Beckett AFII85, AFII150, AFG, AF Installation Guide

FOR

THE

PROFESSIONAL

SERVICEMAN

D_tt_buted

as (t,_z

iru4ustrtj

serviceb_

FOR

THE

PROFESSIONAL

SERVICEMAN

R/C,: Beckett Corporation 38251 Center Ridge Road

P.O. Box 1289 Elyria, Ohio 44036- !289

1-800_OIL BURN (645-2876)

R.W,BeckettCanada, Ltd. Unit 3 - 430LairdRoad

Guelph, Ontario, Canada NIG 3X7

1-800-665-6972

Acknowledgements

R.W.BeckettCorporation is pleased to presentthis new,

revised edition of Guideto Oilheatfor the ProfessionalServiceman

(formerly known as The ProfessionalServiceman's Guide to Oilheat Savings). This new edition has been expanded to include updated information and several additional topics of importance

to the industry as we approach and enter the 21st Century. These topics include direct, side-wall venting and outside

combustion air. We hope this new edition willhelp you achieve

greater success for your business while providing outstanding

service to your customers.

Beckett has distributed many thousands of copies of [his

book, in various editions, since its first printing in 1979.

The original ProfessionalServiceman's Guide to Oilheat Savings

was based primarily on material developed in 1978 by the

Massachusetts Better Home Heat Council and distributed by

them as a manual entitled Oil Heat Energy ConservationManual.

This material is gratefully used with their permission.

The Better Home Heat Council received finandal support for development of this material through the Massachusetts Energy

Office, as part of the 1978 State Energy Conservation Plan, funded

by the U.S. Department of Energy under PL94-163 and 94-384.

BHHC also received technical assistance from the Walden Division

of Abcor, Inc., and from numerous individual members of

BHHCs Technical Review Committee.

Acknowledgements

VCewishto acknowledgeandthank the followingcompanies

and organizations (listedalphabetically)that suppliedillustrations,

photos, and/or information used in the revisededitionof thisbook:

Bacharach,Inc.

Broo'yahavenNationalLaboratory

DanfossAutomaticControls

DelavanInc.

FieldControls

HagoManufacturing

LynnProductsCo.

PetroleumMarketersAssociationofAmerica

$untecIndustriesIra:.

Testo,Inc.

Thermo-DynamicsBoilerCo.

TjernlundProducts,Inc.

Trianco-Heatmak_r,Inc.

Ifwe haveinadvertentlyleftanyoneoffthis list,wesincerely

apologize,and assureyou that your contribution isvery

much appreciated.

TABLE OF CONTENTS

CHAPTER 1

CtD_FrER 2

COMBUSTION THEORY ................................................................................................. 1

Fuel Oil ............................................................................................................................. 1

Combustion ....................................................................................................................... 2

Role of Excess Air in Combustion .................................................................................... 4

Excess Air - Smoke Relationship ....................................................................................... 5

Effect of Air Leaks ............................................................................................................ 6

OILHEAT SYSTEMS ......................................................................................................... 7

Overview of Oilheat Systems ........................................................................................... 7

Basic Oil Burner Design ................................................................................................... 9

Nozzles ........................................................................................................................... 12

Combustion Chambers .................................................................................................... 14

Heat Exchangers ............................................................................................................. 18

Combustion Air Requirements ........................................................................................ 20

Draft ................................................................................................................................ 21

Draft Regulators .............................................................................................................. 22

Flue and Chimney Exhaust ............................................................................................. 24

"ventingMultiple Appliances ........................................................................................... 24

Alternative "venting Systems ........................................................................................... 25

Power Chimney Venting ................................................................................................. 25

Side-Wall Venting ........................................................................................................... 25

PowerVenting ................................................................................................................. 29

Direct Venting ................................................................................................................. 29

Sealed Combustion ......................................................................................................... 29

Outdoor Units ................................................................................................................. 29

CHAPTER 3

EFFICIENCY - DEFINITION OF VARIOUS TYPES OF EFFICIENCY .................. 30

Combustion Efficiency ...................... ............................................................................. 30

Steady_State Efficiency ................................................................................................... 30

AFUE Ratings ................................................................................................................. 30

CHAPTER 4 STEADY-STATE EFFICIENCY MEASUREMENTS ................................................... 32

Stack Loss Theory .......................................................................................................... 32

Measurement of Carbon Dioxide or Oxygen .................................................................. 36

Alternative Measurement Techniques ............................................................................. 38

Other Advanced Multi-Purpose Test Instruments ........................................................... 38

Measurement of Flue Gas %mperature .......................................................................... 39

Smoke Measurement ....................................................................................................... 40

Draft................................................................................................................................ 41

Carbon Monoxide Testing ............................................................................................... 42

CHAPTER 5 RESIDENTIAL OIL BURNER ADJUSTMENTS ......................................................... 44

Facts About High CO 2 Levels ........................................................................................ 44

Procedure Preparation Steps ......................................................................................... 45

Combustion Adjustment Steps ........................................................................................ 46

Recording of Readings .................................................................................................... 47

The Annual Clean-Up ..................................................................................................... 47

Test Report Form ............................................................................................................ 49

Basic Troubleshooting .................................................................................................... 50

CHAPTER 6 ENERGY CONSERVATION OPTIONS ........................................................................ 52

Flame Retention Oil Burners .......................................................................................... 52

Criteria for Installing Name Retention Oil Burners ....................................................... 53

Installation of Matched BoileffBurner or Furnace/Burner Systems ................................ 55

