Know your environment
If you work with LV switchgear, you already know the importance of reliability, safety and long-term performance. What many people underestimate is how strongly these depend on the environment the switchgear is installed in. BS EN 61439-1 gives very clear temperature and humidity requirements for indoor assemblies, and understanding these conditions is essential for a compliant installation.
Lets talk about what the standard expects, why humidity control is critical, and what your responsibilities are as the contractor or installer.
What BS EN 61439-1 Expects From an Indoor Installation
BS EN 61439-1 does not use casual phrases like “heated room” or “dry environment”, but the temperature and humidity limits it sets can only be achieved in a controlled, heated indoor space.
Temperature Limits for Indoor Installations (Clause 7.1.1.1)
Maximum ambient temperature: 40°C
Maximum 24 hour average: 35°C
Minimum ambient temperature: 5°C
This -5°C figure is often misunderstood. It is not an operating rating for the switchgear and it is not a tested value. It only applies when the air remains dry and non condensing, which is only possible in a properly heated and controlled environment.
Humidity Limits for Indoor Installations (Clause 7.1.2.1)
Up to 50 percent relative humidity at 40°C
Up to 90 percent relative humidity at 20°C
Only occasional, brief condensation allowed
These humidity levels require a heated room. An unheated or poorly ventilated space will drop below dew point, creating condensation on copper, steel and insulation. Once condensation becomes routine, the installation no longer qualifies as an indoor installation under the standard.
Why Humidity Is the Real Risk for Switchgear
Cold temperatures on their own are rarely the problem. Cold temperatures combined with moisture are what cause issues. Condensation leads to corrosion, insulation breakdown, tracking, electronic faults and shortened equipment life.
A switchboard that is energised produces enough internal heat to remain comfortably above freezing. However, when the board is switched off for maintenance or during prolonged downtime, the internal temperature quickly drops to match the room. If the room is unheated, condensation forms and the equipment is at risk.
To remain compliant, any space that may fall below freezing needs external frost protection or background heating.
Your Role as the Contractor or Installer
The manufacturer builds the switchgear to the environmental limits. The contractor is responsible for making sure the installation environment actually meets those limits.
This includes:
Controlling Temperature
Heaters, ventilation or air conditioning may be required. The goal is to maintain stable conditions and avoid cold spots or rapid temperature swings.
Managing Humidity
Dehumidifiers, ventilation and moisture barriers may be necessary in damp or basement environments. Condensation must be prevented, not just reduced.
Monitoring Conditions
If environmental treatment is not possible, the minimum requirement is to install a temperature and humidity sensor or remote hygrometer. This gives you early warning if conditions deteriorate and helps demonstrate due diligence.
What Happens If the Environment Cannot Meet the Standard
If the installation space cannot meet the indoor service conditions of BS EN 61439-1, it becomes a special service condition. In this case the standard no longer applies to the installation environment, and the responsibility for suitability and protection sits with the contractor or client.
This is usually a contractual matter and must be addressed early, especially where there is a risk of condensation, freezing or poor building conditions.
Long Term Protection of Your LV Switchgear
Switchgear is a long term investment and relies on a stable environment. Even after installation, the conditions should be checked regularly.
Recommended practices include:
- Routine inspections
- Checking seals and gaskets
- Ensuring ventilation paths remain clear
- Confirming heaters, dehumidifiers or sensors operate correctly
- Responding early to any signs of corrosion or moisture
Wrapping it up
BS EN 61439-1 sets environmental conditions for good reason. They are there to ensure that LV switchgear performs reliably, safely and consistently throughout its life. The equipment is designed for indoor, controlled, non condensing environments. Maintaining those conditions is essential.
We are not trying to block installations. Our responsibility is to ensure the equipment is installed in an environment that supports safe and reliable operation. If the required conditions cannot be met, this becomes a contractual discussion on your side, as the installation would fall outside the standard’s normal service conditions.
If no environmental treatment is provided, the minimum requirement is active monitoring using temperature and humidity sensors. This does not replace a treated environment, but it does provide early warning if conditions begin to move outside acceptable limits.
Disclaimer:
The information provided on this site is for general informational purposes only and may not reflect the most current regulations or standards. Legislation, industry guidelines, and best practices can change over time, and it is the user’s responsibility to research and ensure compliance with the latest requirements for their specific situation. Always consult a qualified professional for advice tailored to your project or application.