Fine tuning air conditioning and refrigeration systems

of the air, is usually all that is needed to determine the efficiency of the unit, or more of these operating factors usually unit.. The best temperature rise of an electric heating unit

air co~ditio~ing and refrigeratio~ systems/

ting machinery” air 4 Air condition in^"

Refrigera~o~ and refrigera~g machinery

Fine t~ning air ~onditioning and re~ige~ation s ~ s t e ~ s ~ i l l ~ C ~ ~ g l e ~

002 by The F ~ i r m o ~ t Press All rights reserved No part of this ~ublication may be

itted in m y form or by any means, ~~ectronic or ~ ~ c h a ~ i c a l , includin

or any i ~ f o ~ a t i o n storage and retrieval system, without erm mission

in w r i ~ g from the publis~er

Published by The Faimont Press, Inc

700 Indian Trail

Lilburn, GA 30047

Printed in the United States of America

While every effort is made to provide dependable information/ the publisher, authors, and editors cannot be held

responsible for any errors or omissions

Distributed by Prentice Hall PTR

Prentice-Hall, Inc

A Simon & Schuster Company

Upper Saddle River, NJ 07458

Prentice-Hall Inte~ational (UK) Limited, London

Prentice-Hall of Australia Pty Limited, Sydney

Prentice-Hall Canada Inc., Toronto

Prentice-Hall Hispanoamericana, S.A., Mexico

Prentice-Hall of India Private Limited, New Delhi

Prentice-Hall of Japan, Inc., Tokyo

Simon & Schuster Asia Pte Ltd., Singapore

Editora Prentice-Hall do Brasil, Ltda., Rio de Janeiro

This manual was written to provide the service t e c ~ i c i a n with the proce- dures necessary to bring heating, air condition~g, and ref~geration sys- tems, including heat pumps, to full operating e~iciency This manual was not intended to present "standard" service procedu~es but rather to pro- vide advanced i n f o ~ a t i o n and procedures that, when followed, cause the e~uipment to operate as it was designed by the manufac~rer

en used properly, the procedures presented in this manual will ensure

ment operates more economically and to full capacity an has a longer life with a minimum amount of repairs

It would have been im

manuf~cturers and friends who are conc with this indus- con~ibutions over the past 35 years have a manual of this

le They have been m

e this text feasib those companies and individuals who value this dust^ as much as I

do

ere are many reasons for fine ~ i n g heating, air condi~oning/ and refrig- eration equipment/ such as energy conservation, cost effectiveness, less need for new power plants, improved perfo~ance, and equipment longev-

ity It is true it takes more time to fine tune equipment so that it operates

at peak efficiency/ and this comes at a greater cost to the customer How-

enefits are properly explained, most are willing to pay the service fee, which is usually saved many times over through the more ef-

onomical operation of the e~uipment Also, the technician ility and desire to fine tune equipment can charge extra for ill always be in demand by the public

cause of the constantly dec ' of oil, every possible step must made to conserve its use ating, air conditioning/ and re-

ration e ui ment is a very good place to start, because air conditioning

est users of electricity in residential and many commercial heating, air conditioning/ and refrigeration units are oper- ciency this percentage of power consumption is reduced much as 25% Several tests have proven that nine out of

eration units are operating at a re- duced efficiency that is between 10% and 40% of their rating

ition~g, and refrigeration equipment is operating and the cost of operation is reduced Thus, the

customer is saving money When the technician fine tunes the equipment so

it operates more economically, the customer is more satisfied and is much more pleased with the service provided The service technician can usually charge more for providing this fine tuning service, because the customer is more willing to pay for d, thorough service that ensures the e~uipment

is operating as des cause of this, both ties are satisfied and the

customer is more a mend the technic to others who may want this type of service

When heating, air conditioning, and refrigeration equipment is working at peak efficiency, power generating plants c m be operated at less than h11 capacity The power company not only saves on operatin expenses, but the need to build new power plants to furnish power to inefficiently operating equipment is no longer a considera~on Thus, the need for costly power plant construction and operation is eliminated

