HVAC System Tip Sheet

8/3/2019 HVAC System Tip Sheet

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Heating, Ventilation and Air Conditioning (HVAC) accounts or a signicantportion o a commercial buildings energy use and represents an opportunity or

considerable energy savings. Tis ip Sheet acts as a primer on energy efcient

HVAC systems and proven technologies and design concepts which can be used

to comply with the HVAC provisions in Energy Conservation Building Code.

EnErgy COnSErVATIOn

BUILDIng CODE (ECBC) TIP SHEET

HVAC SySTEM

Version 1.0 (Reprinted) June, 2009

Credits:

E Source Technology Atlas

US DOEs Building Technologies Program

Alliance to Save Energy

USAID ECO-III Project

International Resources Group

Phone: +91-11-2685-3110

Fax: +91-11-2685-3114

Email: [email protected]

Keepi buildis cool

in hot climates has alwaysbeen a human concern. For

millennia, people ingeniously applied anastonishing array o design eatures totheir shelters to avoid or reject unwantedheat. Windscoops, vents, cool towers,atria, shading, orientation, whitewash,night radiation the whole panoply omodern passive techniques was inventedat least three thousand to ive thousandyears ago and developed to an impressivelevel o matur ity. However, the inventiono rerigerative chiller by WilllisHaviland Carrier in 1902 changed the

world and led to the abandoning oancient and climate responsive buildingarchitecture, as it could cool any sorto boxy and sealed building space andtechnically take care o adverse hotclimat ic conditions. From 1945 onwards,rerigerative air-conditioning becamethe norm to maintain buildings in anarrow temperature range, irrespectiveo weather conditions.

As the Climate Map o India (ECBC,2007) shows, most o India alls mainlyunder three climatic zones (hot-dry, warm-

humid and composite) requiring coolingo buildings or almost 6-8 months toprovide thermal comort to the occupants.All o this comes with signicant energy

consumption and costs. Both need to beaddressed while designing any building.

Whole Buildi Appoach

Reduce cooling load by controlling1.unwanted heat gain: As shown in Fig. 1,

external heat gains can be avoided witharchitectural orm, light-colored buildingsuraces, vegetation, high perormance

glazing, etc. Internal heat gains can bereduced by using more ecient buildingequipment (such as lights, computers,printers, copiers, servers), ecient HVAC

Cooli Load reductio Measues (Souce: E Souce Cooli Atlas)Fi. 1:

Window films reduce solar gain without

sacrificing daylight or esthetics

Plan for smaller cooling equipment and

modified air handlers once internal and

external load reduction measures are in place.

Thermostats and controls should accommodate

load reduction.

Green roofs help in lowering the Roof

Temperature

Trees block solar radiation and provide

cooling benefit through

evapotranspiration

Automatic louvers, fixed louvers, and

solar screens block solar radiation

Movable awnings provide

shade

South

Insulating the roof helps

decrease heat conduction to the

inside of the building

Structural overhangs,

lightshelves reduce solar

gain

Light-colored roof coatings reflect

solar radiation and reduce

conduction potential

Spectrally selective

glazings let light in

but keep heat out

1ECBC/TIP SHEET > HVAC SystemVersion 1.0 (Reprinted) June, 2009


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equipment and direct venting o spot heatsources. Load reduction not only savesenergy, it allows HVAC equipment to besmaller, resulting in rst-cost savings.

Expand the comort envelope with2.reduced radiant heat load, increasedair ow, Less Insulated Furniture,

more casual dress where appropriate:These opportunities are less understoodand deployed but have the potential

to save another 20-30% of remaining

loads. In an indoor environment with

xed air temperature, relative humidity,air speed, and activity, an ofce workerin cotton trousers and half shirt (withan insulating value of 0.5 clo) will becomfortable at almost 3C warmer thanthe same person in a heavy two-piecebusiness suit and accessories (withan insulating value of 1.0 clo). A 3Cextension of comfort envelope can savesignicant energy and capital cost byallowing temperatures to ramp higher

and the cooling system to be smaller.

Optimize the delivery system:3. Hugesavings are available from reducingthe velocity, pressure, and frictionlosses in ducts and piping. Additionalimprovement can be captured withhigh-efciency fans, diffusers, andother components.

Apply non-vapor compression cooling4.techniques: They typically use 20-30%as much energy per unit of coolingas conventional cooling equipmentand can serve much or all of the loadthat remains after the cooling load isreduced. These alternatives includenatural ventilation with cool outsideair, ground coupled cooling, night skycooling, evaporative cooling, absorptioncooling, and desiccant systems fueled by

natural gas, waste heat, or solar energy(See text box on page 6).

Serve the remaining load with high-5.eciency rerigerative cooling: Moreefcient chillers, pumps, and fans,

chilled water systems. Many o thesesystems are particularly ripe targets becausethe phase out o CFCs is orcing themto make signicant investment in theircooling system. Many o the principles andapproaches outlined here, however, applyto non-chiller based systems as well.

getti StatedHVAC systems have a signiicant eecton the health, comort, and productivityo occupants. Issues like user discomort,improper ventilation, and poor indoor ai rquality a re linked to HVAC system designand operation and can be improved bybetter mechanical and ventilation systemdesign.

Factors aecting thermal comort:hermodynamic processes take placebetween the human body and thesurrounding thermal environment.Our perception o thermal comortand acceptance o indoor thermalenvironment is a result o the heatgenerated by metabolic processes and theadjustments that the human body makesto achieve a thermal balance between ourbody and the environment.

Te six actors that inuence the heattranser between the human body and thesurrounding environment are shown inable 2.

Superior HVAC design will considerall the inter-related building systemswhile managing indoor air quality, energyconsumption, and comort. Optimizingthe design requires that the mechanicalsystem designer and the architect addressthese issues early in the schematic designphase and continually improve subsequentdecisions throughout the design process. Itis also es sential that one implements well-thought-out commissioning processesand routine preventative maintenance

programs (see text box on page 7).

Determining loads: Projected load ornew buildings can be analyzed accuratelyby using Computer Simulation. Hourlysimulation models designed or energyanalysis, calculate hourly cooling loadsrom detailed building geometry,scheduling, and equipment data. Usingactual weather data , it is possible to matcha buildings energy usage with actualutility billing data. Computer Simulationcan provide the best understanding o how

a building will operate under dierentscenarios rom a combination o detailedend-use hourly simulation.

multiplexed chillers (to minimize part-load operation penalties), large heatexchangers, low-friction duct layoutand sizing, low pressure drops in air-handling and piping components, andoverall optimization of the entire HVACsystem will further help in making thesystem more efcient (see Table 1).

Improve controls:6. Through betteralgorithms, sensors, signal delivery,user interface, simulators, and othermeasures.

