HVAC Electrical Class - Troubleshooting First Steps

When You Walk into the Client's House

  1. Turn the stat switch to OFF
  2. Turn the Fan switch to ON - If the blower comes on, it tells you several things
    • There is power to the control circuitry
    • The transformer is good
    • The IFR is good on high speed
    • The blower has power (either 110V or 220V) and is good
  3. Turn Fan switch to AUTO and observe the blower going off with no delay
  4. Turn the stat switch to HEAT
  5. Run the temperature setting up and observe flames - After a delay, the blower will come on
  6. Run the temperature setting down and observe no flames - After a delay, the blower will turn off
  7. Turn the stat switch to COOL
  8. Observe cool air from the registers within a few seconds - If air is not cool, check outside for Power, Fuses, Contactor and 24V
  9. Run the temperature setting up and observe the blower stops

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CSR Motor

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CSR Motor Definition and Characteristics CSR means Capacitor Start Capacitor Run (CSCR), typically shortened to CSR High starting torque Can handle high-demand loads 1-10 HP Can be designed for lower full-load currents and higher efficiency Operates at lower temperature than other single-phase motor types of comparable horsepower Only disadvantage to a CSR motor is its higher price - mostly the result of more capacitors, plus a starting switch Able to handle applications too demanding for any other kind of single-phase motor A CSR motor uses a potential relay or start relay (see Discussion below) Discussion Potential or "voltage" starting relays are used with single-phase capacitor-start/capacitor-run motors, which need relatively high starting torque. Their main function is to assist in starting the motor. These starting relays consist of a high-resistance coil and a set of normally closed contacts. The coil is wired between terminals 2 and 5, with the con...
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Electrical Wiring Diagram Star Delta Control and Power Circuit Using Mitsubishi PLC Program

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This article is intended to diagrammatically demonstrate the concept of the wiring principle of a star delta (wye delta) motor control and power circuit when using a PLC (Programmable Logic Controller) ladder program to control the switching of a 440 volts induction motor. The electrical components comprising the hardware parts of the circuit includes: 1.) 440 volts to 220 volts step-down transformer - 1 piece 2.) 220 volts to 24 volts step-down transformer - 1 piece 3.) 24VAC to 24VDC power supply converter - 1 piece 4.) Normally-open push  button  switch -  2 pieces 5.) Mitsubishi PLC (Programmable Logic Controller) Type FX2N-16MR-ES - 1 unit 6.)  Auxiliary  relay with 24VDC coil and minimum 1 Normally-open contact - 3 pieces 7.) 3 phase 440 volts AC NFB (No-fuse Breaker) circuit breaker (ampere rating depends on motor capacity) - 1 piece 8.) 3 phase 440 volts AC magnectic contactor with 220 VAC coil (ampere rating depends on motor capaci...
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Electrical Control Circuit Schematic Diagram of Permanent Split Capacitor Motor

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Electrical Control Circuit Schematic Diagram of Permanent Split Capacitor Motor PERMANENT SPLIT  CAPACITOR  MOTOR Figure 1: A permanent-split capacitor-run motor with the capacitor mounted on the motor Figure 2: An externally reversible permanent-split capacitor motor. To reverse, interchange   leads  T5 and T8 Figure 3: A two-voltage permanent-split capacitor motor connected for 115 volt operation Figure 4: A single-value three-lead reversible permanent-split capacitor motor Figure 5: A two-speed single-value capacitor-run motor Figure 6: A  schematic diagram  of a three-speed single-voltage capacitor-run motor
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