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Breaking myths on regulation 421.1.201 of the 17th Edition of the Wiring Regulations.

We have seen a massive amount of uncertainty regarding Amendment 3 and non-combustible consumer units. While attending various industry events and seminars since the Amendment was announced in January, Steve York, Market Manager has uncovered a number of false perceptions in relation to the subject. In response to this, he has compiled a list of myths and truths using the Hager Design range of consumer units as a case study.
MYTH: We don’t have to install metal consumer units until January 2016
TRUE: Amendment 3 to BS 7671:2008 was issued in January 2015 and came into effect on 1st July 2015. However, 421.1.201 NOTE 2 states that the implementation date for this regulation is the 1st January 2016.

An installation designed before January 1st 2016 can comply with the previous edition of the wiring regulations. The regulations use the term ‘installations designed’ which implies that the installation design has been completed.

The elements of an installation design are listed in section 132 of BS 7671;
MYTH: Glanding, trunking and intumescent strips are essential to contain a fire
FALSE: On a Hager consumer unit extensive testing has proved that none of these are required to contain a fire caused by a poor connection. However, trunking or glands may be required to achieve IP rating. We suggest the use of a cable protector plate or grommet strip and trunking. Intumescent materials are not required by the regulations; however their use is at the discretion of the installer.
MYTH: We are going to need to buy metal trunking and metal blanks
FALSE: Tests have proven that Hager boards with plastic trunking and grommet strips are compliant to the intent of the regulation. All devices and blanks are covered by a non-combustible door therefore protection by the enclosure is maintained.
MYTH: Any plastic consumer unit should be reported as a code C3 from 1st Jan 2016.
FALSE: When completing an electrical installation condition report for inspections carried out after 1st January 2016, if the plastic consumer unit is not within the sole route of escape or underneath a wooden staircase, and the connections inside it are satisfactory then it need not be commented on.
However, if the plastic consumer unit is located under a wooden staircase, or within a sole route of escape from the premises then it should to be classified as C3 on the report.
If unsatisfactory connections are found during inspection, this would warrant a code C2 classification to be recorded. More information on the C1, C2 or C3 coding can be found in IET Guidance note No 3.
MYTH - Consumer units don’t have to comply to Amendment 3 when in a garage
PLAUSIBLE: Any consumer unit fitted anywhere within a domestic (household) application is required to be manufactured from a non-combustible material. If a board is installed within a garage that is linked to the house then this is included within the household application. If the garage is detached from the house, then a risk assessment needs to be carried out in relation to the risk of fire spreading from the detached garage or outbuilding to any dwelling.
MYTH: A substandard connection is only a loose screw.
FALSE: There are many things that may contribute to a substandard connection. Some of these are inadequate tightening of conductors in the relevant terminals or clamping the insulation of the cable rather than the conductor within the terminal. Also if a terminal is over-tightened this can result in the conductor being crushed creating a high resistance connection generating heat. The intent of the regulation is to contain any fault regardless of where it originates within the consumer unit.
MYTH: Fire rated thermoplastic consumer units can still be used
FALSE: The regulation states that the consumer unit must be made from a non-combustible material with ferrous metal as an example, the regulations do not state that it is the only suitable material, however, 960º thermoplastic was described in the draft for public comment as a not readily combustible material, hence its use would not comply.
MYTH: All plastic consumer units will need changing
FALSE: Provided that neither the consumer unit nor its devices are subject to: a manufacturer recall, incorporated components conform to the relevant product standard(s), do not have latent defects and have been installed correctly, the consumer unit does not need changing.
MYTH: Metal boards cannot be used for TT Systems
FALSE: With the introduction of Amendment 3 the option of using an insulated enclosure is no longer permitted. Where a metal consumer unit is installed in an installation forming part of a TT system, the earth fault loop impedance, Ze, is likely to be much higher than that permitted by the overcurrent protection device, i.e. cut-out. Should the tails become loose or damaged and make contact with the metal enclosure, it is likely that the overcurrent device will not operate within 5 seconds. Hence it is recommended to install a metal consumer unit with each outgoing circuit protected by an RCBO or a metal split load board where the double-pole main switch incorporates an S-type (time delayed) RCCB. However the tails will need to be protected to avoid damage and disturbance at the incoming terminals.