Applying Precision Air Conditioning Systems

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Applying Precision Air Conditioning Systems

• Canatal International Inc.

2
Introduction

• Application of Precision Air Conditioning
• Data Centers
• Switching Stations
• Co-Location Facilities

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Topics of Discussion

• Servers / Switch Gear
• Temperature Humidity Control
• Air Distribution
• Redundancy
• Alternating Cold Aisle, Hot Aisle
• Perforated Tile Capacity
• Design Planning Stage
• Maintenance

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Servers / Switch Gear

• Smaller, More Powerful
• Driven by semi-conductor capacity
• More transistors on a chip
• More power consumption per chip
• More heat generation

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Servers / Switch Gear

• Published Power Rating may expect future
  upgrades, higher energy consumption and greater
  heat rejection
• Initial power consumption and heat generation can
  be lower

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New ASHRAE Document

• Thermal Guidelines for Data Processing
  Environments
• Equipment Environment Specifications
• Facility Temperature Humidity Measurement
• Equipment Facility Layout
• Equipment Manufacturers Heat Airflow Reporting

Available _at_www.ashrae.org, Item Number 90431, or
D90431
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Thermal Guidelines for Data Processing
Environments

• Equipment Environment Specifications

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Thermal Guidelines for Data Processing
Environments

• Equipment Environment Specifications

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ASHRAE Class 1 Operating Conditions
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ASHRAE Class 1 Operating Conditions
Increase Equipment Failures
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ASHRAE Class 1 Operating Conditions
Increase HVAC Energy Use
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Thermal Guidelines for Data Processing
Environments

• Facility Temperature Humidity Measurement

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Thermal Guidelines for Data Processing
Environments

• Equipment Facility Layout
• Recommended Airflow Protocol for Computer
  Equipment

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Thermal Guidelines for Data Processing
Environments

• Equipment Facility Layout
• Recommended Airflow Protocol for Computer
  Equipment

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Thermal Guidelines for Data Processing
Environments

• Equipment Facility Layout
• Recommended Airflow Protocol for Computer
  Equipment

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Thermal Guidelines for Data Processing
Environments

• Equipment Manufacturers Heat Airflow Reporting

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Server / Switch Gear
1U (1.70 H) Server
Back View
Front View
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Server / Switch Gear
2U (3.50 H) Server
Back View
Front View
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Server / Switch Gear
4U (6.80 H) Server
Front View
Back View
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Server / Switch Gear
5U Server Tower Configuration
Front View
Back View
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Server / Switch Gear
Front View
Back View
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Heat Density Trends
Source Uptime Institute
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What is wrong with this picture?
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What is wrong with this picture?
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2
1a, 1b Cold aisles. 1a has less airflow then 1b - WHY?
2 Hot aisles
3 Top of hot aisle (from right to left warm to hot)
4 Insufficient cold air and recirculation from hot aisle to cold aisle
5 Mixed return air path
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• External re-circulation
• Top 1/3 portion likely to have higher failure
  rate

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• Internal re-circulation
• Add blanking panels to eliminate the problem

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Positioning of PAC units

• Parallel or Perpendicular to aisles

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Temperature Control

• Challenges
• Hot Spots / Hot Zones / Hot Room
• Uneven heat load on the floor space
• Fluctuating heat loads
• Initial low loads

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Temperature Control

• Servers/Switches generate sensible heat
• Utilize Precision Air Conditioning Systems with
  high sensible heat ratios
• Unwanted dehumidification is a waste of energy
  and money

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Humidity Control

• Independently operated units will fight-
  simultaneously humidify and dehumidify
• Wasting energy and money
• Units should work together as a Team

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Air Distribution

• Raised Floor System
• Generally more flexible
• Easy to move perforated tiles
• Overhead System
• Ducted or Plenum
• Make the last length of duct flexible to enable
  movement of discharge grilles

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Air Distribution

• Deliver Cool Air to the Heat Source
• Eliminate Short Circuiting
• Anytime air returns to the PAC without passing
  through heat generating servers, routers,
  switches etc.

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Air Distribution

• Short Circuiting - Common Causes
• Obstructions to airflow
• Air Leakage
• Location of discharge grilles and perforated tiles

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Air Distribution Obstructions

• Raised Floor System
• Electric cable trays, especially with shallow
  floor heights
• Water damp

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Air Distribution Obstructions

• Practice Recommendations for Position Equipment
  Racks Cabinets
• Power Distribution Unit (PDU) cables should run
  under the Cold Aisles
• Cable trays for telecom cablings should locate
  under the Hot Aisles
• Cabinet should be aligned with one edge along the
  edge of the cold aisle floor tile
• Floor tile cuts should be no larger then
  necessary to minimize air pressure loss

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Air Distribution Obstructions

• Practice Recommendations for Position Equipment
  Racks Cabinets
• Power Distribution Unit (PDU) cables should run
  under the Cold Aisles
• Cable trays for telecom cablings should locate
  under the Hot Aisles

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Air Distribution Obstructions

• Practice Recommendations for Position Equipment
  Racks Cabinets
• Power Distribution Unit (PDU) cables should run
  under the Cold Aisles
• Cable trays for telecom cablings should locate
  under the Hot Aisles

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Air Distribution Obstructions

