If you have ever been asked to provide "ELV drawings" or "ELV design" for a building, the first question is usually what is meant by ELV. The term is used loosely, and it means different things in different standards, markets and trades. Understanding the definition is the first step in scoping the work correctly.
This article explains what extra low voltage means, what ELV stands for, how the term is used in building engineering, which systems are typically included, how ELV differs from mains power distribution, and what design deliverables a project needs. It is general educational information. Project requirements must be checked against the applicable standards and local regulations.
What Does Extra Low Voltage Mean?
Extra low voltage (ELV) is a voltage band below the levels used for ordinary mains supply. The purpose of the band is to limit the risk of electric shock, and to allow circuits to be installed and maintained with reduced protection measures, provided the arrangements meet the requirements for the circuit type.
The exact limit is not universal. International standards define ELV in terms of the maximum voltage that can be maintained under specified conditions, which depends on environment and touch-voltage assumptions. Commonly cited figures for AC and DC systems, such as 50 V AC and 120 V DC ripple-free, appear in several references, but the limit that applies to a particular installation depends on the standard, the edition and the conditions. Always confirm the figure against the standard your project uses.
What ELV Stands For
ELV stands for extra low voltage. In building engineering the abbreviation is used for systems that operate at low energy and that carry signals, data or control information rather than bulk power. Some documents also use ELV to describe extra-low-voltage lighting or appliances, so check the context before relying on the term.
How the Term Is Used in Building Engineering
In a building project, ELV is commonly used as a collective term for the systems that sit alongside mechanical and electrical services. Its scope varies by client and region. Some projects use ELV to mean all low-energy systems; others use it more narrowly for security, communication and control. The first step in any project is to list the systems included in the ELV scope and to agree the responsibilities for each.
Typical ELV Systems in Commercial Buildings
| System | Typical purpose | Common design deliverables |
|---|---|---|
| CCTV | Video surveillance and recording | Camera layouts, cable routes, recorder schedules |
| Access control | Door control and credentials | Door schedules, controller layouts, cable schedules |
| Structured cabling | Data, voice and wireless backhaul | Outlet layouts, riser diagrams, cable and patch schedules |
| Fire alarm signalling | Detection, alarm and signalling | Device layouts, zone plans, cause and effect |
| PA/VA | Announcements and emergency voice | Speaker layouts, zoning, amplifier schedules |
| Building management | Monitoring and control | Point lists, sensor layouts, control schematics |
ELV Systems vs Electrical Power Distribution
The difference between ELV systems and power distribution is one of purpose and risk. Power distribution carries energy to equipment and lighting, at voltages that can cause serious injury. ELV systems carry information or low-energy control signals. Some ELV equipment is supplied from a mains-powered power supply, and the boundary between the two must be designed carefully. The supply, its protection and its separation from ELV circuits are covered by the electrical design rather than by the ELV scope.
Typical ELV Design Deliverables
A typical ELV design package includes:
- System layouts on architectural base drawings
- Riser diagrams and schematic or block diagrams
- Equipment schedules and rack elevations
- Cable schedules and containment routes
- Specifications and device lists for procurement and tender
- Coordination drawings showing containment and clearances
Cable Routing, Segregation, Coordination and Documentation
ELV cables must be routed so that they can be installed, maintained and identified. Segregation from power cables is a common requirement, and the separation distance and method depend on the standard and the cable type. Containment should be coordinated with mechanical and electrical services early, because late changes to ceiling or riser layouts are expensive. Every cable route and termination should be documented so that the installed system can be verified and maintained.
The Importance of Applicable Electrical Safety Requirements
ELV does not mean exempt from electrical safety. The protective arrangements for an ELV circuit depend on how the circuit is supplied and how it is separated from other circuits. The distinctions between SELV, PELV and FELV are explained in our articles on SELV and PELV. The requirements are set by the electrical installation standard in force and by local regulations, and they should be confirmed by a qualified electrical engineer.
When a Project Needs an ELV Design Consultant
An ELV design consultant is useful when:
- A building includes several ELV systems that must be integrated
- The design must meet fire, security or cabling standards
- Drawings must be coordinated with architectural and MEP information
- The client needs a tender-ready specification and layout package
- An existing system is being extended or replaced
ASDV Consultant provides ELV and ICT design consultancy, including the layouts and documentation described above. Our services overview lists the systems we design, and you can contact us to discuss your project.