Properly tuned heating, air conditioning, and refrigeration equipment per- forms better than equipment that is not properly adjusted The customer will be more satisfied with the operation of fine tuned equipment In addi- tion, the unit will keep the building more comfortable, the process refrigera- tion and heating equipment will satisfy the demands much more easily, and there will be less service and maintenance required

Fine tuned equipment has the proper amount of refrigerant and oil flowing through the system to maintain properly lubricated components at their de- sired operating temperatures Properly lubricated equipment operating at the desired tem~erature usually lasts much longer than equipment that does not have these characteristics Thus, the customer is saved the cost of having to replace the equipment, and major repairs are either eliminated or postponed to a much later date

A check of the operating refrigerant pressures and temperatures, along with

determining the airflow through the unit and the temperature rise or drop

of the air, is usually all that is needed to determine the efficiency of the unit,

or more of these operating factors usually unit Of course, the ductwork,, insulation, and the condition of th re will determine, to a great extent, whether

or not the system will the desired conditions inside the building

All of these factors must be considered when fine tuning equipment to ensure more complete customer satisfaction member, the best equipment will not perfom if it is insta llation is also a part of fine ing a unit The unit ma peak efficiency,, but if the con- oned air cannot reach t S not properly distributed, the result will still be or ope ratiộ Give the ins~ãlation a thorough inspec- tion, and inform customer of anything that can,, or must, be done to obtain optimum efficiency an

This Page Intentionally Left Blank

of the amount of heat input to

vered by the hrnace

in both residential and commercial applica-

ree-phase element designs

it is important that electric prevent drafty conditions

units is probably the units available The

e proper test hstr

ny rate, accurate test

inst~ments must be used for testing the efficiency of electric heating units The exact procedures for inst~ment use are found in the manufacturer’s operating il~structions The inst~ments must be properly cared for an their accuracy maintained for optimum performmce

This chapter will discuss the specific procedures used to fine tune electric heating units, not specific inst~ments The following is a list of the basic test inst~ments required for testing and adjusting the efficiency of electric heating units:

1 Dry bulb thermometer

3 Voltmeter (a w a t ~ e t e r eter er may be used in lace of the ammeter and

v o l ~ e t e r )

A dry bulb (db) thermometer is used for checkin

2-1 ~ e t e r ~ ~ n g the temperature rise of the ai

heating unit is a very important step in the fine ~ nprocess The dry gbulb tempera~re is a measure of the heat absorbed from the heating ele- ments by the air The air temperature is measured in two locations: the return air stream and the discharge air stream, Figure 2-2

the tempera~re readings after the mixing of my air and within 6 ft of the

air handling unit The thermometers must be placed where the radiant heat from the elements cannot be measured by the thermometer Radiant heat can cause a faulty tempera~re reading and an incorrect test

Two different thermometers that have been tested an found to produce exactly the same r e a d ~ g s under the same set of cir~mstances should be used If two thermometers that read exactly the same tempera~res are not

ry bulb t~ermom~ters (Cou~esy, wyer Instruments, Inc.)

circulatin~ air te~p~rature

available, then use one thermometer to measure both temperatures An

~ o m e t e r that has se arate, properly adjusted leads also pro- ired results The best temperature rise of an electric heating unit is about 40” to 50°F S the blower to run longer,

the air more evenly thro~ghout the building

e ammeter is used to determine the amount of electrical current used by

-on type ammeter is the most popular, because the

be measured without separating the wire These in s t ~ m e n t s ccurate when the wire being measured is in the center of the

The voltmeter is used to meas~re the voltage in a wire, Figure 2-3 The

-type meter is the most accurate when the indicator is in the center

of the scale The 1 be checked regularly to ensure they are in

n the insulation becomes worn or cracked, firm, solid fit between the meter and the fitting lead can give an improper voltage

Figure 2-3 ~ i g i t a l multimeters (Courtesy, AM Sperry Instruments, Inc.)