HVAC Ecoomics ad

Beefits to Developes

It is diicult to generalize on the prospects or the downsizing equipmentas the cooling load is reduced. he potential capital and operating costsavings are substantial, however, andshould be careully analyzed. It is quitepossible to cut cooling load by hal througha combination o better lighting, glazing,oce equipment, and shell measures.

Operating cost or an HVAC systemo a given size will not all linearly withcooling load, because most o the coolingsystems are less ecient at low loads thanthey are in upper range o their capacity.o ully capture operating cost savings as well as the capital cost savings rom theload reduction, a smaller HVAC system

matched careully to the load proleshould be installed or retrotted. At thevery least, this should mean ewer tons ocooling plant. In some cases it may meansmaller ducts, pipes, pumps, ans, andother auxiliaries.

But why should developers andnanciers care, since they may sell thebuilding to someone else or, i they retainownership, pass along the operating coststo tenants? Saving hal electricity througha high quality, high eciency design would

be equivalent to 3% exibility on the rent. Whichever developer rst captures theeciency opportunity, thereore, will havea huge competitive advantage.

Tis outlines an integrated strategytargeted at owners o large buildings with

Ee Savi Potetial i HVAC Sstem DesiTable 1:

Compoet

Cooli Load (kW/to)

Impovemet

Potetial (%)Covetioal De-

si

Optimized

Desi

Chiller 0.75 0.50 33%

Air Distribution System 0.60 0.06 90%

Water Pump 0.30 0.04 87%

Cooling Tower 0.10 0.02 80%

Total 1.75 0.62 65%


ECBC/TIP SHEET > HVAC System


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System interactions: Cooling loadreduction should be approached in concert with whole-building load reductionmeasures or both cooling and heatingsystems. he objectives o saving coolingand heating energy may be in conlict ormay support each other. For example, betterinsulation and high insulation windows

can reduce both loads while lighting loadreductions may increase heating loads.High-perormance windows may be thelast step needed in eliminating part or allo the perimeter HVAC equipment, while providing superior radiant comort inboth summer and winter.

o take advantage o load variations, itis critical that building mechanical systemsbe capable o reacting to the reduced loads.Tis requires variable capacity pumpsand ans (or variable capacity compressorand condenser units in case o packagedor split-systems) and reliable sensors andcontrols to allow the equipment to powerdown when loads drop.

Ai-Coditioe Basics

Air-conditioners employ the sameoperating principles and ba sic componentsas a rerigerator. An air-conditionercools with a cold indoor coil calledthe evaporator. he condenser, a hotoutdoor coil, releases the collected heatoutside. he evaporator and condenser

coils are serpentine tubing surroundedby aluminum ins. his tubing is usuallymade o copper. A pump, called thecompressor, moves a heat transer luid(or rerigerant such as ammonia and

luorinated hydrocarbons) betweenthe evaporator and the condenser. he pump orces the rerigerant through thecircuit o tubing and ins in the coils.he liquid rerigerant evaporates inthe evaporator coil, pulling heat out oindoor air and thereby cooling the space.he hot rerigerant gas is pumped into

the condenser where it reverts back to aliquid giving up its heat to the air lowingover the condensers metal tubing andins. Because the condenser is the heatrejection unit so it should be located insuch a manner that the heat sink is ree ointererence rom heat discharge o otherequipment or optimum perormance.

Tpe of Ai-Coditioes

Te most common types o air-conditionersare room air-conditioners, split-systemcentral air-conditioners, packaged air-conditioners, and central air-conditioners.Fig. 2 shows market share o dierent typeso vapor compression HVAC technologies(residential and commercial) in India.

Room and split air-conditioners: Roomair-conditioners cool rooms rather thanthe building. hey provide cooling only when needed Room air-conditioners areless expensive to operate than centralunits, even though their eiciency isgenerally lower than that o central air-

conditioners.In a split-system central air-conditioner,

an outdoor metal cabinet contains thecondenser and compressor, and an indoorcabinet contains the evaporator. In many

split-system air-conditioners, this indoorcabinet also contains a urnace or theindoor part o a heat pump.

Packaged air-conditioners: In a packagedair-conditioner, the evaporator, condenser,and compressor are all located in onecabinet, which usually is placed on aroo or on a concrete slab adjacent to thebuilding. his type o air-conditioner istypical in small commercial buildingsand also in residential buildings. Airsupply and return ducts come romindoors through the buildings exteriorwall or roo to connect with the packagedair-conditioner, which is usually locatedoutdoors. Packaged a ir-conditioners oteninclude electric heating coils or a naturalgas urnace. his combination o air-conditioner and central heater eliminatesthe need or a separate urnace indoors.

Central air-conditioners: In Centralair-conditioning systems, cooling isgenerated in a chiller and distributedto air-handling units or an-coil units with a chilled water system. Tis categoryincludes systems with air-cooled chillersas well as systems with cooling towers orheat rejection ( see text box on page 8 fordetailed discussion).

Heati Sstem Tpes

Heating system types can be classiiedairly well by the heating equipment type.he heating equipment used in Indiancommercial buildings include boilers (oiland gas), urnaces (oil, gas, and electric), heatpumps, and space heaters.

Boiler-based heating systems have steamand/or water piping to distribute heat. Teheated water may serve preheat coils inair handling units (see text box on page 5),reheat coils, and local radiators. Systemsthat circulate water or a uid are calledhydronic systems. Additional uses or the

heating water are or heating o servicewater and other process needs, dependingon the building type. Some central systemshave steam boilers rather than hot water

Themal Comfot Paametes (Souce: Fae, 1970)Table 2:

Paametes Siificace Desi/IEQ Implicatios

AirTemperature

Most important parameter fordetermining thermal comfort

Determines thermostat set points, sensibleloads and inuences the perception ofIndoor Environmental Quality (IEQ)

Mean RadiantTemperature

Key factor in the perception ofthermal discomfort resulting

from radiant asymmetry

Radiant panels can reduce the requirementof conditioned air

RelativeHumidity

Excessive dry or humidconditions are immediatelyperceived as uncomfortable

Enthalpy-based economizer, althoughdifcult to control has good potential tosave energy and provide greater thermalcomfort

Air Velocity Key factor in the perception ofdraft due to elevated air velocity

Can be used to reduce thermal discomfortin conjunction with passive design

Activity Level Poses a problem to designersif an indoor space has tobe designed for people withdifferent activity levels

Determines thermal output of individualswhich directly affects cooling/heating loadof a conditioned space

ClothingResistance

Important factor in theperception of thermal comfort;

use of clothing to adjust tothermal environment is a goodexample of adaptive control.

