Results 1 to 11 of 11
  1. #1
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,122

    Trane Mini split-R22

    I have a Trane Mini split unit with no charging chart. I have tried to get one with no success. Guys, I need to know if these units charge similarly to regular R-22 units. I have charged a Mini-split by Mitsubishi before that acted differently than a regular R22 unit. I think that the liquid line and suction lines both were cold and the pressures were strange, but I charged as specified and she purred like a kitten.
    Anyway, please let me know if I should just charge as usual. I know there are no rules of thumb on this site, but we all know what make these things tick and I have a computer server room in need of some backup with this little unit. Thanks

  2. #2
    Join Date
    Jun 2007
    Location
    Greenville,North Carolina
    Posts
    1,902
    The Mini-Splits that I have worked on always have how many ounces per foot they require on the data plate.Good luck man,I am sure that you will get it right.
    Look to the past to learn;look forward to live.

    Coach Dean E. Smith

  3. #3
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,122
    I was thinking more in terms of the pressures. The last time that I checked this unit, the suction was running around 90 PSI. As I said before, the mini's I worked on before were a little different on the pressures, so I am wondering if that may be the deal here, or if there is another problem. Are the pressures similar to a regular R22 unit? Thanks

  4. #4
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,122
    55 people have viewed this post and no one answers. Come on guys.

    Anyway, I played with the unit a little today even though I still don't have a chart. I did not get the head pressure because there is a fan cycle switch hooked up to the unit in a not so safe way right in the way. Anyway, the room temp was around 80, the outdoor temp was 90, the suction pressure was 82 and the suction line temp was 65. If I put freon in, the pressure would go up and the line temp stay about the same, giving me a higher superheat. If I removed freon, the pressure would come down and the line temp would raise to about 71 or so, so there was not much heat being removed doing this. At best, I got about an 8-10 degree temp drop.

    It seems like the numbers are consistent with a unit doing a hot pull down. The problem is that it never gets a chance to pull down. I have addressed another issue with the unit that this one is the back up for that will hopefully bring the room temp down to around 76 or so, hopefully.
    anyway, let me know if it seems like I am missing something here besides the head pressure. I will note that I did notice that the liquid line was cool. I thought these units ran like that, I was just hoping someone would confirm before I played with the charge. I am wondering if anyone knows why the liquid line runs cool on these units. Are the gases mixing or something like that? It was cooler than the 90 degree outdoor temp, so there is more going on here than standard condensing. Thanks

  5. #5
    Join Date
    Jul 2008
    Location
    Minnesota
    Posts
    7
    I have worked on Sanyo, Hitachi, Mitsubishi, and other mini splits, but never a Trane. They should be similar. The reason the liquid line and suction line both feel cold is because they are BOTH suction lines. The metering device is inside the condenser section. Charging off of the pressures will be impossible. These units may run way down in suction pressure, 50psi could be normal. To get head pressure you will probably have to add an access fitting. I would put in the nameplate charge and start there. Your probably good with that charge up to 25'. How long is the line set run?

  6. #6
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,122
    If the liquid line is suction line, then how are they using that same service port to regulate a fan control switch? Right now, the unit is running the best I have seen so far. I have a suction of 80 and a suction line temp of 59 degree. If I take any out, the line temp rises. If I add, the pressure rises and then the line temp follows shortly thereafter, proving that the system is overcharged at that point. As I say, if I remove any to get the pressures down, the line temp goes to 70 plus and I loose all of my cooling.

  7. #7
    Join Date
    Jul 2008
    Location
    Minnesota
    Posts
    7
    What does it have for a metering device? Txv? cap tube? electronic txv? orifice? Ware is the meetering device located? We HAVE to know the head pressure. And that is only 1 deg. of super heat!

  8. #8
    Join Date
    Sep 2004
    Location
    Newbury Berkshire
    Posts
    490
    Pretty much every split has a refrigerant/weight stamp on the plate.Post model numbers or phone trane tech for details..

    I would reclaim back to zero. Measure the piperun and ensure the charge is weighed in. I have only ever seen one mini running at 90 psig and that was over charged by double!

    Over here o/d temps are much lower but 40-45 psig suction is not abnormal for us..

    The possible reason the FSC may be on the pre expansion line is that the previous tech assumed


    If you do nothing else -weigh it in

    Anything else is a guess.

    Cheers

    Richard

  9. #9
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,122
    Quote Originally Posted by toowacked View Post
    What does it have for a metering device? Txv? cap tube? electronic txv? orifice? Ware is the meetering device located? We HAVE to know the head pressure. And that is only 1 deg. of super heat!
    That would be 11 degrees superheat. Sat temp of 22 at 80 psi is 48. 59-48 is 11 degrees superheat. I think that all of these have a fixed orifice. I did not see it when I took the other apart, but I know it is not a txv and I don't recall seeing a cap tube.

  10. #10
    Join Date
    Jul 2008
    Location
    Minnesota
    Posts
    7
    Oop's on the super heat, I'm a pipefitter, not a mathematician! hehe! I meant 11 deg. I agree with Bart. I think that was my first suggestion as well. Start over. Reclaim, and weigh in nemeplate. Call manufacturer and ask how many ounces per foot of line set. You can run your other concerns by them as well, and let us know what you came up with. We had an apprentice go to a service call on a Silent Knight mini split. He thought the smaller line was the liquid line and larger was the suction. He had well over double the charge in that thing! I talked to the manufacturer on it and they said there is no way to charge it by pressures. The txv was in the condenser on the roof and was an electronic one. It spins inside,reverses direction, ODD! Very low suction pressures are normal on these things. A model # would be nice, Google it and read about it. The fan cycle control would not be located on the low side. If it is, it needs to be moved to the liquid line. Or better yet,... use an icm fan speed controller. More consistant, and better for the condenser coil.
    Barty is wright, I did assume it was a mini split. Type used for small computer rooms, trailers, etc. Maybe it's just a regular air conditioner?. That's a whole different deal!

  11. #11
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,122
    I'll bet you guys are right! That will explain why I got oil out when I disconected my hoses on several occasions. I hope they come with plenty of oil! I told my boss that I needed a scrader T fitting and a book on the units and still haven't gotten it. I told him I remembered something was very different about these units and he acted like it shouldn't be. It is all becoming so clear now. Thanks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event