LIST OF FIGURES

FIGURE PAGE

1 Viscosity vs. temperature, No. 2 fuel oil .......... 1

2 "viscosityconversion, Centistokes vs. Saybolt

Universal Seconds............................................. 1

3 Combustion products by weight and volume,

1lb. fuel oil, 0% excess air...............................3

4 Combustion products by weight and volume,

1lb. fuel oil, 50% excess air.............................3

5 Relationship between excess air and CO2 .......4

6 Effect of excess air on CO2 ..............................5

7 Effect of excess air on combustion gas

temperature ........................................................ 5

8 Smoke &efficiency vs. excess air curve ..........6

9 Typical oilheat system components .................. 7

10 Underground tank .............................................7

11 Above ground tank............................................7

12 Indoor tank ........................................................8

13 Typical oil burner components ....................... 10

14 Burner air patterns ........................................... 10

15 Burner flame configurations ........................... 11

16 Cutaway view of a fuel oil nozzle .................. 12

17 Beckett Multi-Purpose Gauge......................... 13

18 Nozzle spray patterns ...................................... !3

19 Combustion chamber design .......................... 14

20 Air tube insertion ............................................ 15

21 Soft fiber refractory combustion

chambers ......................................................... 16

22 Combustion chamber sizing data.................... t7

23 Recommended minimum inside dimensions

of refractory-type combustion chambers ........ 17

24 Heat exchanger designs .................................. !8

25 Oil furnace heat exchanger ............................. 19

26 Condensing furnace heat exchanger ............... 19

27 Approximate relationship of % excess air

with flame temperature and volume of

combustion cases ............................................ 19

28 Outside air combustion ................................... 20

29 Tjernlund Combustion Air In-ForcerTM ..........21

30 Draft changes in a chimney ............................ 22

31 Field draft controls ..........................................23

32 Common chimney sizes vs. Btuinput ............ 24

33 Multiple appliances vented separately ............ 24

34 Square inch area of flue collars ......................25

35 Tapered manifold vent system ........................ 25

36 Constant sized manifold vent system .............25

37 Barometric damper locations when venting

multiple appliances .........................................26

FIGURE 38

Power chimney venting system ..................... 26

Efficiency vs. net stack temperature ............... 26

Common chimney troubles and

theircorrections ............................................... 27

41 Power side-wall venting.................................. 28

42 Field power venter .......................................... 28

43 Sealed combustion furnace and boiler ............ 28

44 Outdoor appliance installation ........................ 29

45 Distribution of heat as determined by the

stack loss method ............................................32

46 Theoretical combustion relationship between

CO2 and 0 2for No. 2 heating oil .................. 33

47 CO2 gas analyzer ............................................ 34

48 Graph of heating appliance efficiency ............ 34

49 No. 2 fuel oil efficiency table ......................... 35

50 Construction of CO2 analyzer ........................ 36

51 Lynn Model 6500 Combustion Efficiency

Analyzer .......................................................... 38

52 Testo 342 Combustion Analyzer .....................38

53 Bacharach CA 40H Combustion

Analyzer .......................................................... 39

54 Flue gas thermometers .................................... 39

55 Bacharach smoke spot tester........................... 40

56 Oil burner smoke scale.................................... 41

57 Draft measurement devices ............................. 41

58 Lynn Model 7400 Carbon Monoxide

Analyzer .......................................................... 42

59 CO level standards .......................................... 43

60 Flue pipe sampling hole locations ..................44

61 Correlation of percent of CO2, 02 and

excess air ......................................................... 45

62 Typical smoke vs, CO2 percent ...................... 46

63 Test report form ............................................... 49

64 Name retention combustion heads ................. 52

65 Non-flame retention and flame retention

combustion ...................................................... 53

66 Recommended firing rates for Beckett AF

andAFG burners ............................................. 53

67 Beckett AF II air tube combination and

firing rate chart ................................................ 54

68 Air tube/head combinations for wet base

and wet legboilers ..........................................54

69 Name retention heads for furnaces,

dry base boilers, and water heaters ................. 55

70 Outdoor winter design temperatures............... 56

7t Nozzle manufacturers, spray patterns,

and capacities ..................................................58

PAGE

PurposeofManual

This manual has been prepared for use by oilheat

service managers and service technicians_

It provides a brief overview of oilheat systems, as well as a review of basic oil burner combustion

theory. Included are suggested procedures for

adjusting and maintaining oil burners-and other

oilheat system components-to provide your

customers with maximum efficiency,comfort,

and safety.

Modification and installation procedures recom-

mended herein apply to domestic oil burners installed

in houses ranging from single-family dwellings to

multi-family units They apply generally to acapacity

range up to approximately 400,000 Btu/hr. input.

The proceduresin this documentshould beused asa supplement to the equipmentmanufacturer's

recommendedinstallationand serviceinstructions

and do not precludeother acceptedguideline documents on good industrypractice,

This chapter reviews the basic concepts about the process of combustion. You should understand this process before tackling the other chapters in this manual! It's likely that a good deal of material presented is familiar to you, but there's an even better chance that you might learn something new. It's worth reading, since this information develops the foundation from which

every dependable oilheat service technician should work.

CENT1STOKESvs.SAYSOLTUNWERSAL SECONDS VISCOSITy"CONVERSION ATi 00' F

iUJ _

02 _,. ............ ,

3o 3"I _2 3'334 3s 36 37 _ 39 40

FIGURE 2 \_scosity conversion,Centistokesvs.Saybolt

UniversalSeconds

SAYBOLT UNIVERSAL SECONDS

FUEL OIL

No. 2 distillate fuel oil (domestic heating oil) is a product of the refining of crude oil, which was formed underground through decomposition of

marine organisms, fish, and vegetation. This organic matter eventually became liquid or gas concentrated underground in pockets or pools. All petroleum products, including natural gas, gasoline, kerosine, No, 2 fuel oil, etc., axe chemical compounds that make up crude oil, and

they all contain carbon and hydrogen. The process of separating these various compo-

nents can be quite complex, but is commonly referred to as "refining". Eventually, one of the

products of the refining process is No. 2 fuel oil, which is suitable for use as a fuel in residential

oil burners. The designation "No. 2" is used as a specification guide that defines some physical

characteristics such as flash point, ash, viscosity, etc.

