Mounted on a wall, the indoor unit of this ductless system supplies a room with either cool or hot air.

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A GUIDE TO DUCTLESS HEAT PUMPS

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Comfort firstBy going ductless, you get room-by-room temperature control

IN THE PAST, the only way to enjoy year-round comfort was to have ducts convey cool air—and often warm air—throughout the house. But ducts don’t deliver that air evenly; they also leak, harbor dust, and eat up space in basements, attics, and closets. And if a house doesn’t have ducts already, installing them is a remodeling nightmare.

In the 1980s, another all-season option became available: ductless heat pumps. These systems have components similar to a typical AC setup: an outside unit with a fan, and refrigerant lines that run to an inside coil. But that coil sits in an enclosed unit right in the room—not in a duct—directly supplying cool or warm air. That makes the indoor unit its own independently controlled comfort zone. A single outside unit can operate as many as eight zones.

Heat pumps are superefficient—they deliver up to 5 kilowatts of energy for every

kilowatt they consume—but their Achilles’ heel has been cold weather. Many models start working harder when outdoor temperatures hit 40ºF, and lose all operating efficiency below 32ºF. That all changed thanks to recent advances in compressor technology. Now there are heat pumps able to work at peak capacity down to 5ºF and maintain 75 percent capacity as low as minus 13ºF, and they’re proving their worth all across the U.S., even in frigid states like Maine and Minnesota.

This soup-to-nuts guide will acquaint you with the basics of ductless heat-pump systems—how they work, how they’re controlled, and how they’re installed— and with the critical factors that will help you make a smart purchase. Do that, and you’ll soon be enjoying the efficiencies and individualized comfort these systems deliver so well.

These heat-pump systems use 1⁄2-inch tubing to circulate refrigerant between the outdoor and indoor units, eliminating the need for ducts.

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VitalsCOST A single-zone system with one indoor unit starts at about $2,400, including installation. A four-zone system costs about $12,000, installed.

INSTALL This project is for HVAC pros, not a DIYer. A simple system with one indoor unit can be finished in half a day. Installations with multiple indoor units will take longer.

SIZE System output is measured in Btus or tons (1 ton equals 12,000 Btus.) To make sure the system is the right size to cool and heat your house efficiently, ask the installer to perform a heat-load calculation. Ductless heat pumps have an output ranging from 3⁄4 ton to 4 tons.

UPKEEP The filter on each indoor unit should be removed and cleaned every month. Once a year, have a technician check refrigerant pressure and clear condensate lines.

WARRANTY These range from five to 12 years, but you can expect this sort of mechanical equipment to last 15 to 20 years before it needs to be replaced.

1 > Dust

An electrostatic mesh captures airborne particles, ensuring that the unit, and your lungs, stay clean. Some meshes are infused with green-tea- based antioxidants that neutralize odors, bacteria, and viruses. Rinse the mesh monthly; it lasts indefinitely.

2 > Odors A micro-perforated ceramic is coated with a platinum catalyst that absorbs and oxidizes odor molecules. Rinse it off every three months with lukewarm water. Replace it when it can’t do its job anymore, usually every two years. Available only in high-end indoor units.

3 > Allergens After the polyester mesh traps pollen, dust mites, pet dander,and germs, enzymes embedded in the mesh break down the allergen proteins. Soak it every three months in lukewarm water; replace annually. Available only in high-end indoor units.

HOW TO KEEP AIR CLEANFor maximum effectiveness, an indoor unit can get rid of three things

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In cooling mode, ductless indoor units are efficient humidity

reducers. One unit can remove up to

8 pints of water from the air every hour.

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Who needs inverter-driven compressors?IN A WORD, EVERYONE. Systems with inverter-driven compressors are more comfortable, more efficient, and longer-lasting than those that depend on standard one- or two-speed compressors. That’s because the inverter, which turns AC power into DC, allows the speed of the compressor motor to be precisely modulated to meet the constantly changing demand for cooling or heating. As a result, you don’t get the uncomfortable up-and-down temperature swings of an AC compressor that’s either on or off. And because the inverter-driven units run more or less continuously, they do a better job of extracting humidity, they’re less likely to break down, and they draw fewer watts than a compressor that constantly cycles on and off.

How do heat pumps work?It’s a matter of pumping refrigerant in the right direction

As its name implies, a heat pump simply moves heat from one place to another. To capture that heat (and release it), it uses refrigerant circulating in a closed loop between the outdoor unit and indoor unit (or units). Refrigerant enters the compressor as a warm gas and leaves as a hot, highly pressurized gas.

In hot weather, the reversing valve directs that gas to the outdoor unit, where a fan blows the heat off the tubing and into the surrounding air. The refrigerant, now somewhat cooler, passes through the expansion valve and condenses into a cold liquid at the indoor unit. The unit’s fan blows over the cold tubing, cooling the room as it warms the refrigerant, which returns to the compressor.

In cold weather, the reversing valve redirects the flow so that hot refrigerant goes from the compressor directly inside the house, and the liquid refrigerant travels from the expansion valve through the outdoor unit, absorbing warmth from the outside air.

cool indoor air

COOLING CYCLE

OUTDOOR UNIT

COMPRESSOR

EXPANSION VALVE

INDOOR UNIT

REVERSING VALVE

HEATING CYCLE

INDOOR UNIT

OUTDOOR UNIT

COMPRESSOR

EXPANSION VALVE

REVERSING VALVE

warm indoor air

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Control optionsThe system actually doesn’t need a thermostat. You set the temperature with a remote control, and the indoor unit automatically informs the outside unit and adjusts its fan speed to reach and hold that temperature. The remote can override those settings if needed.

> Wireless wall-mount If you tend to mislay your remotes or you have a multizone system, this type of control may be a better option.

