Ductless Mini Split System Maintenance: The Challenges…and Opportunities

Ductless Mini Split System Maintenance: The Challenges…and Opportunities

Unless you’ve been under a rock over the last few years, the ductless mini-split system is in full invasion mode. More than likely you’ve installed a few yourself already. These super-efficient and highly practical systems have been heating and cooling spaces internationally for decades, but the U.S. market is finally starting to expand – and somewhat dramatically, in fact. According to leading statistics over 1.5 M units will be installed this year and the number is growing at about 15% a year. As a contractor, that’s thinking about this business, there’s nothing more to wait for. It’s already here.

The system is referred to in many ways. A ductless split, a mini split, a multi-split, duct-free system, ductless  or a variable refrigerant flow (VRF) heat pump system. Regardless of the name they all tend to have similar functionality and purpose. Spot cooling without duct work.

Cleaning Mini Split Ductless Systems is big business

Cleaning Mini Split Ductless Systems is big business

Whatever you call it, it’s a lot like a standard air-source heat pump: there’s an outdoor condenser unit and an indoor evaporator/air handler unit. The main difference is that the indoor unit is placed in the single room or zone that it serves; it doesn’t rely on ductwork to deliver conditioned air. Without ductwork (where 30% of a system’s cooling/heating power can be lost) it’s more efficient than a central air system. And because the compressor is distanced from the air handler, operation is far quieter than the PTACs found in motel and dorm rooms.

Ductless mini-splits are ideal for retrofitting older homes with baseboard heating and window air conditioners. They’re great for room additions when it is inefficient or expensive to extend existing ductwork. And they’re godsends for hard-to heat spaces like attics, sunrooms and basements. This basically refers to millions and millions of residences.

Also used in light commercial HVAC applications (typically less than 10 tons), these systems can be installed and operated for substantially less than traditional ducted HVAC systems. But they are essentially the same system with the same physics and therefore very similar maintenance needs.

And therein lies the rub.

Mini-splits should be maintained on a similar calendar as central HVAC systems. Twice yearly service helps maintain system efficiency and indoor air quality. Among other things, here are the basic steps to maintaining a ductless mini-split.

  1. It goes (almost) without saying, turn the unit off and disconnect power before cleaning.
  2. Clean or replace filters. Additionally, encourage your customers to inspect their filters monthly or more often and clean or replace them as needed. If you are cleaning, use a HEPA vac or follow directions from the manufacturer for a wet cleaning,.
  3. Remove and clean the IAQ components. These vary depending on manufacturer and model. For instance, some models use negative ion technology to further purify air.
  4. Clean the evaporator coils. You’re dealing with a unit in a finished living space, so it’s especially important not to overwhelm the condensate line. The easiest solution we know of is from a company called BBJ Environmental. They offer a ready-to-use cleaning kit. It includes an aerosol called Micro Coil Clean, available this April. It’s an aerosol spray that clings to coils and cleans them without overwhelming the unit’s drainage capacity. Follow with a light rinse, and your coil cleaning is done. Be careful to check that condensate lines are not blocked prior to rinsing.
  5. For best results, once coils are clean apply a fungistat and bacteriostat to keep dangerous biological growth at bay. Mold Control, an EPA registered mold, mildew and odor inhibitor battles odor-causing organisms for up to one year, and it’s safe for use inhabited areas.
  6. Inspect and clean the outdoor condensing unit as you would for a central air conditioning system. Inspect the refrigerant lines and insulation wraps.
  7. Make sure the unit is solidly mounted on its base and that the fan wheel and blower assembly are balanced. Remove excess debris from the outside of the unit, then spray the coils clean. It’s more effective to clean coils from the inside out. Check out our Condenser Needle that turns a standard water hose into a specialized coil cleaning machine.

Mini split, ductless units whatever you call them are here to stay and offer a great way to increase maintenance revenue.

What do you think? Have you installed or serviced mini-splits, and do you see an increase in your area? We’d love to hear from you.


  1. G deboer May 20, 2018 at 10:43 pm

    Even though it is hard to reach the blower wheel Is the product safe to use on fijitsu blower wheel? We have gotton various answers to this question.

