Lesson 9. Electricity Basics

Electricity Basics

Electricity is a form of energy that has been generated from coal, natural gas, nuclear and hydro energy.  Electrical energy is convenient to use in small and large appliances because of its magnetic qualities.  Electric motors and controls are easy to manufacture, compact and are low cost compared to the alternatives.

Most of the electrical power we use in our homes or buildings is alternating current (AC).  Direct Current (DC) is primarily used where storage of energy in a battery is required.

It is important to understand how to measure electricity and how to meter electricity.  Following are terms you must understand in order to work in the HVAC Industry.
• Volt:  This is a measure of electrical pressure.  Low voltage electricity is safe in comparison to higher voltage.  Low voltage, 24 volts is commonly used to control HVAC units using a thermostat or other switching control.  120 volts is common for portable household appliances where plugs are connected and disconnected.  220/240 volts is the highest voltage found in the home and is permanently connected.  440/480 volts is a common commercial voltage.
• Ampere:    The amp is a measure current quantity or flow.
• Ohm:  The ohm is the measurement of resistance to electrical flow.  Ohms law is: Volts =  Amps x resistance (ohms)
• Watt:  A measure of power.  The typical measure may be in 1000 watt increments or kW (1000 watts) volts x amps x pf = watts.  A 100 watt light bulb operating on 120 volts would draw .83 amps. (100/120=.83)
• Power Factor (pf):  Power Factor is a measure of the electrical system efficiency.  A .95 pf is normally assumed if you don’t have a power factor meter.

We can measure volts, amps, resistance (ohms) and pf (power factor) with meters.  One common tool a HVAC tech needs is a multimeter to measure volts and ohms and an amp or current meter to measure amps.  You can purchase a multimeter that that will measure everything, but the recommended meter is a single multimeter to measure volts, ohms and amps.  Fieldpiece has a multimeter with a detachable amp clamp that can be very useful.

Electricity flows freely (low resistance) in some materials like copper.  Other materials like plastics or glass have high resistance to electricity.  Copper wire is used to transport electricity and plastics are used to insulate the copper to make the use of electricity safe.

It’s time to purchase a multimenter, study ecletricity safety and start using your new knowledge.

Start getting ready for your EPA Test with our EPA Study Guide and sample test questions.

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