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INCREASING ENERGY EFFICIENCY

IN BUILDINGS PROJECT CHINA

LEARNING UNIT 04

ENERGY EFFICIENT HVAC SYSTEMS

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Source Document

DESSAU-SOPRINBuilding Engineering

Prepared by: Marie-Judith Jean-Louis, E.I.T.

Martin Par, P.Eng.

Laurier Nichols, P.Eng.

Dessau-Soprin Inc.1441 Ren-Lvesque Blvd. West, Suite 500

Montreal (Quebec) Canada H3G 1T7Phone: (514) 281-1010

Fax: (514) 875-2666Email: allen.zhai@dessausoprin.com

Website : www.dessausoprin.com

June 2002O/Ref.: 680514

mailto:allen.zhai@dessausoprin.comhttp://www.dessausoprin.com/http://www.dessausoprin.com/mailto:allen.zhai@dessausoprin.com

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TTAABBLLEEOOFFCCOONNTTEENNTTSS

Page

4

AIR CONDITIONERS....................................................................... 1

4.1

INTRODUCTION .....................................................................................................1

4.2

ROOM AIR CONDITIONERS ..................................................................................... 2

4.2.1

Description ........................................................................................................................................ 2

4.2.2 Operation.......................................................................................................................................... 3

4.3

CENTRAL AIR CONDITIONERS ................................................................................ 6

4.3.1

Description ........................................................................................................................................ 6

4.3.2 Operation.......................................................................................................................................... 8

4.4

EFFICIENCY AND PERFORMANCE ...........................................................................9

4.4.1 Energy Efficiency Regulations................................................................................................................ 9

4.4.2 Sizing ............................................................................................................................................. 11

4.4.3 Dehumidifying .................................................................................................................................. 12

4.5

MAINTENANCE ....................................................................................................12

4.6

AIR CONDITIONERS IN CHINA ...................................................................... 14

4.6.1 Introduction ..................................................................................................................................... 14

4.6.2

Chinese Room Air Conditioners ........................................................................................................... 15

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4 AIR CONDITIONERS

4.1 INTRODUCTION

The American engineer Willis Haviland Carrier (1876-1950) is considered to be the father of air

conditioning. He was the first to develop a safe, low-pressure centrifugal refrigeration machine

using non-toxic and non-flammable refrigerant, capable of controlling the humidity and the

temperature in a room. The formulas he worked out and the equipment he used are the basis of

todays air conditioning units.

The air conditioner is a space cooling and dehumidifying unit. There are two basic types of air

conditioners: the room air conditioner and the central air conditioner, both described in more

detail in the next sections. Each of them has its benefits and limitations.

Room air conditioner: Room air conditioners tend to be less expensive than central air

conditioners. They provide zonal cooling. These types of systems dont take much space in a

house and are easy to install. However, they can only condition a small number of spaces and

have a tendency to be noisy because the compressor is situated within the living space it is in.

The cooling efficiency is lower than a central unit because of the installation of only basic

controls.

Central air conditioner:Unlike room air conditioners, central air conditioning units provide

space cooling for the entire house and generally have a larger cooling capacity. On the other

hand, they are more expensive, cost more to install and cost more to operate.

The present chapter will be discussing the different types of air conditioners, their operation and

application.

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4.2 ROOM AIR CONDITIONERS

Description4.2.1

A room air conditioner (Figure 4.2.1) is a small electrically powered unit in an encased assembly

designed to deliver cool conditioned air into a small area, usually one room. These units do not

require any ductwork. There are three main types of room air conditioners: the window-mounted,

the wall-mounted and the portable room air conditioners.

Cooled Room Air

Filter

Warm Room Air

Evaporator

Compressor

Flow Restriction

Fan Motor

Blower

CondenserDischarge Air

Condenser

Outside Air

Figure 4.2.1 Typical Room Air ConditionerSource: Office of Energy Efficiency

Window-mounted: Window-mounted air conditioners can be installed in single and doublehung windows, horizontal sliding and casement windows. These systems are one of themost economical to use when only one room requires cooling.

