Length of tails between meter and consumer unit

[Gigsy]

Except where 434.3 applies, which is why I referenced it

434.3(iv) states that DNO rules permission must apply where their fuse is being used as fault protection. DNO rules will generally stipulate a length no more than 3m

But am I correct in saying this omission is relating to regulation 434.2

434.2 - A device providing protection against fault current shall be installed at the point where a reduction in CSA applies.

So regulation 434.3 is saying the omission of devices for protection against fault current need not be provided for (i.e. an omission required by regulation 434.2)
(iv) agreement with the DNO

So this is saying that you can reduce the size of the CSA and omit a protective device if the DNO agrees?

 

[buzzlightyear]

So this is saying that you can reduce the size of the CSA and omit a protective device if the DNO agrees

Isolation of meter tails at the origin

Regulation 537.1.3 states that, where the distributor provides a means of disconnection at the origin of the installation, it may be used, subject to the agreement of the distributor, as the means of isolation for the part of the installation between the origin and the main linked switch or circuit-breaker required by Regulation 537.1.4. This isolator can take the form of an integral switch within the meter (Fig. 1).

The distributor will usually require that a means of isolation is installed if the meter tails exceed a certain length. Distributors often stipulate different maximum lengths for meter tails but a maximum length of 3 metres is common.

A fused switch is recommended over 3 m by the Distribution Connection and Use of System Agreement (DCUSA).

The Note to Regulation 537.1.3 draws our attention to the fact that a cut-out fuse cannot be used for isolation by persons who are not authorized to do so by the distributor.

Regardless of whether or not it is required by BS 7671, there can be little doubt that the provision of an isolator at the origin of an installation is good practice. Where a contractor has called out the distributor to withdraw the cut-out fuse, a convenient opportunity is presented for an isolator to be fitted at the origin of the installation. This could be carried out either by the distributor or by the contractor. Thereafter, it would no longer be necessary to call out the distributor to withdraw the cut-out fuse.

 

[Gigsy]

Isolation of meter tails at the origin

Regulation 537.1.3 states that, where the distributor provides a means of disconnection at the origin of the installation, it may be used, subject to the agreement of the distributor, as the means of isolation for the part of the installation between the origin and the main linked switch or circuit-breaker required by Regulation 537.1.4. This isolator can take the form of an integral switch within the meter (Fig. 1).

The distributor will usually require that a means of isolation is installed if the meter tails exceed a certain length. Distributors often stipulate different maximum lengths for meter tails but a maximum length of 3 metres is common.

A fused switch is recommended over 3 m by the Distribution Connection and Use of System Agreement (DCUSA).

The Note to Regulation 537.1.3 draws our attention to the fact that a cut-out fuse cannot be used for isolation by persons who are not authorized to do so by the distributor.

Regardless of whether or not it is required by BS 7671, there can be little doubt that the provision of an isolator at the origin of an installation is good practice. Where a contractor has called out the distributor to withdraw the cut-out fuse, a convenient opportunity is presented for an isolator to be fitted at the origin of the installation. This could be carried out either by the distributor or by the contractor. Thereafter, it would no longer be necessary to call out the distributor to withdraw the cut-out fuse.

I was discussing regulation 434.2. I was asking if a device providing protection against fault current was needed (i.e. a fuse) if the tails were longer than 3 meters.

You are discussing a different regulation, concerning isolation.

 

[Keith Roszell]

Is there a law on meter tails or is there just a recommend length ?