Electricity As Applied to Gas Systems (Part 1)
by Timmie McElwain

I am often asked by technicians in the plumbing and heating industry for some information on Basic Electricity. So I thought I would do several articles on some really basic electricity. I do not want to get into a lot of formulas but just want to give some of the fundamentals to help those who are interested in this particular technology.

These articles are designed to assist the heating technician in diagnosing and troubleshooting electrical circuits used on heating systems. It is specifically targeted toward gas heating systems. It should however be noted that many of the techniques used herein can be applied to troubleshooting any type heating system.

It is our approach that practical application to actual troubleshooting is what is needed. These articles are not for the purpose of teaching electrical or electron theory. That is not to say that any knowledge of electricity and electronics will not help you it most certainly will.

THIS SERIES IS FOR YOU IF:
• You have trouble knowing where to start in a circuit diagnosis. 
• You are intimidated by circuitry 
• You spend a lot of time troubleshooting heating systems. 
• You find that you have a lot of callbacks.

In the first few articles we will include some definitions and some electrical theory – or better electrical relationships. There is also a section on circuit components and symbols used in wiring diagrams. There will be a section on circuits and diagrams. We will also go over test equipment and meters.

APPLIED ELECTRICITY FOR GAS APPLIANCE SERVICEMEN 
Everything on this earth is made up from tiny particles, so small they cannot be seen with the most powerful microscope. These particles are attracted to each other with great force in the case of solid materials like iron or copper, with less force in the case of liquids like water or oil, and with the least force in the case of gases like oxygen or hydrogen.

Story continues below ↓

advertisement | your ad here

Scientists have identified several different kinds of these particles, but the only one that holds our interest when learning about electricity is the electron. Electrons exist everywhere -- in the air, water, in every single object in the world.

During normal conditions, each object on the earth has its own definite number of electrons. The number depends upon the size and nature of the object. In metals like copper, silver, or aluminum, some of the electrons are continually wandering around inside the metal itself. These electrons are known as “free electrons”, because they are free to move. The rest of the electrons always stay in the same locations; in fact, if we could move them, we would be able to change one metal to another. We could then make gold out of lead. Whenever an object has its normal number of free electrons, that object has no electricity and is said to be “neutral” or “uncharged”. We can secure electricity either by taking some of these free electrons away from an object or by adding more free electrons to an object, because we then upset the normal balanced condition.

It can be said then, whenever an object has more or fewer electrons than normal, electricity exists in an object. An example of this is an automobile, which will collect free electrons from dust particles in the air as it is being driven. When the automobile is stopped and a person standing on the ground touches the automobile, the extra free electrons rush to the earth to neutralize the automobile and a slight shock may be felt if enough current passes through the body.

But where can we get extra free electrons? We get free electrons in our work from a battery, a power line, a thermocouple, or a thermopile. So that we can understand the movement of electrons, which would be an electric current, let us examine the law of electric charges. There are two kinds of charges, quite unlike, and for convenience they are called “positive charges” and “negative charges”. An object or terminal that has a “negative charge” contains more electrons than normal. An object or terminal has a “positive charge” when ever it has fewer electrons than normal.

Two electric charges cannot exist side by side without trying to move each other. Nature has its own law, which tells which way they will move. If two charges are alike (either positive or both negative) they will repel each other or tend to push each other away. If the two charges are unlike (one positive and one negative) they will attract each other and tend to move together. Lets repeat this law. Like charges repel. Unlike charges attract.

FIGURE 1

Let us apply this to a fl ashlight battery (Fig. 1). A battery always has two terminals, one having more electrons than normal and the other having fewer electrons than normal. The battery itself produces this condition by chemical action, which need not be studied here.

The battery terminal, which has more electrons than normal, is called the “negative terminal” (An electron is a negative charge). We use a minus (-) sign to indicate that this terminal is negative. The battery terminal, which has fewer electrons than normal, is called the positive (+) terminal.

