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21 thoughts on “2013 Defrost Systems in Commercial Refrigeration

  1. Pete Deiler says:

    In have worked as a building mechanic for over 20 years. I am in Sanger Texas (45 MILES NORTH OF DALLAS) I Have never gone through the certification process  (working on HVAC was only part of my duties or functions. What do I need to do to become certified? I have been out of the field for several years. I worked for the creator of the ABS sensors, low tire pressure (Among other things) I am experienced in the building portion (including up to 100 hp compressors) (carpentry, plumbing, electrician as well ) not the technician or manufacturing or machine maintenance. Who do I contact about becoming certified. My bet is a refresher style course but with or through.

  2. hvac01453 says:

    Am I the only one to catch the error in the slide that 22-8 divided by 2 does not = 15. That should have been a plus sign on that slide. Wake up!… The glide on 409a is likely why you never see it anymore. Most blend glides now are negligible.

  3. hvac01453 says:

    It would be nice to mention that when the time clock solenoid is energized, it's only momentarily, as it mechanically takes itself out of the circuit through the cam action of the slide switch

  4. Jeff Hall says:

    No offense RSES, maybe it is, that's up to you, but you made a MAJOR SCREW-UP in this presentation. With the defrost time clock, the "X" terminal is the termination of the defrost. NO OTHER WIRE SHOULD EVER BE CONNECTED TO IT EXCEPT FOR THE DEFROST TERMINATION WIRE!!!!!!!!!! You, RSES, made a MAJOR MALFUNCTION in your "school" here! You have proved that you do not know what you are talking about in this category, plain and simple. Your "X" terminal should be the "N" terminal for 120v time clocks, or "L2" terminal for 208/240v time clocks, and there should be a terminal labeled ""X" where it is not labeled for defrost termination in your schematic. As a former mechanical engineer for Abbott Laboratories, I know this, and as a current tradesman, I know this. Perhaps you need to speak with Paragon and Grasslin defrost controls manufacturers to gain more sophistication concerning these matters. Your demonstration is absolutely wrong. You have taught your members the wrong terminals for a Paragon or Grasslin time clock. You have failed as an HVAC&R knowledge base.

  5. Tony Kang says:

    We Sinjin Enertec supply an infrared LED based photoelectric defrost sensor/controller that detects the frost level in the evaporator coils of commercial refrigerators/freezers to provide a more efficient defrost cycle for the energy saving with no ice than existing timer based defrosting. If need more details, please send e-mail to for products leaflets.

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