In ofce environment, chair upholsterycan increase the resistance by as much

as 0.15 clo; difference in the clo valuesof male and female dresses should betaken into account while designing indoorenvironment

Environmen

tal

P

ersonal

Maket Shae of Diffeet Tpesi. 2:

f AC Uits i Idia (Souce: 2007 Sales

ata Emeso Climate Techolo)

Water

Chiller

11%

VRF Chillers

1%

Room AC

69%

Ducted/

Package

AC 19%

3Version 1.0 (Reprinted) June, 2009 ECBC/TIP SHEET > HVAC System


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Air System Balancing: Adjustingairlow rates through air distributionsystem devices, such as ans and diusers,by manually adjusting the position odampers, splitter vanes, extractors, etc.,or by using automatic control devices,

such as constant air volume or variableair volume boxes.

Boiler: A sel-contained low-pressureappliance or supplying steam or hotwater. A packaged boiler includes actory-built boilers manuactured as a unit orsystem, disassembled or shipment, andreassembled at the site.

Coeicient o Perormance (COP):Chiller e iciency measured in Btu output(cooling) divided by Btu input (electric power). Multiplying the COP by 3.412yields the energy-eiciency ratio.

Constant Volume System: A space-conditioning system that delivers aixed amount o air to each space. he volume o air is set during the systemcommissioning.

Economizer, Water-side: A system bywhich the supply air o a cooling system iscooled indirectly with water that is itsel

cooled by heat or mass transer to theenvironment with the use o mechanicalcooling.

Economizer, Air-side: A duct anddamper arrangement and automaticcontrol system that together allow acooling system to supply outdoor air toreduce the need or mechanical coolingduring mi ld or cold weather.

Energy-Eiciency Ratio (EER):

Perormance o smaller chillers androotop units is requently measuredin EER rather than kW/ton. EER iscalculated by dividing a chillers coolingcapacity (in Btu/h) by its power input (inwatts) at ull-load conditions. he higherthe EER, the more eicient the unit.

Heat Pump: A heat pump consists oone or more actory-made assemblies thatnormally include indoor conditioning coil,compressor, and outdoor coil, includingmeans to provide a heating unction. Heat

pumps provide the u nction o air heating with controlled temperature, and mayinclude the unctions o air cooling, air

circulation, air cleaning, dehumidiying,or humidiying.

Hydronic System Balancing: Adjusting water low rates through hydronicdistribution system devices, such as

pumps and coils, by manually adjustingthe position o valves, or by usingautomatic control devices, such as lowcontrol valves.

kW/ton Rating: Commonly reerred toas eiciency, but actually power inputto compressor motor divided by tonso cooling produced, or kilowatts perton (kW/ton). Lower kW/ton indicateshigher eiciency.

Integrated Part-Load Value (IPLV):his metric attempts to capture a morerepresentative average chiller e iciencyover a representative operating range. Itis the eiciency o the chiller, measuredin kW/ton, averaged over our operatingpoints, according to a standard ormula.

Outdoor Air : Air ta ken rom outdoors andnot previously circulated in the building.For the purposes o ventilation, outdoorair is used to lush out pollutants producedby the building materials, occupants and

processes.

Part-Load Perormance: For Waterchilling packages covered by thisstandard, the IPLV shall be calculated asollows:

Determine the part-load points. Use theollowing equation to calculate the IPLV.

IPLV = 0.01A+0.42B+0.45C+0.12D

For COP and EER:

Where: A=COP or EER at 100%B=COP or EER at 75%C=COP or EER at 50%D=COP or EER at 25%

For kW/ton:

IPLV:

Where:A=kW/ton at 100%B=kW/ton at 75%

C=kW/ton at 50%D=kW/ton at 25%

he weighting actors have beenbased on the weighted average o t he mostcommon building types and operation

using average weather in 29 U.S. cities,with and without air side economizers.

Return Air: Air rom the conditionedarea that is returned to the conditioningequipment or reconditioning. he air mayreturn to the system through a series oducts, plenums, and airshats.

Seasonal Energy Eiciency Ratio(SEER): SEER is a meas ure o equipmentenergy eiciency over the cooling season.It represents the total cooling o a centralair-conditioner or heat pump (in kWh)during the normal cooling season ascompared to the total electric energy inputconsumed during the same period.

Supply Air: Air being conveyed to aconditioned area through ducts or plenumsrom a heat exchanger o a heating, cooling,absorption, or evaporative cooling system.Supply air is commonly considered airdelivered to a space by a space-conditioningsystem. Depending on space requirements,

the supply may be either heated, cooled orneutral.

Tons: One ton o cooling is the amounto heat absorbed by one ton o ice meltingin one day, which is equivalent to 12,000Btu/h or 3.516 thermal kW.

Variable Air Volume (VAV) System: Aspace conditioning system that maintainscomort levels by varying the volume oconditioned air. his system delivers

conditioned air to one or more zones. heduct serving each zone is provided with amotorized damper that is modulated by asignal rom the zone thermostat.

Zone: A space or group o spaces withina building with heating and coolingrequirements that are suicientlysimilar so that desired conditions(e.g., temperature) can be maintainedthroughout using a single sensor (e.g.,thermostat or temperature sensor).

0.01 0.42 0.45 0.12A B C D

+ + +

1

Ke Techical Tems




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boilers because o the need or steam orconditioning needs (humidiers in air-handling units) or process needs (sterilizersin hospitals, direct-injection heating inlaundries and dishwashers, etc.).

Te remaining heating systems heatthe space directly and require little or nodistribution. Tese include heat pumps

and space heaters.

ECBC requiemetshe Energy Conservation BuildingCode (ECBC) includes provisions ormost HVAC system types. All coolingequipment are required to meet or exceedminimum eiciency requirements in theECBC 5.2. 2. Systems not included arereerred to ASHR AE 90.1 2004. Singlezone unitary systems are covered as wellas multiple zone air and water systems.he more complex the system, the morerequirements apply to that system: asingle-zone unitary system has ewer

requirements than a complex system madeup o chillers, boilers, and an coil units.

For natural ventilation requirements,buildings are required to ollow the designguidelines provided or natural ventilationin the National Building Code o India,2005 [ECBC 5.2.1].

Te ECBC contains several prescriptive

requirements or HVAC systems includingrequirements or economizer, duct andpipe insulation, controls optimization, andsystem balancing.

EcoomizesAn economizer is simply a collection odampers, sensors, actuators, and logicdevices that together decide how muchoutside air to bring into a building (see Fig. 4). When the outdoor temperatureand humidity are mild, economizers saveenergy by cooling buildings with outsideair instead o by using rerigerationequipment to cool recirculated air.

