canatal applying precision air conditioning systems canatal international inc

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Applying Precision Air Conditioning Systems

Canatal International Inc.

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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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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 @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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ASHRAE Class 1 Operating Conditions

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Increase Equipment Failures

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Increase HVAC Energy Use

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Facility Temperature & Humidity Measurement

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Equipment & Facility Layout Recommended Airflow Protocol for Computer

Equipment

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Equipment Manufacturers Heat & Airflow Reporting

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Server / Switch Gear

Back View Front View

1U (1.70” H) Server

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5U Server – Tower Configuration

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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?

1a 1b2

3

4

5

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

22

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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 – ObstructionsPractice 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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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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Cabinet should be aligned with one edge along the edge of the cold aisle floor tile

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Air Distribution – Oversized Openings


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 ObstructionsMaximize 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 – Air LeakageRaised 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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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 LeakageOverhead 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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Overhead System Discharge diffuser too close to the PAC Air discharge from one unit enters the

return air of another

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Redundancy

N+1 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 N+1 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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Raised Floor System Controlling the Return Air

Drop ceiling = return air plenum

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Cost Effective Solution

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Cooling Capacity – One Tile

Perforated Tile Cooling Capacity

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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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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

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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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29.921 inHg0 ft

F 45 50 55 60 65 70 75 80 85 90

0.002lbm/lbm

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

0.02

0.022

0.024

0.026

0.028

1

Btu/lbm 45

40

35

30

25

20

15

10

ft^3/lbm 12.6 13.2 13.8

17˚F

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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

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 layoutInitial & final load

Factors affecting air flow distributionPlenum static pressureObstructions 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 systemsRefrigeration, electrical, blower RPM, etc.

Programming of controllerConfigure 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 - 54˚F)

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Thank You

canatal applying precision air conditioning systems canatal international inc

Documents

view slide

canatal thermal guidelines

canatal internal

canatal external

lower slide

problem slide

d90431 slide

equipment failures slide