hvac training final

8/3/2019 HVAC Training Final

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Fundamentalof

HVAC for IT


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HVAC Terms

The Refrigeration Cycle

The Nature of Heat In The It Environment

Application Of The Refrigeration Cycle In It Cooling

The 5 Basic It Environment Heat Removal Methods

The Nine Types Of Cooling Systems

Types Of Cooling In The Hard Floor Environment

Types Of Cooling In The Raised-floor Environment

PrecisionAir Conditioning

Content

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HVAC Term

Air-Cooled System

Condensing Coil exposed directly to the outside Atmosphere.

ASHRAE

American Society of Heating, Refrigerating, and Air-Conditioning Engineers

BTU

British Thermal Unit. A BTU is defined as the amount of heatenergy required to raise the temperature of one pound of waterby one degree Fahrenheit in one hour.

CFM

Cubic feet per minute. CFM is used to measure the flow of airthrough a delivery system or space.

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HVAC Term

Clean Room

A room that is virtually free of dust or bacteria

Compressor

The compressor is an essential component in the refrigerationcycle that uses mechanical energy to compress or squeeze

gaseous refrigerant.

Condensate

The water that results as a by-product of dehumidification.

EER

energy efficiency ratio, a measurement quantifying theperformance of a compressor relative to its energy consumption.A higher number is generally better.

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HVAC Term

Enthalpy

The total quantity of energy used to heat or cool a substancebetween two temperatures including the energy used to changethe state of the substance if applicable. For example, if we heata sample of water at normal atmospheric pressure from 33F to275F (1C to 135C), the enthalpy is the sum of the sensible

heat energy added (from 33F / 1C to 212F / 100C and from212F / 100C to 275F / 135C) and the latent heat energyadded (state change from liquid to vapor at 212F / 100C).

Latent Heat

Heat energy that must be transferred to or removed from a

substance to change its state.

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HVAC Term

Psychometric Chart

The properties of air and the water contained in it at differenttemperatures arranged in the form of a chart. In particular itshows the quantitative interdependence between temperatureand humidity.

Relative Humidity

The amount of water vapor contained in air relative to themaximum amount the air is capable of holding. Expressed in %.

Sensible Heat

Sensible heat is defined as the heat energy that causes a change

in temperature of a substance but does not contribute to achange in state for the substance. The only type of heat energyproduced by computers and IT equipment.

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HVAC Term

Sensible Cooling Capacity

The amount of heat energy the air conditioner can be expected toremove from the IT room or data center.

Latent Cooling Capacity

The fraction of total capacity a computer room air conditioner or airhandler uses to condense liquid water from the air stream being

cooled.

Sensible Heat Ratio

The ratio between a air conditioners sensible heat removal capacityand its total heat removal capacity. In an IT environment, highersensible heat ratios contribute to lower operating costs and more

effective equipment cooling. Ideally, this ratio is 1, meaning the entireair conditioner capacity is available to cool the IT loads.

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HVAC Term

Ton (Cooling)

A measurement of heat energy commonly usedhistorically to measure heat loads. A ton is equal to12,000 BTUs and is the amount of heat energy requiredto melt 2000 pounds (907kg) of ice in one hour.

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HVAC Term

Conversion Table

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Click to edit Master text stylesSecond level Third level

Fourth level Fifth level

The refrigeration cycle is a closed cycle ofevaporation, pressure change, condensation, andflow regulation applied to a fluid called refrigerant.

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Evaporation

Warm air from the computer room is blown across theevaporator coil by a fan, while the pipes comprising thecoil are supplied with cold liquid refrigerant.

Even though the evaporator coil is cold, at approximately

46F (7.8C), the refrigerant inside is evaporating, orboiling, changing from liquid to a gaseous state.

The refrigerant at this point is a cool gas in a small pipethat is carrying the heat energy away from the computerroom.

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Compression

The vaporized but cool refrigerant carrying the heat fromthe data center is drawn into a compressor.

This compressor has two important functions:

It pushes the refrigerant carrying the heat energyaround the refrigeration loop.

It compresses the gaseous refrigerant from theevaporator coil to over 200 psi or 1379 kPa.

The compression of a gas causes its measured

temperature to rise. Therefore, the moving gaseousrefrigerant exiting the compressor is hot, over 125F(52C), as well as compressed.

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Condensation

The hot compressed refrigerant carries the computerroom heat energy from the compressor to the CondenserCoil. This coil transfers heat to another medium, like air.

Heat is flowing from the refrigerant to the air. The air is

typically blown across the hot coil by a fan whichexhausts the hot air to the outdoors.

In this way the heat energy from the computer room hasbeen pumped to the outdoors.

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Expansion

The refrigerant exits the Condenser Coil as a high-pressure liquid, although at a lower temperature. Therefrigerant then passes through an expansion valvebefore returning to the Evaporator Coil.

