Troubleshooting & Servicing HVACR Electrical Systems for Non-Electricians

1. Troubleshooting & ServicingHVACRElectrical Systemsfor Non-Electricians NEXT

2. Section 1WHAT IS ELECTRICITY? NEXT

3. ELECTRONS 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

4. POTENTIAL 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 VOLTS Voltmeters are used to measure potential difference between two specific points. Voltmeters are available in analog or digital types. NEXT

6. POTENTIAL DIFFERENCE There must be a potential difference for the meter to register a voltage reading. NEXT

7. POTENTIAL 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

8. POTENTIAL DIFFERENCE NEVER TOUCH AN ELECTRICAL WIRE BECAUSE 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! NEXT

9. AMPERAGE 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. RESISTANCE Electron flow is energy in motion and must be controlled. Resistance refers to anything offering opposition to current flow. 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 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. Ohm’s Law Pie Chart 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”. NEXT

13. TYPES OF RESISTANCE Pure Resistance Pure resistance remains constant, such as in a heating element or a light bulb. Inductive Reactance Inductive reactance is caused by the magnetic field that develops around a conductor, especially in coils or motors. Capacitive Reactance 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 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. WATTAGE 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 E 746 Watts is equal to 1 horsepower. NEXT

16. WHEEL OF ELECTRICITY Volts ( E ), Amps ( I ), Ohms ( R ) or Watts ( W ) can be calculated if you know two of the values. NEXT

17. Section 2SAFETY and HAZARD PREVENTION NEXT

18. ELECTRICAL SHOCK Current is the killing factor in electrical shock. Currents between 100 and 200mA generally cause the heart to fibrillate. A 110 volt power circuit will generally cause between 100and 200mA current flow through the bodies of most people. NEXT

19. LOCKOUT – TAGOUT PROCEDURES Whenever a piece of equipment is being worked on, it should be disconnected from the power source and locked. The person working on the equipment should carry the only key to prevent accidental activation. NEXT

20. DO NOT WORK ALONE If you must test a live circuit, have someone with you ready to turn off the power, call for help, or give cardiopulmonary resuscitation (CPR). NEXT

21. LEARN FIRST AID Anyone working on electrical equipment should take the time to learn CPR and first aid. NEXT

22. ELECTRICAL BURNS Do not wear rings or jewelry when working on electrical circuits. Never use screwdrivers or other conductive tools in an electrical panel when the power is on. NEXT

23. PORTABLE ELECTRIC TOOLS Electric tools constructed with a metal frame should have a safety ground wire in the power cord. When using an adapter for a two prong receptacle to a three prong cord, be sure the adapter is properly grounded. More modern hand held tools are constructed in a plastic case for double insulation. NEXT

24. NON-CONDUCTING LADDERS Aluminum ladders can be hazardous if they come in contact with power lines. Fiberglass or wood ladders should be used. NEXT

25. Section 3SCHEMATIC DIAGRAMS & PICTORIALS NEXT

26. PICTORIAL & SCHEMATIC DIAGRAMS Schematic diagrams present the logic of the circuit in an organized fashion. Schematic diagrams are less cluttered because they use symbols to represent components. Pictorial diagrams show how components are actually wired. However, pictorial diagrams become cumbersome when many components are involved. NEXT

27. LADDER DIAGRAMS A ladder diagram is arranged with the power supply lines drawn vertical as the legs of a ladder. Each horizontal line contains one load and its control switches. Each load line may be numbered for ease of identification. NEXT

28. READING A WIRING SCHEMATIC • Reading a wiring schematic is easier if you follow a few simple rules. • Schematics are read like a book, top to bottom, left to right. • There must be a complete circuit for current to flow through a component. • Electrical contacts and switches are always shown in their normal position (power off). • When a relay is energized, all of its contacts will change position. Normally open contacts will close. Normally closed contacts will open. • Switches or components that are used to provide the function of stop are normally closed and generally wired in series. • Switches or components used to provide the function of start are normally open and wired in parallel. NEXT

29. START – STOP PUSH BUTTON CIRCUIT Notice there is no complete circuit to motor starter coil “M” because the start switch and auxiliary contacts ( M ) are open. When the start button is pressed, both “M” contacts will close and the motor will run. The auxiliary contacts will serve as a hold-in circuit to keep the circuit complete when the start switch is released. The circuit will remain energized until the stop button is pressed, interrupting current flow to the “M” coil. NEXT

30. Section 4CIRCUITS & THEIR COMPONENTS NEXT

31. SERIES CIRCUITS A series circuit has one single path for current flow. If the connection is broken or if one of the components fail, current flow stops in the entire circuit. NEXT

