How Ductless A/C Systems Work

Older houses without modern duct systems can be tricky to keep cool, as traditional central air conditioning systems rely on ductwork to carry cooler air to various parts of the home. Typically, these older homes use radiant heat, which can’t exactly be converted for cooling purposes at the flip of a switch.

For those without forced air systems in their houses, there is another alternative to sweating it out in front of the fan on those sweltering summer days. Ductless air conditioning systems, also known as mini-split systems, can cool specific areas of your home – and, in many cases, are an advantage over basic window units. Here’s how these systems work, courtesy of plumbing and heating contractor Richard Trethewey of This Old House magazine.

Mini-split systems consist of two main units: An interior unit mounted on one of your home’s inside wall surfaces, and an outside unit that’s attached to the exterior of the home. The interior unit delivers cooler air to the living space. A couple of refrigerant lines connect the two units, with one eliminating moisture and the other serving as a conduit for electricity. Mini-split units also feature low-noise blowers and thermostats.

For houses without ductwork, high velocity mini-duct systems might be a good option. To cool just one room, however, the mini-split might be the better way to go.

In any event, bear in mind that mini-split systems have a few advantages over window units: The system’s thermostat can maintain an even room temperature without having to loudly cycle on and off. The mini-split doesn’t have to be removed and re-installed as the seasons change each year—saving you costly labor as well as potential wear and tear on the window frames themselves. And mini-splits do not pose the security concern of some window units, which can be removed relatively easy by someone wishing to enter your home.