> Occupancy heat sensor It wakes up the unit when a person enters the room and puts the unit to sleep when the room is unoccupied, maximizing energy savings.

> Web access Adding a RedLINK Internet Gateway to your system allows you to monitor and adjust everything from your smartphone, computer, or tablet.

Choose your indoor unitIt doesn’t have to sit on the wall

CEILING RECESSED

If you have 10 inches of clearance above

the ceiling, this unobtrusive unit sucks in air at its

center and blows it out in four directions

for quick, even cooling and heating in large

open spaces.

DUCTED The least obtrusive

option, it can feed air through as much as

12 feet of buried ductwork—all you see are the grilles. Needs at least 10

inches of clearance between the floor

and ceiling, and access from the

side for servicing.

FLOOR-MOUNTED Resting on the floor (or mounted up to 5 inches above it) and projecting about 7 inches off the wall, it blows air from the top, which is helpful in cold climates. It’s easy to maintain; no stepladder is needed to access the filter.

WALL-MOUNTEDThis quick-to-install, easy-to-maintain unit takes in air at the top and expels it from the bottom. The only unit with an optional platinum catalyst odor filter.

With a remote or a smartphone, you have control over the temperature

and humidity levels, the fan speed, and

even the unit’s fins.

PHOTO: PETER EVANS PHOTOGRAPHY

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A GUIDE TO DUCTLESS HEAT PUMPS

If going ductless seems right for your house, schedule a visit with an HVAC professional who has experience installing ductless heat pumps. Manufacturer websites can pinpoint contractors in your area and are a good place to start your search. Here are the key concerns to be addressed during that visit.

> Where will the outside unit go? Outdoor units perform best in a shady location—on the north side of a house, or under a deck, as long as there’s enough clearance in front, above, and to the sides for sufficient airflow and ease of maintenance.

> Where will the indoor units go? If using wall-mounted indoor units, installation will be simplified by locating them on an outside wall on the same side of the house as the outdoor unit. But that’s not a requirement; refrigerant lines can connect units up to 100 feet from the compressor.

> What size should the system be? Beware of installers who give you a “rule of thumb” sizing estimate for the system. The best way to get a system that performs as efficiently and effectively as possible is to have the installer do a Manual J calculation, which mathematically assesses the cooling and heating load in each room.

> What’s next? Expect to get an estimate of the project cost (equipment and labor), warranty information, a workers’ comp certificate, and references. Ask about financing options. But before you put money down, check all customer references, online reviews of the company’s performance, and the company’s standing with the local Better Business Bureau.

Contact an installer

It’s the contractor’s job to ensure that the installation process goes smoothly. That means, among other things, obtaining the necessary town permits and reviewing the existing conditions with a licensed electrician before the work starts. A single-zone installation should take about 4 hours. Each additional zone adds about 3 hours.

> Outside When the equipment arrives at the house, the outdoor unit is mounted in the agreed-upon location, either on the ground on a solid base or attached to the wall with a metal

bracket. The electrician connects the unit to the house’s breaker panel, and the installer connects the bundled refrigerant lines (lineset) and runs them up the side of the house toward the indoor unit’s location.

> Inside If the indoor unit is the type that mounts on the wall, its base is screwed into place, and a 3-inch hole is drilled through the outside wall for the unit’s refrigerant-line stubs; for the control cable, which allows the indoor and outdoor units to communicate; and for the tube that drains condensate. The

installer feeds all three through the hole and hooks the unit to the base. Back outside, the stubs are connected to the lineset, the cable is connected to the outdoor unit, and the condensate drain is led away from the house.

> Wrap up If a test shows the system is working properly, the hole is sealed with spray foam and the lineset is hidden under a protective cover. Before the contractor leaves, he or she should clean the site, teach you how the system operates, and leave a number to call if any questions or problems arise.

Installation day

An outdoor unit can be mounted on the ground or attached to a wall, as shown.

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Ductless livingOther than cleaning the filters, there’s not much you need to do. Have a technician come once a year to make sure the condensate lines aren’t clogged and the refrigerant pressure is on target. Most contractors offer that service on systems they install. Otherwise, just sit back and enjoy the comfortable environment created by your new ductless heat pump.

HEAT PUMPS IN THE WINTERThey’re working better than ever in the cold—as low as minus 13°F for some—but pay attention to these details

OUTDOOR UNIT> Mount it high. Snow can clog the airflow necessary for the unit to work. Attach it to the wall at least 2 feet above likely snowpack or drifts.> Install a drain-pan heater. This device keeps the condensate that’s generated during defrost cycles from freezing and building up.> Add baffles. These metal panels help prevent wind- driven snow and ice from getting inside the unit.

INDOOR UNIT> Use a ceiling fan. Hot air is naturally buoyant, so it heads toward the ceiling after it comes out of the unit. A fan can help keep the heat evenly distributed. > Avoid cold drafts. Many indoor units start blowing before their coils are warm. Units with Mitsubishi Electric’s “hot-start technology” make the fan wait until the coils warm up.

SUPPLEMENTAL HEATINGIn climates where the temperatures regularly get too low for a heat pump to handle, it may still make sense to have a heat pump paired with a traditional heating system. The pump can operate at peak efficiency during spring and fall and on milder winter days. And if things turn really frigid, the dedicated heating system kicks on, and the pump takes a rest.Because electric heat pumps are so efficient, overall energy costs will be lower with a properly sized and calibrated dual system than with a stand-alone heating system.

A ductless heat pump with an inverter-driven compressor is an effective heating option in cold climates.

Indoor-unit fans blow quietly—19 decibels at low speed, 48 at high. A whisper generates 30 decibels, and a normal conversation, 60. P

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