Heritage Restoration, Inc.

Ductless Mini Split AC

Funny things come up when talking to friends and neighbors. We were talking the pain of air conditioners the other day, and this is what we came up with. Air conditioning systems seem to fit in two categories: break your back or break your wallet. But there is another option that may fit nicely in between called a Ductless Mini Split AC system.

The ductless mini split AC systems, or “mini splits”, were first introduced in Japan and quickly became popular around the world. The system is basically a central system without ductwork. It works by a ground or roof based condenser (a heat pump that can create the hot or cold) delivering hot or cold through small lines to a wall or ceiling mounted blower. The condenser can feed up to four separate blower units each with their own thermostat. The condenser size you need largely depends on the size of the spaces, and the efficiency of the building (you can reduce the expense and unit size by making your building more energy efficient).

We typically run window units until they blow warm air, or worse, get them fixed to keep them alive. I used to have a great old unit from a factory in my house, but I think I spun the electric meter off my house. The older the unit, the less efficient it is (you can get utility rebates to replace older units). It’s crazy that a window unit’s noise can be 65dB, equal to standing next to a highway. The mini split blower runs at about 26dB or a little louder than rustling leaves. The noisier outdoor condenser can be as far away as 50-70 feet from the blower.

A centralized outdoor condenser can feed up to 4 blowers. You can get a bigger condenser than you need for one blower, and install more blowers as you get spoiled or realize you need more. The mini split can augment an existing ineffective heating or cooling system, or just give you permanent air conditioning in one or two rooms. The units can produce from 9,000–36,000 Btu.

Mini splits are easier than retrofitting a ducted central air system, but it is not cheap per se. Many old buildings are impossible to introduce even the smallest 3-1/2 inch ductwork, or the introduction of ductwork may be detrimental to the aesthetics. I would be very forthcoming about how I wanted the lines to be run and where, since looks are important, especially for “new” retrofits on a building. The hook-up between the outdoor and indoor units generally requires only a three-inch hole through the wall, so technically they are “reversible”, meaning they do not do irreparable harm. Although the aesthetics of the blower may not work for some people, since they can be pretty big.

I have found that window units are getting heavier and heavier, despite it being the same unit I have installed year after year. A permanent install is a good alternative to a chiropractor.

Mini splits can save money and energy through proper use and installation. There are individual thermostats for each unit, so you regulate temperature room by room. There is no heat loss or gain from long lengths of ductwork. Also, once the blowers are installed, the condenser can be upgraded as technology gets better, or it someday we come up with an even better cooling and heating system than a heat pump.

Bottom Line
There are always trade offs. I suspect there will be a time when I do not want to lug and install 7 air conditioners in my windows every year. I don’t like putting screws into my sash, or the weight of air conditioner resting on my storm window, or the fact that I bump into trim all the time when moving them around, and I don’t like the poor air seal around a window unit. The mini split can be 2-3 times the cost of a window unit but they are certainly less than trying to stick ducts into an existing building. I may choose to do them in our most popular room, and bring in the smaller window units for secondary rooms.

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