A properly operating economizer cancut energy costs by as much as 10 percentoa buildings total energy consumption,depending mostly on local climate andinternal cooling loads. he ECBCrequires an economizer or coolingsystems over 1,200 (continued on page 9)

Oveview

On an annual basis, continuously operatingair distribution ans can consume moreelectricity than chillers or boilers, whichrun only intermittently. High-eiciencyair distribution systems can substantiallyreduce an power required by an HVACsystem, resulting in dramatic energy

savings. Because an power increases atthe square o air speed, delivering a largemass o air at low velocity is a ar moreeicient design strategy than pushingair through small ducts at high velocity.Supplying only as much air as is neededto condition or ventilate a space throughthe use o variable-air-volume systems ismore eicient than supplying a constantvolume o air at all times.

Te largest gains in eciency orair distribution systems are realized

in the system design phase duringnew construction or major retrots.Modications to air distribution systemsare dicult to make in existing buildings,

except during a major renovation.Design options or improving air

distribution eciency include:Variable-air-volume (VAV) systemsVAV diusersLow-pressure-drop duct designLow-ace-velocity air handlersFan sizing and variable-requency-drive

(VFD) motorsDisplacement ventilation systems.

Air-handling systems deliver reshoutside air to disperse contaminantsand provide ree cooling, transportheat generated or removed by space-conditioning equipment, and create airmovement in the space also being served,deliver heated or cooled air to conditionedair to conditioned spaces (see Fig. 3). Passiveor natural air transport systems have thehighest eciency, and successul, modern

examples o this approach are steadilyaccumulating. For buildings that requiremechanical ventilation, innovative designapproaches and a methodical examinationo the entire air system can greatly improveeciency and efectiveness.Air-handling eiciency: he energyrequired to move air is:

All our o these actors can be manipu-lated to reduce the energy consumption o

the system.

Flow: Air low has a dominant eect onenergy consumption because it shows up

twice in the energy equation: as the irstterm and as a squared unction in thesecond term (pressure).

Te energy required to move airthrough a ducted system increases withthe cube o the ow rate. Tis importantrelationship, known as the cube law,points to a meticulous and comprehensive

examination o required ow as the start odesigning an ecient air-handling system.

Pressure: he pressure a an must workagainst depends on two primary actors:the low and duct design eatures such asdiameter, length, surace treatment, andimpediments such as elbows, ilters, andcoils. ypical pressure losses are on theorder o 2 to 6 inches water gauge (wg);an eicient system operates at less than1.5 wg.

Duty actor: A ans duty actor is thenumber o hours per year that it operates,sometimes presented as a percentage.Many large ans spin at ull speedcontinuously (8,760 hours per year).Using simple or complex controls, dutyactors can oten be reduced to about3,000 hours per year or less by limitingan operation to occupied periods.

Eiciency: he mechanical eiciency othe an and its drive system, can typically

be raised rom the 40 to 60 % range to themid-80 % range.

Energy =Eiciency

Flow x Pressure x Duty Factor

Most of the air in commercial buildings is

recirculated (returned) through the space. Only

about 10 percent is exhausted and replaced with

outside air.

SupplyA

ir100

%Re

turnA

ir100

%

Outsi

deAir10

%

RecirculatedAir

90%Exhaust Air

10%

Ai Flow ad its Make UpFi. 3:

(Souce: E Souce Cooli Atlas)

Ai Hadli Uit Cocepts

Logic ControllerOutdoor

Temperature

Sensor

Outside Air

DamperLinkage

MotorizedActuator

Motorized

Actuator

Linkage

Return-Airdamper

Supply Air

Cooling

Coil

Heating

Coil

Mixed Air

Return Air

Outside Air

Key

InformationFlow

AirFlow

The Compoets of a Ecoomiz-Fi. 4:

e (Souce: E Souce Cooli Atlas)



6/12

Evapoative Cooli

Evaporative cooling is an ancient airconditioning technique that is growingin popularity due to increased interest inenergy eiciency, reduced peak demand,improved indoor air quality, and non-

CFC cooling. Evaporative coolingtypically uses less than one-ourththe energy o vapor-compression air-conditioning systems, while using nomore water than a power plant uses toproduce the electricity needed or the sameamount o vapor-compression cooling.he cost o an evaporative cooling systemmay be higher than a vapor compressionchiller system, but payback is typically1-5 years depending on climate.

Te most common type o directevaporative cooler uses a cellulose berpad, permeable to both water and air,which has water pumped into its top edge.As the air passes through the wetted pad,water evaporates, taking heat rom the air,and the air cools adiabatically to balancethe heat it has lost to evaporation.

Indirect evaporative coolers (see Fig. 5)eliminate the problem o increasing themoisture content o the air that entersthe conditioned space by using a heatexchanger. In an air-to-air heat exchangersystem, secondary (exhaust) air lows

through one side o the heat exchangerwhere it is sprayed with water a nd cooledby evaporation. he building supply airlows through the other side o the heatexchanger where it is sensibly cooledby the evaporative cooled secondaryair. Because o the heat exchanger, theeectiveness o indirect evaporativecooling is reduced to about 65-75 %, but ithas wider applicability to climates whereincreased air humidity is unwelcome.

Desiccat Heat recove

Properties o desiccants materials toreadily attract water and thus dehumidi y

air can be used in HVAC applicationsto reduce cooling loads, improve chillereiciency, and widen the applicabilityo evaporative cooling, while providingimproved indoor air quality andeliminating the use o CFC rerigerants.

In combination with evaporativecooling, desiccant cooling can eliminatererigerative air conditioning in manyclimates.

A conventional cooling systemdehumidies bypassing the supplyair across a cooling coil that is coldenough to condense water vapor. Tisdehumidication requires a colder coilthan would be required or sensible coolingalone, oten doubling energy requirementsat typical low-load conditions where it isnecessary to dehumidiy but not cool.Oten in these conditions, the air is cooledor dehumidication and then must bereheated or comortable supply. Withdesiccants, dehumidication takes placeindependently o sensible cooling. In largebuildings, desiccants can reduce HVACelectricity use by 30-60 %. Fig. 6 showshow the desiccant wheel alternately passesthrough two separate airstreams; one tobe dehumidied and used in the building,and one to regenerate the desiccant withwarm, dry air.

goud Souce Heat Pump:

Water-loop heat pump (WLHP)systems have captured a small (3 to 4%) butslowly growing percentage o the U.S.commercial cooling market and havegood potential in India as well.

Ground coupled systems provide passiveheating and cooling by using the ground asa heat source or a heat sink. Tere are twobasic varieties.

Groundwater-source heat pumps(GWHPs) draw water rom wells, lakes,or other reservoirs o groundwater, pass

the water through an open loop, anddischarge it back to the environment.

Ground-source closed-loop heat pumps(GSHPs) system use a pump and ground-coupled heat exchanger to provide a heatsource and heat sink or multiple GSHPswithin the building.