Wall-mounted:Wall-mounted units are essentially the same as the window-mounted units.

They are also one of the most economical units to use to cool only one room.

FreeStanding Portable: Freestanding portable units are provided with casters, which makethem easy to move from room to room. These units are very economical and practical ifdifferent rooms need to be cooled alternatively, according to the needs of the occupants. In

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this case, moisture from the air is either collected in a built-in tray or sent outdoors throughtemporary coupling sleeves.

Operation4.2.2

Just like a refrigerator or a heat pump in cooling mode, the room air conditioner works by

extracting heat from the space to be cooled and transferring it outside that space. It is important

to note that no fresh air enters the house. The heat transfer is done through the refrigerant lines

but no air is exchanged between the indoor and the exterior. The indoor air is simply cooled,

dehumidified, filtered and returned back in the room. The main components of the room air

conditioner are the condenser, the evaporator, the compressor, the fan, and the refrigerant lines.

The cooling cycle (Figure 4.2.2) operates the same way as the cooling cycle of an air-source

heat pump does, as discussed in the previous chapter. The cooling cycle diagram shows that the

refrigerant goes through four main states (Figure 4.2.3 to 4.2.6) during the cooling process.

Cool dried air Warm moist air

Condenser

Expansion Valve

Evaporator

Air Flow

High-Pressure,High-Temperature Vapour

High-Pressure,High-Temperature Liquid

Low-Pressure,Low-Temperature Liquid

Low-Pressure,Low-Temperature Vapour

CompressorCompressor

Figure 4.2.2 Basic cooling cycleSource: Office of Energy Efficiency

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Low-PressureLow-Temperaturevapor

Low-PressureLow-Temperatureliquid

Figure 4.2.3 Evaporation process

Air Flow

Warm moist air

Low-PressureLow-Temperature Liquid

Low-PressureLow-Temperature Vapour

EVAPORATOR

A fan blows the warm, moist room air to be conditionedthrough the evaporator containing the circulating refrigerant.

As the warm air passes the evaporator, the low-pressure and

low-temperature liquid refrigerant absorbs the heat from the

air and evaporates to become a low-pressure, low-

temperature vapour. During the evaporation process of the

refrigerant, the tube and the fins of the evaporator cools

down, and the moisture from the air condense on the outer

surface of the evaporator. The air that passes through the

evaporation is cooled and its humidity is removed.

COMPRESSOR

High-PressureHigh-Temperature

Vapour

Low-PressureLow-TemperatureVapour

Figure 4.2.4 Compressing process

The cooled air is returned to the room while the low-pressure

and low-temperature vapour refrigerant is sent to the

compressor, which will raise the pressure and the

temperature of the refrigerant by compressing it. The

refrigerant is then a highly pressurized vapour at high

temperature.

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Once the temperature and the pressure of the refrigerant have

been raised by the compressor, it passes through the condenser.

A second fan blows outdoor air onto the condenser in order for

the heat from the refrigerant to be released into the outside air. In

an ideal case scenario, the refrigerant returns to a liquid state

with high temperature and high pressure. However, most of the

time, the refrigerant will return to a mix of liquid and gas at high

pressure and high temperature.

High-PressureHigh-Temperatureliquid

High-PressureHigh-Temperaturevapour

Cool dried air

High-Pressure

High-Temperatureapour

High-PressureHigh-Temperature

Liquid

Figure 4.2.5 Condensation

process

CONDENSER

The high temperature refrigerant at high pressure goes through

the expansion valve where it loses its pressure. Its temperature

is lowered because of the evaporation of refrigerant at this low

pressure. The refrigerant returns to its initial low-pressure and

low-temperature liquid state and the cycle can then be

repeated.

