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  1. #1
    Join Date
    Jun 2008
    Posts
    63

    Flooding freezer-Need Hepl!

    Well, I had a call this week that started off as a basic service call that has turned out to 3 days of real wonder for me.
    Original call was for a cooler that was off on Hi head but when I went up on the roof to check the remote condensing units I found all 3 freezer units flooding. One had gone off on oil failure and has since thrown a rod out of the compressor, I suspect from all this flooding. This is a new customer for me but the units have been running for just over 1 year.
    I had tried to adjust the superheat on the ALCO TXVs but I couldnt get the flooding symptoms to stop so I dove in further. I Checked the distributor to make sure it has the correct orifice and then changed the TX vavle to Sporlan and I am still getting flooding symptoms. The only way to get the flooding to stop is to crank the valve in sooooo much that I am running at a low suction press for the gas(9psi). You can see by the info that I have provided that I am reading superheat but I have provided some cell phone pics that I think disagree.
    Now for a little technical info.

    Refrigerant R-507
    Suction 14psi
    Discharge 180psi
    Liq line temp 67f
    suction line temp 0f at coil/16f at comp
    EAT 0f
    LAT 5f

    Suction line size 2 1/8
    Liq line size 7/8
    TXV- Sporlan OVE 12 with pressure limiting head
    Condensing unit -Cancoil model ACU1E031L5E052PO44
    Evap -Cancoil model EHP107005B






    This frosting on the suction line cannot be melted by hand.



    Accumulation on distributor tubes.

  2. #2
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,092

    Flooding?...

    Quote Originally Posted by Jangles View Post

    Refrigerant R-507
    Suction 14psi
    suction line temp 0f at coil/16f at comp
    Ice buildup like that is not a sure indicator of a flooding condition. It can be, but your data says not in this case.

    At 14 psig R507's corresponding saturation temperature is -25F.

    With 0F at the outlet of the evaporator you have a superheat of 25F. (Way too high)

    With a suction line temperature of 16F at the compressor, your system superheat is 41F. (A little high)

    Definitely not flooding with those numbers.

    You may have other causes for that broken rod like flooded starts or oil slugging though.

  3. #3
    Join Date
    Mar 2008
    Location
    North Queensland, Australia
    Posts
    1,050
    Quote Originally Posted by Jangles View Post
    Well, I had a call this week that started off as a basic service call that has turned out to 3 days of real wonder for me.
    Original call was for a cooler that was off on Hi head but when I went up on the roof to check the remote condensing units I found all 3 freezer units flooding. One had gone off on oil failure and has since thrown a rod out of the compressor, I suspect from all this flooding. This is a new customer for me but the units have been running for just over 1 year.
    I had tried to adjust the superheat on the ALCO TXVs but I couldnt get the flooding symptoms to stop so I dove in further. I Checked the distributor to make sure it has the correct orifice and then changed the TX vavle to Sporlan and I am still getting flooding symptoms. The only way to get the flooding to stop is to crank the valve in sooooo much that I am running at a low suction press for the gas(9psi). You can see by the info that I have provided that I am reading superheat but I have provided some cell phone pics that I think disagree.
    Now for a little technical info.

    Refrigerant R-507
    Suction 14psi
    Discharge 180psi
    Liq line temp 67f
    suction line temp 0f at coil/16f at comp
    EAT 0f
    LAT 5f
    Suction line size 2 1/8
    Liq line size 7/8
    TXV- Sporlan OVE 12 with pressure limiting head
    Condensing unit -Cancoil model ACU1E031L5E052PO44
    Evap -Cancoil model EHP107005B
    This frosting on the suction line cannot be melted by hand.
    Accumulation on distributor tubes.
    So you have 14 PSI suction which gives about -25F saturated.
    You have 0F leaving the evap which means 25F superheat in the evap. OK, That's starving quite a lot. you need to open the TX valves and set them up properly. You want something like 6 to 8F superheat.
    That means with 14PSI suction you'd want -17 to -19F at the TX valve bulb.

    You've got +16F at the compressor. That's 16F below freezing. Of course you have ice on the compressor.
    That gives a total lowside SH of 41F. That's pretty high.
    You have Ice on the compressor.
    Is this what worries you?
    Look at the return bends in your bottom photo. That coil is starving.
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  4. #4
    Join Date
    Mar 2008
    Location
    North Queensland, Australia
    Posts
    1,050
    Damn Icemeister!
    Beat me by || that much!

    Of course I had to download a Fahrenheit PT chart first
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  5. #5
    Join Date
    Jun 2008
    Posts
    63
    I understand what you are all saying but yes I was worried about the frost on the compressor and the fact that one is smashed. I guess I am a little too old fashoined in using the "look/touch/listen" sometimes. I absolutely cannot melt that ice on the suction line with my hand. I get rid or it and put my hand on there and it freezes. I know that all instruments tell me I have too much and I guess they dont lie. So your all OK with the frosted end bell? How far up is normal for frost line on a Semi-Herm? I do realize that I am running a very low SST. I have limited experience with this type of system. Thanks for all the help on this guys.

