Ductless Air Conditioning & Heating In the past, an addition, office, garage or other living space without access to ducting was kept cool by loud, unsightly window and floor units. The noise almost made the conditioned air not worth it. Maybe you’re thinking, “I still use a window unit.” Those days can be over with a ductless air conditioning and heating system! How Ductless Air Conditioning Works Normal residential HVAC systems are called “split systems” because the equipment is split up between inside and outside the home. A ductless system is called a “mini-split” because it too operates in a split system design. A ductless air conditioner or heat pump sits outside the home, and a is mounted inside on an adjacent wall (or recessed in the ceiling). How Do They Compare? A ductless air conditioning and heating system offers quiet, efficient comfort that is pretty surprising. The indoor air handlers are designed to condition a specific room, but more than one indoor air handler be run from a single outdoor unit.

This offers room by room comfort control, without the need for ducting or the noise of portable units. This manufacturer owns the majority of the ductless heating and air conditioning market. Mitsubishi ductless products for both residential and commercial are tough to beat. Highly efficient, reliable and backed by great warranties. In fact, the standard 10-year compressor warranty on Mitsubishi ductless systems is higher than Daikin, Fujitsu, LG and Panasonic. Mitsubishi ductless solutions offer all of the traditional desired installation types including wall, floor or ceiling recessed indoor air handlers. Various Mitsubishi ductless outdoor unit models can power multiple indoor units, and they also boast H2i® Technology which allows a ductless heat pump to heat even down to sub-zero temperatures. Another popular manufacturer of ductless air conditioning and heating solutions is LG. In our opinion, LG’s indoor air handlers look a little better than Mitsubishi. So of course, you’ll need to chat with your HVAC contractor about efficient ratings, sound levels and other items before making a decision based just on looks.

Another cool thing from LG in addition to their already slick-looking air handlers is their Art Cool™ option. LG Art Cool uses a ductless air handler that’s designed to look like a painting on your wall. For unobtrusive comfort, LG Art Cool is worth a look. Fujitsu pushes ductless efficiency over 27 SEER which is pretty impressive! They’ve been a long-standing player in home comfort, and continue to manufacture quality ductless solutions. Fujitsu Halcyon® ductless air conditioning and heating solutions can power up to eight indoor air handlers from a single outdoor configuration! that means you could use this solution to implement zoning in your home. All of the manufacturers listed here offer some level of multiple indoor to single outdoor ratio, but Fujitsu Halcyon definitely is not last on the list! Daikin also sells millions of systems worldwide, and is definitely another trusted leader in the ductless mini-split space. One notable thing about Daikin: their standard warranties can be bumped to 12-year compressor and parts with a 6-year labor warranty.

Now that’s pretty cool. And like other manufacturers above, they feature inverter technology for high efficiency comfort. window ac unit 24 000 btuTheir units also sense if you leave the room, and after 20 minutes will auto adjust comfort in order to not waste money.hvac unit dripping water2012 was a hot one. daikin ac outdoor unitWe’ve had at least 31 days over 90F, something which hasn’t happened since 1988, and July 2012 was the second warmest July on record in the Twin Cities. This is a departure from the norm; for example the average number of 90F days is 13 – we almost tripled it this year.  The 1930’s homes in our neighborhood weren’t built with AC, and retrofitting ductwork is tough.  And although I obsess over our energy use like some people obsess over Kim Kardashian, we do have to be able to function on those sweltering days.  

Last year we struggled through the hot week with a single 8,000 BTU window unit upstairs, which was cumbersome, noisy, ineffective, and inefficient. This year we decided to give in and install something more efficient, permanent, attractive, and convenient – a Fujitsu ductless mini-split AC (our model is here). These units come in various configurations, but simple ones like ours have an outdoor compressor/condenser similar to central AC and a single indoor air handler that hangs on the wall.  Refrigerant, power, and control lines run back to the outdoor unit.  Because it’s a matched set, and because there are no ducts to blow through a hot attic and leak air, they can be very efficient – ours is 25 SEER, 13.8 EER for cooling.  For comparison, Energy Star standards for central AC require >=14 SEER/ >=11 EER. We weren’t going for perfect comfort, just something to keep it tolerable, and keep the upstairs cooler at night for sleeping.  One consideration with these units is that they are a single point of conditioning, and distribution can be an issue*. 

We installed only one unit at the top of the stairs, figuring some cold air could fall and hot air could rise.  If we’d been going for more consistent whole-house comfort, at least one more head would have made sense, and we may still do that in the future. In the end, we selected a single 12,000BTU (1 ton) unit after doing a whole-house heat gain analysis to determine the necessary cooling capacity.  I contacted the fine folks at The Neighborhood Energy Connection in Saint Paul to do the analysis. Overall, it’s been pretty good.  We put it in just before a perfect storm of hot:  103F days, both sides of the family visiting, and a birthday requiring use of the oven to bake a cake.  That was a struggle, but it kept things reasonable – around 80F downstairs – and much drier, which makes a huge difference.  Distribution was a bit of an issue; it’s hard to cool a hot kitchen with a unit on the 2nd floor. Here might be a more representative day: Sept 11 2012 had a high of 93F. 

We closed the house and set the unit to 74F at about 11:00AM, and turned it back off around 7pm.  The bigger spikes are likely the espresso machine.  Stuff later in the evening is cooking & running the dishwasher. The graph shows indoor & outdoor temperatures, solar PV power production, and household power use.  Outdoor temp peaked at 93F at 4pm, and indoor temps on the first floor peaked at about 76.5F around 1pm.  On the energy side, we used 13kWh and produced about 13.5kWh.  If we’d anticipated a string of hot days, we would have just left it on 24/7 to keep things cool and dried out. In July 2011, with the window unit struggling to keep up, we used 33kWh-38kWh per day for the hot days.  In July 2012, with the mini-split running 24/7 on the hottest days, we used between 19kWh and 28kWh per day – quite an improvement. The unit can also work in reverse, as an air-source heat pump, with an HSPF of 12.0, meaning for every BTU watt-hour it consumes, it moves 12 BTUs of heat into the house. 

Converted to Coefficient of Performance, this indicates that it transfers about 3.5 units of energy into the house for every unit of energy it consumes – or 3.5x more efficient than a resistance space heater.  It maintains rated heating capacity down to 20F outside, and continues to function even in -5F weather. I haven’t yet decided if we’ll use it much for heating, but it might make sense in the “shoulder seasons” when our 83 AFUE boiler would be operating infrequently and at lower efficiency.  Because these electric units can heat and cool so efficiently, they are often used in the design of well-insulated net-zero or near-net-zero homes with PV installed. Overall I’m pleased with this thing.  It’s quiet, efficient, attractive, and made the hottest weeks quite tolerable.  It helps that we’ve done air-sealing and insulation of our home, so the single unit is better able to meet our cooling load.  I may experiment with sun control screens on the south windows next year to cut down on solar heat gain.