High-PressureHigh-Temperatureliquid

Low-PressureLow-Temperatureliquid

Figure 4.2.6 Expansion process

Low-PressureLow-Temperature

Liquid

High-PressureHigh-TemperatureLiquid

EXPANSION VALVE

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4.3 CENTRAL AIR CONDITIONERS

Description4.3.1

The central air conditioner is designed to cool an entire house through a system of supply and

return ducts. It is composed of an outdoor unit and an indoor unit. A large compressor and a coil

unit are located outdoors and connected by refrigerant lines to the indoor unit composed of a coil

unit and a fan. In some cases, the indoor coil can be mounted in a furnace, as shown in Figure

4.3.1, and the same duct system can be used to heat or cool the house.

ExpansionDevice

Compressor

Outdoor Coil

apourRefrigerant Line

VapourRefrigerant Line

OilBurner

Warm Air Supply Plenum

FurnaceBlower

Add-OnIndoorCoil

Cool AirReturn

Figure 4.3.1 Typical Central Air Conditioner with furnaceSource: Office of Energy Efficiency

Central air conditioners come in various types: the single-package, the split-system, the mini-split,

the mini-duct, and the water-cooled unit.

Single-Package:In the single-package unit, also called the packaged air conditioner, all the

elements are combined in one unit and the conditioned air circulates in a system of supply

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and return ducts. This type of unit is usually mounted on top of a roof or on a concrete slab

next to the houses foundation and going through a wall. This type of system often includes

an electrical heating coil or a natural gas furnace, which eliminates the need for an additional

heating system.

Split-System:The split-system unit is composed of an indoor unit and an outdoor unit. The

indoor unit is connected to the outdoor unit through refrigerant lines and can be mounted on

a furnace. This system resembles the air-source heat pump.

Mini-Split:The mini-split system contains an outdoor unit and 2 or 3 indoor units. This type

of system resembles the split-system unit but does not require any ductwork. The indoor

section is usually mounted on an interior wall, a ceiling or a floor. This type of system is ideal

for houses with new additions. Its lower efficiency has to be taken into consideration.

Mini-Duct:The mini-duct unit also has an indoor and an outdoor component. The indoor

component is generally installed in the attic. Plastic pipes installed in partition walls distribute

both the conditioned air and return air through inlets and outlets. This type of system is ideal

for retrofitted houses where electric or hydronic baseboards are already installed.

Water-Cooled: The water-cooled unit is a system that can be connected to water well or

city water where it is permitted. This type of system is usually not permitted or is used with

restriction in Canada.

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Operation4.3.2

Typical central air conditioners work like room air conditioners, as explained previously. Through

the circulation of the refrigerant, heat is transferred from the space to be conditioned to the

exterior, as shown in Figure 4.3.2.

Cool Indoor AirFan

Inside Coil

Low-Pressure

Low-Temperature Vapour

High-PressureHigh-Temperature Vapour

Outdoor Coil

Compressor

Expansion Device

RefrigerantRelease Heat toOutside Air and

Returns to aLiquid State

Refrigerant AbsorbsHeat from Air andBoils to a VapourState

Low-PressureLow-Temperature Liquid

High-PressureHigh-Temperature Liquid

Figure 4.3.2 Compressor Cycle of a Central Air Conditioner

Source: Office of Energy Efficiency

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4.4 EFFICIENCY AND PERFORMANCE

Air conditioners in Canada have an energy efficiency-rating label that gives information to

consumers on how many Btu per hours of heat is removed for each watt of power supplied to the

unit. For room air conditioners, the energy efficiency rating is the Energy Efficiency Ratio (EER),

while for the central air conditioner the energy efficiency rating is Seasonal Energy Efficiency

Ration (SEER).

Room Air Conditioner:Most room air conditioners range from 5,500 Btu to 14,000 Btu. In

North America, the EER of window-mounted air conditioners can vary between 8.0 and 12.0,

while the EER of wall-mounted air conditioners usually ranges between 8.0 and 8.5. Highly

efficient room air conditioners will generally have efficient rotary compressors, largeevaporators and condensers, efficient fans and slinger rings to deposit water collected from

the evaporator onto the hot condenser.

