Not necessarily. Provided a SY/CY/YY cable is used:
Then the Designer, or person selecting the cable, may use such products, where they are confirmed to provide at least the same degree of safety as that afforded by compliance with the Regulations, in accordance with Regulation 511.2. The use is to be recorded on the appropriate certification, and documentation confirming the safety attached.
Guidance specifically on non-standard cables, including SY/CY/YY types, is provided in Section 7.9 of the IET's On-Site Guide.
Your cable selection should consider the External Influences set out in Appendix 5 of BS 7671. One option might be HO7 RNF cables depending on the actual circumstances.
Ultimately this is a matter of contract, and perhaps who is going to sign the Electrical Installation Certificate.
Ultimately this is a matter of contract, and perhaps who is going to sign the Electrical Installation Certificate.
It could do. The important thing is the designer has to certify that whatever does not comply with BS 7671 is no less safe than meeting the requirements of BS 7671.
It would depend on the type of animal, the current path through the animal and the duration of the shock current. There is no fixed voltage.
This is not a requirement of BS 7671, nor of ENA Engineering Recommendation G12/4.
If the outbuilding has extraneous-conductive-parts, then, where PME conditions apply, main bonding conductors in the outbuilding must meet the requirements for main bonding conductors, as must the circuit protective conductor of the sub-main supplying the outbuilding. In some cases, this is cost-prohibitive, and a TT earthing arrangement is used at the outbuilding.
If the outbuilding has no extraneous-conductive-parts, this consideration is unnecessary.
The Fundamental Principles are set out in Part 1 and the Assessment of General in Part 3. The application of these Parts are covered in many IET Guidance Notes and the Electrical Installation Design Guide.
Electrically Skilled Person' is defined in Part 2 of BS 7671.
Not necessarily. Provided a SY/CY/YY cable is used:
Then the Designer, or person selecting the cable, may use such products, where they are confirmed to provide at least the same degree of safety as that afforded by compliance with the Regulations, in accordance with Regulations 511.2. The use is to be recorded on the appropriate certification, and documentation confirming the safety attached.
Guidance specifically on non-standard cables, including SY/CY/YY types, is provided in Section 7.9 of the On-Site Guide.
It can be found in document TB210 from the Fire Protection Association.
Early discussions with the DNO can be fruitful and reading their published guides to supplies online is recommended.
No. See Appendix 6 of BS 7671.
It would depend on the size of premises and the possible load growth over the life of the installation, as well as the requirement from the client.
All standards undergo revision, and these are usually addressed by contract variations, to be agreed or rejected by the Client. Most standard forms of contract include procedures for this.
Risk assessments should be reviewed when standards change, and CDM risk assessments are no exception.
It depends firstly on the requirements of the client or the client's representative who may specify what spare capacity is required. Then what about load growth over the life of the installation? How much capacity is there in the local DNO network? It is good practice to allow something like 20% spare capacity on the supply, on the distribution circuits (cable or bus bar) and 20% spare ways in distribution boards, and agree this with the client.
There are no guarantees as yet, that any changes to BS 7671 proposed in the Draft for Public Comment of Amendment 2, will actually be part of Amendment 2:2020.
All standards undergo revision, and these are usually addressed by contract variations, to be agreed or rejected by the Client. Most standard forms of contract include procedures for this.
This is highly unlikely. Colour codes are actually harmonized via BS EN 60445, not BS 7671, and the changes proposed in the Amendment 2 DPC are as a result of changes in BS EN 60445:2017.
BS EN 60445 aligns with IEC 60445, and is an international standard.
When electric currents travel in any conductor, electrostatic and electromagnetic fields are generated.
When the current changes, such as with alternating current or harmonics, the electrostatic and electromagnetic fields emitted from conductors also changes. The resulting fields travel as electromagnetic radiation, and these are known as radiated emissions.
Current fields may also travel down conductors. These are known as conducted emissions.
Where emissions create unwanted interference, or ""noise"", we also call these disturbances.
Equipment can be made with a tolerance to disturbances (noise or emissions) – we call this the level of electromagnetic immunity.
Yes cables are readily available. The Fire Risk Assessment, Fire Strategy and BS 7671, BS 8519 and other standards will determine what is required. There are changes proposed in the DPC for BS 7671 AMD 2 so we must wait to see what the outcome is when AMD 2 is published.
