DC isolators for photovoltaic systems (FB 68)

BRE (Building Research Establishment) is an independent, research-based consultancy, testing and training organisation, operating in the built environment and associated industries.

On 7 October 2014, BRE published DC isolators for photovoltaic systems (FB 68), by Steve Pester.

Photovoltaic (PV) power systems are becoming increasingly commonplace. But rapid expansion of the market brings with it a need to be vigilant in the maintenance of standards. Misunderstanding the details of the technology can prove dangerous.

DC isolators are a critical component for the safe design and installation of PV systems, and were made mandatory by the Wiring Regulations (BS 7671). But a lack of understanding has led to a few incidents of fire in UK installations. In most cases they are safe and reliable, but if they are incorrectly specified or installed isolators can cause fires. This 28 page guide explains the key points that should be taken into account when specifying DC isolators, including the standards and certifications required.

The guide describes the purpose, functions and features of isolators on PV systems as well as some of the available products. It explains some of the issues found in the field, with a rogues’ gallery of examples and reviews the relevant standards and guidance currently available

The contents of the guide include:

• Introduction.
• What is an isolator?
• Current issues and rogues’ gallery.
• AC and DC electricity.
• Typical PV systems.
• Types of DC isolator on the market.
• Specifying DC isolators for PV systems.
• Standards and certifications.
• Conclusions and recommendations.
• Appendix: Utilisation categories.
• References and further reading.

--BRE Group

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