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

A lot of the building industry and homeowners in the United States don’t want to see their HVAC systems exposed, even if it means high performance, healthy living environment, and total control. There is a magical 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 even more efficient and effective than ground source heat pump systems (a.k.a. geothermal), and they cost less to install. I can prove it, but not now.

LG Ductless Mini-Split

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.

LG Ducteless Mini-Split Ceiling Cassette

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

Me: “ABRACADABRA!”

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. They need to have the clearance all around them to be effective at circulating 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, 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 a Serenbe is a perfect example; 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.

LG Ducted Mini-Split Fan Coil

The 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 ridiculously 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

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16 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

    http://www.lg-vrf.com/indoor-units-ducted.aspx.

    http://www.lg-vrf.com/multi-v-mini.aspx

  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.

    EFFICIENCY RATINGS

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

    When

  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