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O/T Mini Split Heat Pump

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  • O/T Mini Split Heat Pump

    Just a FYI for folks with a Mini Split. I installed my Mitsubishi nearly 3 years ago and no issues until last summer. Had to replace a split flare on the liquid line and recharge with R410a. This fall we had beautiful weather and it still did fine, not much air flow but Ok. Now a few weeks ago it turned into a real winter!!! Still Not much air flow and very low heat output. After checking the charge level and topping off a bit, no improvement. Pulled the cover off the inside unit.... the squirrel cage fan vanes packed, and full of Dirt!! In spite of keeping the filter clean, washing every couple of months.

    Cleaned the fan blades with compressed air, yes a mess on our 4 season porch. But Wow what a difference!

    I have some filter coating spray to use on the filter that washes out with hot water, I hope that helps. I understand this is an ongoing issue with the Mini splits.
    Retired - Journeyman Refrigeration Pipefitter - Master Electrician

  • #2
    I installed a couple mini splits a couple months ago. Reasons were that the existing heat pump was a 13 seer and the air handler pretty old, the main reason was that I have been on off-grid solar (still have grid if needed) since May and the mini's are WAY more efficient. So far, no complaints at all, very pleased in fact. We had a couple nights in the teens and it heated the house very well. The one unit is 23 SEER and its low temp heating performance is outstanding. Normal winter days its coast along drawing 400-500 watts, unbelievable.

    As for your unit, I have one suggestion. Mini splts have pretty small freon charges, topping them off is not a great idea, better to empty and weigh in the factory charge as shown on the sticker. In heat mode, a tiny change in freon level can make quite a big difference in output. The inverter compressors make it even more difficult to judge charge by gauges or superheat/subcooling. I am guessing you knew all this but it was worth mentioning.

    Yes, the air filters on the mini splits are not the greatest. I will have to keep a eye on the fan blades as time progresses. Thanks for the tip !

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    • #3
      Do you burn candles or incense?

      Comment


      • #4
        Originally posted by macona View Post
        Do you burn candles or incense?
        Nope not even the wacky tobacco.

        Sparky I am not a fan of flare nuts on the R410a systems, but the skill level with some of the installers I can see why. I know these are critical charge units, but sometimes you have to do what you need to do... it was darn cold. In my experience with HPs back in the 70s & 80s when I learned to Hate air to air HP systems, we always had to boost the charge for winter. But times changed and I am impressed with mine, and its So complex but I do have the official service manuals for both sides of the system.
        Last edited by wmgeorge; 01-18-2022, 10:18 AM.
        Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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        • #5
          I have installed 3 Mitsubishi mini splits.
          One is in my workshop.
          The squirrel cage fan gets so dirty,
          that it slings the dirt off when it gets
          to a certain point. Cleaning the green
          dust screens is kinda worthless.
          I think it has been running for 8 years
          or more, non stop. Cool in the summer
          and warm in the winter. I kinda went
          oversize on purpose. I went with a
          31,000 BTU unit for my 900 sq foot
          shop, just so the heat pump feature
          would work well. And it does.
          No fear about an oversize unit in A/C
          mode not running enough to take the
          humidity out. The beauty of these
          systems is the compressor and the
          condenser and evaporator fans are
          all variable speed. The real benefit
          of the compressor being variable
          speed and the fixed metering oriface
          is infinite variable control of the system.
          Traditional A/C systems are binary
          digital on and off control. This means
          you have hysteresis in your temperature
          control. With the variable system
          it will run at whatever speed is needed
          to maintain desired room temperature.
          Not an all or nothing approach, which is
          smooth and unobtrusive to your living
          environment. I think all this cooling
          and heating technology with continuously
          variable heating and cooling was the
          basis for the system in the Moore jig
          borer factory. People think this stuff
          is new and invented in Japan.
          Think again.

          --Doozer
          DZER

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          • #6
            Well I am hoping that washable filter coating spray will work. But instead of compressed air cleaning next time I am going to use this. Fill the pot with soapy water and 75-90 psig compressed air, and it will go into the vanes when the unit is powered off, they are stepper motors can be moved as needed. From Amazon.



            Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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            • #7
              We're currently building a rental unit in our back yard, almost finished for a tenant to move in Feb 1. The mini-split heating system was roughed in by the contractor several months ago. Now time to finish up with installation of the heat pump. Guess what...? Major supply issues, the heat pump we ordered is not available so we were considered lucky contractor found a larger unit at more cost. Once the dust settles contractor will replace larger unit with what we ordered and large unit will be installed to replace gas fired furnace in our home.

              In Seattle where construction is booming and city is discouraging gas heat so there just aren't enough heat pumps to go around. Not sure if this is Covid related or too much unanticipated demand.

              I watched contractor charging the system, almost a day long process. Then a required 12 hour wait period before starting. Works great now.

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              • #8
                Originally posted by wmgeorge View Post

                Nope not even the wacky tobacco.

                Sparky I am not a fan of flare nuts on the R410a systems, but the skill level with some of the installers I can see why. I know these are critical charge units, but sometimes you have to do what you need to do... it was darn cold. In my experience with HPs back in the 70s & 80s when I learned to Hate air to air HP systems, we always had to boost the charge for winter. But times changed and I am impressed with mine, and its So complex but I do have the official service manuals for both sides of the system.
                Absolutely, a lot of the problems encountered are due to the flare connections. The newer elliptical flaring tools help a lot. Also, there is a sealant, called Nylog, that is well respected in the trades for flare fittings, some of the mini split manufacturers even recommend it in the installation instructions. Its not unheard of for some of the good-ol-boys to cut off the flares and braze the connections.

                Yea, heat pumps have come a LONG ways. Used to be they fell on their face at about 40deg outside for heating, now zero and below is not a problem for the high efficient models.

                While on the subject.... I have always wondered why all the mini splits are made over seas and the US manufacturers have not jumped on the wagon. I know Trane has one but its a foreign unit re-badged for them.

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                • #9
                  Yes I have what I considered the best flaring tool in the business, a Roll Air that I Never have leaks with, ever. But in this case on the Install I used the flares on the line set. Used silicone grease behind the flare and blue leak lock / Loctite on the threads because of the temperature swings. That one liquid line was a cracked flare... not mine! But I now have the Nylog stuff. Yes I considered cutting off the flares on the inside unit stub outs but when I cut the insulation off to check this time around but zero leaks on all!!

                  The Made in Japan units have less than a 1% failure rate, I do not think China has the same standards. My son who is Service Manager and Estimator at a commercial HVAC business says they have zero claims on the units he sells. They install for small computer and telephone switch gear rooms.
                  Retired - Journeyman Refrigeration Pipefitter - Master Electrician

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