Best Practices in HVAC Design/Retrofit

1. Best Practices in HVAC Design/Retrofit Little Server Room – BIG$AVINGS Justin Lewis, P.E., LEED AP, DCEP Sr Energy Project Manager C:530.400.6042 | O:530.754.4870 | jlewis@ucdavis.edu

2. What’s the problem here? Hot Exhaust Here Seismic Brace Here New computers placed with inlets facing exhaust. Plate leaned against rack to direct cold air into computer inlets Not Enough room for a ventilation tile

3. What’s a Data Center? Enterprise Data Center – Focus on cost and uptime Background on the Speaker: I helped save 11enterprise class data centers and colocations around the country a total of 19.5 million kWh while working for SynapSense as a Sr. Field Engineer. Today I’ll share those techniques.

4. This is a “Server Room” Grad Student built “Super Computing Center” – Focus on “Get it working.”

5. Servers put out a ton of heatand need cooling or they break They also compute My experience has been server racks are more typically in the 6-12 kW range That is still 1.7 to 3.4 tons of cooling per rack.

6. How to Optimize the Data Center’s HVAC Optimize the heat equation Reduce fan speed Increase delta T

7. Optimization Opportunities New Conditions Old Conditions • Setpoints: 80.6°F, RH 10%-80% • Coils have high Delta T • Hot aisles Hot, Cold aisles Cold • Balanced ventilation • 2011 ASHRAE recommends inlet conditions to servers be: • between 64.4 and 80.6 °F, and dew point between 41.9 and 59 °F • Typical Server Specs (Dell PowerVault MD3000) • between 50 and 95 °F, and RH between 20% and 80% Setpoints: 65°F, 50%RH ±5% Coils have low Delta T Hot and cold spots Unbalanced ventilation

8. Heat Equation for Air Q = 1.08 * (Air Flow) * (Temp) [BTU/hr] [CFM] [oF] Divide by 12000 to get [Tons] Divide by 3412 to get [kW] For Example: 1 kW = 1.08 * (150) * (20°)

9. Goal: Raise return temps to at least 80.6 °F Reduce Air Mixing Slow Fans Down Q = 1.08 * (Air Flow) * (Temp) Heat remains constant For every 10% reduction in fan speed An increases temp rise by 10% equal$ Decrea$e power of 25% Fan Affinity Law: Power% = (Speed%)^3 (…really more like 2.5) Flow%=Speed%

10. Implement Hot/Cold Aisle Return Plenum Orient Equipment to have common intake and exhaust directions to reduce hot air mixing with cold air.

11. Reduce By-Pass Air • Don’t over blow cold aisles • Block penetrations outside of cold aisles • (Power/Data penetrations)

12. Manage Recirculation < 80.6°F Use Blanking panels Manage air to keep top servers below ~80.6 °F

13. Servers aren’t that sensitiveYMMV (your may vary) 7 months of no mechanical cooling, no air filtering, no humidity control -date: 2008

14. Servers aren’t that sensitiveYMMV -date: 2008

15. What UCD did in their Server Room • Area: 125,810 sqft • Load: 31.3 tons cooling≈ 110 kw plug load • Approximately 37 populated racks. 46 capacity • improved ventilation (delta t of 12 to 20°f) • by removing the over provisioned tiles • by balancing the air to top server intake temperature to below 80 °f • plugging holes • installing controls in the returns • installing pressure controls in the floor • control fan speed to maintain hottest return temp

16. Why a pressure sensor? 3kW = 1.08 * (476) * (20°) [oF] [CFM] 1x perf = 3kw 1x Grate =

17. Results Graphs

18. Old “Economizer” Mode

19. New Economizer Mode

20. Delta T Rose

21. Fan Power Reduced 78%

22. Challenges: Communication Culture Change In a culture of only answering maintenance calls, it’s hard to sell a higher touch continual optimization process. Set it and forget it is the norm. Communication Silos: IT services has not had to check with HVAC in the past.

23. What’s the problem here? Hot Exhaust Here Seismic Brace Here New computers placed with inlets facing exhaust. Plate leaned against rack to direct cold air into computer inlets Not Enough room for a ventilation tile Better Solution: Better hot/cold aisle planning. Disconnect seismic brace, move rack, or just move some cardboard boxes on the adjacent rack.

24. What we did… in summary Improved air flow by blocking leaks and orienting servers Hot/Cold Aisle Balanced air to servers so tops of servers were below 80 °F Placed return grills and temperature sensors in hot aisles Control supply temp to a constant temperature (57 °F) Control supply fan speed to maintain hottest return temp is <82 °F Control return fan to maintain room pressure only

25. Looking Ahead Until then… I suggest you implement these easy improvements Virtualization – Eliminate 80% of your plug load. Fanless cooling – Oil bath, Chilled plate. Outsourced Computing – Cloud providers may offer computing power and storage cheaper than the cost to maintain onsite servers.

26. Questions?