Central Air Conditioner:The split-type central air conditioner is required to have a minimum

SEER of 9.7, while package-type central air conditioners are required to have a minimum

SEER of 10.0. Currently, some central air conditioners reach a SEER of 17.0. Energy

efficient central air conditioners differentiate themselves from conventional systems by using

components such as more efficient compressors, larger and more effective heat exchanger

surfaces and better refrigerant flow.

Energy Efficiency Regulations4.4.1

In Canada, the room air conditioner and the central air conditioner are both covered by the

federal Energy Efficiency Regulations. Air conditioners are required to meet minimum energy

efficiency standards of performance in order to be either imported in Canada or shipped abroad.

Room Air Conditioner:Room air conditioners are required to carry an EnerGuide label. The

purpose of this label is to accurately inform customers about the relative energy efficiency of

these units. The EnerGuide contains information about the energy efficiency ratio (EER) of

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the room air conditioner, a scale that compares its EER with other models from the same

class of air conditioner, and the type of unit. Room air conditioners are grouped into louvred

or non-louvred units and classified according to the category of cooling capacity they belong

too.

Figure 4.4.1 is an example of an EnerGuide label showing: (A) the energy efficiency ratio of

the room air conditioner, (B) the energy efficiency ratio of the least energy efficient model and

(C) the energy efficiency of the most energy efficient model compared to others that fall

within the same class as the model tested, (D) the energy efficiency ratio indicator, and (E)

the type and the cooling capacity range of the model tested and similar models compared.

Figure 4.4.1 EnerGuide label (EER)Source: Office of Energy Efficiency

Central Air Conditioner:Central air conditioners are also required to carry an EnerGuide

label. However, the seasonal energy efficiency ratio (SEER) is used in the regulations for

this type of system. As for the EnerGuide for the room air conditioner, the one for the

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central air conditioner contains information about the SEER of the model being tested, and

its comparison with other models (Figure 4.4.2).

Figure 4.4.2 EnerGuide label (SEER)Source: Office of Energy Efficiency

Sizing4.4.2

The capacity of an air conditioner depends on the size of the house or rooms to be conditioned,

window exposure, size and orientation, the material used in the construction of the house, the

level of insulation, air infiltration, internal heat gains and the lifestyle of the inhabitants. It is

important not to oversize an air conditioner because although it will cool the air faster, it will not

run long enough to properly dehumidify the space to a comfortable level, as explained in the

previous chapter.

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Dehumidifying4.4.3

The dehumidifying process requires a substantial amount of energy, which reduces the efficiency

of an air conditioner. Many manufactures reduce condensation by keeping the condenser

somewhat warmer to help improve the efficiency of the unit. As a result, some of the new high-

efficiency air conditioners do not dehumidify as effectively as other systems. Some air conditioner

models have a humidistat that controls the speed of the fan in order to help reduce the humidity.

4.5 MAINTENANCE

Regular maintenance of an air conditioner ensures its longevity and its efficiency. Failure to

properly maintain the unit will reduce its efficiency while increasing its operational cost. The

following is a list of maintenance procedures necessary to protect the efficiency of an air

conditioner.

Unit Location:When possible, the outside compressor unit should be located in the north

side of a house or where there is the most amount of shade, when possible, to reduce the

work provided by the unit and increase its efficiency.

Outside Compressor: The outside compressor should always be kept clean and free of

grass, twigs or leaves as they could cause the compressor to overheat and therefore

seriously damage the unit.

Window Units: If a window unit is left in place in the winter, the portion inside should be

wrapped and weather-stripping should be added around the unit to block the infiltration of

cold air into the house. It is important not to wrap the portion of the unit located outdoors

because the warm, moist air from inside the room could infiltrate the unit. If this were to

happen, the water contained in that air would freeze and cause serious damage to the unit.

Filters:The filters of an air conditioner should be replaced and cleaned regularly. Failure to

do so will result in a significant reduction of the efficiency of the system. Dirty or clogged

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filters will reduce the airflow and the dirt will most probably be carried directly to the

evaporator coil, and alter its heat absorbing capacity.

