Appliance Electrical - Basic Electricity for Appliance Repair

Appliance Electrical - Basic Electricity for Appliance Repair
If you are reading this, then most likely you are not an experienced Appliance Service Technician. Good, well qualified Appliance Service Technicians, have a thorough understanding of electricity, and how that relates to repairing major appliances. Most likely if you are here, you are an inexperienced Appliance Service Technician, or someone who wants to repair their own broken appliance, and save some money. A complete explanation of the theory of electricity, Ohms Law, series and parallel circuits etc., as it relates to major appliances is beyond the scope of this forum. Our intention here is to help you understand some basics, so that you can get by and repair your broken appliance.

The Flow of Electricity
A simplified way to understand how electricity gets from the power plant to your home, is to visualize the fact that the power company is producing electrons. Electrons need a complete path back to the source, or ground, in order to flow. It is the flow of electrons passing through a conductor, then through a component that does work, such as a heater, or motor, that makes your appliance work. Visualize a pipe loaded with ping-pong balls. If that pipe is completely full of ping-pong balls, when another ball is inserted in the end, a ping-pong ball must come out the other. For our purposes here, all you need to do is realize that electrons are like the ping-pong balls passing through the pipe. Although these electrons are incredibly small, and pass through wire. It is the movement of electrons, through a dryer heater for example, that causes it to heat up. A heater has resistance to the flow of electrons, and therefore causes friction as they pass-through. The friction produces the heat to dry your clothes. Electrical wires are called conductors, because they offer no resistance to the flow of electrons. If they did, they would heat up. The components on a major appliance that controls the electrical flow, such as, switches, timers, electronic controls, thermostats, and other devices have no resistance to the flow of electrons. If they did, they would heat up. Which is exactly why sometimes you will see a switch that shows evidence of having been hot, and may even be melted. Since it is the flow of electrons that allows work to be done in your home, operating your appliance, lighting your lights, etc., there must be a continuous flow of electrons. These electrons must find a way out of your home and return the source, or ground. Technically electricity leaves your home and returns to the closest transformer, usually located on a pole, but for our purposes, remember that it must come in and out of your appliance. Electricity delivered to homes is actually alternating current. In other words, it moves back and forth. But for our purposes, imagine that it comes in your home, through your service panel, through your appliance, and back out of your home through the service panel.

What Is a Load
A load in an electrical circuit is the device that does the work. For example, a washing machine fill valve is a load, along with the motor. On a dryer, the heater and the motor are the major loads to electrical current flow. A load must be controlled by switches, electronic controls, or another type of device that controls the flow of electricity.

A load must have resistance to the flow of electricity. This resistance to the flow of electricity allows the load to do its work. For example, a motor on a dryer has two sets of winding, the run winding, and the start winding. Both windings have different resistances to the flow of electrons. This allows the windings to create electromagnetic fields at different points within the motor to force the motor to start turning. Loads on major appliances can be checked using an ohmmeter. All loads will show resistance, otherwise they would be conductors.

What Is a Switch
A switch controls the electrical flow to a load. For our purposes, electronic controls and timers are switches. Timers are actually made up of a series of switches that control the flow of electricity. Most electronic controls use low voltage relays to switch a set of contacts that control the loads. A simple control thermostat on a dryer for example, is nothing more than a switch. A switch opens and closes a set of contacts to allow electricity to flow to the load. Switches have no resistance. A lot of experienced Appliance Service Technicians will check a switch when the appliance is energized with electricity. That's because sometimes when you check a switch, it will read good, but when it comes time for the current to pass through it, there will be a voltage drop across it. When you see voltage across a switch that is supposed to be closed, it is open. Furthermore, the circuit is complete in both directions, in and out of the switch. That's because in order to read voltage across a switch, the circuit through the load must be complete. Plus any other switches must be electrically closed to allow electricity to get to that point. If you are inexperienced, you should not check an appliance that is plugged into an electrical circuit, there is a significant danger of electrical shock. You will have to rely on your ohmmeter to check loads and switches.