Essential Earthing Guide for Your Garden Shed’s Electrical Safety

Ensuring the electrical safety of your garden shed in the UK requires a thorough understanding of earthing systems, especially when your property is equipped with a Protective Multiple Earthing (PME) system.

This guide combines expert advice from Alto Electrical with electrical standards, including the BS 7671 regulations, to help homeowners navigate the complexities of safely powering garden sheds and outbuildings.

Understanding the Risks with PME Systems

PME systems, while efficient and safe for main residential use, pose specific challenges when extended to outbuildings like garden sheds.

The risk of an open circuit in the PME system can turn exposed conductive parts dangerously live, leading to potential electric shocks.

This is particularly concerning in scenarios where the PEN conductor fails, making the neutral and earth supplied go open circuit or high resistance.

The Right Earthing Approach for Garden Sheds

When it comes to ensuring the electrical safety of your shed, there are critical considerations to make, informed by both the risk assessment of extending PME earth and the specific regulations guiding such installations.

Exporting PME Earth

A Cautious Approach

Regulation Insights

While no regulation outright forbids the export of PME earth to another building, the BS 7671 highlights scenarios where PME shouldn’t be used without precautions.

DNO Guidelines

Some Distribution Network Operators may restrict exporting PME earth from the supplied building, emphasising the need for a tailored approach based on local guidelines and the unique risks involved.

Opting for TT Earthing System

Given the potential risks associated with PME systems, especially concerning shock hazards in case of a PEN conductor failure, switching to a TT earthing system for your garden shed offers a safer alternative.

SWA Cable Application

Using SWA cable? Ensure its steel armour is connected to the installation earth at the supply end to mitigate shock risks from accidental cable damage.

RCD Implementation

Essential for safety, installing an RCD main switch in your shed’s distribution board provides critical protection. Depending on the size of the installation, the specific type of RCD may vary, but 30mA RCDs are generally recommended for additional circuit protection.

Earthing Terminal Connection

Connect the Main Earthing Terminal in your shed to an earth electrode, adhering to BS 7671’s Table 41.5 standards for earth resistance.

Making Informed Decisions

Choosing between extending PME earth or opting for a TT system involves considering the specifics of your shed, such as flooring material and the presence of conductive parts.

A professional electrician can help assess these factors and recommend the safest earthing solution, ensuring compliance with the latest electrical regulations.

Professional Guidance is Key

For comprehensive safety and compliance, consulting with a professional electrician familiar with BS 7671 and local DNO regulations is crucial.

They can provide tailored advice and ensure your garden shed’s electrical installation meets all safety standards.

Understanding the complexities of earthing for garden shed electrical installations ensures the safety and compliance of your setup.

Whether you’re dealing with PME system limitations or deciding on the best earthing approach, professional advice and a detailed risk assessment are invaluable.