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  1. #1
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    Jul 2012
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    NH
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    Question Used condensing unit.. High head pressure

    OK new tech here but i tried... Work at a place with random used equipment to mess/learn with.. Had a burned out compressor on a condensing unit.. Found a similar HP condensing unit with barely legible label.. the RLA numbers seemed similar so I went for it... flushed out lines/system nitro purged, deep vac and charged with virgin liquid 409a (type that was already in there)

    Now this is my first/experimental unit, the box has 2 units to cool, I fixed(?) the burnt out one because the other one is on it's way out.. now mine is doing the job that both were doing by itself, a feat deemed impossible from the last refrig. tech. So the unit is cooling great evap temps can dip down to about 15-20.. box temps about 32-40 got a bulb in the evap coil for brick protection.

    With ambients of 82 i have condensing temp of 120! I am suspect of the condenser here is why..

    Steel vs. Aluminum fins
    less fins per inch
    about 2 inches smaller width wise
    old coil 3 tubes deep, new one 2
    RLA rated at 7 pulling about 8
    I can spray water on it condensing temp drops right down..

    I think if the compressor has the capacity, i either need a larger (more efficient rather) coil OR a condenser fan setup pushing more CFM??!!
    Is this noob right??? Any suggestions??

    SC and SH both about 10 degrees.. head 200psi (minimum!)

  2. #2
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    Sep 2002
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    Virginia
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    Quote Originally Posted by jurtaman View Post
    OK new tech here but i tried... Work at a place with random used equipment to mess/learn with.. Had a burned out compressor on a condensing unit.. Found a similar HP condensing unit
    You found a Heap Pump and are trying to use it for a walk-in ?

  3. #3
    Join Date
    Jul 2012
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    Richland, WA
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    248
    I am thinking he is talking about horsepower but don't know


    Sent from my iPhone using Tapatalk

  4. #4
    Join Date
    Apr 2010
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    Minnesota
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    Maybe dirty?


    Or maybe it could possibly be slightly miss matched all to hell!

  5. #5
    Join Date
    Feb 2012
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    Toronto Canada
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    What are you asking???? In your post you say that "yours" is doing the job of 2 units and that you did the Impossible. So whats your Problem?

    Is this the same unit that you had moisture in?

  6. #6
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    Jul 2012
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    NH
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    ..My problem is high condensing temperature. the reason (i believe) is the coil isn't as good at rejecting heat as the old one was. The compressors are same HP so I'd imagine they have about the same capacity. Thinking at this point of putting the tecumseh compressor on the old copeland platform and it's condensing coil/fan setup.. I am looking for opinions of where maybe I should go with this... maybe i could just increase the CFM through the condenser by getting stronger fan??? No sprinklers please!

  7. #7
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    Jun 2005
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    Compressor model numbers are required for us to help you.

  8. #8
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    May 2010
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    Oxford, UK
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    Quote Originally Posted by jurtaman View Post
    ..My problem is high condensing temperature. the reason (i believe) is the coil isn't as good at rejecting heat as the old one was. The compressors are same HP so I'd imagine they have about the same capacity. Thinking at this point of putting the tecumseh compressor on the old copeland platform and it's condensing coil/fan setup.. I am looking for opinions of where maybe I should go with this... maybe i could just increase the CFM through the condenser by getting stronger fan??? No sprinklers please!

    Things are not as simple as you think they are, there could be upto four different displacements for the same motor horsepower to cater for different evaporating temperatures and different refrigerants. Likewise the condenser will have been sized to match the compressors duty in the temperature range it should be operating in. The fact it is running 10% over its maximum run current should tell you some sort of motor overloading is going on.

    Would make more sense to replace the original compressor on the copeland unit.

    There are some things in life where its great to learn as you go, refrigeration is not one of them being either dangerous to yourself or the environment when things go wrong.