There are already requirements in BS 7671 concerning harmonics. The problem of exporting harmonics to the grid will increase with local generation and more electronic controlled devices, switch mode power supplies and VSDs. We suspect the need for harmonic filtration will increase.
This will depend on the responsibilities for a particular contract. This may not be the same for every job, especially where different organisations are responsible for the electrical installation and the LPS. The design should take into account the requirements of both the electrical installation (to BS 7671) and the lightning protection system (to BS EN 62305 series). It may be necessary for the electrical designer/contractor and the LPS specialist or contractor to discuss the interface to ensure that both standards are met by the designs.
Such interface work is also required in respect of SPDs and overvoltage control, as well as earthing, to meet the various requirements of BS 7671.
Fundamentally, this depends on the terms of the contract, and the complexity of the installation. Complexity doesn't always relate to size, for example, there are hazards not covered in "standard electrical training" for installations with control systems – including SMART installations. Not all electricians and technicians have been trained with this type of system, so certainly if there is an O&M organisation they may well need training on certain aspects.
This is clearly stated in Regulation 644.4 of BS 7671 – joint responsibility of the person or persons responsible for design, construction and verification of the installation (or addition or alteration). Ultimately, though, it may be a matter of contract for an individual project, as to which legal person or persons are considered to be responsible for the design, construction and verification.
Diversity is mentioned in BS 7671. The IET On-Site Guide and IET Guidance Note 1: Selection and Erection also provide guidance for calculating diversity.
No. However the IET On-Site Guide provides guidance on the sizing of conduit and trunking so that cables may be easily and safely drawn in. Good engineering judgement would dictate that spare capacity in containment would permit later alterations and additions.
All standards undergo revision, and these are usually addressed by contract variations, to be agreed or rejected by the Client. Most standard forms of contract include procedures for this.
Risk assessments should be reviewed when standards change, and CDM risk assessments are no exception.
This is a very broad question, although interestingly the person working for the Contractor also becomes a Designer under CDM Regulations. See also answer to question 39 below.
BS 7671 requires that the designer be an 'Electrically Skilled Person' and that definition can be found in Part 2 of BS 7671. No specific qualifications are required, however, City and Guilds offer the Level 4 2396 design course.
We do not know of any proposed legislation in respect of EV charging. The government have indicated that fossil-fuelled vehicles will be phased out by 2030.
Do you now lower over current settings to reduce potential arc energy?
Energy let through I2t will depend on the impedance of the supply and the protective devices is a circuit.
Protective devices will limit energy let through. For circuit breakers to BS EN 60898 they have specific maximum let through Classes. Manufacturers publish let through data graphs for their specific devices. It may be necessary for designers to verify the thermal withstand of cables is sufficient for the energy let through.
Yes. Also the Fire Protection Association document TB 210.
It is not as simple as that. It depends on the connected loads and how they are used. The IET's Guidance Note 1: Selection and Erection and the IET On-Site Guide provide some useful guidance.
There is no substitute for manufacturer's data. For an outline draft design, a designer can use their knowledge and experience and use an estimated figure until they obtain the required data.
This depends on contractual arrangements, but don't forget that an Electrical Installation Certificate should be signed by the person responsible for the design – so the person signing that should.
It is a very good question - because if the design drawings are not 'as built', or a key safety feature such as a point of isolation has been omitted, and not reflected in the CDM risk assessments, someone should expect to be held to account in the event of a safety incident further down the road.
Yes, in all cases. Where the maximum demand of the installation exceeds 13.8 kVA, or will exceed 13.8 kVA after installation of EV charging equipment, the notification must be made in advance to check the supply capability. For maximum demand up to 13.8 kVA, the notification is done within 28 days of the installation. See Section 11 of the IET Code of Practice for EV Charging Equipment Installation, 4th Edition.
Selectivity is a requirement of BS 7671. See section 536.
Maybe. It depends firstly on the requirements of the client or the client's representative who may specify what spare capacity is required. Then what about load growth over the life of the installation. How much capacity is there in the local DNO network. It is good practice to allow something like 20% spare capacity on the supply, on the distribution circuits (cable or bus bar) and 20% spare ways in distribution boards and agree this with the client. For EV charging it may be necessary to use load curtailment to limit maximum demand.