All fuel oil is not alike, and variations can have

an impact on burner operation. Here are a few of the variations within each grade of fuel oil which are measured by ASTM (American Society for

Testing and Materials standards):

VISCOSITY vs. TEMPERATURE No, 2 Fuel Oil -TYPICAL

30 -- _'%._%.

20 40 60 80 100

TEMPERATURE _F

FIGURE 1 Viscosity vs. temperature, No. 2 fuel oil

This is the oil's resistance to flow. The viscosity rating is a measure of how much oil flows

through a standard orifice within a certain amount of time. Oil with high viscosity can contribute to poor atomization, delayed ignition, noisy flame or pulsation, increased input and possible sooting.

This is particularly true in temperatures below 50°E (See Fig, 1,) Viscosity measured by the

Kinematic viscometer is reported in centistokes. (See Fig. 2 for cross reference.)

Pour Point

Pourpoint is the temperature at which oil will barely flow. This is usually 5°F above the point

where oil forms a solid mass. The ASTM D396 Standard for fuel oils lists 20°F as the maximum

pour point for No. 2 fuel oils. However, random analyses show that the typical pour point is

approximately -20°E To avoid problems in certain cold ambient applications, No. 2 fuel oil is

sometimes blended with approximately 25% or more of No. 1 distillate fuel (kerosine) to lower

the pour and cloud points.

Cloud Point

This is the temperature at which wax crystals begin to form, typically 10°to 20°F above the pour point. These crystals can clog filters and

strainers, restricting oil flow. Raising the oil temperature causes the wax to go back into solution. ASTM D396 does not list a specification on cloud point.

Distillation Temperature

No. 2 fuel oil can be vaporized and distilled (condensed) to determine the volatile compo- nents. Modern refinery methods use straight-run

distillation and catalytic cracking processes, resulting in slightly different chemical hydrocar- bon composition which can affect combustion performance. Therefore, the distillation tempera-

turetestisvaluable.It consistsoffueloilbeing heatedgraduallyinaflaskuntilitvaporizes,then

iscondensedintoagraduatedcylinder.The temperatureatwhichcondensationbeginsis

calledtheinitialboilingpoint(IBP).Therising temperatureisrecordedforeachfractiondistilled. Itisusuallyreportedin10%incrementsuntilthe finaldropisrecoveredorendpointisreached.

Theinitialboilingpointcouldcauseignition problemsif itistoohigh(over400°F).The

ignitionarcmustprovideenoughheatenergyto elevatethetemperatureoftheatomizedoil dropletstotheinitialboilingpoint.If theIBPis low,theignitionshouldbeimmediate.Forthe flametobesustained,the10%pointortempera-

tureatwhich10%ofthetotalvolumeisdistilled mustberelativelyclose.If thespreadistoolarge,

thentheflamecouldpulsateorevenbeextin- guished.

Foranestablishedflame,theremainingfractions of20-80%shouldnotpresentanycombustion

problems,butthe90%andtheendpointcould. The90%pointisthetemperaturewhere90%of

theoilisdistilled.ASTMD396requiresthistobe between540°Fminimumand640°E

Awidespreadbetweenthe90%andendpoint cancausepoorcombustion,sootaridcarbon depositsontheheatexchangerbecausethe remainingheavyendsmaynotburncompletely.

Detecting "Out of Spec" Oil

Your first clue that oil is not within ASTM specs might be a sudden rash of problems: delayed

ignition, smoky fires, appliance sooting and noisy, dirty flames. If an analysis by a competent

laboratory shows the oil is out of spec, the supplier should be advised. However, if it is

within spec, but is near the maximum level for viscosity, pour point or has an IBP above 400°E chemical additives or blending with about 25% kerosine might be considered to make the oil

more compatible with cold temperatures, and to improve its ignition and combustion qualities.

COMBUSTION

When fuel oil is burned, the chemical energy that is stored in the oil is released in another form of

energy: heat. But to create this conversion of energy, an external source of heat must be applied to the oil droplets to start the reaction. The

electric spark delivered by the electrodes of an oil burner provides the initial heat. The heat from the electrodes causes oil droplets to become oil vapor and eventually burn continuously. This burning then heats the surrounding oil droplets causing them to bum. This process continues until all or most of the droplets are vaporizing and burning.

If the conditions for combustion are ideal, all oil droplets will burn completely and cleanly within

the combustion zone. Combustion is the process of burning, p

Combustion, as we normally think of it, is generally described as "rapid oxidation" of any

material which is classified as combustible matter. The term "oxidation" simply means the

adding of oxygen in a chemical reaction, and "combustible matter" means any substance which combines readily and rapidly with oxygen under

certain favorable conditions. Since fuel oil primarily consists of carbon (85%) and hydrogen

(15%), combustion of fuel oil, according to our previous definition, is the rapid combining of carbon and hydrogen with oxygen.

As you know, the oxygen needed for combustion comes from the air provided by the burner blower. Approximately 21% of the air is oxygen. The other 79% is nitrogen. Therefore, to supply

the oxygen needed for combustion, a great deal of

nitrogen goes along for a free fide. This will

become an important factor in later discussions of

proper oil burner adjustment!

