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Thread: Display Cooler

  1. #1
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    Display Cooler

    Tonight I got an after hours call to a sea food display cooler that was 70 degrees. I've only been on one refer call in my short career, so I was a bit nervous.

    r134a unit, I put my gauges on it and the low side is like 60, compressor is smoking hot. So I go to pull the charge out, and the recovery machine pretty much instantly starts drawing it into a vacuum, so there was no charge present. I was told by my boss that they don't like to pay, so just to evac quick, dump a charge in to get them by and we'd go back during normal hours to find the leak.

    I evac'd, managed to get 3 ounces in before it stopped. I go to start the unit and could have kicked myself that the compressor was out on thermal. So after an hour of standing there packing it with ice trying to bring it down, I couldn't get it to run.

    I told them I would be back first thing in the morning to start it up and weigh in the charge. Do you think I did the right thing? Or was there something more I could have done?

  2. #2
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    Might want to leak check it with a mix of 134a and nitogen.. Or R22 and nitrogen.
    I would head right for the evap coil.

    I'm guess the compressor was off on OL when you were reading 60 pounds. It might not reset if you had ice on it that long and it still didn't close the OL.

    Did you actually check the windings?

  3. #3
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    No, I didn't check the windings, by the time I thought of it so much time had gone by I figured the cheapest option was leaving and heading back in the morning. I felt bad about the bill until he said "Oh hey, no problem, I got PLENTY of space in my other cooler!" He wasn't being sarcastic.

  4. #4
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    If the compressor was off on OL, recovering the charge really shouldn't have been the first thing you did. You should of gave that guy a freebee lol. Seriously though i would of electrically checked my comp & start components . . I'm always offering good insight as well as other guys here. My question is why did you choose to recover?

  5. #5
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    Well, because I knew there was a leak, and I know r134a fractionates (however you spell that), so the proper way to charge would be to pull it and put it back in. I totally overlooked the compressor being out on OL.

  6. #6
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    Like I said this is my second refer call. In actuality this is only my 13th service call alone. And 98% of my daily work is installs, I very rarely get to shadow a service tech. Being on call really is my only chance to learn service.

    But I don't mind, I can count a bunch of new things I learned last night that I won't forget again. I suppose if I encounter a compressor that screeching hot again I should ohm out the windings first before investing time in recovering and trying to recharge huh?

  7. #7
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    Quote Originally Posted by Kaedos View Post
    Like I said this is my second refer call. In actuality this is only my 13th service call alone. And 98% of my daily work is installs, I very rarely get to shadow a service tech. Being on call really is my only chance to learn service.

    But I don't mind, I can count a bunch of new things I learned last night that I won't forget again. I suppose if I encounter a compressor that screeching hot again I should ohm out the windings first before investing time in recovering and trying to recharge huh?

    I would, if I were you: call the service manager and explain that the unit is extremely hot and will take a while to cool down. He may want you to pull the plug and let it cool while he sends you on another call, so you can come back, check the windings with the compressor cool, and then assess what is going on.
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  8. #8
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    If the OL is tripped on a fractional HP compressor, part of the ohming process is going to show open windings until the OL resets.
    One way to outthink people is to make them think you think. They'll think you're not really thinking what you're trying to get them to think you think...........

  9. #9
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    Quote Originally Posted by Kaedos View Post
    Well, because I knew there was a leak, and I know r134a fractionates (however you spell that), so the proper way to charge would be to pull it and put it back in. I totally overlooked the compressor being out on OL.
    R134A is a single component refrigerant, not a blend. Therefore, it will not fractionate.

    I the refrigerant were a 400 series blend and you suspect it has indeed fractionated, then it's useless and should be recovered and discarded.

    Fractionization isn't as big an issue as we were once warned. I've been dealing with various blends for nearly 20 years and have never encountered a serious case. generally, if the system has been running while leaking, the chances of it fractionating are very small.

    As for the overload issue, learn how to verify an open overload. If it's an external overload, checking it with a volt/ohm meter is easy. If it's internal, check for continuity through the start and run windings. (The overload is always on the common.) If you find it's open, wait for it to cool and reset. An internal overload can take up to two hours to reset, but a bag of ice or cool water will speed it along.

  10. #10
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    Thanks for all the good info!

    I went back this morning, and the OL was still clicking and the compressor would not start. So I put my amp meter on the compressor, jumped out the OL and the compressor went locked rotor and blew the breaker. So I diagnosed dead compressor got the info and left. Definitely a great learning experience!

  11. #11
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    And Ice, not that I doubt you, but both of my lead techs told me r134a fractionates and was a royal PIA.... And to never top it off, always pull the charge and put in new stuff.

    And after I looked it up in my old text book, I guess they are dead wrong. :/

  12. #12
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    Quote Originally Posted by Kaedos View Post
    And Ice, not that I doubt you, but both of my lead techs told me r134a fractionates and was a royal PIA. :/
    Ice knows his sh!t lol. Seriously ...... I'm not doubting your diagnosis as i wasnt there but there was once upon a time i was in your shoes man. do some reading on start components & how to check them. Start carrying some 3 in 1s & various start caps if your gonna be doing a lot of small refer stuff. Bypassing the OL only took the compressor safety out of the circuit & really isn't a good method for troubleshooting .. I.m.o anyway

  13. #13
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    Never jump out the overload protector. By doing so, if the compressor doesn't start (for whatever reason), the locked rotor current will fry the windings very quickly.

    The compressor may well have been mechanically seized and therefore toast, but it could be that there was a faulty start component (like a start capacitor or start relay) which was preventing the compressor from starting.

    Here's a very good source of information on servicing hermetic compressors from Tecumseh:

    http://www.tecumseh.com/en/united-st.../~/media/North America/Files/Marketing Brochure/North America Library/Tecumseh Service Handbook.ashx

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