32. TOTAL RESISTANCE IN A SERIES CIRCUIT A series circuit has only one path for current flow. Therefore, the total resistance is the sum of all of the resistances in the circuit. Rtotal = R1 + R2 + R3 …. NEXT

33. PARALLEL CIRCUITS A parallel circuit has more than one path for current flow. Current flows through each load independent of the others. The current flow through each load is not necessarily equal, but the voltage supplied across the load is always equal. NEXT

34. TOTAL RESISTANCE IN A PARALLEL CIRCUIT Since a parallel circuit has more than one path for current flow, adding additional paths (loads) will decrease the total resistance in the circuit. The formula to calculate the total resistance in a parallel circuit is: Check your math! The total resistance in a parallel circuit will always be less than the smallest resistance in the circuit! NEXT

35. THREE PHASE CIRCUITS The power plant generator rotates three conducting loops, each spaced 120 degrees apart, through a magnetic field. The induced power pulses take turns changing polarity from positive to negative to zero at a rate of 7200 times per minute (60 times per second). NEXT

36. THREE PHASE CIRCUITS Each wire has the same voltage but different polarity ( + vs. - ). The potential between any two wires is additive. 120 volts positive plus 120 volts negative equals 240 volts. NEXT

37. SINGLE PHASE CIRCUITS Some loads are designed to operate with just two hot wires from a three phase system. These two wires will alternate from positive to negative polarity. This “push-pull” effect can be obtained with any two phases. NEXT

38. THE NEUTRAL WIRE The earth is always at zero potential (no voltage) and can be used to complete an electrical circuit. Many electrical loads operate with just one hot wire from a three phase source and another wire called the neutral. A potential difference exists because the hot wire has voltage and polarity but the neutral wire is connected to the Earth (grounded) which is zero volts. The neutral wire is a current carrying conductor, but has no voltage. NEXT

39. THE SAFETY GROUND WIRE The safety ground is connected to the frame of a motor or appliance and provides an alternate pathway for electrons to travel to ground should a fault occur. The safety ground connects to the same terminal as the neutral wire at the service panel. The neutral wire normally carries current. The safety ground only carries current in the event of a short circuit. NEXT

40. CONDUCTORS In general, any material that has three or less electrons in its outer orbit is considered a conductor. Copper is the most commonly used conductor. Wire size and type determine the current carrying ability. NEXT

41. INSULATORS Insulators offer high resistance to current flow. Materials that have five or more electrons in the outer orbit are considered insulators. The type of insulation determines where a conductor can be used safely. NEXT

42. SEMICONDUCTORS The outer ring of a pure silicon atom has 4 electrons , but there is room for 8. The atoms share electrons. NEXT

43. N-TYPE MATERIAL If an impurity with only 3 electrons were added to the silicon, the structure would have a “hole” and will allow an electron “in”. NEXT

44. P-TYPE MATERIAL If an impurity with 5 electrons is added, the structure would already have an extra electron and will not allow more in. NEXT

45. DIODE By sandwiching a piece of N-type and P-type material together, an electrical “check valve” can be produced. Electrons would be allowed to flow into the N-type material and out of the P-type material. However, electrons attempting to enter the P-type material would be blocked and no current would flow. This simple solid state device is called a diode. NEXT

46. CIRCUIT PROTECTION Fuses and circuit breakers are used to protect a circuit against over current. The amperage rating of a fuse must not be greater than the ampacity of the wires being protected. Fuses and breakers are used to protect wires, not people. NEXT

47. LOADS AND SWITCHES Manufacturers design devices with the correct amount of resistance for the device to perform the desired amount of energy conversion. Electrical energy flows through the device and is converted to another form of energy ( light, heat, motion, etc.). A load cannot operate unless the circuit provides a complete path for electrons to flow. Switches are used to control and / or provide safety protection. Switches are wired in series with the load. NEXT

48. LOADS AND SWITCHES When more than one load is connected to a power source, switches are connected in series with each load and each load is connected in parallel with the power source. NEXT

49. SINGLE PHASE TRANSFORMERS Transformers have two windings, a primary (incoming voltage), and a secondary (outgoing voltage). Voltage at the secondary (step-up or step-down) is determined by the number of coils in the secondary versus the number of coils in the primary. Single phase transformers are rated by VA (volts x amps) at the secondary. NEXT

50. THREE PHASE TRANSFORMERS Three phase transformers are wound in “wye” or “delta”configurations. Combinations of wye and / or delta primary and secondary coils provide a variety of voltage and current outputs. NEXT