AFDDs are not mandated in the current edition of BS 7671 they are only recommended. The DPC for Amendment 2 to BS 7671:2018 requires them to be mandatory. That said we do not know what the outcome will be of the result of the public consultation until the Amendment is published.
Some DNOs are already offering three-phase supplies to new build housing developments.
Diversity is difficult to apply in smaller installations, but is no longer prohibited for EV charging installations (the prohibition having been removed in Amendment 1:2020 to BS 7671:2018). However, if load curtailment is used, this can be taken into account. Load curtailment was discussed in an earlier webinar. You can view this on-demand.
Yes, in all cases. Where the maximum demand of the installation exceeds 13.8 kVA, or will exceed 13.8 kVA after installation of EV charging equipment, the notification must be made in advance to check the supply capability. For maximum demand up to 13.8 kVA, the notification is done within 28 days of the installation. See Section 11 of the IET Code of Practice for EV Charging Equipment Installation, 4th Edition.
See BS 8300-1 and BS 8300-2, along with the building regulations accessibility guidance publications for the particular devolved nation. It may also be prudent to consider a means of limiting access to unsupervised young children whilst facilitating the accessibility requirements. The height recommended in Section 3.1.3 of the IET's Electrician's Guide to the Building Regulations is 1350-1450 mm above finished floor level.
The total volt drop is from the origin of the installation to the point of use.
It can be found in document TB210 from the Fire Protection Association.
This depends on the construction of the cable, and its installation conditions. For example, some manufacturers of PVC sheathed and insulated SWA that is subject to regular or long-term immersion quote much lower service life than the same cable installed in dry conditions.
The ratings for cables in BS 7671 are to be found in Appendix 4. Appendix 4 is 'Informative' so does not have to be complied with if a designer, using his/her engineering judgement, decides on an alternative solution. BICC data can be found in some proprietary software.
Individual DNOs publish their own requirements. In addition, see the Distribution Code Annex 1 and Annex 2 documents, available from www.dcode.org
Yes, see Appendix 17 of BS 7671, and BS HD 60364-8-1.
Definitely, this is a good point. The only issue to watch out for, is that industry guidance and Codes of Practice (and similar) may not be updated at the same pace as the relevant standards. However, the same also holds true of some standards that reference other standards.
Discrimination' is now termed 'selectivity'. Selectivity is a requirement of BS 7671. See section 536.
Very difficult to do without software as the running temperature will depend on the type of cable, the installation method and rating factors.
Manufacturers do publish cable data which may be of some help.
In short an awful lot. Things like fault current rating, overload and short circuit protection, achieving ADS for circuits connected to the panel board, physical size, cable entry, cable terminations etc.
Yes, the general view is if the building is already on fire you want the fire pumps to continue running to destruction if necessary.
This will depend on a particular defect, and the conditions in the particular installation. For example, a damaged cable sheath is not necessarily an immediate hazard, providing conductor insulation is intact, but a further impact could make it an immediate hazard. This is a matter for the relevant duty holder to assess according to the Electricity at Work Regulations?
This can be found in document TB210 from the Fire Protection Association.
With the given information it is difficult to say. The design should have considered the External Influences as listed in Appendix 5 of BS 7671. On a farm there will nearly always be the presence of rodents and rodents love chewing on PVC to keep their teeth sharp and short. Ask the contractor for the design information, CDM 2015 requires them to supply it, and ask what considerations were given to External Influences? Assuming the contractor has supplied an EIC for his/her work what have they put against 8.2 of the inspection schedule?
Is it true that the sheath on SY cable is mostly not UV stable and will deteriorate early when installed outside? External influence & conditions.
Not necessarily. Provided a SY/CY/YY cable is used:
Then the Designer, or person selecting the cable, may use such products, where they are confirmed to provide at least the same degree of safety as that afforded by compliance with the Regulations, in accordance with Regulations 511.2. The use is to be recorded on the appropriate certification, and documentation confirming the safety attached.
Guidance specifically on non-standard cables, including SY/CY/YY types, is provided in Section 7.9 of the On-Site Guide.
This is definitely a requirement in some other standards, see for example Clause 37.2.3.3 of BS 9999 regarding primary and secondary supplies for fire protection systems, and similarly Clause 6.3.2.3 of BS 9990 for the primary and secondary supplies (where used) for dual electric wet fire mains pumps.