  9. #9
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    Sep 2008
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    Quote Originally Posted by monkeyspanners View Post
    Things are not as simple as you think they are, there could be upto four different displacements for the same motor horsepower to cater for different evaporating temperatures and different refrigerants. Likewise the condenser will have been sized to match the compressors duty in the temperature range it should be operating in. The fact it is running 10% over its maximum run current should tell you some sort of motor overloading is going on.

    Would make more sense to replace the original compressor on the copeland unit.

    There are some things in life where its great to learn as you go, refrigeration is not one of them being either dangerous to yourself or the environment when things go wrong.
    We've tried telling him this all before.

    He doesn't want to hear about training and education, he wants to hear "all you need to do is put a #14 fuzzlebitser valve on it and you're good to go."




    I'll be watching the news for outbreaks of food-borne illness in his area because of his rigged up contraption.

  10. #10
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    Jul 2012
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    Western KY
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    Well it's cooling. Whether its right seems to be irrelevant. If it were this thread won't not exist. I admire your lack of fear to some degree but this is not like rigging a go kart together in the garage. There's alot of things that have to work together in a prescribed way to achieve the goal of moving heat from one place to another. there are so many unknowns in your frankincooler any attempt to help would be futile. Don't missunderstand I'm not knocking you, I don't know your situation or customer. You may be just doing best you can with what you have available to work with. If so please run run run away from that situation as fast as possible. Bad habits are as bad as a bad rep in this industry. If you are indeed a new tech you need to know that your reputation will dictate your success or failure in this field. You get a rep as a hack oppertunities and $$$ will dry up pretty quick. Good luck

  11. #11
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    Jan 2010
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    Quote Originally Posted by jpsmith1cm View Post
    We've tried telling him this all before.

    He doesn't want to hear about training and education, he wants to hear "all you need to do is put a #14 fuzzlebitser valve on it and you're good to go."




    I'll be watching the news for outbreaks of food-borne illness in his area because of his rigged up contraption.
    I love at least one good laugh each day. Thanks jp

  12. #12
    Join Date
    Feb 2008
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    California
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    Quote Originally Posted by jurtaman View Post

    With ambients of 82 i have condensing temp of 120!


    less fins per inch
    about 2 inches smaller width wise
    old coil 3 tubes deep, new one 2

    SC and SH both about 10 degrees.. head 200psi (minimum!)
    So let me get this right...you installed a smaller condenser coil...

    and

    You really don't know why you are running a high condensing pressure?

    You installed a smaller condenser and are expecting it to perform the same as a larger original one...




    I hope this is a test cooler at a school or workshop and not a customers..

  13. #13
    Join Date
    Jul 2012
    Location
    NH
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    OK I've said it time and time again, but I'll say it again... I am an "in-house tech" with no liability... I can take what jobs I want. Leave what ones I dont. We have lots of small appliances in service and in storage, some in storage do not work. Same case with split systems for walk-in coolers and a/c units. My boss wanted me to go through all the **** save what's worth saving fix whats worth fixing learn on whatever i want to learn on. I have free reign.

    I praise open-minded people like tommy.. Yes.. I am frankensteining and quite frankly there is nothing wrong with that so long as it's safe and nobody cares about the mistakes (they dont.. They know I'm learning). So while some of you need to goto school because you are doing this as your trade.. I'm merely doing this as a side job as my real job is multifaceted, and I get to pick and choose what I want to do from many possible jobs for the day. Our very own hired and went to school refrigeration tech said the company would benefit if I had a license to mess with all this old mystery crap.

    Long story short, I have some other non-refrigeration stuff going on right now and when I come back to my slightly overworked ***condensing unit*** (-->phase pay attentiion since you must not have read everything earlier) I will frakenstien the new similar compressor to the old condenser (after i flush the burnout out of it) And then we will ALL have answers.. Seems we are all curious to see and apparently school or not nobody has come out and dead on called it so looks like the noob is going to have to!!

    New job added today! LG Neo-Plasma a/c R410 Split system... water all over inside/ fan vibration. only 2 years old! Looks like a new thread is about to be born!

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