Absoptio CooliOn the surace, the idea o using anopen lame or steam to generate coolingmight appear contradictory, but theidea is actually very elegant. Insteado mechanically compressing a gas(as occurs with a vapor-compressionrerigeration cycle), absorption coolingrelies on a thermochemical compressor.Absorption cooling is more commontoday than most people realize. Large,high-eiciency, double-eect absorptionchillers using water as the rerigerantdominate the Japanese commercial air-conditioning market. While less commonin India, interest in absorption coolingis growing, largely as a result o highelectricity taris and growing availabilityo natural gas on a commercial basis.

Absorption cooling is most requentlyused to air-condition large commercialbuildings. Absorption cooling equipmenton the market ranges in capacity romless than 10 tons to over 1,500 tons (35 to5,300 kW). Coecients o perormance

range rom about 0.7 to 1.2, and electricityuse ranges rom 0.004 to 0.04 kW/ton ocooling. Absorption chillers may makesense in the ollowing situations:

Electric demand charges are highElectricity use rates are highNatural gas prices are avorableUtility and manuacturer rebates exist

Te potential o absorption coolingsystems to use waste heat can greatlyimprove their economics. Indirect-red

chillers use steam or hot water as theirprimary energy source, and they lendthemselves to integration with on-sitepower generation or heat recovery romincinerators, industrial urnaces, ormanuacturing equipment. Indirect-red,double-efect absorption chillers requiresteam at around 190C and 900 kPa, whilethe less ecient (but also less expensive)single-efect chillers require hot water orsteam at only 75-132 C. High-eciency,double-efect absorption chillers are moreexpensive than electric-driven chillers.

Tey require larger heat exchangersbecause o higher heat rejection loads; thistranslates directly into higher costs.

no refieative Techoloical Optios i HVAC Sstem

Heater

To Outside

Outside Air

Desiccant WheelDehumidified

Supply Air

Partition separates heated

exhaust air from supply air

Solid Desiccat Wheels (Souce:Fi. 6:

E Souce Cooli Atlas)

Conditioned airHeat Exchanger

Supply Fan

Secondary

air Fan

Secondary Air

Wetted pad of other direct

evaporating media

Pump Reservoir

Outdoor Air

Idiect Evapoative CooleFi. 5:

(Souce: E Souce Cooli Atlas)




7/12

Oveview (US DOE, 2008)

Building commissioning is a systematic process o ensuring that a building perorms in accordance with the designintent, contract documents, and theowners operational needs. Due to the

sophistication o building designs andthe complexity o building systemsconstructed today, commissioningis necessary, but not automaticallyincluded as part o the typical design andconstruction process. Commissioningis critical or ensuring that the designdeveloped through the whole-buildingdesign process is successully constructedand operated.

Building commissioning includes theollowing:

Systematically evaluating all pieceso equipment to ensure that they are working according to specications.Tis includes measuring temperaturesand ow rates rom all HVAC devicesand calibrating all sensors to a knownstandard.Reviewing the sequence o operations toveriy that the controls are providing thecorrect interaction between equipment.

In particular, building commissioningactivities include:

Engaging a commissioning authority

and teamDocumentation Verication procedures, unctionalperormance tests, and validationraining.Commissioning HVAC systems is

even more important in energy-ecientbuildings because equipment is less likelyto be oversized and must thereore runas intended to maintain comort. Also,HVAC equipment in better perormingbuildings may require advanced control

strategies. Commissioning goes beyondthe traditional HVAC elements. Moreand more buildings rely on parts o theenvelope to ensure comort.

Commissioning includes evaluatingthe building elements to ensure that shademanagement devices are in place, glazing isinstalled as specied, air-leakage standardshave been metthese are the staticelements o the building. Commissioningcan also evaluate other claims about theconstruction materials such as VolatileOrganic Compounds (VOCs) emission

content and durability.Continuous commissioning ensures

that the building operates as eciently

as possible while meeting the occupantscomort and unctional needs throughoutthe lie o the building. It is worthnoting that Continuous commissioningis diferent rom building operation andmaintenance.

Benets o building commissioninginclude:Energy savings and persistence osavingsImproved thermal comort with properenvironmental controlImproved indoor air qualityImproved operation and maintenancewith documentationImproved system unction that easesbuilding turn-over rom contractor toowner.

Commissioi Cost

Building owners are inding thatthe energy, water, productivity, andoperational savings resulting romcommissioning oset the cost oimplementing a building commissioning process. Recent studies in the U.S.indicate that on average the operatingcosts o a commissioned building rangerom 8 to 20% below that o a non-commissioned building. he one-timeinvestment in commissioning at the

beginning o a project may result inreduced operating costs that will last thelie o the building.

Te cost o commissioning isdependent upon many actors includinga buildings size and complexity, and whether the project consists o newconstruction or building renovation. Ingeneral, the cost o commissioning a newbuilding ranges rom 0.5% to 1.5% o thetotal construction cost. For an existingbuilding, never beore commissioned,

the cost o retrocommissioning can rangerom 3% to 5% o the total operating cost.For HVAC and Control Systems, cost ocommissioning ranges rom 1.5 to 2.5% omechanical system cost.

Testi, Adjusti, ad

Balaci (nolfo, 2001)

esting, Adjusti ng, and Bala ncing (AB)reers to the process whereby a systemor a component must irst be testedto determine its operating state, thenadjusted, and inally balanced to produce

the desired results and perormance inaccordance with the design documents.Te primary objective o carrying out the

AB unction is to help the system to workproperly by balancing the uid ows totheir correct proportion and in the processidentiy design and installation errors, ithey exist, to ensure the perormance othe HVAC system. Some key issues that

a rm undertaking AB unctions mustaddress are listed below:

Identifcation o a Traverse Location:1.o ensure that accurate meas urementso airlows inside ducts can beobtained. his inormation is thenused by HVAC control system toregulate the low o air and optimizesystem operation.

Determining Outside Air Quantity:2.I supply and return airlow aremeasured accurately, outside airlowcould easily be determined rom theollowing Equation:

Qsupply

= Qreturn

+Qoutside

Duct Leakage:3. A good duct traversecan also be used to determine ductleakage.

Determining Pump Flow:4. Like measuringairlow on a an, pump lowmeasurements can sometimes be

suspect. Most AB technicians willdetermine low by measuring thedierential pressure between pumpdischarge and pump suction. Byusing the manuacturers pump curveand the pressure measurements, thetechnician can estimate total low.

Sizing Balancing Valves:5. A balancingdevice is similar to a control deviceand should be sized accordingly.Balancing devices should be sized

based on the design pressuredifference at that part of the system.

Fan and Pump Curves:6. Manufacturersperformance curves are graphicrepresentations of measured

performance under laboratoryconditions. The combination offield measurements and associatedcalcu lations can be plotted on the fancurve. If accurate, careful, thoughtfulmeasurements can be taken, themeasured data usually matches the

published data within the normaltolerances of the performance tests.

