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  • defrost timer on walk in cooler

    need to add a defrost on walk in cooler. dont have heater or hot gas valve, so its "compressor shutoff" type of defrost. I've got 208v power, so two hot legs, no neutral, and a ground.

    as wired above, setup won't work. compressor doesn't kick on no matter how I set the timer. I assume this is because one leg is normally open for some reason on this unit. so I rewired it. black hot leg goes into spot of L1, and I took the red leg and just connected it directly to compressor leads. now it works on timer.

    so- is that normal? for the timer/switch to only switch one leg off and on? Id assume it would switch both, but it won't work for me with both hot legs into the timer/switch. any issues with leaving one hot leg going to compressor at all times? seems odd to me. dont wanna cause issues for the compressor.

    it seems there should be two normally closed legs in the timer. maybe I bought the wrong type of timer? but the manual says it works for 208-240v with timer on and timer off, compressor shutoff.



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  • #2
    This is pretty much normal for a defrost timer. While you would normally use a double-pole switch for 208, it works if you just interrupt either leg. As shown in the wiring diagram.

    I just use the timer to interrupt the solenoid circuit. Usually makes for shorter wire runs.
    Timm Turrentine

    Brewerywright,
    Terminal Gravity Brewing,
    Enterprise. Oregon.

    Comment


    • #3
      So i shouldn’t see any issues on the compressor with having one leg constant and the other switching on and off? Thats my real concern. Our hvac guys around here charge outrageous fees so i dont want to see them again for as long as possible....

      Comment


      • #4
        I had one of those on our old walk-in cooler, but it was wired to break the circuit to the solenoid valve. The solenoid valve is usually controlled by the thermostat. When it opens, liquid refrigerant starts flowing to the expansion valve, raising the suction pressure to the cut-in point. When it closes, the compressor pumps down the suction pressure to the cut-out point and then the compressor shuts itself off. I don't think you want to mess with shutting the compressor off without it pumping down first. I'm not an HVAC expert like some others here, but that seems like a bad idea.


        Originally posted by brain medicine View Post
        need to add a defrost on walk in cooler. dont have heater or hot gas valve, so its "compressor shutoff" type of defrost. I've got 208v power, so two hot legs, no neutral, and a ground.

        as wired above, setup won't work. compressor doesn't kick on no matter how I set the timer. I assume this is because one leg is normally open for some reason on this unit. so I rewired it. black hot leg goes into spot of L1, and I took the red leg and just connected it directly to compressor leads. now it works on timer.

        so- is that normal? for the timer/switch to only switch one leg off and on? Id assume it would switch both, but it won't work for me with both hot legs into the timer/switch. any issues with leaving one hot leg going to compressor at all times? seems odd to me. dont wanna cause issues for the compressor.

        it seems there should be two normally closed legs in the timer. maybe I bought the wrong type of timer? but the manual says it works for 208-240v with timer on and timer off, compressor shutoff.



        [ATTACH]64694[/ATTACH]
        Linus Hall
        Yazoo Brewing
        Nashville, TN
        [url]www.yazoobrew.com[/url]

        Comment


        • #5
          Yeah, what Linus says. The solenoid valve should be located right behind the evaporator, so the wiring is right there and easy to get to. As Linus point out, compressors run on cycles, and it's not a good idea to just shut them down at the wrong point.
          Timm Turrentine

          Brewerywright,
          Terminal Gravity Brewing,
          Enterprise. Oregon.

          Comment


          • #6
            Ok, so i swapped the timer for a different model that will handle 120v. If im understanding correctly i need the shutoff timer wired between the temp controller and the solenoid? Or in front of the temp controller? I assume in front of temp controller is easier so i can get a hot and a neutral legs to power the timer clock. Kill power to temp controller, kill power to solenoid. Yes?

            Comment


            • #7
              Get the hot and neutral to power the timer. Then run the hot wire to the solenoid through the normally closed contacts on the timer. When the timer actuates, it will open the contacts, preventing the solenoid from getting power and opening.
              Linus Hall
              Yazoo Brewing
              Nashville, TN
              [url]www.yazoobrew.com[/url]

              Comment

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