Feeling the heat? Prepare your data centre for extreme weather
Wed 19 Sep 2018 | Time of Talk 3
Tom Ryan, UK Head of Service at Stulz, explains why upgrading your systems can help defend against damage caused by soaring temperatures
With the recent British heatwave abating for the year, the data centre industry can breathe a sigh of relief – but for how long? The global trend seems to suggest that it is to become progressively hotter in the coming years, and perhaps now is the time to consider how this could impact our data centres and critical equipment.
Summer is often accompanied by “Head Pressure faults”, not just in the data centre industry, and a substantial increase in the number of emergency call outs, both in hours and out of hours. Typically, system “High Pressure faults” are brought on by higher than expected ambient temperatures.
The culprit in most cases can be a poorly cleaned condenser coil, and often accompanied by coil fin oxidisation. The majority of heat exchange is from the fins, and not the tubes, so even small amounts of oxidisation can have a significant impact on performance.
But what is higher than expected ambient temperatures? This summer brought us some ‘unexpected’ temperatures, and on one day in London 35°C, and while welcome for the most part, it can spell disaster for air conditioning and refrigeration equipment that have condenser issues.
This is where the following factors come into play; apart from the cleanliness and mechanical integrity. The design ambient temperature for the condenser, and also the amount of extra capacity in the condenser. The design ambient temperature is a moveable feast, and often varies from company to company and consultants alike. For London, in the past, some firms and consultants have been ok with selecting 32 to 35°C as the maximum ambient temperature (maximum air on to the coil temperature, in the shade).
For the most part, we now select the maximum ambient temperature as 35°C, and on special request, often select 38°C, so older systems can struggle on very high temperature days, especially if the coil has been either undersized or tightly sized for the Total Heat of Rejection (THR) or is suffering from cleanliness and mechanical integrity issues. A well sized, or marginally oversized (say 10%) will help with those higher than planned for ambient temperatures.
Upgrading to a newer model of condenser can reduce both power consumption and annual running costs
Some will argue, that it is better to size correctly, however, when it comes to your condenser, its better looking at it than for looking for it, slight oversizing can also contribute to lower system running costs, if your system is properly optimised.
With temperatures expected to soar, the head pressure will increase drastically with each degree causing the system’s performance to deteriorate. Power consumption will increase significantly too, and greater strain is placed on the compressor which may contribute to premature compressor failure.
With this in mind, particularly as we head for an even hotter future, cleaning condensers, properly, just before the summer is a ‘must’. Many operators are turning to new technologies to upgrade their existing equipment and implement up-to-date condenser system technology to ensure a lower running cost, avoid downtime and reduce call out for nuisance head pressure faults, as well as bringing all equipment in line with current standards.
Whether for commercial or environmental reasons, upgrading to a newer model of condenser can reduce both power consumption and annual running costs – equating to power savings between 10 – 25% per fan annually. And also save significant power at the compressor. The latest fan technology uses electronically commutated (EC) fans which can control their own speed based on head pressure, which is read by a pressure transducer.
Beyond high head pressure causing system Head Pressure faults, it is thankfully very rare to see the hot weather disturbing any other aspects in the data centre. While the heat gain in a building is substantially increased and the original heat load design may be exceeded, it is only in extreme circumstances that this provokes a failure. Higher humidity can often accompany an increase in temperature, typically in August and September bringing different challenges, but these are easily overcome.