What we see and feel from combustion--flames,

smoke, heat--is a result of chemical reactions.

Since we can't see carbon, hydrogen or oxygen

atoms (smallest units to combine), we symbolize

the reactions with formulas that describe the

process. For example:

Carbon +Air oxygen + ] f_

nitrogen

carbon dioxide + nitrogen + heat (1)

Hydrogen +Air [ oxygen +

nitrogen ]

watervapor + nitrogen +heat (2)

These reactions can be rewritten using symbols in the following manner:

C+O2+N 2 -_ CO2+N2+heat (1) 2H2+O2+N 2 -_2H20+N2+heat (2)

Both chemical reactions produce entirely new products, and each reaction gives off heat. However, you may have noticed that in

each reaction nitrogen (N2) has not changed,

OIL

(t pound)

-t-

AIR

(14_36 pounds

or 188 cubic feet)

[Air is 20.9% oxygen

and 79.1% nitrogen]

1.00 lb. oil

14.36 lb. air

15.36 ib. total

FIGURE 3Amount byweightand volumeof combustion products when 1 lb. offuel oil is burned (0% excess air)

OIL

(1 pound)

-I-

50 pementexcess

AIR

(21.54 pounds

or281 cubicfeet)

[Airis 20,9%oxygen and 79.1%nitrogen]

1,00 lb. oil

21.54 lb. air

22.54 lb. total

FIGURE 4 Amount by weight andvolume ofcombus- tion products when 1 lb.of fuel oil is burned (50% excess air)

[

FORMS > I

FORMS _)

(1.18 pounds)

I WATER

(amount of water vapor is not considered in % of

CO2 determination

84.7% by volume NITROGEN

(11.02 pounds or

150 cubic feet)

CARBON DIOXIDE

(3.16 pounds or

15.3% by volume

27.2 cubic feet)

1.18 lb. water

11.02 lb. nitrogen 3,16 lb. carbon dioxide

15.36 lb. total

WATER ](1.18 pounds)

56.1% by volume NITROGEN

(11.02 pounds or

150 cubic feet)

10.2% byvolume ]

CARBON DIOXIDE

(3.16 pounds or

27.2 cubic feet)

33.8% by volume i

EXCESS AIR

(7.18 pounds or

90.4 cubic feet)

1.18 lb. water

11.02 lb. nitrogen

3.16 lb. carbon dioxide

7.18 lb. excess air

22.54 lb. total

indicating that nitrogen does not participate in the reaction. Consequently, because of the

large amounts of nitrogen in the air, the bulk of the flue gas is made up of unreacted nitrogen.

Note: Some nitrogen does react with oxygen to create a small amount of nitrogen oxides or NOx.

If exactly the right amount of air (no excess air) were supplied for complete combustion of the carbon and hydrogen in the fuel oil, the products of combustion would be as indicated

in Figure 3. However, with typical oilheat equipment, it is usually not possible to get a perfect mixture in which all the carbon and hydrogen are supplied with the exactly correct quantity of oxygen. To insure that all the carbon and hydrogen come into contact with enough oxygen to burn completely, excess air must be supplied, The excess air is simply air over and above the theoretical requirement for

the combustion of fuel oil. With excess air needed for combustion, reaction (1) becomes:

C+02+N 2 -* C02+N2+O2+heat (3)

Note that the only difference between reaction (3) and reaction (1) is that 0 2 (oxygen) is a product of the reaction. This 0 2 is the oxygen

in the excess air that does not combine with carbon to make carbon dioxide. In essence, extra 0 2 is provided, as acomponent of the

excess air, to ensure that all the carbon and hydrogen comes in contact with the oxygen

and bums. This excess air does not react during the

combustion process, but enters the heating unit at room temperature and reduces the tempera-

ture of the combustion gases so less heat is available to be transferred to the distribution

medium. As a result, excess air is a source of heat loss. By introducing 50% excess air, the

situation shown in Figure 4 is created.

Compare this with Figure 3. Note that:

Y The amount (weight) of H20, CO2,

and N2 formed in Figure 4 is the

same as that in Figure 3.

• ' Percent by volume of CO2 and N2 in Figure 4 is less than is formed in Figure 3.

_' Oxygen (_ partof excess air) is a

pr_._ductin Figure 4 but not in Egtue 3.

24 22

< O

ILl

-J

It.

O O

LI.I

LU I3u

4 2 0

0 i0 20 3o 4o so eo 7o 8o 90 i30 i40 1;50

FIGURE 5 Relationship between excessair and CO2

PERCENT EXCESS AIR

! ! I I ! !

MEASURE PERCENT CO2 TO D_ERMINE _

PERCENT EXCESS AIR

_" _IIii _._,m_mi " .iii--

In Figure 4, since 20.9 percent of the excess air is oxygen, 7.1 percent of all the combustion gases is oxygen. You determine this by multiplying the percent excess air (33.8%) times that portion of excess air which is oxygen (.209). This gives approximately 7.1 percent oxygen.

Note that in Figure 4 the percentage of CO2 or 0 2 changed from Figure 3 as a result of excess air, therefore, we can use the percent CO 2 or 0 2

in the flue as a measure of excess air or vice versa

las a general rule.

'_' The more CO 2, the less excess air

• ' The more 0 2, the more excess air

ROLE OF EXCESS AIR IN COMBUSTION

You have seen that excess air must be supplied to insure adequate mixing of fuel and oxygen.

However, excess air is one of the major causes of low efficiencies. To see how this occurs consider

that excess air:

Y dilutes combustion gases Y absorbs heat

• ' drops overall temperature of combustion gases

The dilution of combustion gases occurs simply

because of the presence of additional gas in the form of excess air. The excess air absorbs heat in

Figure 5 displays the relationship between CO 2 and excess air.

