I’m an HVAC Magician, I Make Mini-Splits Disappear

Making Mini-Splits Disappear

A lot of homeowners and folks in the building industry in the United States don’t want to see their HVAC (a.k.a. heating and air) systems exposed, even if it means high performance, healthy living environment, and total control. There is a magical (OK, maybe that’s a bit of a stretch) way to have cake and eat it, too.

I design, specify and recommend mini-split heat pump systems because they are the quietest, most energy efficient, and most effective systems available for mechanically heating and cooling a home (or any building). Yes, they are generally more efficient and effective than residential ground source heat pump systems (a.k.a. geothermal), and they definitely cost less to install. I can prove it, but not now.

LG Ductless Mini-Split

LG Ducteless Mini-Split Ceiling Cassette

Most homeowners who say “no” to mini-splits are only familiar with the ductless fan coils (mini air handlers) that mount on the wall just above eye-level, in the ceiling above, or on the floor next to wall. They say, “Those things are too ugly, Chris!” By saying “no”, they give up the performance, low operation cost, location flexibility, indoor air quality, zoning capabilities, and controls of the mini-split technology. All of which are superior to conventional equipment. This is not to say that ductless is the superior option. In fact, when all factors are weighed, including initial costs and effectiveness, ductless (or duct-free) is NOT the be all to end all, despite what the industry and manufacturers try to tell you.

Here are a couple photos of a design, by students from Stanford University Architecture, for a Solar Decathalon project, showing a creative way to “hide” ductless mini-split air handler. While it will technically work, it’s performance is cut short by the millwork that is hiding it.

Homeowner: “If you could make them disappear, Chris, then I would consider them.”


The Magic

Hiding the wall-mounted units behind a dropped soffit or in a wall recess behind a decorative wood grille has been tried many times before, and it doesn’t work. OK, well it does “work”, but it may or may not be as effective as it could and provide the occupants the maximum comfort and efficiency. They require clearance all around them to effectively circulate the air in the room they are in.

LG Ducted Mini-Splits Its Magic

The magic is in the selection and design process. Instead of ductless, I specify the ducted fan coils that fit nicely in to a dropped ceiling cavity, crawlspace or attic (encapsulate these spaces, please), or just suspended from the ceiling in the mechanical room. They’re no more than 10″ tall, 48″ wide, and 32″ deep, depending on manufacturer. Conventional ductwork is used to deliver the air, and what the homeowner sees inside the home is no different than what they’re used to.

Some argue that the ductwork essentially wipes out the performance benefits of mini-split equipment, and I say, “Trust the duct design!” A properly designed and installed duct system will perform well if it follows industry standards and best practices. I use the a Manual D, a protocol from a ACCA, and design ductwork as long as 30′ that are tested after install and show that they meet the required air flow.

Integrated Design

Every home we design and build, we integrate the HVAC design with the architecture, interior and structural designs early on to make sure the systems both physically fit and are sized appropriately to meet the heating and cooling demands. The Proud Green Home at Serenbe and the High Performance Bungalow are perfect examples; we decided on ducted mini-split heat pump system even before we started sketching the floor plan. On the main level, we designed dropped ceilings in closets, and we’ll run the ductwork through pre-engineered wood “I”-Joists above. For the second floor, we put the fan coil and ERV (Enthalpy / Energy Recovery Ventilator) in the encapsulated attic, which means all equipment and ductwork will be above the ceiling joists and below insulated roof rafters. In other words, within the building enclosure of the home.

LG Ducted Mini-Split Fan Coil

This system is made by LG‘s HVAC division. I chose their Multi-V line to get more flexibility (more available static pressure) with the duct design. Plus, we can specify equipment with enough heating capacity to avoid using expensive resistance back up heat. Here is the indoor fan coil (above – 10″h x 18″d x 35″w) and the outdoor unit (below – 54″h x 37″w x 13″d). Both are quiet. The outdoor unit will never get louder than whispered conversation (35-45 db). The indoor units are even quieter (25-35 db).

LG Ducted Mini-Split Heat Pump Outdoor Unit

Here’s a short video me describing the benefits of ducted mini-split heat pump system:

And, here are a few photos of a few installations of ducted mini-split air handlers, by Mitsubishi HVAC, that I specified for new homes throughout the US.:

Mini-split heat pump systems with concealed ducted air handlers offers a LOT of flexibility in the design or renovation of a home, when it comes to the heating and cooling systems. There are also many creative ways to conceal return air pathways (grilles), and use supply diffusers that are less of an eye sore, and more effective than conventional diffusers. In other words, you can have your cake and eat it, too. We can make the heating and air conditioning systems “disappear”.

Thanks for stopping by. Hope this is a useful post, and look forward to having you visit in the future.

27 Responses so far.

  1. Mike Cartwright says:

    So with a ducted system do you have a HEX on the fresh air side leaving the ERV to precondition the air prior to going to the mini-split? Is this required for humidity control in summer time or does the ERV do all of this?

