Applying Precision Air
Conditioning Systems
Canatal International Inc.
CANATAL
Introduction
Application of Precision Air Conditioning
 Data Centers
 Switching Stations
 Co-Location Facilities
CANATAL
Topics of Discussion
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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
CANATAL
New ASHRAE Document
“Thermal Guidelines for Data Processing
Environments”
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Equipment Environment Specifications
Facility Temperature & Humidity Measurement
Equipment & Facility Layout
Equipment Manufacturers Heat & Airflow
Reporting
Available @www.ashrae.org, Item Number 90431, or D90431
CANATAL
“Thermal Guidelines for Data Processing
Environments”

Equipment Environment Specifications
CANATAL
“Thermal Guidelines for Data Processing
Environments”

Equipment Environment Specifications
CANATAL
ASHRAE Class 1 Operating
Conditions
CANATAL
ASHRAE Class 1 Operating
Conditions
Increase Equipment
Failures
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ASHRAE Class 1 Operating
Conditions
Increase HVAC
Energy Use
CANATAL
“Thermal Guidelines for Data Processing
Environments”

Facility Temperature & Humidity Measurement
CANATAL
“Thermal Guidelines for Data Processing
Environments”

Equipment & Facility Layout

Recommended Airflow Protocol for Computer
Equipment
CANATAL
“Thermal Guidelines for Data Processing
Environments”

Equipment & Facility Layout

Recommended Airflow Protocol for Computer
Equipment
CANATAL
“Thermal Guidelines for Data Processing
Environments”

Equipment & Facility Layout

Recommended Airflow Protocol for Computer
Equipment
CANATAL
“Thermal Guidelines for Data Processing
Environments”

Equipment Manufacturers Heat & Airflow
Reporting
CANATAL
Server / Switch Gear
1U (1.70” H) Server
Back View
Front View
CANATAL
Server / Switch Gear
2U (3.50” H) Server
Back View
Front View
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Server / Switch Gear
4U (6.80” H) Server
Back View
Front View
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Server / Switch Gear
5U Server – Tower Configuration
Back View
Front View
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Server / Switch Gear
Back View
Front View
CANATAL
Heat Density Trends
Source: Uptime Institute
CANATAL
What is wrong with this picture?
CANATAL
What is wrong with this picture?
5
3
4
2
1a
2
1b
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
2
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External re-circulation:
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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
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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
CANATAL
Humidity Control

Independently operated units will fight
- simultaneously humidify and dehumidify
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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.
CANATAL
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
CANATAL
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”
CANATAL
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”
CANATAL
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”
CANATAL
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
CANATAL
Air Distribution – Obstructions
CANATAL
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
CANATAL
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
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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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What is the right distance
from 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
CANATAL
Air Distribution – Airflow
Pattern
CANATAL
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
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N+1 PAC Units
i.e. 20 ton load, three 10 ton units
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Only one pump on glycol/water loop
 Multiple feeds to PAC units, but only
one breaker for all rooftop condensers
CANATAL
Redundancy of Airflow
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Can air reach each part of the room from
more than one unit?
 If the answer is no, then N+1 may be
negated
CANATAL
Alternating Cold Aisle, Hot
Aisle
Computer Equipment Air Flow Pattern
 In the front, out the back
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Racks face each other along one aisle
 Backs face each other on alternate aisle
CANATAL
Alternating Cold Aisle, Hot
Aisle
CANATAL
Alternating Cold Aisle, Hot
Aisle
CANATAL
Alternating Cold Aisle, Hot
Aisle
CANATAL
Air Distribution – Airflow
Pattern
Raised Floor System
 Controlling the Return Air
Drop 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
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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 @ 0.10” w.c.
200 cfm @ 0.02” w.c.
 Thus, leakage and too many perf. tiles
will reduce static pressure and reduce the
ability to control air flow
CANATAL
Cooling Capacity – One Tile
Maintain high sensible heat ratio
 AT 72˚F, 50%RH or 68˚F, 50%RH,
excessive condensation occurs after a
17˚F temperature drop
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Cooling Capacity – One Tile
17˚F
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Cooling Capacity – One Tile
Cooling Capability
600 cfm x 17˚F x 1.08 = 11,000 Btuh
Airflow volume critical to cooling capacity
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Cooling Capacity – Per Rack
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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
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Factors affecting air flow distribution
 Plenum
static pressure
 Obstructions beneath plenum
 Configuration to prevent air mixing
CANATAL
Design & Planning Stage
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Mechanical system selection:
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Air / water cool
Refrigeration/water piping layout
 Keep it simple
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Noise concerns:
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Energy factor
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Local or remote compressor
Condenser / condensing
Dual / Free Cooling
NSB, increase of useable floor space
Free cooling system
Risk factor
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Chilled water /water cooled system
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Maintenance
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Commissioning of basic systems
 Refrigeration,
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electrical, blower RPM, etc.
Programming of controller
 Configure
alarm responses
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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 - 54˚F)
CANATAL
Thank You
CANATAL