What Are PELV and SELV?

A Simple Guide for Homeowners and Business Owners

Electrical safety is at the heart of every compliant installation. If you’ve ever read an electrical report or spoken to an electrician, you may have heard terms like PELV and SELV. These can sound technical, but they simply describe different ways of keeping people safe by using extra-low voltage systems.

Let’s break down what they mean, where you might find them, and why they matter in your home or workplace.

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Extra-Low Voltage Explained

In the UK Wiring Regulations (BS 7671:2024), an “extra-low voltage” system is defined as operating at: • 50 volts AC or less, or • 120 volts DC or less

At these low levels, the risk of dangerous electric shock is greatly reduced. That’s why extra-low voltage systems are often used in places where there is a higher chance of contact with water or metalwork, or where small control circuits are needed.

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What Is SELV?

SELV stands for Separated Extra Low Voltage.

Key points about SELV: • The supply is electrically separated from earth and from any higher-voltage circuits. • This separation is usually achieved through a transformer or power supply unit. • Because it is both low-voltage and isolated, the chance of electric shock is extremely low.

Common example of SELV in the home: A 12V bathroom extractor fan supplied through a safety transformer. This allows the fan to be installed close to a shower or bath (Zones 1 or 2), where a standard 230V fan would not be permitted.

Other examples include: • Some doorbell systems • Garden or decorative lighting using a 12V driver • Certain toys or household appliances designed to be especially safe

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What Is PELV?

PELV stands for Protective Extra Low Voltage.

Key points about PELV: • Like SELV, it operates at extra-low voltage. • The difference is that a PELV system may be connected to earth for extra safety. • It doesn’t need to be as strictly isolated as SELV, but it still provides effective protection against shock.

Common example of PELV in the home: Some central heating thermostats and control wiring. These often run at 24V or 48V and may be earthed, but because they are low voltage, they are much safer than mains-powered controls.

Other examples include: • Intercom and access control systems • Certain control panels in appliances • Low-voltage control wiring in ventilation and air conditioning systems

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Why Do Electricians Use SELV and PELV?

These systems are chosen for one main reason: safety.

• Bathrooms, kitchens and swimming pools are classed as “special locations” in BS 7671. Because water increases the risk of electric shock, SELV is often used here.

• Control circuits and automation often use PELV because it allows safe, low-voltage wiring but still benefits from being connected to earth.

• Children’s toys and consumer devices often use SELV so they can be handled without risk, even if damaged.

Both methods help reduce risks in situations where standard 230V mains power could be dangerous.

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Key Differences Summarised

To put it simply: • SELV = Extra-low voltage, separated from earth and mains. Maximum safety, often used in wet or high-risk areas. • PELV = Extra-low voltage, may be earthed, commonly used for controls and automation where isolation isn’t critical.

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What This Means for You

As a homeowner or landlord, you don’t need to design these systems yourself — but it’s useful to know why your electrician may recommend a 12V fan in a bathroom or low-voltage controls in heating systems.

Using SELV and PELV is about: • Reducing the chance of electric shock • Complying with modern safety regulations • Giving you peace of mind that your home or business is protected

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✅ At Switch Electrical & Mechanical Services Ltd, we make sure all bathroom fans, heating controls, and other low-voltage systems are designed and installed in line with the latest BS 7671:2024 Wiring Regulations. That means your installation is not just functional, but also as safe as it can be.

📞 Call us on 0191 9052723 💬 WhatsApp us on 07388 439427 🌐 Visit us at switchelectrical.uk ✉️ Email: switchtoday@mail.com

Frequently Asked Questions (North East UK)

What are my legal electrical responsibilities as a Landlord in Newcastle? As a landlord in the North East, you are legally required to ensure that all electrical installations in your rental property are safe when tenants move in and are maintained in a safe condition throughout the duration of the tenancy. This includes obtaining a satisfactory Electrical Installation Condition Report (EICR) every 5 years or at the start of a new tenancy. Switch Electrical & Mechanical Services provides comprehensive EICR audits for landlords across Newcastle, Sunderland, and Gateshead.

How much does an EICR cost for a standard property in the North East? The cost of an EICR depends on the size of the property and the number of circuits. Switch Electrical & Mechanical Services provides highly competitive, transparent pricing for landlords in the North East. We also offer discounted rates for landlords with multiple properties or HMOs requiring block certification.

What happens if my rental property fails an EICR? If an EICR identifies 'C1' (Danger Present) or 'C2' (Potentially Dangerous) codes, the installation is deemed 'Unsatisfactory'. Landlords have exactly 28 days to complete the necessary remedial work. Our team at Switch Electrical & Mechanical Services can provide immediate, fixed-price quotes for all remedial work following an inspection to ensure you remain legally compliant.