1. Best Practices in HVAC Design/Retrofit
Little Server Room – BIG $AVINGS
Introduce yourself: My name is Justin Lewis…
Today I’m going to present to you what I feel are best practices in the data center, and how I implemented them in one of our server rooms to save a lot.
I’m going to go quick because I only have a short time, and hopefully I can have some time for questions at the end.
Justin Lewis, P.E., LEED AP, DCEP
Sr Energy Project Manager
C:  | O:

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 11 enterprise 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.
Data centers could invoke different images for different people.
Your Background

4. This is a “Server Room”
Grad Student built “Super Computing Center” – Focus on “Get it working.”
Sometimes Data Centers can be ad-hoc group of computers wired together to accomplish some task using whatever available space. Usually the issue of cooling is an afterthought, let alone thinking about how to cool the computers efficiently

5. Servers put out a ton of heat and 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.
But Servers NEED cooling… A LOT of cooling. This is an outdated slide, but it shows a configuration of multiple blade chassis in a single rack to build a possible load of 32 kW in a single 24”x48” space on a datacenter floor.

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

7. Optimization Opportunities
Old Conditions
New Conditions
Setpoints: 65°F, 50%RH ±5%
Coils have low Delta T
Hot and cold spots
Unbalanced ventilation
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%

8. Q = 1.08 * (Air Flow) * (Temp)
Heat Equation for Air
Q = 1.08 * (Air Flow) * (Temp)
[BTU/hr]
[CFM]
[oF]
Divide by 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
Slow Fans Down
Reduce Air Mixing
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
This is how you should go about increasing your return temp.
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 sensitive YMMV (your may vary)
7 months of no mechanical cooling, no air filtering, no humidity control
-date: 2008

14. Servers aren’t that sensitive YMMV
-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. 3kW = 1.08 * (476) * (20°) 1x perf = 3kw 1x Grate =
Why a pressure sensor?
3kW = 1.08 * (476) * (20°)
[CFM]
[oF]
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
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.
Until then… I suggest you implement these easy improvements

26. Questions?