Coils:The evaporator and the condenser coils will inevitably collect dirt over their years of

service. The dirt will act as an insulation film and reduce the transfer of heat between the

coils and their environment. It is therefore important to check and clean the coils regularly.

The fins of the coils are also easily bent. They should be straighten back to their original

position in order for the airflow not to be blocked, which would reduce the efficiency of the air

conditioning system.

Ducts: 10% to 30% of the air from conventional systems is lost through duct leakages. In

order to limit duct leakage, a professional using the necessary test equipment should inspect

the duct. They should be sealed with mastic and should be airtight in order for the system to

be efficient.

Temperature differences between the ducts and the duct space causes heat transfers. For

this reason, it is important to insulate air ducts to save energy. In many cases however, the

cost of insulation will be greater than the potential energy savings of insulating the ducts. This

is why, in the majority of homes using ducts to circulate cooled air, the ducts will not beinsulated.

Obstruction:Obstruction can be as unfavorable as air leakage and reduce the efficiency of

an air conditioner. It is important not to block the flow of the air supply or the air return with

objects like furniture or drapes.

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4.6 AIR CONDITIONERS IN CHINA1

4.6.1 Introduction

The Shanghai Refrigerator Factory was the first to produce a Chinese air conditioner in 1963. Atthat time, air conditioners were not very popular because the consumption standard at the time

was low and power companies imposed very strict policies with regard to the use of electricity.

The production of air conditioners in China started slowly but has accelerated rapidly since the

mid-80 due to the increase in Chinese living standards and the changing attitudes towards

energy consumption.

In 1989, the State Bureau of Quality and Technical supervision approved the National Standard

GB12021.3 Room Air Conditioner Energy Consumption Limits and Testing Method established

by the National Technical Committee for Energy Basis and Standardization of Management. One

year later, this standard went into effect as the second of the first 8 standards developed for

household appliances. The implementation of this standard created a stimulus to increase the

production of more energy efficient air conditioners and to purchase models of a higher quality.

As a result, the production of Chinese air conditioners started to increase from 1990 onwards

(Figure 4.6.1).

1The information in the following section comes primarily from a report entitled Technical and Economic Analysis of

Energy Efficiency of Chinese Room Air Conditioners (Fridley et al., 2001). An analysis of Chinese room airconditioners was conducted in order to evaluate the Chinese National Standard GB12021.3 (1989) and proposechanges. The purpose of this section is to give some basic information on the background and status of airconditioners in China. For more information, please refer to the above-mentioned report.

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Currently, air conditioners are one of the top three household electricity consumers, along with

lighting and refrigerators. During the summer months, air conditioners are the largest consumers

of domestic electricity. The Chinese market is increasing at a very rapid pace. According to a

China Statistical Bureau evaluation, in the three years between 1995 and 1998, the production of

air conditioners increased by 125%. The demand and production of air conditioners in China is

expected to continue to grow in the years to come.

Figure 4.6.1: Air Conditioner Production, 1980-1998Source: Fridley et al., 2001

Chinese Room Air Conditioners4.6.2

In the GB1202.3 (1989), air conditioners were classified in six groups according to the

configuration of the unit and its cooling capacity, as shown in the following table (Table 4.6.1).

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Table 4.6.1 Types of room air conditioners from GB12021.3

Configuration of the unit Cooling Capacity (thermal watts)

Split Below 2500 W Window-type Between 2500 W and 4000 W

Above 4500 WSince air conditioners were changing, China issued another standard called the GB/T7725

Room Air Conditioners in 1996. This standard classifies air conditioners into 14 types according

to their cooling capacity under different climate conditions, their structure and their function as

shown in the following table (Table 4.6.2).

Table 4.6.2 Types of room air conditioners from GB/T47725

Maximum Cooling Capacity Type of Structure Type of function

Class T1 Single packages Cooling only Class T2 Split Heat pump Class T3 Cooling with electrical components

After studying Chinese air conditioners, Fridley et al. proposed the following design options that

would increase the efficiency of the air conditioners.