Buildi Commissioi ad Sstem Balaci



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liters/sec (2,500 cm) and with a coolingcapacity > 22 kW [ECBC 5.3.1.1].

Cotols

Controls determine how HVAC systemsoperate to meet the design goals ocomort, eiciency, and cost-eectiveoperation. he ECBC requires that all

HVAC equipment (>28 kW cooling and/or >7 kW heating capacity) be controlled with a timeclock capable o retaining programming or at least 10 hours,controlling diering schedules or threedierent day types, and have a manualoverride or up to two hours. [ECBC5.2.3]

All heating and cooling systems arerequired to be temperature controlled[ECBC 5.2.3]. Each zone must becontrolled by an individual temperaturecontroller.

3C dead band (5F) is required orequipment that supplies both heating andcooling. Termostats must also preventsimultaneous heating and cooling. [ECBC5.2.3.2]

Further energy savings can be achievedby controlling the uid ow rate in hydronicheating and cooling systems. Very otendemand on these systems is not 100% othe design ow rate. Controls capable oreducing pump rates cut energy costs bymodulating the ow to meet demand. Te

ECBC addresses Variable Flow HydronicSystems [ECBC 5.3.2] in several ways.First, by requiring that pump ow rates becontrollable to either 50% o the design orthe minimum required by the equipmentmanuacturer or proper operation o thechillers or boilers. Second, the ECBCrequires that circulation pumps 3.7 kW(5 HP) in water-cooled air-conditioningunits or heat pumps contain a two-wayautomatic isolation valve to shut of thecondenser water ow when the compressor

is not operating [ECBC 5.3.2.2].Tirdly, the ECBC requires pumpmotors in all hydronic systems 3.7 kW (5HP) shall be controlled with variable speeddrives [ECBC 5.3.2.3]. While thrott lingreduces the ow, the motor is still runningat ull speed and works even harder as it hasto work against a restriction. By reducingthe speed o the motor, the variablespeed drive ensures no more energy thannecessary is used to achieve the requiredow.

Ai Sstem Balaci

Air balancing is a small part o the buildingcommissioning process. Commissioninginvolves the unctional testing o all

components o an HVAC system toinsure proper operation. Commissioningis a systematic process o veriicationand documentationrom the designphase to a minimum o one year ater theconstructionthat all systems perormin accordance with design documentationand intent, and in accordance with the

operational needs. he air-balancing portion o the commissioning process isusually done at the completion o a newconstruction project.

Air balancing should veriy damperoperation and adjust settings to deliverthe designed airow to each zone. It isimportant that some balancing be doneprior to occupancy or several reasons.Some equipment has minimum airowrequirements across the coils to avoidcompressor damage. Generally beoreproject acceptance the building ownerwould like to know that comort conditionscould be maintained in the buildingbeore occupancy, particularly in thewarmer and cooler months. Tis does notnecessarily need to be a detailed room-by-room balance o every register dependingon the requirements o the contract. Tetotal supply, return, and outside airowquantities should be measured or eachair handling system. A detailed balanceis oten done beore occupancy because itis much easier to do measurements when

the building is unoccupied. For smallerbuildings (those under or about 25,000 sq.t.) with relatively uniorm occupancy andequipment levels in each zone, a detailedair balance beore occupancy should beadequate.

Te ECBC requires that air systems bebalanced in a manner to rst minimizethrottling losses; then or ans > 0.75 kW(1.0 HP) the an speed needs to be adjustedto meet design ow conditions. [ECBC5.2.5.1.1]

Hdoic Sstem Balaci

A balanced hydronic system is one thatdelivers even low to all o the deviceson that piping system. Each componenthas an eective equal length o pipeon the supply and return. And when asystem is balanced, all o the pressuredrops are correct or the devices. Whenthat happens, the highest eiciencies are possible in the system, which translatesinto reduced pumping costs.

ECBC also requires hydronic systems to

be proportionately balanced in a mannerto rst minimize throttling losses; then thepump impeller must be trimmed or pumpspeed adjusted to meet the design ow

conditions. [ECBC 5.2.5.1.2] Te ECBCallows the ollowing exceptions to thehydronic system balancing requirement:

Pump motors o 7.5 kW (10 HP) or less,and When throttling results in no greaterthan 5% o the nameplate HP draw, or2.2 kW (3 HP), whichever is greater.

Scale Cotol i Wate-Side

Sstem

In a water-cooled air-conditioning system,heat is rejected rom the rerigerant tothe cooling water in the condenser. heimpurities in the cooling water circuitget accumulated, and thus the scales anddeposits are built up in the condensertubes, creating ouling problems on thecondenser heat transer suraces. hisreduces the heat transer eiciency othe condenser and thus increases chillerenergy consumption. he ECBC requires[ECBC 5.2.6.2] use o sot water orcondensers and chilled water systems.

Distibutio Sstem

Distribution systems carry a heating orcooling medium to condition the space.he two most common distributionsystems use either air or water. Air-basedsystems are oten called orced airbecause they use a an to push the air romthe urnace or air-conditioner through

the duct work to the conditioned space. Water-based systems are oten calledhydronic, and steam-based systems arecalled steam systems, both o which use apiping system to circulate water or steam.

Forced hot air systems are more commonthan hydronic or steam heating systemsbecause they cost much less to install.However, hydronic systems perorm betterthan orced hot air because they leak lessheat, are easier to insulate, make almost nonoise, can be easily zoned and can provide

more even temperatures. Hydronic systemsalso do a much better job o serving aradiant heating system.

Te energy eciency o a distributionsystem depends largely on the design andinstallation quality. Duct distributionsystems are prone to the most signicantlossesespecially i the ducts are poorlysealed and/or installed outside thethermal envelope o the building (inan unconditioned attic, or example).Hydronic systems are typically installedwithin conditioned or bufered spaces like

an unconditioned basement. In either case,it is important to insulate ducts/hot waterpipes that are in unconditioned spaces.

Small commercial buildings typically



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insulation requirements or pipes carry ingluids at dierent temperatures.

Techical Tips fo HVAC

Sstem

Reduce cooling loadAbout hal o the cooling load in aninecient building comes rom solargain and lighting, so careul treatment othese two sources o heat gain can yieldimpressive savings. Well-designed building orm andorientation can maximize daylighting andnatural ventilation, while minimizing

unwanted solar gain and the need orelectric lighting.Appropriate envelope materials,including advanced solar controlglazing, insulation, venting, andlight-colored aades and roos cansignicantly reduce cooling loads andenhance comort.Landscaping and vegetation can costeectively reduce heat gain and provideevapotranspiration cooling whileenhancing esthetics.