  2. Chris, do you have photos of what the ducted mini-split heat pump system looks like when it is installed throughout the home? During the construction phase?

  3. David Butler says:

    Static pressure (blower power) is definitely an issue for these ducted heads. You really have to know your stuff to be able use a low static head for more than a token duct run. Mitsubishi’s M series ducted head can handle 0.20 IWC, which is better than LG’s low static model, but still too low for many applications. I checked out the LG high static model, but unfortunately, the smallest head is 15k btu. It matches up with a VFR ($$$) outdoor unit, the smallest of which is 38k btu.

    Hopefully one of these companies will come out with smaller units with a bit more fan power.

  4. Mike: The mini-splits handle de-humidification well enough on their own that additional equipment is typically not necessary, other than in extreme cases. The fans are constantly running on a mini-split (very low amperage), so even when the system stops calling for cooling it continues to dehumidify because the coil is still cold enough for the constant air flowing across it to reach dew point, which removes moisture. The system has the capability of varying the amount of refrigerant flowing the coils ever so slightly maintain set point temperature better than most (if not all) systems. As for the ERV, I have gone away from connecting them to the central duct work, as both systems perform at their best when isolated from each other.

  5. Sandra: I have plenty that I would be glad to share with you. They will probably show up in a future post, but I will be sure to email you some sooner so you can have a look. I’d also be glad to take you to one of our local projects so you can see first hand.

  6. David: So true! Most manufacturer’s recommendations of no more than 10′ are a result of too many contractors not doing a proper Manual D duct design, and just winging it in the field.

    Check out LG’s Multi-V Mini Heat Pumps and Ducted Units.
    They get up to 0.31 ESP, and get down as low as 7,500 btu



  7. David Butler says:

    Chris, I missed the “small chassis” model. Thanks!

    Best I can tell, these only work with the Multi-V outdoor units (VFR). The smallest outdoor unit is 38k. If load is that large, I’m usually not looking at a mini-split solution.

    BTW, I’m having trouble finding efficiency ratings for these units on the LG website. Can you point me in the right direction?

  8. David,

    With VRF (aka mini-splits), I specify equipment based on the larger of the two loads (heating or cooling). In all climate zones other than 1 & 2 (and parts of 3), heating is the larger one. I specify the larger capacity units so that the equipment can keep up with the load as the temperature drops.

    For example, we’re using the 38k outdoor unit on a home (2,700 s.f) that has a heating load of 24k (in Atlanta) because the equipment capacity drops to around 30k at around 17 degrees outside. This avoids the need for back-up heat, which these systems are not equipped with and something I avoid like the plague.

    If I go to a 24k outdoor unit on this home, the capacity at 17 degrees outside is less than 20k. I would need some kind of auxiliary heat if I did that.

    The cooling load is slightly less than the heating in this home, so I was able to focus on satisfying the heating first. I still had to make sure the equipment could “dial down” to handle the very low cooling loads. One of the considerations with mini-splits, as you have pointed out to me before, is that even they can short cycle because there IS a minimum capacity, as well as a maximum, and if a load is small enough the equipment won’t satisfy the latent load.


    If you look under the specifications tab on this page, and then download the submittal, you can get the SEER, EER, and COP.


  9. Jeff Mucha says:

    Can you run the mini-split in fan only mode to circulate air and prevent mustiness?

  10. Yes, Jeff, you can. You can also run in de-humidification mode, and it will focus on moisture removal.
    Keeping your systems “on” at your desired set-point and never turning off, or having too much of a set back maximizes efficiency, humidity levels, and comfort. The systems use so little energy to operate in the first place, they use even less when they are set to maintain set-point.

  11. […] response to the demand to “conceal” these “mini” air handlers, or make them disappear, manufacturers started making ducted mini-split systems, where the indoor fan coil is concealed in […]

  12. kellybort says:

    We were unfortunate enough to have one of these hideous things installed in our living room. I absolutely hate the thing. Is there any way to cover it up?

  13. Jie says:

    im renovating my new apartment, it’s a prewar building. my apt doesn’t have access to outdoor space. can you recommend what type of HVAC i should look at? i prefer the split system, any options? do you consult in NYC?

  14. Marleen says:

    I am interested in mini splits that are not visible… can you please post pictures of your installations? Also, I would have a hard time meeting the access panel requirement for the units is there a less ugly option than the wall mounted units?

  15. Walter says:

    Can you effectively hide the condenser unit? Our HOA has some strict guidlines.