The above discussion is a simplification of the actual combustion process. The chemical reactions provided are only those that are

important to the overall combustion process. Nevertheless, the information in this section is

sufficient to support you in your oil burner service work. Make sure you understand the concepts and, if necessary, reread this section or

ask a knowledgeable person to assist you. Don't go on without understanding the basic concepts!

the combustion zone and reduces the flame

temperature. This in turn reduces the transfer of heat to the heat exchanger since a significant amount of heat is transferred by radiation. Moreover, as excess air is introduced, the overall

temperature of the combustion gases drops because the heat from these combustion gases is used to raise the temperature of the excess air.

Think of this process as being similar to adding

refrigerated cream to a cup of coffee as shown in Figure 7. The cup of coffee is originally 160°F (high temperature) and occupies a small volume (half a cup). Adding cream at 40°F increases the

volume (almost a full cup) and lowers the overall temperature to 120°F (mild temperature). Note that the temperature of the mixed coffee and cream is higher than the temperature of the cream

alone and lower than the temperature of the coffee alone. Heat from the coffee went into

heating the cream and the overall temperature dropped. In other words, the cream absorbed

some heat from the coffee.

Also,bylookingatFigure6youcanseethatthe coffeeexampleillustratestheeffectofexcessair (shownaswater)indilutingthegas(coffee)and theresultingreductionintheCO2percent.

Bearinmindthatthistemperaturereductionand dilutiontakesplaceinthecombustionzone,not intheflueorstack.Itisimportanttonotethatthe

effectofexcessaironthetemperatureoftheflue gasisdifferent.Withmoreexcessair,thefluegas

Water (ExcessAir)

Cream 1CO21

_._ coffee

(C02)

% Cream =13.6%

85+15+10

Amount of CO2 remains

the same, the percent

of CO2is

less

temperature tends to rise. This happens because the volume of combustion gas per unit of fuel

burned is now greater than before, so the gases pass over the heat exchanger surfaces more

rapidly, reducing the contact time. This reduces the heat transfer rate to the heat exchanger.

To review, remember that excess air causes the

following:

• ' lower flame temperature Y lower combustion gas temperature

T higher flue stack gas temperature T poorer heat exchange to the distribution

medium

All of these changes reduce the efficiency of the heating system• So minimizing excess air is essential in the proper adjustment of oil burners.

However, you will find out in the next section

that simply reducing excess air without concern

for other factors could lead to a great deal of

trouble! Keep reading, you'll see what we mean.

Excess Air. Smoke Relationship

During the combustion of oil, some smoke is

Cream (CO 2)

usually generated, since some of the oil droplets do not contact enough oxygen to complete the

reaction which forms carbon dioxide. This smoke

.,,...,_ ( N t oge | _,,_,,...,,._

consists of small particles of mainly unburned carbon. Some of these particles stick to the heat

exchanger surfaces acting as insulation and can

(C02)

% Cream 15%

85+15

eventually clog up the flue passages, while others

are emitted through the stack. Now you are ready for discussion of the issue that

FIGURE 6 The effectof excess air on CO2

is all important to the proper adjustment of oil

Addingexcessairtoflameislikeaddingcreamtoacupofcoffee.

.SmallVolume

•HighTemperature

.LargerVolume

•LowerTemperature

burners: excess air-smoke relationship.

You have learned that

there must be sufficient excess air to provide good

mixing of combustion air

and fuel oil. Wqthout this excess air, incomplete

combustion occurs and

smoke is formed. Thus, to minimize smoke, you

generally add excess air.

FIGURE 7 Representation of theeffect of excess air on combustion gas temperature

Unfortunately, as you have learned, as the amount of excess air is increased, the transfer of heat to the heat exchange medium (hot water, warm air, or steam) is reduced. A delicate balance must be

achieved between smoke generation (caused by insufficient excess air), reduced heat transfer (due to reduced combustion gas temperature), and an increased volume of combustion products (caused

by unnecessary excess air). Figure 8 illustrates the typical relationship between smoke, effi- ciency, and excess air. Notice that smoke and efficiency increase as the excess air is decreased. The exact shape of this curve varies from unit to unit. Knowing this, the curve can give you a general idea of where the burner air should be adjusted. The highest efficiency occurs when you properly balance the trade-off between smoke

and excess air.

Effect of Air Leaks

Now that you understand what goes on inside the heating unit, it will be easier to follow why air leakage into the appliance causes lost efficiency. This air leaks into the combustion gases before they pass through the heat exchanger and acts

like excess air. The air leaks dilute the combus- tion gases, cooling them and increasing their

volume so that they pass through the heat exchanger more quickly, However, an air leak is

even worse than excess air in the combustion chamber because an air leak can not reduce the

smoke formed in the combustion zone.

Excess combustion air reduces heating plant efficiency.

Too much smoke will eventually reduce efficiency also.

LLI

<1 Operating Level

o')

k'_L SMOKE

o% % Excess Combustion Air

FIGURE 8Smoke & efficiency vs. excessair curve

Recommended

i i

OILHEAT SYSTEMS

OVERVIEW OF OILHEAT SYSTEMS

The primapy emphasis of this manual is on oil burners. However, abrief look at total oilheat

systems would be appropriate. Maximum heating efficiency, reliability, and safety cannot be achieved unless all components of the system are

compatible and in top working condition. It is vital, therefore, that the technician consider the

entire system when installing new equipment or servicing existing equipment.

The purpose of any oilheat system is to convert fuel oil into heat, and distribute as much of that

heat as possible to the home.

