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HVACR317 - Refrigeration

HVACR317 - Refrigeration. Residential Defrost Timers. General Information. Residential defrost timer: Has a simple purpose Switch between Cooling and Defrost Controlled by a timer motor Time length for cooling Example: 12 hrs cooling Example: 21 minutes defrost

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HVACR317 - Refrigeration

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  1. HVACR317 - Refrigeration Residential Defrost Timers

  2. General Information • Residential defrost timer: • Has a simple purpose • Switch between Cooling and Defrost • Controlled by a timer motor • Time length for cooling • Example: 12 hrs cooling • Example: 21 minutes defrost • Time sequence will change with different models

  3. Composition • Make-up of residential defrost timer • Shaded pole timer motor • Normal terminals are #1 & #3 • Term. #1 normally parallel to cooling and Defrost contacts and motor. • Small motor and has high ohm readings.

  4. Example of Residential Defrost Timer

  5. Operation • Operation of Residential Defrost Timer • Timer motor switches contacts • N.C. contact is cooling • N.O. contact is defrost • Time is pre-set by MFG • Cooling is controlled by T-Stat • Defrost duration can be shortened by termination switch. • Termination switch does not terminate drain heater ( If one is there )

  6. Two Types of Defrost Cycles • Continuous and Cumulative • Continuous defrost refers to how a defrost timer motor is wired. • Motor voltage is NOT interrupted • Cold control is wired after cooling terminal. • Defrost will be at exact time intervals.

  7. Defrost Timer and Motor

  8. Continuous Run Timer

  9. Types of Defrost Cycles • Cumulative defrost, where the defrost motor is controlled by the thermostat. • When the thermostat is open, there is no cooling, and no defrost. • Dryers will be energized; examples: • Mullion heaters • Style heaters • Dryer heaters

  10. Advantages • Advantages of these types of defrost: • Savings to the customer • Components last longer

  11. Termination Switch & Drain Pan Heater • A DTS (defrost termination switch) will be in series with defrost heater only. • Drain pan heater stays energized throughout defrost cycle. • Allows water to leave evaporator • Frost is normal and removed by defrost • Ice is drain problem, and can crush evaporator coil. Service call required.

  12. Termination Switch

  13. Electric Defrost

  14. Electric Defrost With Accessories

  15. Diagram With Ice Maker

  16. Refrigerator Diagram

  17. Field Parts Diagram

  18. Field Wiring Diagram

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