Ductless Heat Pumps – A New Option for Home Heating

The ductless heat pump is a new option for homeheating that offers

• Efficient operation at outside temperatures of

17°F. and below without electric backup

• Quiet operation – both indoors and outdoors

• Heating and cooling

• Simplified installation

Ductless heat pumps are appropriate for bothreplacement of existing heating systems, especiallybaseboard/wall heaters, as well as for newconstruction. Ductless heat pumps have beeninstalled in commercial buildings for more than 20years and are available from many manufacturers.

Ductless heat pumps are very efficient for severalreasons: Since the heated or cooled air is delivereddirectly to the room, ductless heat pumps avoidefficiency losses associated with ductwork –typically 15-20 percent. Variable speed compressormodels, usually labeled “inverter technology,” avoidon-off cycling losses and are able to provide usableheat efficiency on all but very cold days. And,because they provide heat/cooling to specific areasof the house, they can be more efficient since each“zone” can be heated to the desired temperature.

Ductless heat pumps are sometimes called a “mini-split” heat pump* and consist of an outsidecompressor unit and one or more inside “heads” thatdeliver conditioned air to the room or rooms. Insideunits are typically mounted high on the wall, butcertain models can be recessed in the ceiling or eveninstalled with a short duct run to serve adjacent

and expanding a refrigerant. Most new ductless heatpumps use the newer, less environmentally-harmfulrefrigerant R-410a. Depending on the rated capacity,they require 110 or 220 volt AC power.

A very quiet oscillating fan delivers conditioned airmore evenly to all parts of the room. The indoortemperature and other settings, such as automaticnight temperature setback are set with a hand-heldremote control. Like any air conditioner in coolingmode they provide some dehumidification of theindoor air.

Applications for Ductless Heat PumpsDuctless heat pumps are most appropriate for homeswith open floor plans, since each indoor “head” canserve the entire “zone” not blocked by doorways.Some typical applications for ductless pumpsinclude:

Replacing an existing zonal heating system –Ductless heat pumps can replace existing electricbaseboard/wall units, woodstoves. A cost effectiveelectric heat conversion in a small house mightconsist of single system serving the main area of thehouse, leaving existing electric baseboards inbedrooms and bathrooms.

Room additions – Another application for ductlessheat pumps is when a room is added to a house or anattic is converted to living space. Rather thanextending the home’s existing ductwork or pipes oradding electric resistance heaters, the ductless heatpump can provide efficient heating and cooling.

New construction –New homes can be designed oradapted to take advantage of the characteristics of

rooms. The inside and outside units are connected byrefrigerant lines, usually concealed in the walls orceilings or under a cover on the outside of the house.Some models allow several indoor heads to beconnected to a single outside compressor.

Ductless heat pumps operate on the same principleas traditional heat pumps - using electricity to moveheat between outdoor and indoor air by compressing

*So-called “mini-split” because they tend to be smaller capacity

(BTU/hour “tonnage” rating) and because they are “split system”with separate compressor (outside) and expansion heat deliveryunit (inside) units, similar to traditional heat pumps, but unlike athrough-the-wall unit, sometimes used to heat motel rooms.

ductless heat pumps. Typically one or more systemsmight be installed in various “zones” of the house tosimplify installation and minimize refrigerant linelength.

Cost of Ductless Heat PumpsThe cost of the ductless heat pump equipmentappears to be comparable to traditional heat pumpsystems. Installation costs are based on the difficultyof running refrigerant lines and whether the existingelectrical service can handle the new equipment.

The best way to determine how much a ductless heatpump will cost in your situation is to get severalbids. Be sure to specify that you want models that

qualify for the Oregon Residential Energy TaxCredit. Most contractors that install ductless heatpumps can provide comparison bids for traditionalheat pumps or furnaces, as well. Manymanufacturers’ Web sites have lists of installers invarious areas.

Oregon Residential Energy Tax Creditand Other IncentivesDuctless heat pump models eligible for the OregonResidential Energy Tax Credit must meet thefollowing specifications:

• Have variable speed compressor (“inverter

technology”) – providing more efficientoperation to match the heating/cooling needsof the house under a variety of weatherconditions

• Be listed in the ARI directory and provide at

least 50% of rated capacity efficientoperation when outside air is 17° F. andhave no built-in electric resistance heat.

• Be installed by a technician that has

received factory-sponsored training withinthe past 5 years

The Oregon tax credit for ductless systems iscalculated at $50 per 6,000 BTU/hour (“half ton”) ofrated capacity with a maximum of 25 percent of theequipment cost or $400 per residence, whichever isless. There is no state tax credit for ductless airconditioner-only models.

Properly sizing the system to the heating/coolingloads of the house is important, but not as critical aswith traditional single speed heat pumps, sincevariable speed compressor allows ductless heatpumps to operate efficiently in “part load”conditions.

The inside and outside units should be located tominimize refrigerant piping runs (typically less than50 ft. unless special measures are taken). Becausethe outside unit is considerably quieter thantraditional heat pumps, installers have somewhatgreater flexibility in deciding where to locate thecompressor to keep refrigerant line lengths as shortas possible.

Some people are concerned that the wall-mountedunit will be an “eyesore” in the room, but mostreport after a few weeks they forget they’re there.Indoor units can be painted if desired. Indoor unitsare usually powered by the outside unit and do notrequire separate electrical connection. Because theseunits dehumidify the air in the summer, they requirea small condensate drain line from the indoor unit tothe outside.

Indoor and outdoor units are connected by tworefrigerant lines and an electrical cable. Each modelhas a maximum distance and height differencebetween inside and outside units that must beobserved. A technician familiar with high pressureR-410a refrigerant is needed to insure the systemsare installed and “commissioned” at the initial startup.

Your electric utility may have rebates or otherincentives that include ductless heat pumps. Notemodels which qualify for the Oregon ResidentialEnergy Tax Credit may not meet utility or EnergyStar requirements.

Installation considerations for DuctlessHeat Pumps

Several options may be considered when installing aducted heat pump in homes:

• Multi-zone with one outside compressor unit

serving several indoor units

• Two separate single zone systems may be

less expensive and easier to install than amulti-zone system, particularly if long runsof refrigerant lines are required for one ormore indoor units

For More Information

For more information and a list of manufacturers andwebsites, see the Air Conditioning and RefrigerationInstitute website:www.ari.org/sections/section_groups/DuctlessEquipment

For information about the Oregon Department ofEnergy’s Premium Efficiency Ductless Heat Pumptax credit, see our Web site atwww.Oregon.gov/energy or contact us 1-800-221-8035 or by email: energywebincoming@state.or.us

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