  16. Dan says:

    this things are great I got three of them for my fam in mex and took out the wall units wich still worked after 8 years, I just put the wall units back in mini splits worked for 3 years and every one wants what the cost new to fix them its crap. I sold 2 of them and kept one and still cant get it fixed

  17. Matt P says:

    I would like to see proof how an 11 eer mini split is more efficient than even a 25eer geo split or a 40+ eer gshp

  18. Eric says:

    I would love to put in a mini-split in my home. The looks are the least of my issues however. I have a well that flows about 2.5 gpm 24/7/365 unless I pump water out faster. Why don’t they make a mini-split with a watersource unit to replace the outside component? With my well I ran the runoff through my basement for two purposes. One, if the power is out I can get a bucket of water to flush the toilet. The other is to use for geothermal. It would be quite easy to replace the air heat exchangers of the outdoor unit with liquid heat exchangers. If I needed more water flow from the well I could do that with a circulator pump and a pipe down 60 or so feet in the well and then returning it to the top to flow back out the overflow. With a couple extra heat exchangers for air conditioning I could heat my domestic hot water and my hot tub while I cool my house.

  19. David Butler says:

    @Eric, I’m not aware of any residential water source mini-splits. You can install a regular water-to-water heat pump (ClimateMaster, WaterFurnace, etc) and connect hydronic ductless wall units, or simply add a hydronic fan coil to your existing air handler. A buffer tank is required. I’m thinking a water-to-air ground source heat pump would probably cost less, and certainly a lot less complex.

    Sounds like you have an artesian well. It’s not just a matter of routing your well overflow to the water-cooled heat exchanger. A pump would be required to overcome the resistance of the heat exchanger, or at least regulate the flow on demand. In any case, 2.5 gpm can only support about a ton of capacity (most gshps are designed for 2.5 to 3 gpm per ton).

    you wrote: “It would be quite easy to replace the air heat exchangers of the outdoor unit with liquid heat exchangers.”

    No, this is not easy or likely even possible. That is, unless you or your HVAC tech is a serious mechanical engineer and done this type of surgery before.

    BTW, water filtration & treatment is nearly always necessary to protect the source pump and expensive heat exchanger(s). I think the reason open loop fell out of favor is because so many of the earlier systems experienced frequent and expensive failures, mostly because of a lack of attention to water quality issues.

    you wrote: “then returning it to the top to flow back out the overflow.”

    Not sure exactly what this means, but you don’t want any possibility of mixing return and supply water as this could cause your supply to overheat in summer and over-cool in winter. Perhaps this isn’t an issue with an artesian well? But be aware that the EPA and many states regulate surface discharge of water that’s been heated and/or treated. Often a separate discharge well is required. Even then, the permitting process can be arduous depending on where you live. So even though open-loop typically costs less and is more efficient than closed-loop, there’s a lot more to it than meets the eye. Good luck.

  20. Thank you, David.

    Eric, I have been begging WaterFurnace and Mitsubishi to do just what you’re talking about for single-phase projects (Residential) – WaterSource Heat Pump, but neither see the demand for residential projects.

    I have specified Mitsubishi’s 3-phase, CITY MULTI, water source system, but the cost was prohibitive for a single home. The biggest expense was bringing 3-phase power to the property. This product is used mostly for commercial projects.


    WaterFurnace is supposedly working on “something” for their 7 Series products, but I have yet to see anything to date.

    I believe we’re close, but, yet, so far away…

  21. Larry Cote says:

    Tastes Great! Less Filling! So how bout a small RV? 48 volt compressor-condsensor, 12-48 volt fan coil.. (Solar cell backing up 4-12volt DC batteries lithium in parallel =48volts) ideally, a flush fit air handler for max. Head clearance.
    Thanks, Larry.

  22. am1 says:

    Do you think it would be possible to install the ceiling recessed cassette type of units in a home with a flat roof and exposed beams? My ceilings are only 8′ high and are much too low for a false ceiling.

  23. Ruth says:

    In my project, the indoor unit will be installed above a bookcase system that is about twice as wide as the unit. Do you see any reason I can’t fill out around the sides of the unit with a small cabinet and some trim? At least that way the unit won’t stick out of the wall. I wouldn’t cover the front of the unit at all. Thanks for your advice.

  24. Carolyn S says:

    Any recommendations for a ceiling without an attic?

  25. John says:

    It’s amazing that there still isn’t a viable ductless solution for this. All we really need is a unit that will fit in the standard 2×8 joist cavity of older homes: about 14″ by 7.5″ by whatever width the unit needs to be. Samsung almost did this with their “1 Way Cassette” (see: https://www.dvmdownload.com/DVM-S-Series-(VRF)/DVM-S-Indoor-Units/1-Way-Cassette–%7C-AM***FN1DCH ), but the darn thing needs 16″.

    Thoroughly confused on why Split AC manufactured haven’t addressed this issue. In early to mid century homes, most of us simply don’t have the space for clothes in our closets, much less ducted systems. But we also don’t want to ruin the look of our homes with ugly ductless wall mount units… So the annual ritual of installing and uninstalling window shakers persists.

  26. David Butler says:

    @John, one option for a historic home is a high velocity (SpacePak or Unico). They have 2″ ducts that can be routed through walls in a rehab project. The downside is high velocity imposes a significant energy penalty.

  27. Tech41 says:

    God I hope I’m never the technician who has to work on one of these “disappearing” units.. all I can say is good luck home owners!! Sorry ma’am, there is zero access to your unit..

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