FIGURE 2

When we connect a wire between the two terminals of the battery, we secure a “complete circuit” (Fig. 2). Here is what happens: The instant the circuit is completed, the extra electrons on the negative terminal rush into the wire because they “sense” a clear path ahead to the (+) terminal. These moving electrons from the battery bump into free electrons in the wire, and push the free electrons forward toward the positive terminal. In no time at all, every electron gets bumped. All along the wire, electrons begin pushing other electrons toward the (+) terminal. Each time an electron is pushed into the (+) terminal, another electron enters the wire from the (-) terminal.

FIGURE 3

The movement of electrons through a complete circuit can be compared to the movement of marbles through a length of tubing (Fig. 3). Each time a marble is pushed in one end of the tubing, an entirely different marble pops out of the other end of the tube. The movement of electrons through a complete circuit is called an electric current. The more electrons we have moving past a given point in the wire each second, the greater is the value of current fl owing through the wire.

Reviewing the behavior of current through a wire we realize that when one end of a wire is connected to one terminal of our 1-1/2 volt battery, the free electrons in the wire are ready to “go places” but nothing can happen yet. Our wire is merely an extension of the terminal it is connected to. When we connect the other end of the wire to the remaining terminal of the battery, we get action immediately because the circuit is completed.

CONDUCTORS
Conductors have many free electrons. These electrons are easily pushed around; therefore, it is easy to pass current through a conductor. Most metals are good conductors of electricity (Fig. 4). Copper is generally used because of its abundant supply, thus being more economical. Copper offers very little resistance to electron flow, and when used as short pieces of connecting wire, such as in an appliance, the resistance is considered to be zero.

FIGURE 4

CONDUCTOR SIZE
The size of the wire is important when designing the electrical section of an appliance. Wire size is determined by the amount of electricity that must be supplied to a current using device. For instance, a thin copper wire will relay a few electrons easily; however, if the electrons are pushed too fast, they resist this fast movement in the form of friction.

This friction produces heat and could possibly melt the wire. This is called overloading (Fig. 5). Heavy copper wire has many more free electrons than the small copper wire. This means that many electrons may be relayed along the wire to do heavy work without having to travel so fast, thus avoiding overloading.

FIGURE 5

INSULATORS
Insulators have very few free electrons and these free electrons cannot be pushed from one section of the insulative material to another section. Since these materials will not allow their electrons to be relayed, they will not pass an electrical current (Fig. 6). By covering conductors with insulative material, the current must follow through the conductor and perform the work it was intended to do. The type of insulative material chosen should depend upon the conditions of installation. Plastic material is a good insulator where heat is not involved. High temperature insulation is preferred where the surrounding temperature is high.

FIGURE 6                                                                                      FIGURE 7

RESISTORS
Resistive materials have a few free electrons but not an abundant supply like conductors. These electrons can be pushed if sufficient force acts against them. When they are moved, the friction caused by resistance produces heat (Fig. 7). Further, the resistance of the material increases with heat. This is fortunate because we can use the increased resistance of heat to regulate the flow of current through a current using part. For instance, we want the filament of an electric light bulb to get to a white heat to emit light, but not hot enough to melt. The manufacturer of the bulb carefully selects the type of filament material, the cross sectional size, and length to produce the amount of light desired without burning up. As the filament gets to a white heat, the increased resistance of the material limits the flow of current through the filament.

ELECTRICAL MEASUREMENTS
The following electrical measurements are compared to gas for ease of understanding. Although this cannot be done with complete accuracy, the similarities will help to understand electrical measurements. Let us review for a moment how natural gas accomplishes its work. First, we need a quantity of gas. Second, we need pressure to force the gas to a burner so that the ultimate power can be realized. The amount of power developed depends upon how many B.T.U.’s are consumed during a certain time, normally expressed in “B.T.U.’s per hour”. If the pressure remains constant we can increase the power by increasing the B.T.U. content of the gas. Or, if the B.T.U. content remains constant, increasing the pressure can increase the power. A third consideration is the resistance in the transmission lines, which reduces the pressure along the line. In fact, an orifice is used at a burner to limit the flow of gas to only that quantity desired for the burner.

