1 / 75

HVAC 132

HVAC 132. Unit 12. Safety Checklist. Do not make any electrical measurements without specific instructions from the instructor. Use only electrical conductors of the proper size and insulation. Electrical circuits must be protected with fuses or breakers.

rnicholls
Download Presentation

HVAC 132

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HVAC 132 Unit 12

  2. Safety Checklist Do not make any electrical measurements without specific instructions from the instructor. Use only electrical conductors of the proper size and insulation. Electrical circuits must be protected with fuses or breakers. Extension cords used by the technician for portable tools and other devices should be protected by ground fault circuit interrupters. When possible, the power should be turned off when servicing equipment. Lock out/Tag out should be practiced.

  3. 12.1 Atom Structure • Matter is made up of atoms, which are the smallest amounts of a substance that can exist • Atoms are made up of protons, neutrons and electrons • Protons and neutrons are located at the center or nucleus of the atom

  4. 12.1 Atom Structure • Protons have a positive charge • Electrons have a negative charge • Neutrons have no charge • Electrons travel around the nucleus in orbit • There are equal amount of electrons and neutrons in an atom • Electrons in the same orbit are the same distance from the nucleus

  5. ELECTRON - + PROTONS + - Atomic Structure fig. 12.1

  6. 12.2 Movement of Electrons Like charges repel Unlike charges attract The electron is kept from falling into the nucleus by centrifugal force

  7. Centrifugal Force - Attraction of Unlike Charges + + -

  8. 12.3 Conductors • Three common metals that are good conductors. Copper, silver and gold. Electrons flow through these easily • Copper is the one most commonly used • A good conductor of electricity is said to have FREE electrons which can move easily from atom to atom

  9. 12.4 Insulators • Glass, rubber and plastic are good insulators • Electrons do not flow through these easily

  10. 12.5 Electricity Produced From Magnetism • Electricity can be produced in many ways, chemical, pressure, light, heat and magnetism • Magnets have a north pole and a south pole and they also have a field of force shows the lines of force around a permanent bar magnet (fig.12.5)

  11. 12.5 Electricity Produced From Magnetism • If a conductor, such as a copper wire is passed though this field and crosses these lines of force. The outer electrons in the atom of the wire begin to move, this movement of electrons is considered to be electrical current (fig. 12.6)

  12. S N Moving a conductor through a magnetic field will cause current to flow in the wire. This movement will move in one direction. This is called Direct Current (DC)

  13. 12.6 Direct Current • Direct current travels in one direction because the electrons have a negative charge and travel to the atoms with positive charge • DC is considered to flow from negative to positive • DC voltage is generated by a chemical reaction knowns as battery power

  14. Direct Current flows in one direction through a conductor. An electrical circuit must have: a power source, conductor and a load SW1 + - Load When SW1 is closed, electrons flow from the negative terminal of the battery, through the lamp, through SW1 and back to the positive terminal of the battery for a complete circuit.

  15. Alternating Current is continually reversing itself and changing the direction of electron flow in the conductor. AC is the choice of power companies to deliver power to the customer. It is easier to deliver and “transform” to the various voltage requirements of the customer. As a result, AC is delivered as a sinusoidal voltage. (Sine Wave)

  16. + 169.7 Volts 0 Volts - 169.7 Volts

  17. 12.7 Electrical Units of Measurement Electromotive Force (EMF) or Voltage (V) – used to measure volts, the difference in potential between two points. The Ampere (A) is the unit used to measure current moving past a point in a specified amount of time. (rate of electron flow) One Amp is One Coulomb per second. Coulomb - the measurement of the quantity of electrons. One coulomb contains 6.24 X 1018 electrons. 6,240,000,000,000,000,000 electrons = 1 coulomb

  18. Electrical Units of Measurement (Cont’d) Resistance,)measured in Ohms (W), is the opposition to the flow of electrons in a conductor. Good conductors have very little resistance, while poor conductors have higher resistances. If a voltage of 1 Volt is applied (the push) to a load and 1 Amp of current results (the flow), then the load has a resistance of 1 Ohm.

  19. 12.8 The Electrical Circuit • An electrical circuit must have a power source, conductor to carry the current and a load to use the current.

  20. SW1 + - Load The Electrical Circuit An electrical circuit must have: 1. A power source 2. Conductors 3. A load to use the current

  21. 12.9 Making Electrical Measurements • Electrical measurements can be made in the circuit (fig.12.10a-12.10b) • Voltmeters are used to measure the potential difference between two points in an electrical circuit • Ammeters are used to measure the intensity of the current in a electrical circuit

  22. Ohm's Law

  23. Fig.12.16

  24. Sample Math

  25. R1 400W R1 400W 120 VAC R1 400W Series Circuits RULES Current is the same through the circuit Only one path of current The voltage is shared between the loads or resistances Add resistance

  26. Series Circuit Amps- 120v / 1200 ohms = .1a Volts- .1a x 400 ohms = 40v Ohms- 120v / .1a = 1200 ohms

  27. R1 400W R1 400W Parallel Circuits RULES Same voltage Current is shared between the branches in the circuit. More than one path of current to flow For Two Loads Only: R1 X R2 Rtotal = R1 + R2 120 VAC

  28. Parallel Circuit 400 ohms x 400 ohms =160,000 ohms 400 ohms + 400 ohms = 800 ohms 160,000 ohms / 800 ohms = 200 ohms Amps- 120v / 200 ohms = .6a Volts- .6a x 200 ohms = 120v Ohms- 120v / .6a = 200 ohms

  29. 12.14 Magnetism • Magnets are classified as either permanent or temporary • A magnetic field is generated around a wire whenever an electrical current is flowing through it. (fig.12.23) • If the wire or conductor is formed in a loop, the strength of the magnetic field will be increased (fig.12.24)

  30. 12.14 Magnetism • If the wire is wound into a coil, a stronger magnet field will be created (fig.12.25)

  31. Heat Relay

  32. Diagram

  33. Coil

  34. Points

  35. Fan relay

  36. Diagram

  37. Coil

  38. Contact

  39. Coil

  40. Points

  41. 12.16 Transformers • Are electrical devises that produce voltage in a second circuit through electromagnetic induction • Transformers have a primary winding, a core usually made of thin plates of steel laminated together and a secondary winding • There is a step up and a step down transformers

  42. Transformer (fig. 12.32a)

  43. Step Down Transformer

More Related