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Thread: Walk in Freezer

  1. #14
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    Yep, beer can cold method not the way to check compressor superheat.

  2. #15
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    Yeah, it's a classic rookie mistake. And, just to take it one step further, you can even have an air conditioning system with the evap, suction line, and compressor all in a big ball of ice, and it is still NOT flooding back.


    Quote Originally Posted by Olivero View Post
    I love how people associate ice with flood back.

    It's a freezer, the refrigerant is like -10*F if not lower. WELL below freezing, any moisture would just freeze onto the pipe. All that ice means is that there's humidity in the air and the pipe is below freezing, that's it.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

    Did you really need the " If you were a real tech " ??

  3. #16
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    Quote Originally Posted by BBeerme View Post
    Yeah, it's a classic rookie mistake. And, just to take it one step further, you can even have an air conditioning system with the evap, suction line, and compressor all in a big ball of ice, and it is still NOT flooding back.
    Sure, our information is limited here though. We have no idea how much ice there is. Not sure how long the line set is, superheat, insulation condition, etc. RT unit or rack system? What we do know is that the unit is going into oil failure which is caused by either low oil pressure or a bad sentronic/sensor.

    Anyone fighting oil failures knows it can be a major PITA to track down the root cause. Refrigerant floodback is on that list.

  4. #17
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    Quote Originally Posted by ATX_Dan View Post
    Sure, our information is limited here though. We have no idea how much ice there is. Not sure how long the line set is, superheat, insulation condition, etc. RT unit or rack system? What we do know is that the unit is going into oil failure which is caused by either low oil pressure or a bad sentronic/sensor.

    Anyone fighting oil failures knows it can be a major PITA to track down the root cause. Refrigerant floodback is on that list.
    Could be all sorts of shit.
    Officially, Down for the count

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  5. #18
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    Quote Originally Posted by ATX_Dan View Post
    Sure, our information is limited here though. We have no idea how much ice there is. Not sure how long the line set is, superheat, insulation condition, etc. RT unit or rack system? What we do know is that the unit is going into oil failure which is caused by either low oil pressure or a bad sentronic/sensor.

    Anyone fighting oil failures knows it can be a major PITA to track down the root cause. Refrigerant floodback is on that list.
    IDN

    Flood Back
    Bad oil pump
    Plugged Screen

    Not much else!

  6. #19
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    Quote Originally Posted by pecmsg View Post
    IDN

    Flood Back
    Bad oil pump
    Plugged Screen

    Not much else!
    Ok I'll bite, it COULD be a few other things

    - Blowby from compressor pressuring crankcase during low loads causing intermittent loss of net oil pressure on some semi hermetics. Had a Discus 3D that when it pumped down and suction was below 10psi, the blowby would pressurize crankcase to 35psi, and oil pump was only putting out about 40psi, so net oil pressure only 5psi. If it took too long to pump down it would trip oil safety. Once suction pressure was above 20 psi or so it would somehow stop pressurizing the crankcase as much and maintain net oil pressure.

    - the o-ring on the sentronic sensor can fail and cause sensor not to read oil pressure

    - had one where headmaster had failed and during low ambient + low load (at night), suction pressure got very low and i guess stopped returning oil to compressor. Once headmaster was replaced oil failures stopped.

    - improper piping can cause oil to not return to compressor

    If it is a rack, then the possibilites are endless!

    - Oil reservoir check valve leaking by
    - Clogged oil filter
    - Mechanical float oil level control sticking
    - On traxoil systems the board can intermittently fail to energize solenoid due to weak transistor and cause intermittent oil failure
    - Oil separator not returning oil to reservoir

    But yeah we need a lot more information from OP. Intermittent oil failures are definitely some of the most frustrating issues to diagnose




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  7. #20
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    Add weak compressor to the list.

    Told this story on here at least once before, but this would be a decent place to share it again. Anodize tank. Probably sulfuric acid. We get called to check out the refrigeration. The operator says, yeah, time for our annual compressor replacement. Need a quote.

