Ductless mini-split heat pumps

Mini-split heat pump systems provide air conditioning without requiring ductwork. They belong to the family of air-source heat pumps, and work like a refrigerator in reverse. They are in direct competition with ductless air conditioners. Though they are mainly used for cooling purposes, ductless mini splits heat pumps may also provide heating like other heat pumps and can be more efficient than conventional air-conditioners.

The technology

In common air-source heat pumps systems, air is cooled at the outdoor evaporator coil and distributed around the house through ductwork. In typical mini-split heat pumps the refrigerant is produced at the outdoor unit and driven via small-diameter insulated refrigerant lines directly to the rooms or parts of the house, where the air is blown by fans located in small indoor units. Each room unit may have its own thermostat.

Less energy losses and less operational costs

Because they do not rely on ductwork, mini-split heat pumps can boost energy efficiency (energy losses in conventional systems based on ducts are often estimated at 30%, especially if the ducts are in non-insulated spaces like typical attics).

Besides, the possibility of restricting the heating or the cooling to a specific part of the house (zoned heating and cooling), means that the operational costs can be reduced with a proper use and a careful design.

To get it, the number of indoor air handling units may vary with the specific heating and cooling needs in each home's rooms, and will be commanded through different thermostats – a way of saving energy and money.

Other possible advantages

Mini-split heat pumps may also provide...

- high flexibility in interior design options: there are floor-standing, ceiling-suspending, wall-hanging models…
- easy installation; they do not require large holes in the walls: a three-inch hole is often sufficient.

Disadvantages

Like other air-source heat-pumps, mini-split heat pumps aren't efficient enough on heating mode in freezing climates, for negative temperatures (see air-source heat pumps). Besides, if the ductwork already exists, installing a mini-split heat pump will demand an higher investment than installing an alternative central air conditioning.

Costs

Costs between $500 and $1,000 per ton are common. They depend upon the configuration and the number of zones covered by each unit. These prices are higher than those of central air conditioning systems.

Installation

Sizing and installation should be done properly: oversized or incorrectly located air-handlers are a cause of higher operational costs and inadequate temperature and control of humidity.

These issues are similar to those of ductless air conditioners.

Warranties

Warranties vary with manufacturers. Warranties of one year on indoor units and 3-6 years on compressors are common.