Breaker Panel Basics

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Breaker Panel Basics

Breaker Panel Basics

Service Panel | Breakers | 240-Volt Circuits | GFCI | Neutral & Ground


appliance repair safety

The breaker panel is your home’s electrical jugular vein and a safe way to CUT power to an appliance for a successful and safe repair. We have become so accustomed to electricity that we sometimes forget that it can also be extremely hazardous.  Because of this often overlooked fact, several types of electrical safety devices are installed into every home to make the use of this modern day necessity a little less dangerous.

Service Panel

Electricity enters the house through three incoming electrical service wires that are attached the two top lugs of the meter mount inside the main service panel.  At the top of the service panel a meter is installed to measure the amount of electricity being used within your home.  When the meter is in place, power is supplied to two bottom lugs. The main breakers then close the circuit from the bottom lugs to a set of separate, metallic strips that extend through the center of the service panel called buss bars.  Which, in turn, pass it along to the circuit breakers.

Breaker Panel Basics Video

breaker panel safety Do Not Remove The Breaker Pannel Cover!appliance repair safety

Breakersappliance breakers

Breakers are designed to tolerate a predetermined amount of amperage or current flow before they will automatically open and break the circuit.  Every separate circuit within your home has its own breaker switch.  Most breakers’ amperage ratings are clearly marked on the switch as 15A, 20A, 30A, 40A, 50A, etc.  (Electricity 101 has a more thorough explination of amperage and wattage loads as well as the relationship between the two.) Your home circuits should be labeled within the service panel for example, Kitchen Circuit, Dishwasher, Master Bath, or Sub Panel.  A sub panel is an additional service panel located in some other location that receives its electricity supply from the main panel.  In addition to automatically opening to remove power from a circuit, you can also manually turn the power off to an individual circuit or the entire house with these switches.

How It's Made

240-volt circuits

240 volt appliance circuit

A 120-volt circuit will be connected to only one of the two buss bars while a 240-volt circuit will be connected to both bars, each supplying 120 volts.  A 240-volt circuit requires ether one special breaker switch that attaches to both buss bars or two switches tethered together.  If one of these two breakers “trip” or open the 240-volt circuit will only be supplied 120 volts.  This is especially important for electric dryers, electric cooking appliances, and air conditioner units.

GFCIgfci appliance outlet

Outdoor, kitchen and bathroom receptacles should be protected by a special ground-fault circuit interrupter (GFCI, or GFI) circuit breaker to guard against electrocution. Ground fault receptacles are highly sensitive to any short, and will trip or open at the slightest sign of trouble. These devices are often the cause of multiple dead outlets, as soon as a GFI receptacle “trips” it will stop electricity from flowing to the entire electrical circuit on which it is installed. You can test a GFI receptacle by pressing the test button. If the GFI plug is active you should hear a pop as the internal breaker clicks open. If the GFI plug is tripped you can reset it by pressing the bottom button. If the plug will not reset you will need to look for the source of a short within the home circuit.

Neutral & Groundneutral appliance circuit

A Circuit must also have a neutral connection for electricity to flow and do its work. The third supply wire entering the house attaches to a neutral connector this creates an area of electrical “low pressure” causing the electrons to flow.  If this neutral return connection is broken electricity will not flow.  All circuits should also be grounded.  A continuous conductor (often solid copper) ground appliance circuitconnects the neutral connector inside the panel to a ground such as a water pipe or metal rod driven into the ground.  This serves as a secondary safety in the case that the neutral connection is lost you wont become the path of least resistance to ground.  Most components within modern appliances have a connection to ground; however, never assume anything.

How Electrical Parts Work

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washer drain pump

How Appliance Electrical Parts, Controls, & Devices Work

appliance repair meter

Home appliances use circuit control and safety devices as well as resistance loads to make our lives considerably easier. A simple understanding of the function and appearance of the electrical parts used in appliances, as well as the wire diagram symbols used to portray their use will give you a huge advantage in troubleshooting and repairing your home appliance problems. It may seem a little overwhelming at first…Start with an aspirin and the Electricity 101 Page and I think you’ll feel a little better.

Transducer | Thermostat | Thermistor | Light Dependent Resistor | Motor
Coil  Solenoid | Buzzer | Fuse | Resistor | Heater | Lamp | Rheostat
PotentiometerTimer | Transformer | Diode | Capacitor | Ground | Switches


A transducer is a device that converts one type of energy to another. The conversion can be to or from electricalelectro-mechanicalelectromagneticphotonicphotovoltaic, or any other form of energy. With appliances the term transducer commonly implies use as a sensor or detector. However, any device that converts energy can be considered a transducer.



