Cooling: Best Practices and Economizers

1. Cooling:Best Practices and Economizers Randall Poet A C Systems

2. Ideal Situation • Server Load = CRAC Capacity • Server Airflow = CRAC Airflow

3. Agenda • The Conventional Approach – Base Case • Raise the Return / Supply Air Temp • Contain the Cold Aisle • Add Intelligent Control • The Set-up • Summary

4. Start with Best Practices • Hot aisle / Cold aisle • Blanking panels in racks • Blanking panels between racks • Blanking Panels between racks and floor • Cable cut-outs covered • Relatively clean underfloor area • Proper location of CRAC units • Vapor barrier around space

5. Base Case – 75F Return Air Control • 4 CRACs (N+1) • 54 kW each • 21F delta T design • 20 Racks • 8 kW each • 35F delta T

6. Base Case – 75F Return Air Control • 3 CRACs Running • 54 kW each • 21F delta T design • 20 Racks • 8 kW each • 35F delta T

7. Base Case Operating Scenario 75F • Unit Airflow – 24,000 CFM • Rack Airflow – 14,600 CFM • Bypass Airflow – 9,400 CFM 89F 54F CFM 100% 54F

8. The Airflow Pattern

9. Typical Air Cooled DXEnergy Consumption Condenser Fan Motors Evap Fan Motor Compressors

10. Typical Energy Consumption • Compressors run at full capacity • Fans run at full speed Condenser Fan Motors Evap Fan Motor Compressors

11. Agenda • The Conventional Approach – Base Case • Raise the Return / Supply Air Temp • Contain the Cold Aisle • Add Intelligent Control • The Set-up • Summary

12. New Operating Scenario 85F • Unit Airflow – 24,000 CFM • Rack Airflow – 14,600 CFM • Bypass Airflow – 9,400 CFM 99F 64F CFM 100% 64F

13. Increased Capacity at Full Airflow

14. Increased Capacity at Full Airflow

15. Operating Systems Comparison • Compressors run at reduced capacity or unloaded • Fan motors run at full speed

16. Sanity Check –100 dF OAT, 6400’ ASL

17. Sanity Check

18. Agenda • The Conventional Approach – Base Case • Raise the Return / Supply Air Temp • Contain the Cold Aisle • Add Intelligent Control • The Set-up • Summary

19. Contain the Cold Aisle 85F • Unit Airflow – 21,600 CFM • Rack Airflow – 15,800 CFM • Bypass Airflow – 5,800 CFM 94F 62F CFM 90% 62F

20. Operating Systems Comparison • At the higher RA temperature, the contained system has very similar operating costs as the non-contained • Fan motors run at full speed but at a reduced CFM and HP due to the higher static pressure • Compressors run at reduced capacity or unloaded but slightly higher than the non-contained

21. Why use Containment?? System operating costs are similar Containment partitions and doors cost $$

22. Hot Spots in Racks due toWrap-Around

23. No Leakage into the Cold AIsle

24. Higher Temperatures without Containment

25. Containment of Cold Aisle

26. Issues to Consider • Fire Detection / Suppression • Wide variation between municipalities • If local Fire Inspector involved early, typically goes well • Curtains usually eliminate this issue • Installation • Will be site specificy • Irregular row length/height, gaps, etc. • Site conditions critical, one size does NOT fit all

27. Issues To Consider • ADA • CAC space is for Service Personnel (Section 4.1.1) • What about cooling for components in rest of room? • Best solution today may be ducted return from hot aisle • Perf tiles near other equipment requiring cooling (eg. UPS) • 85⁰ Room temperature?

28. HAC vs CAC • Main Purpose of Cooling in Data Center? • Cool the equipment • Data Centers commonly on raised floor • CAC allows current investment to be used • HAC typically requires in row cooling • So, refrigerant or chilled water and condensate intermingled with IT equipment and racks • Which aisle does majority of work take place in? • CAC hot aisle likely in 85⁰F range • Can use perf tiles in other space • HAC hot aisle likely in 100⁰F range

29. Agenda • The Conventional Approach – Base Case • Raise the Return / Supply Air Temp • Contain the Cold Aisle • Add Intelligent Control • The Set-up • Summary

30. Closer to Matching the Load to the Cooling 92F • Unit Airflow – 16,800 CFM • Rack Airflow – 14,600 CFM • Bypass Airflow – 2,200 CFM 97F • Variable Capacity Compressors • Variable Speed Fans • Intelligent Control 62F CFM 70% 62F