Increase the heat transfer surface area by improving the performance of the coil Improve heat transfer rate Increase the efficiency of the compressor Increase the efficiency of the fan and fan-motor

Integrate control systems Integrate a flow control device Use alternative refrigerant

According to their analysis, if an EER standard2of 2.92 W/W had come into effect in 2001, over

3.5 billion Yuan would be saved between 2001 and 2020, while carbon emissions would be

reduced by 12 million metric tons. Consequently, increasing the efficiency of air conditioners will

have a significant impact on energy costs and the polluting levels of residential households in

China.

2 An EER of 2.92 W/W in China corresponds to an EER of 9.97 Btu/h / W in North America.

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REFERENCES

ASHRAE, 1996 HVAC System and Equipment Handbook, American Society of Heating, Refrigeratingand Air-Conditioning Engineers Inc., Inch-Pound Edition, Atlanta, United States, 1996FRIDLEY, David; ROSENQUIST, Gregory; LIN, Jiang; AIXIAN, Li; DINGGUO, Xin & JIANHONG,

Cheng; Technical and Economic Analysis of Energy Efficiency of Chinese Room Air Conditioners;[1] Energy Analysis Department, Environmental Energy Technologies Division, Lawrence Berkeley NationalLaboratory, University of California, USA; [2] China National Institute of Standardization (CNIS), Beijing,China; [3] Beijing Energy Efficiency Center (BECon), Beijing, China; LBNL-45550; February 2001, 56pagesENERGY EFFICIENCY AND RENEWABLE ENERGY NETWORK (EREN), Energy-Efficient AirConditioning, Consumer Energy Information: EREC Fact Sheets, U.S. Department of Energy, DOE/GO-10099-379, FS 206, last update: June 1999, http://www.eren.doe.gov/erec/factsheets/aircond.htmlMISSOURI DEPARTMENT OF NATURAL RESOURCES, Residential Energy Efficiency AirConditioning, Energy Center, Residential Energy Efficiency,last update: September 08 2000,http://www.dnr.state.mo.us/de/residential/airconditioning.htm

MASSACHUSETTS INSTITUTE OF TECHNOLOGY, William Haviland Carrier, The Lemelson MITAwards Program, Invention Dimension, Inventor of the Week Archives, last update: June 2001,http://web.mit.edu/invent/www/inventorsA-H/carrier.htmlNAGYSZALANCZY, Sandor, Getting Your Air Conditioner Ready for Summer, Corner Hardware,http://www.cornerhardware.com/html/articles/art50.htmOFFICE OF ENERGY EFFICIENCY (OEE), Air Conditioning Your Home, Natural Resources Canada,Cat. No. M91-23/7, ISBN 0-662-26590-4, 1998, http://energy-publications.nrcan.gc.ca/pub/home/Air_Conditioning_Your_Home.cfm

http://www.eren.doe.gov/erec/factsheets/aircond.htmlhttp://www.dnr.state.mo.us/de/residential/airconditioning.htmhttp://www.dnr.state.mo.us/de/residential/airconditioning.htmhttp://www.dnr.state.mo.us/de/residential/airconditioning.htmhttp://web.mit.edu/invent/www/inventorsA-H/carrier.htmlhttp://www.cornerhardware.com/html/articles/art50.htmhttp://energy-publications.nrcan.gc.ca/pub/home/Air_Conditioning_Your_Home.cfmhttp://energy-publications.nrcan.gc.ca/pub/home/Air_Conditioning_Your_Home.cfmhttp://energy-publications.nrcan.gc.ca/pub/home/Air_Conditioning_Your_Home.cfmhttp://energy-publications.nrcan.gc.ca/pub/home/Air_Conditioning_Your_Home.cfmhttp://energy-publications.nrcan.gc.ca/pub/home/Air_Conditioning_Your_Home.cfmhttp://www.cornerhardware.com/html/articles/art50.htmhttp://web.mit.edu/invent/www/inventorsA-H/carrier.htmlhttp://www.dnr.state.mo.us/de/residential/airconditioning.htmhttp://www.eren.doe.gov/erec/factsheets/aircond.html