Typical Oilheat System Components

HOU_

Storage Tanks

Residential fuel oil storage tan_ksfall into three categories: underground, above ground, and indoor. Each has i_ advantages and disadvantages.

Underground Tanks

Courtesy of Suntec tr_ustdes, In_

FIGURE10Undergroundtank

Advantages:

(1) Take up no space inside or outside the home. (2) Tanks are out of sight,

(3) A large quantity of oil can be conveniently

stored.

Barometric _ Chimney

Draft Control

_, Tile Liner

_ Heat __;>

Cooled Exchan_ Heated

Water or Air Water or Air

(from house (to heat

house)

(4) Better insulation from cold, compared to

above ground tanks.

Disadvantages:

(1) ExNnsive to install, inspect, and service. (2) Subject to effects of cold and underground

moisture.

(3) Well-made, properly installed tanks seldom

leak_ven after decades of service. How- ever, leak detection and clean up are still

important environmental concerns.

Above Ground Tanks

Courtesy of Suntec Industries, Inc.

UNIT

FIGURE 11 Above ground tank

Advantages

(I) less expensive than underground tanks to

install and service.

RGURE 9 _pi_l oilheatsystem components

(2) If leaks occur, they can be easily detected in

time to avoid environmental problems.

Disadvantages:

(1) Exposed to cold and moisture. (These

problems can be reduced by providing a shelter for the _k.)

can be installed. Always follow burner manufacturer's instvactions when adjusting oil

pressure or installing heaters.

(2)Take up outdoor space. (3) May detract from appearance of home.

Indoor Tanks

Courtesy of Suntec Industries, Inc.

VENTll_

FIGURE 12 Indoor tank

• 1%" MIN.

_LK_ SHUT-OFFVALVE

LINE

Advantages:

(1) Not affected by outside cold and moisture. (2) Less expensive to install and service than

underground tanks.

(3) Leaks are unlikely to occur. If they do, they

are easily spotted and repaired.

Disadvantages:

(1) Take up space inside home. (2) Some oil smell may be present.

Oil Delivery Systems

The oil delivery system includes all components required to transport oil from the storage tank

to the burner. These include pumps, pipes, valves, filters, and controls. Inspecting these components should be a part of scheduled

maintenance service. When diagnosing combustion problems, the oil

delivery system should always be considered as a possible contributing factor. Check for proper

oil pressure, viscosity, and cleanliness. Filters should be changed at regular intervals. Compres- sion fittings can cause air leaks and should not

be used.

Oil Burners

The functions of an oil burner are to break fuel oil into small droplets, mix the droplets with air, and

ignite the resulting spray to form a flame.

Combustion Chambers

The purpose of thecombustion chamber is to reflect heat back into the flame to aid the combus-

tion process and achieve more complete burning of oil. See page 14for more details.

Heat Exchangers

The purpose of the heat exchanger is to transfer heat from the burner flame to the water or air used

to heat the home. The heat exchanger is an integral part of the boiler or furnace. The role of

the serviceman is usually limited to inspection and cleaning. However, this is an extremely important role. If soot is allowed to accumulate on the heat exchanger, the efficiency of the heating appliance can be seriously impaired. Proper adjustment of the burner to avoid smoke (the cause of soot) is essential to keeping the heat

exchanger clean. See page 18 for more details.

Flue Pipes

Flue pipes serve two vital functions: (1) They convey combustion gases from the

heating appliance to the chimney or vent. Since these gases are potentially harmful to the home and its residents, these pipes must be sealed tightly to prevent leakage. In most

chimney systems, flue pipes are under a negative pressure created by draft, which aids in preventing leaks.

(2) Flue pipes convey combustion gases that

create the draft to assist in drawing com- bustion air into and through the burner in chimney systems.

In some cases combustion problems can be alleviated by increasing oil pressure to the

nozzle. If cold oil is a problem, oil line heaters

Draft Regulators

Many flue pipes include a barometric draft regulator. This consists of a counterweighted swinging door which opens and closes to help

maintain a constant level of draft over the fire. Modern high-speed, flame retention burners are

much less sensitive to changes in natural draft allowing draft regulators to be eliminated in some

cases. However, check the burner manufacturer's instructions, and local codes, before eliminating

draft regulators. See page 22 for more details.

Chimneys

Chimneys have been used since the earliest days of indoor heating to draw combustion gases out of

the home and provide draft to help draw in combustion air. Correct chimney design and careful maintenance are essential to the operation of any oilheat system.

When chimneys are inadequate or absent entirely (such as in electric-to-oil conversions), alternative

venting systems are available. See page 25 for more details.

Heat Distribution Systems

With furnaces, warm air, propelled by fans, is distributed throughout the house through metal

ducts. With boilers, hot water or steam is distrib- uted through pipes. These heat distribution

systems can be important sources of heat loss. Check air ducts for leaks, and consider insulation

for water and steam pipes.

Controls

The controls used to regulate typical oilheat systems include the following:

(1) The Thermostat "tells" the burner when to

turn on and off to maintain the desired temperature in the house. Programmable

thermostats automatically lower and raise temperature settings at timed intervals throughout the day and night, to conform to the changing ne_edsof the home occupants.

This can produce significant fuel savings.

(2) TheAquastat regulates the temperature of

boiler water.

(3) The Fan Control turns the fan on and off in

warm air furnace systems.

(4) Pump and Zone "/hive Controls regulate the

flow of water or steam in boiler systems.

(5) Safety Controls such as pressure relief

valves, high temperature limits, low water cut offs, and burner primary controls protect

against appliance malfunctions.

When adjusting controls, follow manufacturer's instructions.