  6. #6
    Join Date
    Jun 2005
    Location
    Las Vegas NV
    Posts
    1,139
    Quote Originally Posted by Jangles View Post
    I understand what you are all saying but yes I was worried about the frost on the compressor...
    Jangles,

    It just means the suction line is below dewpoint and colder than a well diggers butt. This compressor has 10 degrees of SH.

    But, you did good by checking the superheat. Now take the advice of the others and find the real problem.
    Attached Images Attached Images  

  7. #7
    Join Date
    Sep 2005
    Location
    florida
    Posts
    5,495
    Like the others have said you need to open the txv the coil is starving and that will cause ice to build on the coil.
    I love the smell of phosgene first thing in the morning:

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  8. #8
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,092
    Don't be worried about the frost:

    Don't be worried about the amount of frost and ice on the compressor....you need only to be concerned with the superheats, both at the evaporator outlet and at the suction 6" before of the compressor.

    Generally speaking, you want to see a minimum of 20ºF SH at the compressor and a maximum of around 40ºF. The evaporator SH, as has been said, should be like 6ºF-8ºF....but if that causes the compressor SH to go below 20ºF you would need to raise it a bit at the evaporator or possibly add a suction/liquid heat exchanger.

    Another Point:

    Your original numbers showed the box temperature at 0ºF and the saturated suction we know was at -25ºF. That's a 25ºF TD on that evap....which is way out of line. The typical LT evaporator is designed for about a 10ºF TD which would place your design suction temp for a 0ºF box at about -10ºF or right around 25 psig for R507. Taking into consideration some suction line pressure losses you should be seeing no less than 20 psig at the compressor for this system.

    Running as low as it is, you're probably losing 20-25% of the compressor capacity due to that starving evap coil. Hopefully once you get the SH set up right, the suction pressure will fall into where it should be and the system should really start to perform a lot better.

    A question or two:

    Is this system electric or hot gas defrost? Does it pump down on the defrost and the off cycle? Does it have an accumulator? Had any oil failure trips lately?

  9. #9
    Join Date
    Jun 2008
    Posts
    63
    Quote Originally Posted by icemeister View Post
    A question or two:

    Is this system electric or hot gas defrost? Does it pump down on the defrost and the off cycle? Does it have an accumulator? Had any oil failure trips lately?

    Electric defrost pumping down on initiation as well as the stat being satisfied. there is an accumulator The 2 units running have had no oil trips. However the unit with the piled up compressor was initially off on oil failure. This is when i noticed I had problems. I reset it and throttled the suction so any liquid that came back wouldnt harm the compressor. I let the unit settle down and returned the next day as a follow-up. I found that when the stat called and opened the liquid solenoid that the suction pressure didnt want to climb past 15 psi for some reason, and even then it took a long time to get there. Thats when I made the call to change TXVs. Although pressure limiting valves were installed they were rated at 35psi and I was far from that.

  10. #10
    4 things come to mind 1)check the feeler bulb of the txv make sure it is installed correctly and is on TIGHT and is on CLEAN pipe , If you can move it around by hand, it's loose. Also make sure it is insulated well some say this is not important but if your draging suction air across it it will make a difference 2) as stated the coil is starved; if the TXV needs adjustment it needs replacing (All my mechanics know this) if you replaced it and it does the same thing TXV is not the problem. 3) make sure there is not a blokage on the coil like a plastic wrap sucked into the coil from a food tray. And 4) check the heads on the compressor by touching them, if one is cooler or cold a valve plate is leaking by or broken all together. So many things so few words

  11. #11
    Join Date
    Sep 2005
    Location
    florida
    Posts
    5,495
    if the TXV needs adjustment it needs replacing.What? then why would they
    put a ajustable stem on them?

    if you replaced it and it does the same thing TXV is not the problem.NO
    kidding.


    check the heads on the compressor by touching them, if one is cooler or cold a valve plate is leaking by or broken all together. So many things so few words.

    Could you please school me on this method of testing a valve plate?In my 20
    + year's I have never herd of that.
    I love the smell of phosgene first thing in the morning:

    To apply for professional membership click here


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  12. #12
    Join Date
    Apr 2002
    Location
    Ann Arbor, MI
    Posts
    2,985
    Quote Originally Posted by crackertech View Post
    if the TXV needs adjustment it needs replacing.What? then why would they
    put a ajustable stem on them?
    It has crossed my mind to come out with a line of TEVs with nonfunctional adjustments, just like the nonfunctional thermostats that get installed for reasons we well know... Ok, how may of you have actually installed nonfunctional thermostats????

    If I could only figure out a way to make sure the TEV gets sized correctly in the first place...

  13. #13
    Join Date
    Sep 2005
    Location
    florida
    Posts
    5,495
    Quote Originally Posted by Andy Schoen View Post
    It has crossed my mind to come out with a line of TEVs with nonfunctional adjustments, just like the nonfunctional thermostats that get installed for reasons we well know... Ok, how may of you have actually installed nonfunctional thermostats????

    If I could only figure out a way to make sure the TEV gets sized correctly in the first place...
    LOL
    I love the smell of phosgene first thing in the morning:

    To apply for professional membership click here


    Educational forums are open.

    If you would like to submit a link or an article or other related info to the EF. click here

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