Ed Haslett, Divisional Director – Critical Facilities UK & Ireland at Zumtobel Lighting, explains how centralised lighting systems and proactive monitoring can enhance reliability, safety, and operational efficiency in data centres.
When standard lighting fails, emergency lighting is a lifeline which provides sufficient illumination to provide orientation, and efficiently light an escape route, preventing panic and ensuring that other safety equipment can be found immediately.
But what happens when the emergency lighting fails? And what might be the cause?
The activation of emergency lighting is designed to occur on failure of the electricity supply, when the batteries take over. Most emergency lighting systems are designed to have one-, two- or eight-hours worth of duration.
In the demanding environment of data centres, ambient temperatures in hot aisles often range from 35-45°C. Here, the operational limitations of integral battery emergency luminaires become evident. The specified operating temperatures for many of these conventional emergency luminaires typically cap at 25-30°C, highlighting a substantial performance gap. Manufacturers may sometimes indicate higher operating temperatures, but it is crucial to distinguish between the case temperature of the emergency kit itself and the tested operating temperature within a luminaire.
The elevated ambient temperatures pose a significant challenge for the integral batteries within emergency luminaires. Ta, or ambient temperature, is a critical factor influencing the performance of emergency lighting systems. In the confined spaces of a luminaire, the Ta inside the fitting is affected by various heat sources, including the driver, emergency converter, charging batteries, and the LED board. As data centres experience rising temperatures, the Ta inside luminaires can escalate rapidly, surpassing the operational limits of integral battery systems.
Addressing temperature challenges
This rise in temperature within emergency luminaires can lead to premature failure, particularly in instances where manufacturers state higher operating temperatures that do not align with the real-world conditions of data centres. Early failures not only compromise the effectiveness of emergency lighting, but also result in frequent replacements, placing demands on time and budgets while introducing unwanted disruptions and traffic in high-security areas. Addressing the temperature challenges with a centralised emergency lighting system eliminates the reliance on integral batteries and ensures consistent operation, even in the extreme conditions prevalent in data centres.
When it comes to human life, fail-safe performance is essential. Which means safety lighting must work at all times while complying with the relevant standards.
The aim: to ensure long-term, fault-free operation with minimum maintenance.
A best practice design comprising LED lighting technology, an intelligent lighting control system and a central power system (CPS) to support a dedicated emergency lighting system will have a positive impact on energy usage. In addition, it will reduce associated manual maintenance costs whilst creating a safer, more flexible lighting solution that can be quickly and easily adapted to suit changing requirements.
Emergency central battery systems using dedicated emergency luminaires can not only reduce emergency lighting loads but the amount of emergency lighting circuits too. This leads to a more cost-effective initial installation and an easier system to maintain long-term. As a general rule of thumb, once more than 120 emergency luminaires are present on a project, the DC central battery system often pays for itself.
When it comes to best practice, we recommend designing your lighting strategy specific to the specialist areas; dependent on the cooling topology used within the space:
Hot aisles
Any data hall with a technical area operating temperature above 35°C should use a Ta 45 rated lighting system to illuminate the areas of operation efficiently.
Dedicated emergency luminaires should be located remotely in a suitably temperature-controlled area to avoid temperature-related battery degradation. These should be fed from a central battery system. By removing the batteries from the hot areas, maintenance and total cost of ownership is therefore improved.
For lighting controls, a strategy of absence/presence detection, such as DALI2 microwave sensors, can offer control in every aisle and should be installed at each end of the aisle, facing outwards from the middle to ensure coverage as necessary.
Cold aisles
For ease of installation and maintenance, consider using the same luminaire system. Both Microwave and PIR DALI 2 sensors should be considered with a manual override located at the local entrance of relevant aisles.
Circulation
We would recommend the same luminaire system in these areas for ease of installation and maintenance, again with a dedicated luminaire type and output to best facilitate the most efficient design to meet criteria.
Emergency lighting should also be based on the same principle as the aisles, including absence/presence DALI2 sensor control with a manual override located at each entrance for timed switch for lighting control of the area, with the addition of exit legends installed on a track system or an adjacent wall to be fed from the central battery system.
CRAH aisles
CRAH aisles are often designed to mimic cold (under 35°C) or hot aisle (over 35°C) lighting strategies.
MMR/Unboxing rooms
Beyond the physical infrastructure, proactive monitoring of emergency luminaires plays a crucial role in maintaining optimal performance and reducing maintenance burdens. Intelligent monitoring systems continuously assess the health and status of emergency luminaires, alerting operators to any potential issues before they escalate into full failures. This proactive approach minimises downtime and maximises the lifecycle of emergency lighting systems, reducing the workload for site operators and facilities teams.
Safety first
The final part of a lighting strategy concerns life safety. Data centres present a unique set of challenges in this area, so it is advisable to have a dedicated, addressable emergency lighting system that allows for full automation of testing – excluding an annual duration test.
Cutting edge technology can automatically report the status of an emergency lighting system. As the batteries have a 10-year life expectancy, the potential for human error is reduced and the costs associated with routine maintenance are lowered. Utilising a remote CPS/eBox-based system also facilitates the support of higher ambient temperatures, as there is no need for a local battery supply to the emergency lighting, while a self-contained system can be easily extended with additional luminaires as required. When considering a system, always remember that robustness is required, aesthetically pleasing is optional.
By implementing centralised emergency lighting supply systems and proactive monitoring, data centres can achieve enhanced reliability, safety, and operational efficiency. This combination ensures that emergency lighting systems remain operational even in challenging environments, providing a critical safety net for personnel and infrastructure.