It precisely regulates the flow of high-pressure refrigerantinto the low-pressure evaporator coil at a rate thatmaintains an optimal difference in pressure.

It is a fundamental property of gases that the expansionof a gas causes its measured temperature to fall. The

result is that the refrigerant is cooled by the release ofpressure.

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The nature of Heat in IT environment

Heat is simply a form of energy. In the data center heat is

produced as electricity is consumed by IT equipment.With few exceptions, over 99% of the electricity used topower IT equipment is converted into heat.

Approximately 50% of the heat energy released byservers originates in the microprocessor itself.

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Application of the refrigeration cyclein IT cooling

IT rooms and data centers are usually cooled with

specialized air conditioning equipment commonly calledprecision cooling systems. These systems differ fromtypical residential or commercial air conditioning systemsin that they provide more precise, stable environmentsfor IT equipment by closely regulating air temperature

and moisture.

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Application of the refrigeration cyclein IT cooling

Equipment located inside the IT environment

Large floor mounted computer room air conditioners(CRAC), computer room air handlers (CRAH), ceiling-mounted air conditioners, and portable air conditionersknown as spot coolers.

Equipment located outside the IT environment

The outdoor heat rejection device. With the exception ofsome ceiling-mounted and portable air conditioners,there are alwaysone or more major componentsessential to the cooling system existing outside of the IT

environment.

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The 5 basic IT environment heatremoval methods

Air-Cooled System (2-pieces)

This type of system is often referred to as a DXsystem orsplit system. In an air cooled system half the componentsof the refrigeration cycle are in the computer room airconditioner(also known as a CRAC unit) and the rest areoutdoors in the air cooled condenser.

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Air cooled self-contained systems (1-piece)

Self-contained systems locate all the components of therefrigeration cycle in one enclosure that is usually foundin the IT environment.

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The 5 basic IT environment heatremoval methodsAir cooled self-contained systems (1-piece)

Advantages:

Lowest installation cost.

All refrigeration cycle components are contained inside one unit as a factory-sealed and tested system for highest reliability.

Disadvantages:

Less heat removal capacity per unit compared to other configurations. Air routed into and out of the IT environment for the condensing coil usually

requires ductwork .

Usually Used:

In wiring closets, laboratory environments and computer rooms with moderateavailability requirements. Sometimes used to fix hot spots in data centers.

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Glycol cooled systems

All refrigeration cycle components in one enclosure (like aself-contained system) but replaces the bulky condensingcoil with a much smaller heat exchanger uses flowingglycol (a mixture of water and ethylene glycol)

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The 5 basic IT environment heatremoval methodsGlycol cooled systems

Advantages:

Glycol pipes can run much longer distances than refrigerant lines


Disadvantages:

Additional required components (pump package, valves) raise capital andinstallation costs.

Maintenance of glycol volume and quality within the system is required.

Usually Used:

In computer rooms and small-to-medium data centers with moderate availabilityrequirements.

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Water cooled systems

Water cooled systems are similar to glycol cooledsystems. However, there are two important differences :

A water (also called condenser water) loop is usedinstead of glycol

Heat is rejected to the outside atmosphere via a coolingtowerinstead of a fluid cooler.

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The 5 basic IT environment heatremoval methodsWater cooled systems

Advantages:

Condenser water piping loops are easily run long distances


Disadvantages:

High initial cost for cooling tower, pump, and piping systems. Very high maintenance costs due to frequent cleaning and water treatment

requirements.

Usually Used:

In conjunction with other building systems in small, medium and large datacenters with moderate to-high availability requirements.

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Chilled water systems

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The 5 basic IT environment heatremoval methodsChilled water systems

Advantages:

Computer room air handlers generally cost less, contain fewer parts, and havegreater heat removal capacity

Chilled water piping loops are easily run very long distances and can servicemany IT environments .

Can be engineered to be extremely reliable.

Disadvantages:

highest capital costs

CRAHs generally remove more moisture from data center air than their CRACcounterparts, requiring more money be spent on humidifying the room in manyclimates.

Usually Used:

In conjunction with other systems in medium and large data centers withmoderate-to-high availability requirements or as a high availability dedicatedsolution in large data centers.

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The nine types of cooling systems

Every cooling distribution system has a supply system

and a return system. The supply system distributes thecool air from the CRAC unit to the load, and the returnsystem takes the exhaust air from the loads back to theCRAC.

For both the supply and the return, there are three basicmethods used to convey air between the CRAC and theload, which are:

Flooded

Locally Ducted

Fully Ducted

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Types of cooling in the hard floorenvironment

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Types of cooling in the hard floorenvironment

Selecting the right type to use in a hard floor

environment

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Types of cooling in the raised-floorenvironment

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Types of cooling in the raised-floorenvironment

Selecting the right type to use in a raised-floor

environment

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Precision Air Conditioning

Why Do I Need Precision Air Conditioning?