e wattmeter is used to measure the voltage to the unit and the total wattage used by the unit ese i n s t ~ m e n t s are usually more accurate than voltmeter and ammeter to determine the total wattage used by the unit wever, w a t ~ e t e ~ s are more expensive The analog-type w a ~ e t e r is the most accurate when the indicator is reading at the mid-scale point

ending on the size and type of installation/ bo single- and three-phase heating elements are used When d e t e ~ i n i n g lowatt input, be sure to measure the total voltage and amperage to the unit, including the fan motor, because it also adds heat to the air en more than one heatin element is used, check the fan motor separately to prevent adding the motor amperage to each element The meas~rements should be taken at a close d i s c o ~ e c t switch or where the electrici~ enters the unit, not at a distant point

To d e t e ~ i n e the c a p a c i ~ of an electric heating unit, first d e t e ~ i n e the

tu input to the unit by p e r f o ~ i n g the following steps:

appropriate formula:

6 Determine the AT by using the following steps:

a Allow the unit to m continuously for about ten minutes

b To avoid t h e ~ o m e t e r error, U

c Measure the temperatu~s at a point where the thermometer can- sure the return and supply air te

not "see" the heat source (see F

cannot be measured when radia

eter

d The air temperature measur~ments must be taken within 6 ft of the air handling unit The return air temperature can be taken at the return air grille if it is located close to the unit, as in Fi

2 The air temperature taken at the supply air grille is not usually accurate enough for this purpose

e M e n more than one discharge or return air uct is connected to the plenum, use the average rature (AT) For example,

1 = 115"F, Duct 2 = llO°F/ Use the f o l l o w ~ g formula:

AT =

Number of ducts

f Be sure to ta the temperature measurements after any source of

7 Check the manufac~rer's speci~cations for the par~cular unit to see

mixed air, such as a fresh air intake

if these conditions meet the design criteria

en the cfm is too high, slow the blower n the discharge cfm is too low, speed up the blower en a direct drive motor is used, the cfrn can

be changed by moving the electric wire to a lower or higher speed t e ~ i n a l

en a direct drive motor c a ~ ~ t be wire to deliver the correct cfm/ use

e the air inlet to the blower Be sure to make

otor to prevent overheatin cfmf and secure

f sheet metal cut

lower is used, the cfm can be c

r shaft To incre~se the the pulley halves

t e ~ ~ e r a t ~ r e ~ i r e ~ ~ r ~ ~ air t e ~ ~ e r a t ~ r e ~ s

city b t is not heat

ure the cfm from each one, and total them If the

insulation

t

en the duct system meets this criteria, the only other alternative is to more capacity This c m be done by either adding more heat strips or installing some with higher capacity ratings Table 2-1 lists the tempera~re rise, the k W rating of the furnace, and the corres~onding cfm This informa- tion can be used to reduce the time required to get a very close estimate of

how efficient the unit is operating

S about insu~icient heat from an electric heating unit, th heating elements are delivering the amount of heat they W

at one or more of the heating elements is not operating properly This is

is easily pe~ormed

er, voltmeter, accurate thermometer, and tool kit An accurate wa~meter may

rocedures:

electricity to any other equipment that is used in conjunction with the electric h

et the thermo~tat to d e ~ a n d heat Allow the heater to operate for approximately 10 minutes so the tempe

tures will st~bilize

easure the voltage an amperage of each heating element and record:

Volts Amps otor: 1

etermine the cfm of the blower and record Use the following instructions:

* Use the same thermometer, or two that measure exactly the some, to measure the return and supply air temperatures

* Do not measure the temperature in an area where the thermometer can sense the radiant heat from the heat strips (see Figure 2-2) True air temperature cannot be measured if the thermometer senses radiant heat

5 Take the temperature measurements within 6 ft of th n at the return and

supply grilles that are at too great a distance from the unit are not usually accurate enough

* Use the average temperature when more than one duct is connected to the supply air plenum

* Be sure the air temperature has stabilized before taking the temperature measurements