• Practice Recommendations for Position Equipment
  Racks Cabinets
• Power Distribution Unit (PDU) cables should run
  under the Cold Aisles
• Cable trays for telecom cablings should locate
  under the Hot Aisles

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Air Distribution Obstructions

• Practice Recommendations for Position Equipment
  Racks Cabinets
• Cabinet should be aligned with one edge along the
  edge of the cold aisle floor tile

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Air Distribution Obstructions
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Air Distribution Oversized Openings

• Practice Recommendations for Position Equipment
  Racks Cabinets
• Floor tile cuts should be no larger then
  necessary to minimize air pressure loss

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Air Distribution Oversized Openings
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Air Distribution Obstructions

• Maximize Floor Height
• Floor height restricts air flow volume
• High airflow velocities under the floor can
  negate static pressure differentials and entrain
  air from above to below
• May need scoops

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Air Distribution Obstructions
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Air Distribution Obstruction

• Overhead System
• Light fixtures, overhead cable trays
• Equipment that is taller than the discharge plenum

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Air Flow Obstruction
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Air Distribution Obstructions
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Air Distribution Obstructions
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Air Distribution Air Leakage

• Raised Floor System
• Behind the PAC unit
• Improper Wire/Cable openings- remove one tile to
  run wires
• Around the perimeter of room
• Adversely effects the under floor static pressure
  hindering the control of airflow

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Air Distribution Air Leakage
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Cleanliness and Proper Vapor Barrier in Subfloor
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(No Transcript)
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What is the right distancefrom PAC to the 1st
Rack
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None-Direction Airflow
Pressure Static Pressure Velocity Pressure
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Perform Better
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Air Distribution Air Leakage

• Overhead System
• No shut off dampers on redundant units
• Back draft dampers or motorized discharge dampers
  with timers

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Air Distribution Airflow Pattern

• Raised Floor System
• Perforated tile quantity and layout
• Perforated tiles too close to the PAC
• 3 foot clearance above computer racks
• Drop ceiling return air plenum

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Air Distribution Airflow Pattern
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Air Distribution Airflow Pattern
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Air Distribution Airflow Pattern

• Overhead System
• Discharge diffuser too close to the PAC
• Air discharge from one unit enters the return air
  of another

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Air Distribution Airflow Pattern
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Redundancy

• N1 PAC Unitsi.e. 20 ton load, three 10 ton
  units
• Only one pump on glycol/water loop
• Multiple feeds to PAC units, but only one breaker
  for all rooftop condensers

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Redundancy of Airflow

• Can air reach each part of the room from more
  than one unit?
• If the answer is no, then N1 may be negated

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Alternating Cold Aisle, Hot Aisle

• Computer Equipment Air Flow Pattern
• In the front, out the back
• Racks face each other along one aisle
• Backs face each other on alternate aisle

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Alternating Cold Aisle, Hot Aisle
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Alternating Cold Aisle, Hot Aisle
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Alternating Cold Aisle, Hot Aisle
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Air Distribution Airflow Pattern

• Raised Floor System
• Controlling the Return AirDrop ceiling return
  air plenum

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Air Distribution Airflow Pattern
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Cost Effective Solution
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Cooling Capacity One Tile

• Perforated Tile Cooling Capacity

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Cooling Capacity One Tile

• Directly dependent on the airflow volume deliver
  through each tile
• Air volume dependent on static pressure under the
  floor

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Cooling Capacity One Tile

• One 2 x 2 Perforated Tile
• Typical Airflow
• 600 cfm _at_ 0.10 w.c.
• 200 cfm _at_ 0.02 w.c.
• Thus, leakage and too many perf. tiles will
  reduce static pressure and reduce the ability to
  control air flow

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Cooling Capacity One Tile

• Maintain high sensible heat ratio
• AT 72F, 50RH or 68F, 50RH, excessive
  condensation occurs after a 17F temperature drop

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Cooling Capacity One Tile
17F
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Cooling Capacity One Tile

• Cooling Capability
• 600 cfm x 17F x 1.08 11,000 Btuh
• Airflow volume critical to cooling capacity

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Cooling Capacity Per Rack

• Four foot wide aisles
• 22,000 Btuh sensible cooling per two feet of
  aisle
• With racks on both sides of the aisle, the heat
  load is 3,200 Watts per two feet of racking

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Downflow Front Discharge
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Design Planning Stage

• Capacity and placement of PAC
• Room Geometry
• Initial final room layout
• Initial final load
• Factors affecting air flow distribution
• Plenum static pressure
• Obstructions beneath plenum
• Configuration to prevent air mixing

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Design Planning Stage

• Mechanical system selection
• Air / water cool
• Refrigeration/water piping layout
• Keep it simple
• Noise concerns
• Local or remote compressor
• Condenser / condensing
• Energy factor
• Dual / Free Cooling
• NSB, increase of useable floor space
• Free cooling system
• Risk factor
• Chilled water /water cooled system

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Maintenance

• Commissioning of basic systems
• Refrigeration, electrical, blower RPM, etc.
• Programming of controller
• Configure alarm responses
• Train End-user
• Follow Maintenance Program

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Maintenance

• Common Deficiencies
• Dirty or blocked filters
• Undercharged DX systems
• Un-calibrated or damaged sensors
• Poor water flow, partially closed valves or other
  piping obstructions
• Chilled water supply temp. (49 - 54F)

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• Thank You