Well-designed load-reduction measures

may allow cooling or heating equipmentto be downsized or even eliminated, thusreducing capital cost as well as operatingcost.

System sizing: Rightsizing means sizingthe HVAC equipment to match the coolingand heating load o the building. Inaddition to reducing energy consumptionand costs, rightsizing will:

Reduce noise.Lower rst costs or both equipment and

installation.Reduce equipment ootprint.Control moisture and improve indoor airquality.

use constant volume rootop HVAC units,and a simple duct layout or circulatingconditioned air. Tey are generally un-engineered systems and it is acknowledgedby the construction industry that rst-cost dominates construction practices.Tis leads to short cuts in constructionpractices and/or the use o lower-grade

materials. In the case o duct workthis shows up as sloppy connections,inexpensive leaky difusers, and low-gradeduct tapes. With respect to the HVACequipment this leads to installations andservice techniques that produce degradedequipment perormance.

Te ECBC requires insulating ductsand pipelines to reduce energy losses inheating and cooling d istribution systems.Insulation exposed to weather is requiredto be protected by aluminum sheet metal,painted canvas, or plastic cover. Cellularoam insulation needs to be protected asdescribed above, or be painted with waterretardant paint.

Duct sealing: Duct sealing applies tosupply and return duct work and to plenums that are ormed by part o thebuilding envelope. Proper duct sealingensures that correct quantities o heatedor cooled air will be delivered to the space,and not be lost to u nconditioned spaces orthe outdoors through leaks in the ducts.

his may be one o the most importantconservation eatures to check. A properlysealed duct system will increase thecomort and lower the energy use o thebuilding. Some areas to be sealed include:

Longitudinal seams are joints oriented inthe direction o air ow.ransverse joints are connections o twoduct sections orientated perpendicular toairow.Duct wall penetrations are openingsmade by any screw or astener.

Spiral lock joints in round and at oval

duct need not be sealed.

Duct insulation: As shown in able 3,insulating supply and return ducts inunconditioned spaces and outside thebuilding is an ECBC requirement.

Pipe insulation: Insulating pipelinesreduces energy losses in heating andcooling systems. Besides insulating pipesto save energy, wrapping exposed cold water lines prevents them rom sweating

and collecting moisture in warmerclimates. his will prevent drippingsand condensation that can cause spotsor water damage. ECBC 5.2.4.1 provides

ChillersChiller eciencies have improved in part because o better heat transer(more surace area through more and/or enhanced tubes). Keep these suracesclean to maintain high eciency,either through automatic or annualcleaning. A control system can monitorheat exchanger approach temperaturesand sound an alarm when increasingtemperatures indicate ouling.Select the chiller and cooling systemswhich minimize energy consumption othe building throughout the year. Mostchillers spend most hours at 40 to 70

percent load, not at design conditions.

Air handing units (A HUs)An ecient air system works romthe end-user upstream. Reducing owrequirements by minimizing internaland external heat gains oers potentiallydeep cube-law savings.Matching air supply continuously tocooling and ventilation loads using a Variable Air Volume (VAV) systemprovides the best system eciency.

Arranging air zones logically is key

to making VAV systems ecient andeective. VAV boxes should be groupedto serve areas with similar cooling and ventilation loads (or example, combinecore oces or one zone, south perimeteroces or another, and so on).Displacement air distribution caneciently provide excellent air qualityand heat removal by moving a large masso air slowly, instead o conventionalturbulent induction systems that moveless air at higher speed.

Measuring an power is critical to ensureenergy savings with VAV systems.Exhaust air ans are a viable alternativeto return air ans. Tey have lower

Duct wok Isulatio (mTable 3: 2-C/W) (ECBC Table 5.2.4.2)

Duct Locatiorequied Isulatioa

Suppl Ducts retu Ducts

Exterior R-1.4 R-0.6

Ventilated Attic R-1.4 R-0.6

Unventilated Attic without Roof Insulation R-1.4 R-0.6

Unventilated Attic with Roof Insulation R-0.6 No Requirement

Unconditioned Spaceb R-0.6 No Requirement

Indirectly Conditioned Spacec No Requirement No Requirement

Buried R-0.6 No Requirement

Insulation R-value is measured on a horizontal plane in accordance with ASTMa.C518 at a mean temperature of 24C (75F) at the installed thicknessIncludes crawl spaces, both ventilated and non-ventilatedb.Includes return air plenums with or without exposed roofs above.c.




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role of Tempeatue ad

Humidit

Te inuence o the indoor thermalenvironment on thermal comort is widelyrecognized. Even in laboratory settingswith uniorm clothing and activity levels,

it is not possible to satisy more than95% o occupants by providing a singleuniorm thermal environment (Fanger1970) because thermal preerences varyamong people. Despite the signicantattention placed on thermal comort bybuilding proessionals, dissatisaction with indoor thermal conditions is themost common source o occupantcomplaints in oce buildings (Federspiel1998).

Air temperature and humidity alsoinuence perceptions o the quality oindoor air and the level o complaintsabout non-speciic building-relatedhealth symptoms (oten called sickbuilding syndrome symptoms). Relativehumidities below approximately 25%have been associated with complaints odry skin, nose, throat, and eyes. At highhumidities, discomort will increasedue substantially to an increase o skinmoisture. he upper humidity limits oASHRAEs thermal comort zone vary with temperature rom approximately

60% RH at 26C to 80% RH at 20C.

Sick Buildi Sdome

Te most common health symptomsattributed by building occupants to theirindoor environments are non-specichealth symptoms that do not indicate aspecic disease, such as irritation o eyes,nose, and skin, headache, atigue, chesttightness, and diculty breathing. Tesesymptoms are commonly called sickbuilding syndrome symptoms. In some

buildings, the symptoms coincide with periods o occupancy in the building.Buildings within which occupantsexperience unusually high levels o thesesymptoms are sometimes called sickbuildings. On average, occupants o sealedair-conditioned buildings report moresymptoms than occupants o naturally ventilated buildings. Most studies haveound that lower indoor air temperaturesare associated with ewer non-specichealth symptoms. Symptoms have beenreduced through practical measures

such as increased ventilation, decreasedtemperature, and improved cleaning ooors and chairs (Mendell 1993).

Impact of IEQ o Health ad

Poductivit

Some characteristics o the indoorenvironment, such as temperatures andlighting qual ity, may also inuence worker

perormance without impacting health.In many businesses, such as oce work, worker salaries plus benets dominatetotal costs; thereore, very small percentageincreases in productivity, even a raction oone percent, are ofen sucient to justiyexpenditures or improvements thatincrease productivity.