IT hardware produces an unusual, concentrated heatload, and at the same time, is very sensitive to changesin temperature or humidity.

Precision air systems are designed for close temperature

and humidity control. They provide high reliability foryear-round operation, with the ease of service, systemflexibility and redundancy necessary to keep thetechnology room up and running 24 hours a day.

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Temperature and Humidity Design Conditions

Design conditions should be 72-75F (22-24C) and 35-50% relative humidity(R.H.).

Problems Caused by the Wrong Environment

High & Low Temperature

A high or low ambient temperature or rapid temperature swings can corrupt

data processing and shut down an entire system.High Humidity

High humidity can result in tape and surface deterioration, head crashes,condensation, corrosion, paper handling problems, and gold and silvermigration leading to component and board failure.

Low Humidity

Low humidity greatly increases the possibility of static electric discharges.Such static discharges can corrupt data and damage hardware.

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Differences Between Precision Air and Comfort Air Conditioning

Sensible Heat Ratio

The total cooling capacity of an air conditioner is the sum of the sensible heatremoved and the latent heat removed.

Total Cooling Capacity = Sensible Cooling + Latent Cooling

Total Cooling Sensible Heat Ratio (SHR) = Sensible Cooling

The required SHR of an air conditioner to match this heat load profile is very high,

0.95-0.99. Precision air conditioning is designed to meet these very high sensibleheat ratios.

In contrast, a comfort air conditioner typically has a SHR of 0.65-0.70, therebyproviding too little sensible cooling and too much latent cooling.

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Precise Temperature and Humidity

Precision air conditioners have the sophisticated, fast-acting, microprocessor-based controls necessary to reactquickly to changing conditions and maintain the tighttolerances required for a stable environment.

Air Quality

Precision air conditioners operate at a high air flow rateper unit heat removed, generally, 160 CFM (76 Lps) perkW or greater. The high CFM / kW of precision coolingequipment also allows more air to move through filters,ensuring a cleaner environment.

Comfort air conditioners operate at a much lower 85-115CFM / kW (40-54 Lps / kW).

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Hours of Operation

Precision air conditioners are designed and built to run non-stop 8760hours a year..

Comfort air conditioners are designed to run during summer days, up toan expected maximum of 1200 hours per year.

Design Criteria

Load Density Load Density Office 5 15 watts / sq. ft. (54 161 watts / sq. m)

Technology Room 50 200 watts / sq. ft. (538 2,153 watts / sq. m)

Temperature and Humidity

Design goal conditions should be 72-75F (22-24C), 35-50% R.H.

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Air Quantity

The high CFM / kW (Lps / kW) inherent to precisionsystems contributes to the high sensible heat ratio,improves air distribution, and increases filtration rates.

Air Cleanliness

Without filters, airborne dust can damage equipment.Filters should be deep pleated for moderate to highefficiency.

Vapor Barrier

Because almost all construction materials are

transparent to moisture, a well-designed technologyroom must include a vapor barrier.

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Outside Air Requirements

Outside air should be minimized to limit the latent loadbrought into the room. A quantity of 20 CFM (9.4 Lps)per person is currently sufficient to satisfy Indoor AirQuality (IAQ) concerns in the U.S.

Redundancy

Redundancy is achieved by operating additionalequipment to provide 100% of the required coolingcapacity even after a unit shutdown or failure of one ormore units.

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Cost of Ownership

Operating Costs

Technology room air conditioning costs are typically ten timeshigher per square foot than office or comfort air conditioning.However, precision air conditioning operating costs are farless than comfort air conditioning if both systems are applied

to a technology room. Precision air conditioning costs are lower than comfort air

conditioning for comparable use because of the following:

Under-floor System

High Energy Efficiency Ratio (E.E.R).

Precision air equipment is designed with high-efficiencycomponents for year-round operation. Look for the following:

Oversized, shallow cooling coil

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High efficiency blower motors

Steam canister humidifiers

Heat pump duty rated compressor

High S.H.R.s

Dedicated dehumidification cycle

Low FLA

100,000 HR L rated bearings

Extended warranties

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Service Costs

The largest costs incurred during the service or repair aregenerally in technology room downtime. For this reason,redundancy should always be designed in first.

Look for the following:

Bolt in refrigeration components. Compressor and filter dryer

should be removable without gas torches.

Components should be out of the air stream in a separatemechanical section.

Removable fan deck assembly.

Color-coded and numbered electrical wiring.

Motor start protectors instead of fuses. Easily removable and/or hinged access panels.

Run-time-based maintenance calls.

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Thank You

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