Recently, while visiting a customer’s site, I was asked "when do I replace my computer room air conditioner?"  It was a straight forward question, but hard to answer, because in my experience the answer is not so much when, but why. 
 

There are many variables to consider when contemplating replacing an HVAC system. 
 

1. First a general understanding of how the system works: Without getting into great detail on the principals of thermodynamics or the refrigeration cycle, it helps to think of an air conditioner as a sponge. An air conditioner that operates in a controlled environment, in this case raised floor, absorbs heat through the refrigeration cycle and has to dissipate, or reject, the heat outside the building. This is accomplished using an air cooled condenser or a drycooler, if the unit is Glycol cooled.   Similar to the way a radiator operates, fans on the unit are used to move air over the heat transfer coil, which is made up of cooper tubing and encased with aluminum fins, making it a very efficient way to reject heat. 

2. Unfortunately, these condensers and drycoolers reside in harsh environments, frequently on the facilities roof.   As the unit ages the aluminum fins oxidize and the system losses efficiency. The oxidation is caused by pollutants in the atmosphere, yearly coil cleaning, and possibly acid rain.  In some cases, they become so inefficient that during high summer temperatures service providers scramble to cool the units and find themselves resorting to putting a water sprinkler under the equipment to help reject heat and prevent down time. As you would expect, this is not considered a standard maintenance or troubleshooting procedure – but a fast reaction to the situation at hand.
   
   
3. What other considerations should be taken into account when considering replacing your computer room air conditioner?  Reliability, parts availability, and cost of maintenance:  Some manufacturers phase out control boards after 15 years of production, so if the microprocessor were to fail - it could render the cooling system useless.   The newer microprocessors used in air conditioners are far more advanced than the microprocessors used in the late 1980's. They can utilize proportional control or an optional fuzzy logic control.  In the data center, this type of microprocessor results in tighter control of temperature and humidity levels, overall improving energy efficiency. The new HVAC units also have advanced alarm, system monitoring functions, and energy efficient humidity controls (ultrasonic) that deliver real user benefits.
   
   
4. The final issue is maintenance cost. Many service providers will only provide time and material contracts on equipment that has exceeded its life expectancy, approximately 12 years depending on cooling load and maintenance history.  In this case the equipment owner assumes the risk of frequent failures and elevated repair cost.  Does cost out weigh reliability?  It is a tough decision to make in a struggling economy, and many facility managers and IT professionals are forced to make it daily. 

 
The bottom line is when looking at replacing an air conditioning system there are many items to consider, and hours of operation is more important to look at than years of possession.  If you would like additional information about HVAC systems, or their life expectancy, or you would like someone to evaluate your system feel free to give me a call, Alex Connolly (781)302-2711 or aconnolly@eecnet.com.