The House

The house itself has a major effect on the

performance of the heating system, especially on the combustion air supply. Newer, tightly sealed houses have different requirements than older

houses with greater air infiltration. Exhaust fans, vented clothes dryers, and ventilating systems

also have an effect on available air for combus- tion. It is essential that the technician consider

these factors when recommending a heating system, or diagnosing system problems.

BASIC OIL BURNER DESIGN

Most oil burners in use today operate as follows: (See Figure 13.)

(1) Oil is delivered under pressure (usually about

100 psig--although some models require pressures in the 140-200 psig range) by the oil pump (A) to the nozzle (B). Check manufacturer's specifications for proper pump

pressure settings.

(2) The nozzle breaks up the oil into a spray of

tiny droplets from .0002 to .0100 inches in diameter which evaporate rapidly into a vapor.

(3) The vapor is mixed at the burner head with a

stream of air from the blower wheel (C).

(4) The oil vapor combines with oxygen from the

air stream and is ignited (initially) by an electric arc from the electrodes (D), powered by a high voltage transformer (E), to produce

a flame.

(5) Heat is reflected back into the flame by the

combustion chamber, to help evaporate the oil droplets. This helps achieve more complete burning of the oil.

(6) This combustion process continues until the

burner is shut down for the off cycle.

(7) The entire process begins again with the next

on cycle.

Combustion Heads

The combustion head (also referred to as the turbulator, fire ring, retention ring, or end cone)

creates a specific pattern of air at the end of the air tube. The air is directed in such a way

as to force oxygen into the oil spray so the oil can burn.

Flame Retention Heads vs. Non-Flame Retention Heads

NOZZLE

ELE

CLAMP SCREW _ STA_dC PLATE _\

SPtDER SPACER ASS'Y J _- KNURLED NUT

FIGURE 13 Typicaloilburner components

Flame Retention Burners

Most oil burners currently being manufactured and installed are flame retention burners. The

name comes from the combustion heads which are designed to hold-in or "retain" the flame.

High-speed motors are used to produce high air pressures. This allows the burner to do a superior

job of mixing air and oil. An intense swirling

motion produces a compact, highly stable flame

which is held (retained) close to the burner head. Flame gases are recirculated, to aid evaporation

of oil droplets and achieve cleaner, more efficient combustion compared to non-flame

retention burners.

The majority of combustion heads in the field today are flame retention heads. These heads

differ from the non-flame retention heads in that the flame is held very close to the face of the

head. The flame is smaller and more compact, and usually is 300°F to 500°F hotter than with non-flame retention heads. (See Figure 15.)

The flame retention head incorporates three basic elements: (1) center opening, (2) primary slots, and (3) secondary opening. The center opening

is an orifice in the center of the head which allows the oil spray and the electrode spark to

pass through the head. The primary slots are the slots that radiate out from the center opening

toward the outside of the head. The secondary opening is a slot which is concentric to the

center opening and follows the circumference of the combustion head. All three openings affect the way air is delivered to the oil spray.

Air Pattern- Non-Flame Retention Burner

Air Pattern-FlameRetentionBurner

In most cases, your customers can obtain substantially improved heating system efficiency

by replacing old non-flame retention burners with new high-speed flame retention burners. Beckett supplies a full line of these burners to accommo- date a wide range of residential and conur_ercial boilers and furnaces. See Chapter 6 for specific

burner recommendations.

10 FIGURE14Burnerairpatterns

Generally speaking, it is advisable to choose a flame retention head over a non-flame retention

head in the majority of applications. There are a few existing heating units in the field which have

used a non-flame retention head in a steel chamber. These units can be retrofitted with a

new burner and non-flame retention head, or could use a flame retention head with the

addition of a chamber liner for protection against the hotter flame temperatures produced by the

flame retention head.

Non-Flame Retention Burner

The fixed head is an excellent performer in most warm air applications. Since the chamber in

these units becomes approximately 2000°E any oil which is not burned in the flame is usually ignited by the heat of the chamber. As with warm

air units, a fixed head will also work very well in the majority of boiler applications.

The variable head is an excellent performer in most wet base or wet leg boiler applications that have minimal or no combustion refractory. The variable head gives the user two advantages over the fixed head. The first advantage is the ability to fine tune the position of the head so as to supply the flame with the precise amount of air through the secondary slot that it needs in order

to achieve the highest performance levels. The second advantage is that most variable heads are actually recessed into the air tube, which protects the flame base from being affected by recirculat- ing combustion gases within the chamber.

Combustion Head 0 Cast Iron

FlameRetentionBurner

FIGURE 15 Burner flame configurations

Fixed Heads vs. Variable Heads

Most flame retention heads found today can be classified as either fixed head orvariable head.

The only major difference is the method of controlling the secondary opening. The fixed head group has the secondary opening preset to a

specific size fora specific firing raterange. The variable head group allows thehead to move forward and backward according to the firing rate

requirements.

Firing Range

It is always necessary to choose a head ',,chose

firing rate range is closely matched to the firing 'rate requirements of the heating unit. As an example, if the firing rate of the heating unit is

1.50 gph, head #1 has a range of .85-1.65 gph,

and head #2 has a range of 1.10-2.00 gph, the head to choose for the highest performance

would be head #1 (the .85-1.65 gph head), The reason is that the higher rated head #2 has a

larger secondary slot than the lower rated head to enable it to reach the top end of its range. Either head will work, but the higher rated head #2

will probably not reach the same high CO2 performance levels as the lower rated head because of the extra air it will allow through the secondary slot.

