Energy Conservation Measure: The Floating Head Retrofit
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.
What does the retrofit entail?
The floating head retrofit is a component-based solution that doesn’t interfere with the legacy system’s controls, programs or safety measures.
The main components replaced include:
- Electronic expansion (EX)valve — Legacy mechanical expansion valves are replaced by electronic expansion valves. This allows the head to float safely through precise control of superheat and prevents liquid refrigerant flood-back to the compressor. EX valves enable low condensing systems to digest flash gas as the head pressure floats with falling ambient temperatures.
- Electronic controller— Installed on the CRAC unit. The controller communicates only with the EX valve and not the unit itself.
- Variable speed drive fan—At the condenser, fan cycling is reconfigured with a variable speed drive fan and other fans (as well as a pressure transducer and temperature sensors) to control to 26.6°C (80 °F) condensing.
As the ambient temperature falls, the head pressure will float down until it reaches the 26.6°C (80°F) minimum saturate condensing temperature. From a retrofit point of view, any time a system is permitted to operate below its traditional 40°C (105°F) saturated condensing temperature set point, energy savings will result.
In Canada and parts of the northern U.S., the ambient temperature is 23°C (73°F) or below for 75% of the year, meaning the floating head could be achieving energy reductions by operating at a lower condensing pressure for a large portion of the year.
Floating Head Retrofit Economics
The energy savings that can be achieved with the floating head retrofit can be as high as 45%. The final energy reduction value is determined by several factors including the cooling capacity of the unit and level of cooling operation. For instance, if the CRAC unit only operates at 25% of its cooling capacity, energy savings will not be as high compared to a cooling unit operating at 100% cooling capacity.
Here’s an example of energy savings that can be achieved in the short payback period of typically, 1.5 years:
- Cooling Unit energy consumption: 30 kW x 8,760 hrs = 262,800 kWh
- Cooling Unit annual energy costs: $39,420
- Floating Head retrofit average energy savings: 35%
- Average Cooling Unit energy savings: 91,980 kWh
- Average Cooling Unit annual energy cost savings: $13,797
Frequently Asked Questions
What models of CRAC units can be retrofitted with Floating Head?
Any DX (direct expansion) computer room air conditioning unit (CRAC) can be retrofitted. Some of the more common makes and models include:
Liebert DS042, DS053, DS070, DS077, DS105
Liebert DH199A, DH245A, DH290A, DH380A
Do I need specially trained HVAC technicians to service the retrofitted units?
The short answer is no. No significant changes are made to the operational controls of the retrofitted units. A new micro–processor based controller is added, which will assist your current technicians in diagnosing problems. As well, training is provided for technicians so they are aware of all changes made on the cooling unit and condenser.
How long does it take to retrofit a CRAC unit?
The entire process will take between 4-5 days per unit. During this time, the unit will not be operational. As part of the retrofit program, SCTi will work with you to determine if temporary cooling is required.
How will my data center be affected during the retrofit work period?
Generally, one CRAC unit is retrofitted at a time, and the unit will be out of commission for the retrofit period. Prior to initiating any work, the cooling capacity of the data center is reviewed to determine if there is adequate cooling with one unit out of commission. In cases where temporary cooling is required, we will work with you to ensure your data center can operate normally during the retrofit period.
Is the retrofit work warranted?
Yes, a one-year parts and labor warranty is included as part of the retrofit agreement. Do note, the components added to the unit as part of the retrofit are standard components that are used in today’s modern cooling units.
Will the retrofit work void my CRAC warranty?
The CRAC units to be retrofitted are generally 5 years old or older. Most new CRAC units have a one–year warranty period. So, unless you are paying for an extended warranty, the original CRAC unit is outside the warranty period.
Are incentives available for this retrofit?
Yes! Incentives are available for this retrofit, provided an application is submitted and preapproved before the end of 2020. Energy incentives can cover up to 50% of the project cost. In many cases, we (SCTi) can act as your application representative and help to expedite the application submission. Post-2020 it is not clear if energy incentives will be available.
How do I get started with this retrofit?
Contact SCTi today to determine if you are eligible for this retrofit. Call us at 1-866-831-4775 or send us an email: firstname.lastname@example.org