  2. G deboer May 20, 2018 at 10:40 pm

    We have been unable to find someone in New Jersey to clean our fitjitsu units. When we mentioned cleaning , I get no response.i was told to say I need servicing – don’t mention cleaning. Doesn’t anyone know of a reliable company in central jersey.

  3. Marty October 25, 2017 at 7:53 pm

    I have had a Mitsubishi Mini Split for 6 years. It works great until the blower fan gets full of crud then it reduces the cooling effect to almost nothing. If it were easy to remove the fan I would clean it myself. To many to things to take apart. There are so many hidden screws, and there is the possibility of breaking plastic parts in the process. Not worth it. If anyone knows of a way to clean it without taking everything apart please let me know. Over the past 6 years it needed to be cleaned 3 times. It cost me $300 the first 2 times and $350 today. Once cleaned it works great. There must be a way to manufacture these units with easy access to the blower fan for cleaning.

    • Tim October 27, 2017 at 3:55 pm

      Thanks for your comment. Mini splits are susceptible to dirty blower wheels due to their poor filtering and exposure to the air. Generally, a cleaning includes more than just cleaning a blower well. It includes a cleaning of the coil (inside and outside coils), inspection of the unit, lubrication, etc. We would always suggest a licensed contractor perform these duties as it can be easy to damage units. If you feel that the few hundred dollar every couple of years is too much, I would suggest calling around. You may find other contractors that charge less.

  4. Shelby January 22, 2017 at 9:57 am

    Everyone says these are so efficient. We went with them in each of our rooms in our old house that underfloor ducts had been damaged beyond repair. They are Fujitsu. Unfortunately, I have found them to be a disappointment for heating. Cooling great, but for heating… they have been unbelievable expensive on my electric bill and my rooms are still cold. I have cleaned the filters which helps tremendously with the cfm they put out and needs done regularly. Has anyone else had this problem?? Is their something I am missing that would make them sooo expensive to run, yet not heat the rooms properly?? Side note- I also detect a weird smell after my last filter cleaning-

  5. Wm Jerkins November 14, 2016 at 9:14 am

    How do you remove the cover on Dakin mini split?

  6. Wm Jerkins November 14, 2016 at 9:13 am

    How do you remove the cover off a dakin mini split?

  7. Lee Ohmart October 28, 2016 at 11:40 am

    I bought 3 Fujitsu units in the past 2 years. Two for my home and one for my woodshop. When the installer sold and installed them one of their selling points was that these units are maintenance free other than vacuuming or washing the large screen. When I did so, I read the manual and found there were two other filters, a polyphenol catechism air cleaning filter, which is disposable and needs to be replaced evert 3 months, and a negative air ion deodorizing filter, which needs to be replaced every 3 years. In addition, when I called the installer to buy these filters, I was offered a “comprehensive maintenance cleaning” for $135 and should be done once a year to every two years. I feel like I was taken in on this.

    • SpeedClean October 28, 2016 at 11:54 am

      Yours is a common complaint we hear about how mini splits are marketed. Just like any air conditioning system, the filters and coils need maintenance and or replacement to keep the unit running at full efficiency.

  8. Hershel Norton August 23, 2016 at 8:43 am

    The main thing to clean on a minisplit indoor unit is the blower fan. The crud build up on the blower fan drastically reduces the efficiency of the minisplit. I just cleaned the fans and coils on 3 of my units and was amazed at the amount of crud that cleaning removed (mainly from fan blower). These units now seem to be cooling even better than when new.

    • Dan Kibler September 7, 2016 at 7:39 pm

      If you do not mind asking how did you go about cleaning the fan barrel and you are correct it’s the most important part because that’s where all the mold build up is.

      • G Woodward September 19, 2016 at 5:33 pm

        After trying many different brushes, we’ve found that a “bell shaped” Mr. Clean Bowl brush works the best. It has the stiffness required to remove crud but doesn’t damage the fins. An added benefit is that the shape actually rotates the fan slightly as you scrub so you don’t have to.

        • Jamie December 12, 2016 at 4:01 pm

          How did you even get to the barrel fan mine has a black metal wires going across it and screwed down? Can the barrel fan be removed

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