best practices in hvac design/retrofit little server room – big $ avings justin lewis, p.e., leed...
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Best Practices in HVAC Design/Retrofit
Little Server Room – BIG $AVINGS
Justin Lewis, P.E., LEED AP, DCEPSr Energy Project ManagerC:530.400.6042 | O:530.754.4870 | [email protected]
What’s the problem here?
Hot Exhaust HereSeismic Brace Here
Not Enough room for a ventilation tile
New computers placed with inlets facing exhaust.Plate leaned against rack to direct cold air into computer inlets
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What’s a Data Center?
Enterprise Data Center – Focus on cost and uptimeBackground 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.
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Servers put out a ton of heatand need cooling or they break
My experience has been server racks are more typically in the 6-12 kW rangeThat is still 1.7 to 3.4 tons of cooling per rack.
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They also compute
How to Optimize the Data Center’s HVAC
• Optimize the heat equation• Reduce fan speed• Increase delta T
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Old Conditions
• Setpoints: 65°F, 50%RH ±5%
• Coils have low Delta T
• Hot and cold spots
• Unbalanced ventilation
Optimization Opportunities
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New 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%
Q = 1.08 * (Air Flow) * (Temp)[BTU/hr] [CFM] [oF]
Divide by 12000 to get [Tons]Divide by 3412 to get [kW]
1 kW = 1.08 * (150) * (20°)For Example:
Heat Equation for Air
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Goal: Raise return temps to at least 80.6 °F
Q = 1.08 * (Air Flow) * (Temp)For every 10% reduction in fan
speed
An increases temp rise by 10%
Fan Affinity Law: Power% = (Speed%)^3 (…really more like 2.5)Flow%=Speed%
Slow Fans Down Reduce Air Mixing
Heat remains constant
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equal$Decrea$e power of 25%
Implement Hot/Cold Aisle
• Orient Equipment to have common intake and exhaust directions to reduce hot air mixing with cold air.
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Return Plenum
Reduce By-Pass Air
• Don’t over blow cold aisles
• Block penetrations outside of cold aisles • (Power/Data penetrations)
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Manage Recirculation
• Use Blanking panels
• Manage air to keep top servers below ~80.6 °F 12
< 80.6°F
Servers aren’t that sensitiveYMMV (your may vary)
7 months of no mechanical cooling, no air filtering, no humidity control-date: 2008 13
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
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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.
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What’s the problem here?
Hot Exhaust HereSeismic Brace Here
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.
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New computers placed with inlets facing exhaust.Plate leaned against rack to direct cold air into computer inlets
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
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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
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