5 Take the temperature measurements downstream from any source of mixed air Use the following formula:

cfrn = Btu

1 .Q8 x AT cfm =

7 Is this what the manufacturer rates the e~uipment?

ultiple tear-out copies

of this worksheet

The purpose of adjustin the e ~ c i e n c y of any piece of equipment is to deliver the most energy ossible to the conditioned space or process The

efficiency of a gas-fired furnace or boiler is the difference between the input and the actual amount of heat produced by the unit The efficiency adjust- ment must provi ain without producing undesirable condi-

tions In mathematical terns, efficiency is explained as:

also affected There is r or r to follow when making efficiency

ral categories of these factors are as follows:

e c o m b ~ ~ o n process

rtant part in overall unit

r are mixed in the proper

set this gas-air relations hi^, th

tion Therefore, the burner m

re are several factors that aff

unit’s e~iciency, such as the

r m ~ x ~ g of the

gas and air

e proper test ~ s t ~ m e n t s are

is chapter will discuss th

heating units, not sp~cific i list of basic test

~ s ~ r n e ~ t s re the efficiency of

6

7

e one of the first steps

t, because if the heat is

eter used for check- tempera~re rise of unit is a very i m p o r t ~ t step in the

heat from the ele-

t heat can cause a

ws the blower to run

air are mixed)

measure the temperature of the flue gases in the vent system, or the stack tem~erature The flue gas tem~erature of a standard gas furnace or boiler

should not be more than 480°F higher than the ambient or combustion air tempera~re The m ~ i m ~ flue gas temperature on a standard gas furnace

or boiler should be 350°F

If the flue gas temper , not enough heat is being removed

from the b~rnin to low circulating airflow, a dirty

heat exchanger, e unit being over-fired The causes of the problem must be found

as tem~erature of a high efficiency gas furnace will range from about 100" to 125°F Chec the manufacturer's specifications for the specific

e other combustion factors will remain the same

l

s an inst~ment used for measuring small pressures It is rate at which flue products are removed from the unit

is taken on the chimney side of the draft

ve pressure reading indicates that there is sufficient air movement the combus~on zone to allow proper and complete combustion If

is past the halfway point on the negative side of the scale, there draft through the unit causing excess heat to be drawn out of the unit and inefficient operation When the hand approaches zero or goes

ositive side of the scale, there is too little draft through the unit and

an insufficient amount of combustion air is being drawn into the combus-

Draft diverter

causing the products to be

re may be an obst~ction in and corrected

ment, a blocked vent usually re-

so, the combustion blower may be

ve combustion air to be delivered to the conditions must be found and corrected

e combustion process A carbon mon~xide er, sometimes called a

n into the draft

ems is to decrease the firing rate and increase the ~ r ~ a r y air to the main b u ~ e r s

Insufficient secon ary air will also cause a hi

carbon dioxide (C readin If the fla S no problems, check

the secondary air

in the heat exchanger and/or

ration workf it is necessary that technicians airflow and what the readings indicate Air

ce air travels in a given period of time It is usually

fpm) When the air velocity is multi~lied by the cross section ct, the volume of air flowing past that point

in the duct can be de This volume of airflow is usually expressed

in cubic feet per mi The velocity or air volume measureme~ts can be used to determine if the airflow system is operating properly, or if some repairs are needed

Some airflow inst~ments, su as the air velocity meter in Figure 3-$ have

a direct read-out in cfm, while others require some ~alculations to deter- mine the cfm flow t~ o u g h the system This is one factor that must be taken

Figure 3-4 Air velocity m wyer ~ n s ~ r ~ ~ e n ~ s , Inc.)

into account when purchasing the ins The instrument

in Be sure to follow th

In use, the airflow inst~ment is held a ainst the air outlet

reading is indicated on the meter scale Figure 3-5 The rea

interpreted according to the instrument m rer’s i n s t ~ c ~ o n s When large grilles are use gs is used to obtain the

take these readings

efficiency of the heatin

~ i s ~ a l l y check the entire u ~ i t for c l e a ~ i ~ ~ s s , and ensure all compo- nents are in proper working condition e sure the heat exchan

passa~es and the venti of all o ~ s t ~ c t i o ~ s

er cubic foot (Contact the local gas company or

Start the heating unit,

to bring eve~thing U

r l~strum~nts, Inc.)

