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  1. #1
    Join Date
    Jun 2008
    Location
    Sparks Nevada but im from Albany NY
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    4

    Question 2.5 ton cu compatible with mini split 2.5 ton cu

    ok so im helping a buddy out with his condensing unit. his compressor was fried and i guess he got a good deal on a same size mini split unit. i have never used a mini split cu to replace a normal split cu. the wire was a little tricky but i got it to run but i am a little concerned with a few things. 1)this is an old seer coil with a piston and i was wondering if this mini cu has a txv inside the unit because unit was very hard to charge. when i released it ran and then after a few the unit shutdown. i had noticed that his coil was very dirty so i cleaned it and gave it time to thaw. now after this i ran unit again but i cant get the liquid side to stablize. started with line temp at 77 deg. added and got down to 60 and then things started to get weird. the temp would flux to 55 then to 62 then down to like 53 then up to like 60 and so on. im wondering if the new unit has a txv inside and the coil still has the orfice in it (he got unit with no paperwork nothing) another thing is that the mini cu has a 5 wire 24 volt tstat board like a furce instead of the common 2 wire in r22 systems. so what i did was run the common to the common and the yellow to the compressor and jumped that to the low fan speed. basicaly is this right? are theses two different systems compatible? im trying to get input and solve before its to late thank you

  2. #2
    Join Date
    Apr 2005
    Location
    new jersey
    Posts
    752
    mix matching is your problem (your friends problem)
    Did you really help your friend out. dont think sooo

  3. #3
    Join Date
    Jan 2004
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    PA
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    68,766
    No, they aren't compatable.
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  4. #4
    Join Date
    Jun 2008
    Location
    Sparks Nevada but im from Albany NY
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    4
    Quote Originally Posted by coolmen View Post
    mix matching is your problem (your friends problem)
    Did you really help your friend out. dont think sooo
    well i didnt buy the damn unit i told him i didnt think that this was a good idea but he was assured by the guy whp sold him this that it would work and so he was all about getting it in no matter what i say sooo did i help him out I THINK SOOO!

  5. #5
    Join Date
    Jun 2007
    Location
    Round Rock
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    3,652
    It sounds as if you know what you're doing. So I also think you have answered your own question about whether it will work or not. Maybe after many wasted hours and him calling you and harassing you it might work at some level, but you just have to know when to cry uncle, otherwise, this thing will be a pain in your arse. It will be your baby if you don't get out.

  6. #6
    Join Date
    Jan 2004
    Location
    PA
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    Well, if the compressor dies during warranty period. And he then has to pay to get another warranty since its voided now. You change your mind when says it must have been something you did, so you should pay for the new compressor.

    Sometimes, the best way to help someone like that out, Is to tell them to get the guy that sold it to install it then. Or anybody else, cause I won't.
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  7. #7
    Join Date
    Mar 2003
    Posts
    7,326
    most mini's have the tx in the condenser, and use different communication than traditional split systems. Maybe someone makes one that is compatible, but i have never heard of it. How do it know what to do????? maybe the fluctuation is caused by the Fuzzy control logic?

  8. #8
    Join Date
    Jan 2004
    Location
    PA
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    Wait till it doesn't get enough oil back from the evap coil. And the comp locks up.
    A standard evap coil can trap a lot more oil then a min splits evap coil.
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  9. #9
    Join Date
    Jun 2008
    Location
    Sparks Nevada but im from Albany NY
    Posts
    4

    Cool

    yeah i talked to the guy who sold it to him and he said that the guys in vegas do it all the time. so just to get into the guys head a little bit i asked him about the txv inside the unit and he didnt have an answer for me. then i asked him about the board in the cu because if you think about it if i am running out to the cu from the furnace then that would mean that it is pulling twice the low voltage and once again he didnt have an answer for me and said that he was gunna call someone about it and call me back which he never did so im thinking that this guy has no clue what he is talking about. well i was brain storming about it today (i know its not my problem but i dont feel comfertable about a system that i install that i think is not right, i cant help it) and basicaly i wonder if i pulled the refridg into the compressor took out the piston and ran a diferent t stat line from the board in the cu to the house with another t stat so i have proper voltage if it would work. i dont know but if it does work like the ass who sold it to him then i think im on the right track.

  10. #10
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    Jan 2004
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    Removing the piston would be a good idea.

    The wiring, maybe.

    The guys out in vegas might be using them with the mini split air handler.

    Or be just quick buck artist.
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  11. #11
    Join Date
    Jun 2008
    Location
    Sparks Nevada but im from Albany NY
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    4
    Quote Originally Posted by beenthere View Post
    Removing the piston would be a good idea.

    The wiring, maybe.

    The guys out in vegas might be using them with the mini split air handler.

    Or be just quick buck artist.
    yeah i explained my all my concernes to him and he said they put them on regular systems like what im working with. he called me back this morning and said that it does have a txv inside so i ok thats what i figured but then he said that i should be fine with the wireing but i still disagree. i had my buddy read the voltage from lowvoltage on cu and he said he was getting 42 volts. now the guy who sold it to him said that he was looking at the wire diagram (would have been nice to send the owner or install manual with the damn thing) and by what he sees that the lowvoltage starts from the inside on the wall unit. ?????? i dont know..... oh well i feel like atleast im am trying. i think ive gone further to help him then alot of others would have

  12. #12
    Join Date
    Jan 2004
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    PA
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    I'm pretty sure all the mini's I've done, the OD unit provides all power.

    Sounds like you might be bucking transformers.
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  13. #13
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
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    14,915
    It can be done with some imagination and the addition of some controls, but it won't ever work "correctly".

    I've put in a few ductless mini split air handlers with conventional outdoor units, but it was a factory approved application. Had to add a metering device to the indoor coil, and had to add a transformer to the outdoor unit to step the 115v control signal from the indoor unit down to 24v for the contactor in the outdoor unit.
    If more government is the answer, then it's a really stupid question.

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