fig 1, the new Schedule of Circuit Details introduced in Amendment 2 (AMD2) published in 2022 requires information relating to both the overcurrent protective device and any installed RCD to be recorded.
.png "Figue-1-Extract-from-BS-7671-model-Schedule-of-Circuit-Details-(1).png")
Completing the 'BS (EN)' columns (numbered 8 and 13 respectively in the BS 7671 model form) is a straightforward matter where the overcurrent protective device and RCD are separate, standalone devices.
However, what is less clear is how these fields should be completed where the circuit-breaker and RCD elements are combined in an RCBO or even more so when such functionality is integrated in an AFDD.
.png "Figure-2-Overcurrent-protective-device-and-RCD-details-recorded-where-a-circuit-is-protected-by-a-separate-circuit-breaker-and-RCD-(1).png")
Note 1 to this clause clarifies that the content of the standard relating to residual current conditions is based on IEC 61008-1 while the content relating to protection against overcurrents is based on IEC 60898-1.
Table 41.3 of BS 7671 (Maximum earth fault loop impedance (Zs) for circuit-breakers with Uo of 230 V, for operation giving compliance with the 0.4s disconnection time of Regulation 411.3. 2. 2 and 5s disconnection time of Regulation 411.3.2.3) specifically references in the descriptors to Parts (a), (b) and (c) thereof that the data within the table is applicable to both circuit-breakers to BS EN 60898 and to the overcurrent characteristics of RCBOs to BS EN 61009-1 (Fig 3).
This clarifies that the device providing the overcurrent protection is the BS EN 61009-1 RCBO and not a circuit-breaker to BS EN 60898.
It would therefore be incorrect, and confusing, to those inspecting the installation at a later date if '60898' was recorded in column 8, as there is not a BS EN 60898 circuit-breaker protecting the circuit; the installed device is an RCBO to BS EN 61009-1.
Where the circuit is protected by an RCBO, '61009-1' should be recorded in both column 8 and column 13 (Fig 4).
Clause 1 (Scope) of BS EN 62606 General requirements for arc fault detection devices states that 'The integrated protection device is either a circuit-breaker in accordance with IEC 60898-1 or an RCD in accordance with IEC 61008-1, IEC 61009-1 or IEC 62423.' In order to determine which of these standards is applicable to a particular device reference should be made to the manufacturer's data for the AFDD being installed.
Where an AFDD incorporating overcurrent protective device and a separate RCD are installed
The device providing the overcurrent protection is the BS EN 62606 AFDD and not a circuit-breaker to BS EN 60898.
As was the case where an RCBO is installed, it would be incorrect, and confusing, to those inspecting the installation at a later date if '60898' was recorded in column 8, as there is not a BS EN 60898 circuit-breaker protecting the circuit; the installed device is an AFDD to BS EN 62606 (Fig 5).
.png "Figure-5-Overcurrent-protective-device-and-RCD-details-1-(1).png")
.png "Figure-6-Overcurrent-protective-device-and-RCD-details-2-(1).png")
As there is a separate RCD installed, the following should be entered in column 13:
Where this type of device is installed:
A summary of this information is provided in Table 1.
Providing the information in this manner is not only a correct reflection of the installed equipment but will also aid those carrying out alterations and/ or additions or periodic inspection and testing at a later date to correctly identify the installed protective devices for the circuits of the installation.
Introduction
Switchgear manufacturers have developed protective device products for use in distribution boards and consumer units (a specific type of distribution board) which contain multiple functionalities, including those of a:- Circuit-breaker
- Residual current device (RCD)
- Arc fault detection device (AFDD).
However, enquiries received by the NICEIC field and helpline teams indicate that the use of such combination protective devices is causing some confusion in respect of the information that must be recorded on the Schedule of Circuit Details which form part of both an Electrical Installation Certificate (EIC) and Electrical Installation Condition Report (EICR).
As can be seen in the extract reproduced in Fig 1, the new Schedule of Circuit Details introduced in Amendment 2 (AMD2) published in 2022 requires information relating to both the overcurrent protective device and any installed RCD to be recorded.
Completing the 'BS (EN)' columns (numbered 8 and 13 respectively in the BS 7671 model form) is a straightforward matter where the overcurrent protective device and RCD are separate, standalone devices.