and stop the fan at 100°F

but is not h tin total them If the

d 9, air is leaking f

ently the leak must

o this, measure the

other a l t e ~ a ~ v e is to

of the main burner

e the recommended

o so is very dangerous

d the test instrument m ructions to determin

manifold pressure

system for cleanliness, and ensu ger passages and the ventin

er cubic foot heating unit, and allow it to operate for about ten minut

inches W.C

the type of flame and record

7 Adjust the burner if needed, and record the type of flam

m~erature rise of the circulatin

AT = Discharge air temperat~re - ntering air tempe

any adjustments or repairs required to increase the combustion e~iciency of the unit Repeat Steps 3

n ~ f ~ c t u r e r rates the unit?

~ u l t i p l e tear-out copies

of this worksheet can be found in

Appendix B

This Page Intentionally Left Blank

an oil burner, the main objective is to ensure the unit pro-

ossible with as little heat input as possible The

reatest heat gain without causing undesirable conditio^, h mathematical terms, efficiency may be explained

The components must be clean and in good working condition, and clean air filters must Le installed

There are several closely factors involved in the adjustment process When an a d j ~ ~ e n t is one of these factors, the other factors are also affected

The proper test ins~uments are needed to make accurate measurements of the product or process bein The old procedure of merely looking at the e ~ ~ i p m e n t or feelin no longer indicates what is happening with the unit

There are many brands and models of test i n s t ~ m e n t s available Which particular i ~ t r u m e n t to use is the user’s choice, but accurate test instm- ments must be used to roperly fine tune oil burners The exact procedure for i ~ t ~ m e n t use can be found in the manufac~rer’s operating instruc- tions These i n s t ~ ~ e n t s must be properly cared for and their accuracy maintained for o p ~ m u m performance

This chapter will discuss the S

equipment, not S

i n § ~ ~ e n t s requ

efficiency of an oil-fired unit:

bustion efficiency arious test results

5 Dry bulb thermometer

This type of thermometer is use er than normal tem-

h flue gas temperatur~s result in excessive

ssive oil c o n s ~ p t i o n and may

Low flue gas t e m ~ e r a ~ r e s

and deterioration of the sm r draft Low flue

gas t e m ~ e r a ~ r e s may also

The flue gas tem~era

about 12 ft from the

before ing the

1 /4 in hole (behin~ thermometer)

determines the amount of combustion air sLlpplied to the burner An exces- sive amoLlnt of draft can reduce the e of CO, in the flue gases and increase the tempera

of instal~ation has its own draft reqLlirements, Not enough draft can cause pressure in the CO bLlstion area, thus allowing smoke and odor

to escape from the wit of draft can also e it impossible to adjust the oil b ~ l ~ e r to maximum efficiency, because irnum efficiency is de-

pendent ~ p o n the proper ~ i x t u r e of air and ing burner opera tion

Q be checked an justed on oil burners:

raft of at least 0.0 inches W.C is considered sLlfficie~t to develop and ~aintain pr hotlld the over-fire draft fall below 0.02 inches w.c., S r may be present in the burner

on may be present when close are completed

The flue pipe drafts must be a justed to prevent positive pressure in the

flue passage requires a

le flue passage requires

or less require a flue pipe draft ntain an over-fire draft of 0.02 inches W.C in the combLlstion zone,

The flue pipe draft is adjusted by changing the position of the draft re lator damper Adjusting the co~terweight so the damper moves toward the closed position causes an increase in the draft Adjusting the counter- weight so the damper moves toward the open position causes a decrease in the draft through the combustion zone

The smoke tester and the smoke scale are used to d e t e r ~ i n e the amoLlnt of smoke in the flue gases Combustion gases containing an excessive amoLll~t

of smoke indicate incomplete combustion and inefficient oil burner opera- tion An excessive amoLlnt of smoke allows soot formation on the heat exchanger surfaces This soot slows down the heat transfer and clogs the flue passages, thus preventing proper draft through the combustion zone

