When optimizing cooling in a data center, we deploy a set of customized energy conservation measures (ECMs) to achieve the highest level of cooling efficiency and overall energy savings. This week, we’re taking a closer look at the floating head retrofit, one of our ECMs that drastically reduces energy consumption, extends the service life of cooling units and reduces carbon footprint.  

DATA CENTER ENERGY CONSUMPTION

In previous blog posts, we’ve discussed how cooling can make up a large part, if not the majority, of the data center energy expense.  If a high proportion of energy cost is being driven by cooling then changes need to be made in the data center.  Ensuring there is adequate and reliable cooling to meet the needs of the IT equipment is critical, however, that does not mean that cooling energy costs should run out of control.  

Cooling, which is essential to the continued operation of IT equipment, is seldom reviewed and is not given the attention it deserves.

Cooling energy costs, cooling capacity and efficiency are generally unknown. Other than regular maintenance checks to make sure the cooling units are operating; nobody pays attention to how much energy is being consumed. The main cooling objective is to avoid alarms and downtime regardless of the cost to run the machines.  

IMPLEMENTING THE ECM

In our recent webinar, “5 Energy Conservation Measures to Optimize Your Data Center Cooling ” we reviewed a case study of a customer site where we deployed 5 energy conservation measures resulting in a reduction of 38% in cooling energy use, saving the client tens of thousands of dollars each year. In addition, the efficiency of the cooling units was improved resulting in an increase of 50% cooling capacity – meaning more IT equipment could be added with no new cooling needed. This was a prime example of how multiple ECMs can be applied seamlessly in a site, demonstrating SCTi’s holistic approach of tailoring a solution to meet the specific needs of the whole data center.  

One of the key ECMs deployed was the retrofit of 4 existing legacy CRAC units with the floating head technology.  The floating head retrofit can be applied to older CRAC units, typically 5 years or older, to make them more energy–efficient. This is achieved through a retrofit to the cooling unit that enables it to adapt to ambient temperatures and regulate condensing temperatures accordingly.  

Energy consumption can be reduced by up to 45%, and the life expectancy of the unit will be extended as there is less wear on the main components.  

The floating head retrofit won’t make the legacy units as energy–efficient as the newest economizer models but, it’s an enticing option when comparing the cost of this short payback retrofit, with the capital cost and disruption in your data center that would be caused by replacing a cooling unit with an economizer system. 

FLOATING HEAD BACKGROUND

 Prior to 2015 most DX based CRAC units were equipped with mechanical thermostatic expansion valves.  These valves operate in a state that maintains a fixed condensing pressure corresponding to 40°C (105 °F) or what they refer to as a ‘design day condition’ at all times and do not have the ability to vary with ambient temperatures. This means the compressor is running at high horsepower, even when the ambient temperature is well below design conditions for the majority of the year.  

The introduction of electronic expansion valves, which are used in most new CRAC units, enables the unit head pressure to fluctuate or float, varying the condensing pressure based on ambient temperature.  Extensive research and development were conducted to determine how to replace the mechanical expansion valves with electronic expansion valves and what additional changes in controls and electronics were required.  To date, over 225 CRAC units have been retrofitted with the floating head technology, making them more responsive to ambient temperature conditions resulting in significant energy reductions.  

An added benefit of the retrofit is if the CRAC units are currently using R22 refrigerant, which is now being phased out, it can be replaced with R407C refrigerant, extending the usable life of the unit – deferring capital cost and disruption of installing new units. 

Our brochure outlines the list of benefits, which include:  

• Lower energy consumption and costs –resulting in a better data center PUE 
• Extended compressor and system life 
• Lower carbon footprint (refrigerant reduction and lower energy consumption) 
• Reduced maintenance due to reduced wear
•  Extended usable life of unit with replacement refrigerant 

HOW IS ENERGY CONSUMPTION REDUCED?

 After the CRAC unit is retrofitted the condensing head pressure will now fluctuate and drop with the falling ambient temperature. This results in a drop in compressor wattage while compressor capacity (BTU/hr) increases.  Because of the increased capacity, compressor runtime hours are reduced, and compressor lifecycle and reliability are improved.  

 Temperatures below 10°C (50°F) ambient typically represents the temperature at which the maximum energy savings from low condensing operation can be achieved.  However, since traditional fixed head pressure systems run at a condensing temperature of 40°C (105 °F), the savings potential for low condensing systems exists whenever the ambient temperature is 23°C (73°F) or lower.