In a critical review and analysis oexisting scientic inormation, Fiskand Roseneld (1997) have developedestimates o the potential to improveproductivity in the U.S. throughchanges in indoor environments. Tereview indicates that building andHVAC characteristics are associated with prevalences o acute respiratoryinections and with allergy and asthmasymptoms and non-specic healthsymptoms. From analyses o existingscientiic literature and calculations usingstatistical data, the estimated potentialannual nationwide (or the US) beneitso improvements in IEQ include theollowing:

A 10% to 30% reduction in acuterespiratory infections and allergy andasthma symptoms.

A 20% to 50% reduction in acute non-specic health symptoms (commonlyreferred to as Sick Building Syndrome)

A 0.5% to 5% increase in theperformance of ofce work.

Associated annual cost savings andproductivity gains of $30 billion to$170 billion.

Tips to Esue good IEQ

While Desii ad Com-

missioi HVAC sstems

Assure Quality o Intake AirAssuring adequate quality o intake airis essential. Outside air intakes shouldnot be located near strong sources o pollutants such as combustion stacks,sanitary vents, busy streets, loading docks, parking garages, standing water, coolingtowers, and vegetation. he outside airintake must be separated suicientlyrom locations where ventilation air

is exhausted to prevent signiicant re-entrainment o the exhaust air. Incomingair should be ltered to remove particles.

Te recommended minimum particleltration eiciencies vary among IAQand ventilation standards and guidelines.

Maintain Min. Ventilation RatesTe minimum ventilation rates specied

in the applicable code requirements shouldbe maintained or exceeded. Te HVACsystem should be designed so that rates ooutside air intake can be measured using practical measurement techniques. Inbuildings with variable air volume (VAV) ventilation systems, special controls maybe needed to ensure minimum outside airintake into the AHU is maintained duringoperation.

Recirculation o Indoor AirRecirculation o indoor air is standardpractice in some countries, such as India,and discouraged in other countries suchas those o Scandinavia. When air isrecirculated, it should be ltered to remove particles. However, lters are ofen usedonly to prevent soiling and ouling o theHVAC equipment. Tese lters have a verylow eciency or respirable-size particles(smaller than 2.5 micrometers). Use olters that exceed minimum requirementsis an option to improve IAQ, ofen with asmall or negligible incremental cost.

Maintenance o the HVAC SystemRegular preventative maintenance othe HVAC system is necessary to assureproper delivery o outside air throughoutthe building and to limit growth omicroorganisms in the system. Elements o periodic maintenance that are importantor maintaining good IEQ includechanging o lters, cleaning o drain pansand cooling coils, checks o an operation,and checks o operation o dampers that

inuence air ow rates.

Integrated Approach to IEQTe IEQ perormance o a buildingalso depends on the interactions amongbuilding design, building materials,and building operation, control, andmaintenance. Tereore, an integrated orwhole building approach is recommendedto maximize IEQ. Such an integratedapproach may ocus on the ollowing:

IEQ targets or objectives;Occupancy and indoor pollutant

sources and pollutant sinks and theirvariation over time;Building and HVAC design.

Idoo Eviomet Qualit



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For more information:

Dr. Ajay Mathur, BEE ([email protected])

Dr. Archana Walia, USAID ([email protected])

Dr. Satish Kumar, IRG ([email protected])

USAID ECO-III Project

Phone: +91-11-2685-3110

Email: [email protected]

Web Site: www.eco3.org

power requirements, move less air, avoidredundancy, and expel their an heatrom the building.

Duct layout

HVAC duct layout must have a gooddesign that is planned early in theconstruction process and understoodby the designer and HVAC contractor.Every joint and bend in the duct systemaects the eciency o the system.Te duct system must be properlyinstalled with the correct amount oairfow.Te duct system must be air sealed,

insulated and appropriately sized.

Operation and maintenance

Maintain high D chilled water systemswith D up to 9C to increase theoverall energy eciency o chilled waterproduction and distribution.Incorporate variable speed drives or

pumps and ans to eciently meet partialload requirements.Use heat recovery or spaces served byAHUs with high OA component.

Use o thermal energy storage systems inplaces where cooling plays a major role inpeak electricity demand and o peak gridenergy rate is considerably lower than thepeak time rate.Have demand control ventilation or highoccupancy spaces. Use o CO

2sensors in

spaces that have varying people densityloads.Plug leakages in ducts and plenums bysealing o all the joints. Ensure goodduct work quality, workmanship, ductsealing, unctionality o dampers, ductcleanliness and testing.Use o building management system

(BMS) to improve energy eciency.Helps in optimizing the run time oequipment at desired levels o eciency tomaintain building inside temp, humidity,air quality etc within set limits.Reduce ace velocities at coils to increaseheat transer eciency and reducecondensate entrainmentDeploy indoor air quality monitoringand Controls system to monitor CO

2and

volatile organic compound levels.

refeences

E Source (1997): E Source echnol-a.ogy Atlas Series- Volume II: Cooling,Boulder, CO, USA.

Energy Conservation Building Code,b.Ministry o Power, Indian, May 2007.

Fanger, P. O. (1970): hermal comortc.analysis and applications in environ-mental engineering. McGraw-Hill,New York.

Federspiel, C.C. (1998) Statisticald.analysis o unsolicited thermal sensa-tion complaints in commercial build-ings, ASHRAE ransactions 104(1):912-923

Fisk, W.J. and Roseneld, A .H. (1997)e.Estimates o improved productivityand health rom better indoor envi-ronments, Indoor Air 7(3): 158-172.

Mendell, M.J. (1993) Non-speciic.health symptoms in oice workers:a review and summary o the epide-miologic literature, Indoor Air 3(4):227-236.

Nolo, A.P. (2001): A Primer ong.esting, Adjusting and Balancing,

ASHRAE Journal, May 2001.

US Department o Energy (2008):h.Building echnologies Program WebSite (http://www.eere.energy.gov/buildings/).

USGBC (2004): he reatment byi.LEED o the Environmental Impacto HVAC Rerigerants, LEED SACask Force, Washington, DC (http://www.usgbc.org/docs/)

he lack o a direct relationship betweenthe Global Warming Potential (GWP)and the Ozone Depletion Potential (ODP)creates a challenge in developing a ratingsystem that a llows the two environmentalactors to be considered together, as they

should be in evaluating the environmental

impact o an HVAC system. In the absenceo perect or ideal rerigerant we shouldollow a trade-o approach to identiy abetter combination o HVAC equipmentand its rerigerants to acilitate optimumenvironmental impact in terms o GWP

and ODP per unit o cooling capacity.refieat ODP gWP Applicatio

CFC-11 1 4600 Centrifugal chillers

CFC-12 0.82 10600 Freezers, chillers, air conditioners

HFC-410A 0 2000 Air conditioning

HCF-134a 0 1600 CFC-12 replacement

HCFC-123 0.012 120 CFC-11 replacement

Eviometal Tips (Souce: USgBC, 2004)


HVAC System Tip Sheet

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