A soot buildup of 1/8" can reduce heat transfer by LI

The purpose of conducting the smoke test is to determine the amount of smoke the flue gases contain The smoke test can then be used along with other tests to adjust the oil burner to obtain maximLlm efficiency The smoke scale has 10 color-graded spots ranging from 0 to 9, where 0 is pure white and 9 is the darkest color on the scale e smoke scale is always used along with the smoke tester for complete results Use the instrLlment manLlfactLlrer's inst~ctions when conducting the smoke test

Not all types of oil burners are affected the same way by the same amount

of smoke in the flue ases The type of comb~lstion zone const~lction, to a great extent, deter~ines how fast soot accLlmLllates on the heat exchanger and other surfaces Soot accumulates very rapidly on some types of con- struction when fired with a #3 smoke spot, whereas other units may accu- mulate soot at a much slower rate with the same smoke content Table 4-

1 shows the possible soot accL~mLllation rate for different amoLlnts of smokc

in the flue gases

The correct percentage of CO, in the flue gases is ry importal~t to oil

burner combLlstion efficiency testing The desired C reading is between

9% and 10% When the reading is below 9%, check for the following con- ditions:

Air leakage

Excess combustion air

Worn, plugged, or incorrect nozzles

High draft conditions

Incorrect or defective combustion zone

Poor atomization of the fuel oil

Incorrect combustion air handlin

Incorrectly set oil pressure

Excessive combustion zone draft or air leaks

Erratic draft regulator

Table 4-1 Smoke effect on burner performance

1 Excellent Reduced, very light accumula-

tion if at all

2 Good Soot accumulation light, will

not appreciably increase stack temperature

3 Fair May be some soot accumula-

tion, will seldom require cleaning more than annually

4 Poor Borderline condition, some

units may require more than annual cleaning

5 Very poor Soot accumulation very heavy

and rapid

There are two factors that determine the amount of heat lost in the flue gases They are the flue gas tempera~re and the percentage of CO, in the flue gases It is the flue as heat loss that determines the combustion effi-

ciency of the oil burner

The CO2 analyzer is an inst~ment that is used to sample flue gases to determine the CO, content A low CO, reading indicates that not all of the fuel is burning completely, thus some adjustments are required It is recom- mended that the CO, analyzer be used along with other testing devices One such device is the slide rule calculator, which can be used to determine the unit efficiency and stack losses in oil burner installations by correlating the temperature of the flue gases and the CO, percentage To properly use the CO2 analyzer, follow the instrument manufacturer’s instructions

When the CO, reading is above lo%, at least one of the following condi- tions must be corrected:

InsLlfficient draft

Oil pump not fLlnctioning properly

Poor fuel supply

Improper fuel/air ratio

Rraft regulator improperly adjusted

Improper combustion fan delivery

Defective or incorrect nozzle type

Wrong burner air handling parts

Excessive air leaks in the combustion zone

A dry bulb (db) thermometer is used for measuring air temperatures (see

Figure 2-1) r et er mining the temperature rise of the air as it passes through

the heating unit is a very important step in the fine tuning process The dry

bulb temperature is a measL~re of the amount of heat absorbed from the

heat exchanger by the air The air tempera~re is measured in two locations:

the return air stream and the discharge air stream, Figure 4-2 Be sure to

take the temperatLlre readings after the mixing of any air The thermometer

must be placed where the radiant heat from the heat exchanger cannot be

measured by the thermometer Radiant heat can cause a faulty temperature

reading and an incorrect test

Two different thermometers that have been tested and found to produce

exactly the same readin S under the same set of CircLlmstances should be

used If two thermometers that read exactly the same temperature are not

available, then use one therm~meter to measLlre both tem~eratLlres An

electronic thermometer that has separate, properly adjusted leads also pro-

duces the desired results The best operating air temperature rise of an oil-

fired unit is between 60" and 80°F This allows the blower to run longer,

distribLlting the heat more evenly through the building

Thermometer

ocated after the

resh and indoor

air are mixed)

I'

Figure 4-2 ~ e a s u r i n t ~ ~ ~ e r a t u r e rise t h r ~ u ~ h a furna~e