A thermostat is a device for regulating the temperature of a system so that the system’s temperature is maintained near a desired level. Almost all appliances use thermostats in some capacity.  A refrigerator uses thermostats to regulate internal temperatures as well as regulate the need for and length of defrost cycles. Washing machines use thermostats to control water temperatures.  Dryers use thermostats to regulate drum temperatures and to protect against fire hazards.  Cooking appliances use thermostats to maintain an optimum cooking temperature. Thermostats are produced in two main styles fixed temperature bi-metal thermostats that open or close at a set temperature and variable resistance thermostats that fluctuate resistance levels with temperature change to operate a temperature control system.

Thermistor: thermistor

appliance thermistor

A thermistor is a sensor that fluctuates its resistance value with temperature change; this resistance value can then be interpreted by a control system.  Thermistors are often used by electronically controlled dryers such as the Whirlpool Duet dryer or Maytag Bravos dryer to measure the dryer’s drum temperature, the control can then cycle the dryer’s burner or heating element on or off to maintain a more accurate drum temperature.


Light Dependent Resistor (LDR):

 LDRappliance LDR

An LDR is a sensor, which uses light to alter its resistance value, resistance decreases as the brightness of light falling on the LDR increases.  Light dependent resistors are often used on a refrigerator’s dispenser to automatically turn the refrigerator’s night-light off and on as needed.


dryer motorappliance motor compressor appliance motor

A motor is a transducer, which converts electrical energy to kinetic energy (motion). A motor may have multiple speeds, or directions of rotation. Most AC and DC motors commonly used in appliances, use a coil or several coils called the stator to create a rotating magnetic field causing the motors rotor to spin.

Inductor, Coil, or Solenoid:

dryer coilsCoil

A coil of wire, which creates a electromagnetic field when current passes through it. A coil can be used as a transducer converting electrical energy to mechanical energy by physically pulling with the use of a temporary magnetic field, or in the case of an inductor magnetically exciting certain metallic materials to generate heat. One of the most common electrical / mechanical components used in home appliances is the solenoid. A solenoid is an electromagnetic coil that will pull a metallic post opening an internal valve or engage some lever or switch to automatically preform some mechanical function at the proper time.

How To Read Wire Diagrams

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Appliance Repair Wire Diagrams

Understanding Wire Diagrams


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Appliance Assistant Electricity

Electricity 101

Terms | Circuit Elements | Voltage
Amperage | Wattage | Resistance | Electricity Types | Electricity Sources

Appliance Assistant ElectricityAn appliance’s electrical system can be compared with your home’s plumbing system. Electrical current flows along wires in much the same way as water flows through pipes. Both electricity and water enter the home, are distributed through the house, do their “work” and then exit. With plumbing, water flows through a pressurized supply system. With electricity, current flows along “hot” wires. Current flowing along hot wires is also pressurized. The pressure of electrical current is called voltage. Larger supply pipes have a greater capacity to carry larger amounts of water. In the same way, larger wires can carry more current than small wires. Water is distributed for use by faucets, valves, and shower heads. Electricity is made available through receptacles, switches, and fixtures. Water leaves the home through a drain system that is not pressurized. Similarly, electricity flows back through neutral wires. The current within neutral wires is not pressurized and is said to be at zero voltage. Many people make the mistake of overlooking the neutral wires and connections during appliance troubleshooting. You would not ignore a leaking drain pipe in your wall! Don’t forget to consider the neutral connections during your appliance repair. Your appliance won’t work without them!

Circuit Basics… A Great Place To Start!


Circuit: A complete path from positive to negative through which electricity can travel.

Load: Component that converts electricity to heat, light, or motion. All loads restrict the flow of electricity while performing their work.

Conductor: Material through which electricity can flow. It will usually be a copper wire, and sometimes the chassis, or metal frame, on which the components are mounted.

Short: A circuit that offers no resistance to the current flowing through it. A direct short will cause a breaker or fues to blow and possibly start an electrical fire. A direct short is when electrons find an alternate path to a ground source that offers no resistance, such as water or a broken wire contacting the grounded metal cabinet of an appliance.

Shorted Switch: A switch that has fused in the closed position and can offer no resistance to the flow of current through it.

Open Switch: A switch that will not allow current to flow through it.

Closed switch: A switch that will allow current to flow through it.

Continuity: When an electrical circuit is capable of conducting current, it demonstrates electrical continuity. It is also said to be “closed” because the circuit is complete.


1. Power Source

A circuit must have a power source such as electricity supplied by a wall socket, battery, or generator.