However, what is less clear is how these fields should be completed where the circuit-breaker and RCD elements are combined in an RCBO or even more so when such functionality is integrated in an AFDD.
Where a separate overcurrent protective device and RCD are installed
Where a circuit is protected by a separate circuit-breaker and RCD, the British Standard for the device installed should be entered in column 8 to identify the circuit-breaker. This might be '60898' (as indicated in Fig 2) or '60947-2' as appropriate and, for example, '61008-1' should be entered in column 13 to identify the residual current circuit-breaker (RCCB) (an RCCB being the specific form of RCD used in this instance).
Where an RCBO is installed
Clause 1 (Scope) of BS EN 61009-1 states that 'This standard applies to devices performing simultaneously the function of detection of the residual current, of comparison of the value of this current with the residual operating value and of opening of the protected circuit when the residual current exceeds this value, and also of performing the function of making, carrying and breaking overcurrents under specified conditions.'Note 1 to this clause clarifies that the content of the standard relating to residual current conditions is based on IEC 61008-1 while the content relating to protection against overcurrents is based on IEC 60898-1.
Table 41.3 of BS 7671 (Maximum earth fault loop impedance (Zs) for circuit-breakers with Uo of 230 V, for operation giving compliance with the 0.4s disconnection time of Regulation 411.3. 2. 2 and 5s disconnection time of Regulation 411.3.2.3) specifically references in the descriptors to Parts (a), (b) and (c) thereof that the data within the table is applicable to both circuit-breakers to BS EN 60898 and to the overcurrent characteristics of RCBOs to BS EN 61009-1 (Fig 3).
This clarifies that the device providing the overcurrent protection is the BS EN 61009-1 RCBO and not a circuit-breaker to BS EN 60898.
It would therefore be incorrect, and confusing, to those inspecting the installation at a later date if '60898' was recorded in column 8, as there is not a BS EN 60898 circuit-breaker protecting the circuit; the installed device is an RCBO to BS EN 61009-1.
Where the circuit is protected by an RCBO, '61009-1' should be recorded in both column 8 and column 13 (Fig 4).
Where an AFDD with integral overcurrent device and/or RCD functionality is installed
The same logic should also be applied when considering an AFDD to BS EN 62606 incorporating an overcurrent protective device and/or an RCD.Clause 1 (Scope) of BS EN 62606 General requirements for arc fault detection devices states that 'The integrated protection device is either a circuit-breaker in accordance with IEC 60898-1 or an RCD in accordance with IEC 61008-1, IEC 61009-1 or IEC 62423.' In order to determine which of these standards is applicable to a particular device reference should be made to the manufacturer's data for the AFDD being installed.
Where an AFDD incorporating overcurrent protective device and a separate RCD are installed
The device providing the overcurrent protection is the BS EN 62606 AFDD and not a circuit-breaker to BS EN 60898.
As was the case where an RCBO is installed, it would be incorrect, and confusing, to those inspecting the installation at a later date if '60898' was recorded in column 8, as there is not a BS EN 60898 circuit-breaker protecting the circuit; the installed device is an AFDD to BS EN 62606 (Fig 5).
As there is a separate RCD installed, the following should be entered in column 13:
- '61008-1' for an RCCB.
Where this type of device is installed:
- The overcurrent protection is provided by the BS EN 62606
- AFDD and not a circuit-breaker to BS EN 60898. It would be incorrect, and confusing, to those inspecting the installation at a later date if '60898' was recorded in column 8.
- The RCD functionality is provided by the BS EN 62606 AFDD and not an RCD in accordance with IEC 61008-1, IEC 61009-1 or IEC 62423. Again, it would be incorrect, and confusing, to those inspecting the installation at a later date if '61008-1' was recorded in column 13.
Conclusion
In order to provide the correct information required for the identification of the functional characteristics of protective devices providing more than one type of protection, whether overcurrent, residual current and/or arc fault current, it is necessary to refer to the relevant product standard to which the installed product conforms.A summary of this information is provided in Table 1.
Providing the information in this manner is not only a correct reflection of the installed equipment but will also aid those carrying out alterations and/ or additions or periodic inspection and testing at a later date to correctly identify the installed protective devices for the circuits of the installation.
