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Thread: Commercial freezer evaporator fans not turning on

  1. #1
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    Commercial freezer evaporator fans not turning on

    Sup experts, and hello! I work as a maintenance man for a chain of restaurants and I fix everything from refrigeration equipment to deep fryers.

    Today I got a call for a freezer that's built to the side of the walk in cooler, compressor is running but evaporator fans ain't budging. Checked the voltage with the fieldpiece, 2 hot wires (120v each), forgot to check if the current returned through N. I did notice some wires that went to the side of the TXV valve on the right side of the evaporator coil, is this another thermostat or something? I had a similar problem with a lowboy freezer with a cursed thermostat that was wrapped around the low pressure line and it shut off the fan in the middle of operation and made the coil freeze up. Still, I'm having my doubts, the system is a hot mess, the wires are floating everywhere and are only being held by the almighty and some zip ties.

    So... any suggestions before I get there tomorrow?

  2. #2
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    The wiring diagram is where i would start at.

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  4. #3
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    Ain't there no more... also, I noticed the mechanical defrost timer does not shut off the compressor and condenser fan.

  5. #4
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    Possibly the fan delay, or its' wiring.

    Remember in your readings that you're dealing with a 230v circuit.

  6. #5
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    Quote Originally Posted by superbanana View Post
    Ain't there no more... also, I noticed the mechanical defrost timer does not shut off the compressor and condenser fan.
    Did you give it time to pumpdown?

  7. #6
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    Quote Originally Posted by IRBH View Post
    Did you give it time to pumpdown?
    Nope... Usually all of our 404a freezers only have a delay when turning on, the ones at other locations shut off as soon as the timer kicks out. Don't know about time delay though, unit's pretty basic, don't remember seeing anything fancy. Its basically a compressor hooked up to a pressure control and defrost timer, no electronics what so ever. Heck, even the thermostat is bypassed.

  8. #7
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    What was the temperature in the box when you were there ? What model defrost clock ?

  9. #8
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    Quote Originally Posted by VTP99 View Post
    What was the temperature in the box when you were there ? What model defrost clock ?
    I honestly did not take a temperature, but I'm sure as hell that it wasn't freezing or cold lol. I did however feel a breeze from the low pressure line and tube itself was cold. The defrost timer we use is a defrost o matic 8 something...

  10. #9
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    search for the make and model to get a wiring diagram.

    Easy Fix

  11. #10
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    Freezers have a lot more stuff going on with them than most people think. Here is a typical sequence of operation for a simple freezer without pumpdown.

    -thermostat calls for cooling.
    -compressor is energized (usually through a small relay or contactor, but sometimes it's switched directly from the thermostat).
    -fan delay thermostat monitors the evaporator temperature, once temperature gets cold enough it allows the evap fans to energize. (almost all freezers do this so that they don't blow warm air and water all over the place when they come out of defrost)
    -compressor and fans should stay running until the stat satisfies, then typically just the compressor shuts off while the evap fans stay running (as long as the evap coil stays cold enough)
    -when unit goes into defrost, the compressor and fans should shut off right away, while at the same time power should be sent to the defrost heaters. Most defrost clocks have an early termination function built in to them. That means that there will be a defrost termination thermostat that senses when that the evap coil has gotten warm enough. When this happens it will send power back to the time clock to kick it out of defrost early. Usually the fan delay and defrost termination thermostats are both built into one little sensor with 3 wires coming out of it. There should also be a separate high limit thermostat attached to the evaporator that will cut out power to the defrost heaters if they get too hot.
    -after unit is done with defrost, the compressor should start up again.

    Be aware that most freezers are 230v units. Usually all of the different controls and safetys in them are just little single pole switches that only cut off power to one leg of voltage, while the other leg stays hot. This can make it tricky to figure out whats going on when you stick your volt meter on different things.

    Also, most freezers don't have a neutral wire. The time clock usually has a "N" terminal on it for some reason, but that really stands for L2, so don't let that screw you up.

    Good luck.

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  13. #11
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    Thank you all! I will report back.

  14. #12
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    System wiring is OK now! Forgot to mention that the txv valve is making a high pitch noise, I notice that yesterday so that might explain why the fan thermostat refused to turn on the fans. Bad txv?

  15. #13
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    What do you mean it's ok?
    You said two key things.......the fans aren't turning on and the unit isn't going into a defrost.........so because of that you need to check xxxx......

  16. #14
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    I'm sorry, I meant to say that the wiring is correct, the reason the fans are not turning on is because the low pressure line is not cold enough, thus the thermo control does not turn on the fans, when the compressor is running you can hear a high pitch sound from the txv valve side. Sight glass has no bubbles, and indicates dry.

  17. #15
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    Just a little background, I'm an ex apprentice, tried to learn the trade. I was working for a contractor, but he didn't teach me anything. Everything I did was charge people 100s for putting gas. He was a darn dishonest one, he didn't even know how to calculate superheat nor subcool and had call backs all the time. Not to mention rude, making me sell things systems didn't even need replaced. That's why I changed jobs, I couldn't forgive myself for being dishonest. I tried to get to hvacr school but it was full. So hopefully I'll be able to register as pro one day.

  18. #16
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    This is the heatcraft manual its a starting point.
    Page 17 covers defrost
    Attached Images Attached Images

  19. #17
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    It sounds like a Rats nest of a job I have gone to, or inherited a time or two... from some folks that just were not up to the level of repairs or trouble shooting and made a cluster of a mess.

    Personally I do not like any freezer that does not, or is not wired for a Pump down defrost cycle... But that's just me, and I guess the Glenn Feller as well, on the old COPELAND Help video's where I first saw about Compressor failures.

  20. #18
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    We ended up calling a real tech, he said the system needed refrigerant and there was a leak on the txv connector. How plausible is this? I had to fix a blower wheel fan and a deep fryer so I couldn't see what he did...

  21. #19
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    If the txv has flare nuts, it's pretty common. Sometimes they also leak at the stem cap.





























    P.S... No offense, but your avator is kind of boring. Might I suggest something more like this...





  22. #20
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    So the full sight glass was a empty sight glass ?

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