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HVACR317 - Refrigeration

HVACR317 - Refrigeration. Commercial Defrost Timers. Defrost Timer, Overview. The Defrost Timer has only two functions, cooling and defrost. Cooling Contacts May have more than one set Cuts down amps Defrost Contacts Defrost terminal Defrost termination solenoid. Timer Composition.

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HVACR317 - Refrigeration

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  1. HVACR317 - Refrigeration Commercial Defrost Timers

  2. Defrost Timer, Overview • The Defrost Timer has only two functions, cooling and defrost. • Cooling Contacts • May have more than one set • Cuts down amps • Defrost Contacts • Defrost terminal • Defrost termination solenoid

  3. Timer Composition • The defrost timer is made up of a timer motor, contacts, and a defrost termination solenoid. • Timer Motor • Shaded pole motor • High ohm resistance • Contacts • Cooling terminals • Defrost terminals

  4. Timer Composition • Defrost timer components, cont’d. • Defrost termination solenoid • Parallel to defrost terminal • Works with DTS/Fan delay switch • Completes path on L2 or N side • Terminates defrost and switches contacts into cooling position. • 55 degrees will terminate • Solenoid connected to mechanical linkage

  5. Clock must be set to correct time • Defrost time sequence must be set • Pins set for defrost schedule

  6. Defrost Timer

  7. Defrost Timer

  8. Defrost Timer

  9. Defrost Timer

  10. Defrost Timer

  11. DTS Fan Delay Switch • DTS / Fan delay switch • Fan delay in cold position (closed) • Completing L2 or N to evap fans • Temperature position 5° to 25° • DTS switch in open position • Closes when temperature reaches 55° • Completing the path to defrost solenoid coil in the timer • Forcing system back into cooling (evaporator fan will delay)

  12. Defrost Timer Diagram

  13. 8145 Defrost Timer

  14. Defrost Termination Switch

  15. Defrost Termination Switch

  16. Defrost Termination Switch

  17. Defrost Wiring Diagram

  18. Defrost Wiring Diagram

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