    There's your first clue. Annual compressor replacement?

    I get to the roof. Tripped on oil pressure. Can't tell if the oil sight glass is full or empty. This was back before recovery, so I valve it off and bleed the refrigerant out. I start to see bubbles in the oil sight glass. So I take it down to very close to zero psig. Get my oil container and drain out a whole lot of oil.

    There was so much oil in the crankcase, the pistons couldn't move.

    Open the valves and start the compressor. It runs just fine.

    I go down and talk to the guy. I ask him if the compressor goes down periodically, he says yes. I tell him the machine is tripping on low oil pressure because there is no oil in the crankcase. And your in house techs are adding oil then restarting the compressor. Now there is too much oil in the system. On a hot pull down, all of the oil comes back to the compressor; too much oil.

    Told him, you don't need a new compressor, you need some re-piping. And yes, we got the job to re-pipe.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

    Did you really need the " If you were a real tech " ??

  8. Likes trippintl0 liked this post
  9. #21
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    Quote Originally Posted by VTP99 View Post
    Yep, beer can cold method not the way to check compressor superheat.
    Beer can cold and your hand stuck to the ball valve and itís getting more stuck by the second, are different things. Doing supermarket refer for 10 years, Iíve seen enough floodback, comps and racks flooded out, and had to deal with that at 3am. You learn fast at that hour and what to check the next time and the next. You can tell if a system is flooding by the look and feel of it.. You can easily tell walking through the machine room which systems are more frosted, more iced, and even at the cases, which case has the most ice and frost on the suction line compared to the others on the same system. And I donít care who you are, any tech at 2am isnít busting their annie out to check superheat at the rack on each system to see which one is flooding, they are going to grab each valve at the header and see which one is the absolute coldest and start there, wether itís a loop or a home run, that will point you in the direction to go.

  10. #22
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    Quote Originally Posted by ihtractors View Post
    You learn fast at that hour any tech at 2am isn’t busting their annie out to check superheat at the rack on each system to see which one is flooding,
    Why would I use a "annie" to check superheat ?
    All that's needed is a stuby gauge, thermistor and a p/t chart.
    Also you could have 3,4,5 etc. evaporators on one circuit which one is flooding by touch ?

  11. #23
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    That method may single out systems for further inspections, not so much for flooding. Remember, the term flooding has a specific definition in our trade. Maybe if you were looking at the oil sight glasses on the compressors, constant foaming would be a clue.

    For what it is worth, the guy I worked for where I cut my eye teeth in this trade used to say the same thing as you. So I'd pull out the gauges and a thermocouple and show him no flooding. Took him several years, but he did stop saying that.


    Quote Originally Posted by ihtractors View Post
    Beer can cold and your hand stuck to the ball valve and itís getting more stuck by the second, are different things. Doing supermarket refer for 10 years, Iíve seen enough floodback, comps and racks flooded out, and had to deal with that at 3am. You learn fast at that hour and what to check the next time and the next. You can tell if a system is flooding by the look and feel of it.. You can easily tell walking through the machine room which systems are more frosted, more iced, and even at the cases, which case has the most ice and frost on the suction line compared to the others on the same system. And I donít care who you are, any tech at 2am isnít busting their annie out to check superheat at the rack on each system to see which one is flooding, they are going to grab each valve at the header and see which one is the absolute coldest and start there, wether itís a loop or a home run, that will point you in the direction to go.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

    Did you really need the " If you were a real tech " ??

  12. #24
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    Quote Originally Posted by VTP99 View Post
    Why would I use a "annie" to check superheat ?
    All that's needed is a stuby gauge, thermistor and a p/t chart.
    Also you could have 3,4,5 etc. evaporators on one circuit which one is flooding by touch ?
    Great question. I have been at this since 72. Guessing I may be learning something new.

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