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Is there a maximum length for a spur cable?

Former Community Member over 5 years ago

Good afternoon, hope you are all well.

Just two quick questions.

Is there a maximum length for a 2.5mm twin and earth spur cable terminated in a ring final wall socket?

Is there a maximum length for a 2.5mm twin and earth spur cable terminated in the Consumer unit RCBO which also supplies a ring final. I understand that there can only be one spur cable from the RCBO. So max three cables in RCBO.

As always, many thanks in advance.

Simon

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0 Zoomup over 5 years ago

simon201:
Good afternoon, hope you are all well.

Just two quick questions.

Is there a maximum length for a 2.5mm twin and earth spur cable terminated in a ring final wall socket?

Is there a maximum length for a 2.5mm twin and earth spur cable terminated in the Consumer unit RCBO which also supplies a ring final. I understand that there can only be one spur cable from the RCBO. So max three cables in RCBO.

As always, many thanks in advance.

Simon

Hello Simon,

see if you can have a look at Appendix 15 (Informative) of B.S. 7671. It is recommended that an unfused spur can be connected at the origin of the ring final in the distribution board or consumer unit, or from a socket outlet or from a junction box connected to the ring final circuit. The unfused spur should supply just one single or one double (twin) socket outlet. It should be wired in 2.5mm2 P.V.C./P.V.C. T&E cable. There is no limit to the length of a spur, but Voltage drop considerations should be taken into account. It is not recommended that large loads like immersion heaters, large space heaters or similar loads be connected to the ring final circuit. It is unlikely that a spur will ever be too long in the average U.K. house.

Edit. B.S. 7671 defines a SPUR as a branch from a ring or radial final circuit.

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0 Zoomup over 5 years ago

simon201:
Good afternoon, hope you are all well.

Just two quick questions.

Is there a maximum length for a 2.5mm twin and earth spur cable terminated in a ring final wall socket?

Is there a maximum length for a 2.5mm twin and earth spur cable terminated in the Consumer unit RCBO which also supplies a ring final. I understand that there can only be one spur cable from the RCBO. So max three cables in RCBO.

As always, many thanks in advance.

Simon

Hello Simon,

see if you can have a look at Appendix 15 (Informative) of B.S. 7671. It is recommended that an unfused spur can be connected at the origin of the ring final in the distribution board or consumer unit, or from a socket outlet or from a junction box connected to the ring final circuit. The unfused spur should supply just one single or one double (twin) socket outlet. It should be wired in 2.5mm2 P.V.C./P.V.C. T&E cable. There is no limit to the length of a spur, but Voltage drop considerations should be taken into account. It is not recommended that large loads like immersion heaters, large space heaters or similar loads be connected to the ring final circuit. It is unlikely that a spur will ever be too long in the average U.K. house.

Edit. B.S. 7671 defines a SPUR as a branch from a ring or radial final circuit.

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Is there a maximum length for a spur cable?

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