31. Operating Systems Comparison • The airflows and capacities/loads are more closely matched • Fan motors run at reduced speed, CFM and HP based on the demand in the contained area • Compressors run at reduced capacity or unloaded but slightly higher than the non-contained

32. Agenda • The Conventional Approach – Base Case • Raise the Return / Supply Air Temp • Contain the Cold Aisle • Add Intelligent Control (Creating SmartAisle) • The Set-up • Summary

33. Sensor Location • Server centric solution, meaning that it focuses on the inlet temperature to the servers • Self adapting to environment changes due to server utilization, equipment location changes and outside variables • Can adapt to situations with no containment, end containment, and full containment

34. Rack Sensors • Rack Sensors without doors can be mounted on the frame of the racks. • Temperature differences were within .5°F

35. Cold Aisle Sensors • Sensors can also be mounted at the top of cold aisles when rack mounting is unavailable

36. Supply Compensation • Compensation is the magical link between controlling sensors • The controller evaluates the Rack Sensors and Fan Speed • If the fan is operating at 100% and remains above the cold aisle set point • Then the supply temperature set point will slowly lower to drive the correct cold aisle temperature Fan Speed 100% Lower Supply

37. Controller and CRAC Operation Unit ON CW Valve Open % Fan Speed % 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Increase in kW Supply Temperature The increase in fan speed will result in a warmer supply air temperature which is detected by the supply air sensor that will increase cooling to maintain supply air setpoint Cold Aisle Containment iCOM will automatically adjust to changes that result in a temperature increase or decrease Fan Speed Increases So that cold aisle temperature is maintained at customer temperature Setpoint IT Load Increases Rack Temperature Sensor detects inlet rack temperature

38. Controller and CRAC Operation • Advanced freeze protection routine • Allow all units to reduce fan speed to 60% • Fan speed and compressor capacity (or CW valve) managed for best unit efficiency and performance • Multiple remote sensors • Controller can use averaged and maximum/minimum values to individually control multiple CRAC systems • CRAC systems work as a team • All remote sensors used • Increase capacity of other applicable adjacent units if one is at maximum and unable to handle the load • Automatically adjust for units not in service

39. Agenda • The Conventional Approach – Base Case • Raise the Return / Supply Air Temp • Contain the Cold Aisle • Add Intelligent Control • The Set-up • Summary

40. Issues to Consider • Fire Detection / Suppression • Wide variation between municipalities • If local Fire Inspector involved early, typically goes well • Curtain eliminates this issue • Installation • Will be a local responsibility • You need to develop relationship with local Cable Contractor or similar company for installation • Irregular row length/height • Site Survey critical • Most expensive component

41. Issues To Consider • ADA • Consultant raised issue at BAIS project • Successfully defended CAC space is for Service Personnel (Section 4.1.1) • What about cooling for components in rest of room? • Best solution today is ducted return from hot aisle • perf tile by IT component • 85⁰ Room temperature

42. Issues To Consider • Purpose of Cooling in Data Center? • Control equipment inlet temps • Data Centers often on raised floor • CAC allows current investment to be used • Which aisle does majority of work take place in? • CAC hot aisle likely in 85⁰F range • Could use perf tile in other space • HAC hot aisle likely in 100⁰F range

43. Summary • Best practices are a must if improved efficiency is a goal • Running warmer temperatures in the space will improve the cooling system operating efficiency • Containment improves the availability of the servers by eliminating hot spots • Intelligently controlling fan speed and compressor capacity “balances” the system to operate at it’s most efficient level

44. Summary • Efficiency is the story, not containment • Containment can be done in several ways, none necessarily fit all situations • Each critical space is unique and merits individual planning • Dynamic Control is (currently )the final element

45. …Shifting on to Economizers and Equipment Considerations…

46. 90.1 Economizer Map

47. Definitions of Cooling Efficiency • EER (Energy Efficiency Ratio) • Total Cooling Capacity (BTUH)/Total power input (watts) • Full-load value on 95F design day • Commercial return air conditions of 80F/50% • SCOP (Sensible Coefficient of Performance) • Sensible Cooling Capacity (kW)/Total power input (kW) • Full-load value on 95F design day • Data Center return air conditions of 75F/45%

48. ASCOP – Efficiency Metric Annualized Sensible Coefficient of Performance(location specific) • Bin efficiency x bin hours/total annual hours • Factors hours at each efficiency operating point • Factors part-load efficiency • Factors economizer hours

49. Single System –Outside Air Economizer

50. Large or Multiple Systems –Outside Air Economizer