Energy Efficiency In the 18th Edition, Explained

April 26, 2018

energy efficiency

With the 18th Edition wiring regulations (BS7671,18th) fast approaching, and energy efficiency being included, it has become one truly hot topic. Energy efficiency has been part of a building design solution for years (especially in Europe due to IEC 60364, Part 8), but in the UK these solutions were implemented at the discretion of the engineer. Often, in the UK, these solutions were not implemented for environmental reasons but rather to reduce equipment demands and sizes.

In this blog, we will look at the IET Designers Guide to Energy Efficient Electrical Installations and what could possibly be included as part of the 18th Edition.

Looking at the draft of the 18th Edition, a number of aspects relating to energy efficiency that have been included in Part 8, cover several different energy saving solutions. For example:

  • Optimising the number of HV/LV substations

  • Working point of the transformer

  • Transformer efficiency

  • Volt drop

  • Increasing of conduct cross-sectional area

  • Power factor correction measures

  • Reduction of harmonic currents

  • Power management system

And the list goes on …

As seen from the list above, a lot of different solutions are available, but it now sounds as if the 25-page draft has been reduced to about 5 pages and moved to appendix 17 for information in the BS7671.

Assuming that the draft will be based off the IET Guide to Energy Efficient Electrical Installations, (IET GEEI), we have summarised some of the main points within this book that we feel may be related to the new appendix 17 section in the regulations. This book covers a number of the same points raised in the draft, but explains these more clearly, therefore giving better guidance on how to obtain an energy efficient design/project.  

The benefits identified by the IET GEEI are that, by putting energy efficient solutions in place, we are able to:

  • Lessen the impact on the environment

  • Reduce energy losses and hence lower energy cost

  • Use energy only when it is required and potentially only during off peak tariffs

  • Lessen unplanned maintenance due to damages caused by heat losses

  • Optimise the electrical system performance throughout the lifespan

Because of the benefits identified above, the industry has started to make a slow shift from the traditional model (mindset) of:

Safety → Capacity → Resilience TO  Safety → Capacity → Efficiency → Resilience.

With this shift in mind, it has also started to make the industry as a whole think about who has responsibility for energy efficiency for the lifespan of the installation. As identified in the IET GEEI, the Designer and Installer would need to take responsibility for the efficiency of the electrical intake and distribution system efficiency while also considering the control system effectiveness. This then means that the User will need to take responsibility for the application efficiency.

Despite the points mentioned above regarding energy efficiency, it should be clearly understood that Energy Efficiency does not take precedence when it comes to safety or the User requirements. This also means that any control systems that are implemented should have manual override options available, if required. Although, the designer may (should) want to consider the following when looking to create or implement a new project:

  • Load energy profile (Active and Passive)

  • Optimal location for the primary energy sources

  • Availability of local generation

  • Reduction of energy losses

  • The arrangement of circuits

  • Use of energy according to customer demands

  • Tariff structure offered by the electrical supplier

Both the IET GEEI and 18th Edition draft have reference to the energy efficiency metrics. This has been included to help engineers assess the energy efficiency of design/installation. This matrix helps to identify possible areas of improvements, while also allowing the client to specify a certain energy-efficiency level.

The matrix are broken down into a number of different sections and categories. The first has 13 energy efficiency measures (EM) with a rating from 0 to 4 and the second is Energy Performance level EPL rating from 0 to 4 as well.

Then, by taking the collective of the above section and categories, it is possible to create Electrical Installation Efficiency Classes (EIEC). These are rated from 0 to 4 again, and could be presented in the following way:

Once the project is completed/installed, this does not mean that the review on energy efficiency stops. Instead, it advises that this energy efficiency metric should still be performed during the life of the building (project). These energy efficiency recommendations should not only be considered for new buildings but should also be considered in existing buildings.

As mentioned above, there are a number of solutions to reduce energy consumption and many of these are covered within the IET GEEI. But attention should also be made to the section related to distribution control, as this helps to identify where/how the applications will be used (zones), what type of appliances will be operated (usage), and then what control would be put in place for similar equipment (meshes).  

Other areas that would help potentially improve the efficiency are the electrical network as a holistic solution, and not just focussing on one small part of the system— though this should also consider the load management system and smart metering system, as these both can help reduce power consumption by monitoring your electrical network and by identifying areas of improvement.

Finally, the IET GEEI also helps to answer some questions that designers and engineers may need to ask themselves when considering energy efficiency. The IET GEEI and the 18th Edition draft also cover aspects related to the Barycentre method to help optimise the location of electrical equipment in your building for distribution of the electrical network.

18th Edition guide

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