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  1. #1
    Join Date
    Jun 2011
    Location
    MN
    Posts
    26

    Mini-Split Misery

    Without naming the customer, we have several mini splits inside a sugar factory in the Northern part of MN where they grow sugar beets. These mini splits are used to cool electrical control rooms and the "outdoor" unit is generally just out in a hallway and rejects heat out into to the plant. Last week I serviced one of these units and ended up removing the reversing valve and just welded up the correct lines so the thing was permanently on "cool." It ran well for a day and now there is just blinking lights that just say "Craig, beat me with the big hammer and put me out of my misery." UGGHHHHHhhh...how do you troubleshoot these things? I downloaded a cheat sheet and every other option is "new board." Just write it up for a new board and hope for the best???

  2. #2
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    6,915
    Post make, model number, and flash code and you might get lucky... Nobody can TS it with that info.

  3. #3
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    4,658
    Quote Originally Posted by cswenson218 View Post
    Without naming the customer, we have several mini splits inside a sugar factory in the Northern part of MN where they grow sugar beets. These mini splits are used to cool electrical control rooms and the "outdoor" unit is generally just out in a hallway and rejects heat out into to the plant. Last week I serviced one of these units and ended up removing the reversing valve and just welded up the correct lines so the thing was permanently on "cool." It ran well for a day and now there is just blinking lights that just say "Craig, beat me with the big hammer and put me out of my misery." UGGHHHHHhhh...how do you troubleshoot these things? I downloaded a cheat sheet and every other option is "new board." Just write it up for a new board and hope for the best???
    Depends on the manufacturer.

    Fujitsu wants you to talk to them.
    Mitsubishi is similar, if I remember correctly, but they're not as hard line as fujitsu.

    One thing to keep in mind, if it's an inverter drive, don't try and superheat/subcool. If you think the charges is wrong, dump, and weight in.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  4. #4
    I feel your pain Craig i just installed an off brand now i know why board died next day worked fine for 1 day changed board and has been working good since good luck!

  5. #5
    Mitsubishi has pretty decent troubleshooting charts to download. Ive worked on alot of those. Depending of the manufacture those things can blink codes for all kinds of reasons so best to just start going thru the charts and narrowing the problem down. Not saying its not a circuit board issue, but with how my luck runs I put on the circuit board and the problem ends up being a sensor!

  6. #6
    Join Date
    Jun 2011
    Location
    Seattle WA
    Posts
    1,225
    Quote Originally Posted by cswenson218 View Post
    Without naming the customer, we have several mini splits inside a sugar factory in the Northern part of MN where they grow sugar beets. These mini splits are used to cool electrical control rooms and the "outdoor" unit is generally just out in a hallway and rejects heat out into to the plant. Last week I serviced one of these units and ended up removing the reversing valve and just welded up the correct lines so the thing was permanently on "cool." It ran well for a day and now there is just blinking lights that just say "Craig, beat me with the big hammer and put me out of my misery." UGGHHHHHhhh...how do you troubleshoot these things? I downloaded a cheat sheet and every other option is "new board." Just write it up for a new board and hope for the best???
    I have never removed a reversing valve but I do know that the inverter Mitsubishi units (PUMY) are sensitive to changes in the refrigeration system. Even hooking up gauges change the compressor frequency. Maybe its pissed off that you removed its reversing valve and its decided to make you cry in your Corn Pops?
    America; first we fight for our freedom,
    then we make laws to take it away.

    -Alfred E Newman

  7. #7
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,826
    These mini-splits are very sophisticated units. They're not your grandfather's system. They're controlling EEV's and the slightest change can drive them bananas. I'd never even consider removing a reversing valve from one. Length of the circuit is changed and any help from the manufacturer probably l went out the door with the old valve. Beats me why you didn't just fix it right. If you've got a load of the same unit, why not put on ball valves and swap out the bad unit a repaired unit in short order? Saves down time, allows for proper repairs in a shop where you've got all the kit and more comfortable facilities too.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  8. #8
    Join Date
    May 2010
    Location
    Oxford, UK
    Posts
    336
    You can check thermistors/sensor with a multimeter, just need to know what resistance they should be at a certain temperature (though they can be fine when cold then go faulty when the warm up and vice versa) I have just got myself a resistance decade box so i can mimic sensors that i think are faulty, that way i don't order and fit a new sensor only to find the board is bad too!

    Recent thermistor/sensor problem on a Toshiba unit i did,



    I have a vid of the decade box on my channel, was about $80.

  9. #9
    Join Date
    Dec 2011
    Location
    bedford ind
    Posts
    1,085
    Did you remove the reversing valve control lead? The board logic may be interrupted/out of sync.

  10. #10
    Join Date
    Jun 2011
    Location
    MN
    Posts
    26
    I think I was voicing frustration more then asking for help. This place is so bad....sugar in the air clogs up condensers, eats away copper, they have condensers out in 110 degree hallways...they really need a big chiller instead of 25 different conventional AC's for each section.

  11. #11
    Join Date
    May 2010
    Posts
    17
    i love mini splits. I do not love working on mini splits however. I have charged a unit based off of performance (DT), without having to dump and recharge. That was on a unit i knew had a small leak. Had lote of service calls and needed to get them cooling. Havent had any problems with it.

  12. #12
    Join Date
    Sep 2004
    Location
    Kansas City, Kansas, United States
    Posts
    13,817
    Rofl!




    Quote Originally Posted by LibertyTree View Post
    I have never removed a reversing valve but I do know that the inverter Mitsubishi units (PUMY) are sensitive to changes in the refrigeration system. Even hooking up gauges change the compressor frequency. Maybe its pissed off that you removed its reversing valve and its decided to make you cry in your Corn Pops?

  13. #13
    Join Date
    Sep 2012
    Posts
    24
    Quote Originally Posted by cswenson218 View Post
    Without naming the customer, we have several mini splits inside a sugar factory in the Northern part of MN where they grow sugar beets. These mini splits are used to cool electrical control rooms and the "outdoor" unit is generally just out in a hallway and rejects heat out into to the plant. Last week I serviced one of these units and ended up removing the reversing valve and just welded up the correct lines so the thing was permanently on "cool." It ran well for a day and now there is just blinking lights that just say "Craig, beat me with the big hammer and put me out of my misery." UGGHHHHHhhh...how do you troubleshoot these things? I downloaded a cheat sheet and every other option is "new board." Just write it up for a new board and hope for the best???
    is there any reason for you to remove the reversing valve from the unit? the unit should always run in cooling in this equipment room, providing the monitoring equipment is working correctly.

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