2. Conductors

Conductors are usually copper or aluminum wire, in some cases it can even be the frame on which the components are mounted.

3. Load

The load is the components that do all the work through the use of resistance, such as a washer motor, heating element, or light bulb.

4. Controls

Controls are devices that control the flow of electricity to the loads. A control is usually some sort of switch that is operated by the user of the appliance, or operated by the appliance itself.

electrical safetyVOLTAGE

Voltage is the electrical force that moves electrons through a conductor. Voltage is electrical pressure, also known as EMF (Electro Motive Force) that pushes electrons. The greater the difference in electrical potential push (difference between positive and negative), the greater the voltage force potential.

A VOLTMETER measures the voltage potential across or parallel to the circuit. The Voltmeter measures the amount of electrical pressure difference between two points being measured. Voltage can exist between two points without electron flow.

Voltage is measured in units called VOLTS. Voltage measurements can use different value prefixes such as millivolt (mV 0.001volts), volt (V), Kilovolt (kV 1,000 volts)


CURRENT is the quantity or flow rate of electrons moving past a point within the circuit in one second. Current flow is also known as amperage, or amps for short. Higher voltage will produce higher current flow, and lower voltage will produce lower current flow. amperage could be compared to how quickly water is flowing from your bathroom faucet or garden hose.

An AMMETER measures the quantity of current flow. Ammeters are placed in series (in line) to count the electrons passing through it, in much the same way as a water meter counts the gallons of water flowing through it.

Current flow is measured in units called Amperes or AMPS. Amperage measurements can use different value prefixes, such as microampere (µA 0.000001), milliampere (mA 0.001), and Amp (A 1).

Two common effects of current flow are the generation of Heat and Electromagnetism.

When current flows, heat will be generated. The higher the current flow, the greater the heat generated. An example would be a light bulb. If enough current flows across the filament, it will glow white hot and illuminate to produce light.

When current flows, a small magnetic field is created. The higher the current flow, the stronger the magnetic field. An example: Electromagnetism principles are used in alternators, ignition systems, and other electronic devices.


A watt is a unit of measurement applied to electrical power in terms of the amount of energy consumed. Watts can be calculated by multiplying the voltage times the amperage in a circuit. If we continue with the water comparison wattage would be like the volume of water required to fill your bathtub or brush your teeth.


Resistance is the force that reduces or stops the flow of electrons. It opposes voltage. Higher resistance will decrease the flow of electrons and lower resistance will allow more electrons to flow.

Infinite Resistance:
so much resistance that current cannot flow through the circuit (“open circuit.”)

Zero Resistance:
no resistance and current can flow through the circuit (“closed circuit”)

An OHMMETER measures the resistance of an electrical circuit or component. No voltage can be applied while the ohmmeter is connected, or damage to the meter will occur.
Example: Water flows through a garden hose, and someone steps on the hose. The greater the pressure placed on the hose, the greater the hose restriction and the less water flows.

Resistance is measured in units called OHMS.
Resistance measurements can use different value prefixes, such as Kilo ohm (K 1,000) and Megaohms (M 1,000,000).

How To Use A Multimeter

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How To Use A Multimeter

How to use a multimeter for testing appliance parts

appliance repair helping hand

Don’t Have a Multimeter?
Get One Here.

appliance repair meter

Super High-Tech Tip: If you need to check a regular wall outlet (110 VAC) for voltage, plug in a hair dryer or night-light. Your measurement will not be accurate enough to solve some of the very rare home electrical problems but good enough for government work!

Measuring Circuit Voltage

Plug the probes into the meter. Red goes to the positive (+) and black to the negative (-).

Turn the selector dial or switch to the type of measurement you want. To measure alternating current, such as a wall outlet for home appliances use ACV or V~.  To measure direct current, a battery for example – use DCV or V-.

Choose the range setting. The dial may have options from 10 to 1000 on the ACV side, and 5 to 1000 on the DCV side.  The meter should be set at the top end of the voltage you are reading.  For example the setting should be higher than 120 for a 120V wall outlet.  (the measurement scale is set too low, the meter’s internal fuse may burn out.)

Hold the probes by the insulated handles and touch the red probe to the positive side of a DC circuit or either side of an AC circuit. Touch the other side with the black probe.

Read the digital display or analog dial for voltage measurement.

Measuring Circuit Resistance

Select a setting within the Ω (ohms) section on the meter dial. (Ohm’s Law)

how to use a volt meter

Setting options are usually between 200 2000k (thousand)

Using higher range settings will increase the meters sensitivity to resistances.

Touch the positive (red) and negative (black) probes together, the reading you receive is a closed circuit (power can flow with 0 resistance.)