The Effects of Pre-Purge and Post-Purge on Oilheat Burners

Without purge capabilities, burner blowers are turned on at the time the flame is ignited, and

turned off when the flame is extinguished. This works well in most cases, but some applications present problems. When a heating system

thermostat signals the need for heat, it is desir- able to supply it promptly. Any delay in

providing heat can cause discomfort for home or building occupants, precipitate nuisance service calls, and have a negative effect on fuel effi-

ciency. To supply heat quickly, the burner flame must ignite instantly and smoothly. It requires adequate airflow (draft) to accomplish this. Typically, when an oil burner has been off for a

while, natural draft in the chimney can become neutral. Cold chimneys contain heavy air that

must become heated and start to flow upward before draft can occur. There could even be a

down draft due to wind gusts. In chimneyless, direct vented systems there may be no draft at

all at start up. With power vented systems, draft levels may fluctuate widely. That's where pre-purge

comes in.

The pre-purge controls currently offered by

Beckett as a factory-installed option on its models AF II and AFG burners turn the blower on several

seconds before the flame is ignited. This estab- lishes the level of airflow required for fast,

smooth ignition. This airflow is already fully established when ignition occurs. The burner doesn't have to "struggle" to achieve ignition under inadequate draft conditions. Another significant factor is the stability and capacity of

the ignition arc. The arc should be at full strength and well established when the oil is delivered

from the nozzle--otherwise, delayed ignition, noisy pulsation, and smoking can occur under certain adverse conditions. With pre-purge, the arc is allowed to reach its maximum potential,

contributing to easier ignition of the oil droplets, and producing a cleaner burning flame from the moment of ignition. In addition, the oil pressure level in the pump is stabilized well before the oil

solenoid valve opens. Oil is delivered to the nozzle at a steady pressure, for optimum atomiza- tion of the fuel.

of combustion gases into the home. The heat from the gases can also affect nozzles and other system components. Post-purge keeps the blower operating for a selected period after burner shut- off. Flue gases are evacuated, draft-reversal is eliminated, and nozzles are protected from overheating. Most controls used by Beckett are

adjustable to the specific requirements of the

heating system. Direct vent systems have created

a special application for post-purge capability. With direct venting, the positive air pressure created by the burner blower is relied on to move combustion gases through the flue and evacuate

them from the system. It is vital, therefore, that

the blower continue to operate for a period of

time at the end of each burner cycle. In the past,

pre-purge and post-purge capability was obtained

for the most part through retrofit installation of

optional kits. Now, factory-installed controls, like

those offered on the Beckett AF II and AFG

burners, provide greater convenience for oilheat

service technicians, and reduced costs for

homeowners.

Oil burner nozzles come in a wide range of

designs and sizes. It is essential that the correct

nozzle be used in each installation to assure

compatibility with the burner and produce the

desired spray pattern for the appliance in which

the burner is used.

Post-purge is involved with the other end of the burner cycle. When the desired heat level in the home or building has been achieved, the thermo-

stat calls for burner shut-off, which occurs immediately without post-purge. As a result,

combustion gases may still be present in the flue without sufficient airflow to evacuate them. Draft

reversals may also occur, forcing flue gases back into the flue pipe and the combustion chamber.

This can cause odor problems and/or the leaking

Cutaway View of A Fuel Oil Nozzle

FIGURE16Cutawayviewofa fueloilnozzle

When replacing nozzles, it is usually best to use a nozzle identical to the one supplied as original

equipment by the burner manufacturer. Consult burner manufacturer specifications whenever possible. If these are unavailable, a call to the manufacturer might be advisable. Do not assume that the nozzle currently in use is the correct one.

It may have been installed in error during a prior burner servicing.

In some cases, improved combustion can be achieved by changing to a nozzle of a size or design different from that of the original equip- ment nozzle. However, such changes should be

attempted only after careful consideration of all relevant factors and checking with the appliance

SERVICEHOTLINE1-800-OIL,BURN

FIGURE 17 Beckett Multi-Purpose Gauge

4. When installing the nozzle, use extreme care to protect the nozzle orifice and strainer. If the

orifice gets dirt in it, or becomes scratched, it will not function properly.

5. Do not over tighten the nozzle when tighten- ing. Excessive tightening can cut grooves into

the adapter and cause leaks when the next nozzle is installed.

Nozzle Spray Patterns and Angles

The size and shape of an oil burner flame are determined by the pattern and angle of the oil spray, which, in turn, are determined by the

design of the nozzle and the pressure of the oil and air supplied to it.

The three principal types of spray patterns are solid, hollow, and semi-solid. (See Figure 18.)

Spray angle categories vary from 30° to 90°. It isessential that the combustion air pattern

conform to the oil spray pattern. If the air pattern is too wide, the droplets at the center of the oil

spray will not be exposed to a sufficient quantity of air for efficient combustion. If the air flow is

too narrow, the droplets on the outside of the oil spray will not receive sufficient air.

Finally, the shape and size of the flame (deter- mined by the nozzle design, oil pressure, and air pressure) must conform to the dimensions of the combustion chamber. The flame should be large

enough, and shaped in such a way, to almost fill

manufacturer--and post-installation testing should be done, to make sure the new nozzle is

performing properly. When installing a nozzle, a gauge should be used

to insure correct depth and concentricity. The gauge shown in Figure 17 is available from

Beckett, free of charge, on request.

Proper Nozzle Installation

1. Make sure the fuel supply is clean and free of air or bubbles.

2. Make sure the pump pressure is set properly. For domestic applications it may be 100 psig to 200 psig. (Check manufacturer's specifica-

tions.)

3. Inspect the nozzle adapter before installing the nozzle. If there are deep grooves cut into it from

over-tightening, replace it. Those grooves, or a scratched surface, can cause leaks.

Solid

Semi-solid

FIGURE 18 Nozzle spray patterns

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