Voltage
The electrical “pressure” which is capable of setting electrons in motion in a circuit is called “voltage” (Fig. 8). The stronger the voltage the greater the effect it has on electrons. Like gas pressure, voltage is the force that moves the electrons along a wire in a circuit. Voltage is sometimes referred to as the electromotive force (E.M.F.). A volt is a unit of electrical pressure.

FIGURE 8

NEW Advanced Electric Ignition Systems Manual

We have just finished with a brand new set of manuals on Advanced Electric Ignition Systems. It includes SmartValve™, Electronic Fan Timers, Integrated Boiler Controls and Integrated Furnace Controls. It will also include the latest Universal Replacement Controls for EFT’s and Integrated Furnace Controls. It is in two volumes Advanced Electric Ignition Systems Volume I with 261 pages filled with information every installer and service technician needs. There are 32 color illustrations in the manual. There is also Advanced Electric Ignition Systems Volume II filled with excellent information on Integrated Controls and Universal replacements with 345 pages and over 50 color illustrations.

We also have a series of manuals just recently completed on Electric Ignition Systems. Volume I contains 11 chapters with 190 pages of excellent information on all systems, which cover Intermittent Pilot Ignition Systems and Universal Replacement Controls. Volume II that contains 311 pages in 10 Chapters is a continuation of Volume I. Volume I include the following in Chapters 1 through 11: Many of the chapters in this manual have been presented here in this paper. This is an opportunity to get everything in one set of manuals: Principles of Flame Rectification; Flame Rectification Applied to Intermittent Pilot Applications; Intermittent Ignition Devices; Intermittent Pilot Controls; Troubleshooting Intermittent Ignition Systems for Gas Furnaces and Boilers; Checkout for All Systems; Johnson Controls; Honeywell Controls; Robertshaw Controls; White Rodgers Controls; and Fenwal Controls.

Volume II contains 10 chapters and is a continuation of Volume I. Volume II covers Direct Burner Ignition, both Direct Spark Ignition and Hot Surface Ignition. Volume II also contains a chapter on Universal Replacement Gas Valves. Universal replacement controls are covered in all chapters. The following are included in Chapters 12 through 21: Direct Burner Ignition Controls/ Honeywell Direct Spark Ignition; Fenwal DSI Controls; White-Rodger DSI Controls; Hot Surface Ignition; Honeywell HSI Controls; White-Rodgers HSI Controls; Robertshaw HSI Controls; Fenwal HSI Controls; Hot Surface Ignition Troubleshooting; and Universal Replacement Gas Valves.

We continue to offer our manuals Circuitry and Troubleshooting Volume I and Volume II.  We have two OTHER manuals in their second printing. The first one is titled FUNDAMENTALS OF GAS VOLUME I. In addition we also have FUNDAMENTALS OF GAS Volume II, which covers “Air for Combustion” and “Venting” it is up to date with the latest changes to the Fuel Gas Code Book.

In addition we have now 63 Troubleshooting Guides and that along with all the manuals we offer (25 different manuals) will give you a well-rounded education on all aspects of gas heating systems and the controls along with the procedures you need.

We also conduct seminars on the following topics and many others: • Fundamentals of Gas • Circuitry and Troubleshooting • Hydronic Controls • Electric Ignition Systems • Advanced Electric Ignition Systems • Powerpile Systems • NEW Combustion Testing Design Gas Equipment • Conversion Burners • Modulating/Condensing Boilers

If you are interested in information call 401-437-0557 or write to: Gas Appliance Service Training and Consulting; 22 Griffi th Drive; Riverside, RI 02915 or E-mail gastc@cox. net.