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NORA Oilheat Technicians Manual

8-6 Basic Electricity Figure 8-4: Open and closed switches Chapter 8 Basic Electricity Figure 8-3: Water circuit Electrical circuits The most important thing to understand about electricity is the electric circuit. Electricity has to flow from a source out into the circuit and back to the source. Figure 8-3. A typical circuit, then, has a conductor that carries the electric current from the source, through a switch, to a load—and back to the source. Current flows only in a complete circuit. However, the energy it gains in the electromotive force (measured in volts) from the power source is lost in the resistances (ohms) it encounters in the circuit. The switch is a device that interrupts the circuit. When it is open, electricity can’t flow. When closed, the circuit is complete and the flow continues. See Figure 8-4. materials are used to contain or control the flow of electricity along a conductor, such as a copper wire. Because air is a good insulator, the resistance of the air stops the electricity at the end of a wire like a wooden plug stuck in the end of a pipe. If enough water pressure is put on that plug it will pop out and the water will flow. If enough electric pressure (volts) are put against the insulating air it, becomes a conductor and lets the electricity flow in the form of a spark. A ten thousand volt transformer can make electricity jump across the air space between the ignition electrodes in an oilburner. This creates the “spark” that ignites the oil. Loads A load is a device that converts electrical energy to some other form of energy in order to do work. A load also creates resistance that opposes electrical flow. Here is an example: a light bulb converts electric energy to heat and light because the filament resists the flow of electricity, getting so hot it actually glows. Another example: a motor changes electric energy into mechanical energy. Some of the loads found in oil burner circuits are: • Motors—in the burner, circulator, fan, power venter, humidifier • Electromagnetic coils—in relays, solenoid valves • Transformers—in ignition and control • Heaters—in the primary control safety switch, thermostat heat anticipator


NORA Oilheat Technicians Manual
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