1

HVACR114 – Electrical for Gas Heat

HVACR114 – Electrical for Gas Heat

What is electricity?What is electricity?

2

SECTION 1SECTION 1WHAT IS ELECTRICITY?WHAT IS ELECTRICITY?SECTION 1SECTION 1WHAT IS ELECTRICITY?WHAT IS ELECTRICITY?

NEXT

3

ELECTRONSELECTRONS

Atoms are made of particles called protons, neutrons, and electrons.

Protons have a positive charge. +

Electrons have a negative charge. -

(Neutrons have no charge and have no electrical effect.)

NEXT

4POTENTIAL DIFFERENCEPOTENTIAL DIFFERENCE

An imbalance of electrons is called a potential difference, or an electromotive force (emf).

A potential difference can be created by:

•Friction (static electricity)

•Chemical action (batteries)

•Magnetic activity (generators)

•Thermoelectric (heat)

•Photoelectric (light)

The unit of measurement of emf is the VOLT.

NEXT

5

MEASURING VOLTSMEASURING VOLTS

Voltmeters are used to measure potential difference between two specific points.

Voltmeters are available in analog or digital types.

NEXT

6

There must be a potential difference for the meter to register a voltage reading.

POTENTIAL DIFFERENCEPOTENTIAL DIFFERENCE

NEXT

7

POTENTIAL DIFFERENCEPOTENTIAL DIFFERENCE

The voltage tester reads zero when no potential difference exists between the two probes.

Likewise, if the voltage is 120 at both probes, the meter reads zero.

NEXT

8POTENTIAL DIFFERENCEPOTENTIAL DIFFERENCE

NEVER TOUCH AN ELECTRICAL WIRE BECAUSE NEVER TOUCH AN ELECTRICAL WIRE BECAUSE A ZERO VOLTAGE READING WAS OBTAINED!!A ZERO VOLTAGE READING WAS OBTAINED!!

You may be reading the same potential (no difference) between the probes.

Additional tests are required to determine if voltage is (or is not) present.

WARNING!WARNING!

NEXT

9

AMPERAGEAMPERAGE

Ampere, amperage, amps, and current are terms commonly used to describe the quantity and intensity of electrons moving through a conductor.

When current flows through a conductor, a magnetic field is created.

The clamp-on ammeter is most commonly used on AC circuits.

NEXT

10

RESISTANCERESISTANCE

Resistance refers to anything offering opposition to current flow.

Electron flow is energy in motion and must be controlled.

There are several types of resistance that will be discussed,

but a basic understanding of Ohm’s Law is is necessary before that discussion.

NEXT

11

OHM’S LAWOHM’S LAW

The relationship between Volts ( E ), Amperes ( I ), and Resistance ( R ) can be expressed mathematically in the formula E = I x R.

Therefore, if two of the values are known, you can solve the equation to find the other.

The following pie chart example may help you remember the formula.

NEXT

12

Using the pie chart, cover the value that you want to find.

By covering the “I”, you see that the formula is “E” divided by “R”. By covering the “R”, you

see that the formula is “E” divided by “I”.

By covering the “E”, you find that the formula is “I” times “R”.

Ohm’s Law Pie ChartOhm’s Law Pie Chart

NEXT

13TYPES OF RESISTANCETYPES OF RESISTANCE

Pure Resistance

Inductive Reactance

Capacitive Reactance

Pure resistance remains constant, such as in a heating element or a light bulb.

Inductive reactance is caused by the magnetic field that develops around a conductor, especially in coils or motors.

Capacitors store and discharge electrons that create an opposition to current flow.

The total of pure resistance, inductive reactance, and capacitive reactance is called Impedance.

NEXT

14

MEASURING RESISTANCEMEASURING RESISTANCE

An ohmmeter is used to measure pure resistance. Batteries inside the meter provide a power supply to measure electron movement. NEVER connect an ohmmeter to a circuit with the power on or damage to the meter may occur.

Also, be sure that the component you are measuring is electrically disconnected to prevent a feedback circuit and false readings.

Resistance can be calculated on live circuits by measuring voltage and amperage, then using Ohm’s Law, voltage divided by amperage equals resistance.

NEXT

15

WATTAGEWATTAGE

Electrical power is the rate at which electricity is used to perform useful work.The work performed is measured in units called watts.

Watts are calculated by multiplying amperage x voltage.

W = I x E746 Watts is equal to 1 horsepower.

NEXT

16WHEEL OF ELECTRICITYWHEEL OF ELECTRICITY

Volts ( E ), Amps ( I ), Ohms ( r ) or Watts ( W ) can be calculated if you know two of the values.

NEXT

17