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All Your Ductless HVAC Questions Answered

Published on: March 21, 2014

The word is out about ductless systems, and their popularity is rising fast. Read through these frequently asked questions and answers to learn why ductless heating and cooling systems may be the perfect fit and solution for your home-improvement project.

What Are Ductless Systems?

Ductless systems are air-source heat pumps or air conditioning systems that provide space and home heating and cooling without the need for air ducts. There are three basic components to a ductless system:

  • Indoor air-handling units (AHUs) – The AHU is the component that’s installed inside the living space(s) that needs heating and cooling. The AHU contains the evaporator (heat-exchange coil), fan, condensate drainage, air filtration components, and various electronics and sensors. All these sophisticated components are housed within a stylish covering, and offer several installation options, including universal surface mounting, wall or ceiling recessed, and concealed mounting inside the ceiling, wall or floor.
  • Outside unit – The outside unit of the ductless system houses the compressor, condenser (heat-exchange coil), fan and other parts. The compressor/condenser may connect to one or more indoor AHUs, depending on the selected model.
  • Conduit – A thin flexible conduit is the technology that makes ductless heating and cooling possible. The conduit connects the outside unit to each indoor AHU. It only needs about a 3-inch hole in the exterior wall of the home. It gets routed through inconspicuous spaces (attic, inside walls and crawl space) to the AHU(s). The conduit houses the refrigerant lines, power cable and condensate line.

Is Ductless Heating and Cooling New Technology?

Ductless systems have been around for a while. They were developed in Japan during the 1970s in an attempt to find a practical means to heat and cool homes and offices that had very little room (or no room at all) for air ducts. Window units were a noisy disturbance to home comfort and the workplace, blocked sunlight, and were inefficient.

Ductless heating and cooling systems became popular throughout Asia and Europe, but the widespread use of ductless systems in America did not occur until more recently. Ductless technology continued to develop, and they are now much more than just an alternative to other systems. Ductless systems are quickly becoming the primary choice for heating and cooling homes and offices for a plethora of applications.

How Does a Ductless System Work?

Ductless heating and cooling systems provide point-of-use heating and cooling at the indoor AHUs. The conduit housing the refrigerant lines drives this technology, allowing ductless mini split and multi split systems to be refrigerant distribution systems, rather than air distribution systems, as is the case with conventional heat pumps and air conditioning units.

The process of using refrigeration principles for heating and cooling is the same in ductless systems as with conventional systems. This is the basic operation of the heating cycle:

  • The compressor squeezes high-efficiency refrigerant in preparation for heat exchange.
  • The refrigerant flows through the refrigerant lines inside the conduit to the indoor AHU.
  • The refrigerant is condensed to a hot liquid and transfers heat energy to the zone (room).
  • The fan inside the AHU smoothly and quietly pulls air across the evaporator, which absorbs the heat energy, and circulates the heated air to the zone.
  • The refrigerant flows to the outdoor condenser where it extracts heat energy from outside air.
  • The refrigerant flows to the compressor to repeat the heating cycle.

In the cooling cycle, a reversing valve reverses the direction of refrigerant flow, which provides cooling and dehumidification for the home.

What Applications Are Ductless Systems Designed For?

Ductless systems were originally designed to offer an alternative to forced-air systems and portable units, providing versatile installations for home and business owners. Ductless technology and design have exceeded those early goals. Ductless mini and multi split configurations (AHU locations) are designed and sized to meet the cooling and heating load in each zone. These are some of the applications perfectly suited for ductless heating and cooling:

  • Remodels – If you are converting unused space inside your home, such as attic or basement spaces, to living spaces, you’ve probably thought about different ways you might heat and cool the new room. Ductless systems are ideal for space conversions, since you don’t need to extend ducts, and portable and window units are inefficient or perhaps impractical.
  • New additions – Room additions are common, and figuring out how to heat and cool new rooms is a common problem. That is no longer the case with ductless mini splits. Your HVAC professional installs the indoor AHU in the most practical location you choose, and you’re in business.
  • Spare rooms – Do you have rooms that are seldom used in your home, such as extra bedrooms? With a ductless system, you can heat and cool these rooms on demand – separately from the rest of the home.
  • Outbuildings – Pool houses, guest cottages and workshops are easily heated and cooled with ductless systems. With a multi split configuration, you may use the same outside unit to heat and cool rooms in the main house, too, depending on the selected model and conduit length.
  • Whole-home – More homeowners are discovering the power of ductless systems for heating and cooling an entire home. If you are designing a home, consider a modular ductless configuration that links mini and multi ductless systems to heat and cool all the zones efficiently and comfortably.
  • Replacement and supplemental – If it’s time to replace your current system, or you need to supplement the system, consider a modular ductless configuration instead.
  • Older homes – Many older homes across the Southeast don’t have air ducts. It can be expensive to heat and cool these homes, and comfort is often less than desirable. Ductless systems are the natural solution to this dilemma.
  • Vacation home – Ductless systems use electricity (not gas or oil), so they are easy to maintain and may sit idle for extended time periods between uses. (Note: if you cut all electricity at the circuit panel to your ductless system when you’re not using it for extended periods, turn on the circuit panel several hours before using it. Check the owner’s manual for specifics for your ductless model.)
  • Rental properties – Ductless systems are low maintenance, making them ideal for rental properties. (The benefits of ductless systems are appealing to potential renters, too.)
  • Offices – Ductless systems are available for small offices and substantial commercial applications.

Are Ductless Systems Energy Efficient?

In addition to offering versatile installation options, ductless systems deliver exceptional energy efficiency, for both heating efficiency (HSPF) and cooling efficiency (SEER). With variable-speed compressors (inverter-driven technology), multi-speed fans and high-efficiency refrigerant, ductless heating and cooling lowers energy bills and delivers supreme home comfort.

How Do I Install a Ductless System?

Unless you are a certified HVAC specialist and electrician, it’s recommended to have an HVAC contractor design and install the ductless system. There are installation steps that must be performed correctly, or system damage and/or personal injury may occur.

Moreover, to leverage peak performance from a ductless system, it must be designed (sized and installed) for optimal results. Each AHU is sized specifically to the zone that it’s intended to heat and cool. The conduit must be installed correctly so as not to damage components, and to ensure the drainage system is performing correctly or you may have a water leak inside the home. These are the basic steps for designing a ductless system:

  • Inspect the home for air leaks and insulation deficiencies that may compromise energy efficiency, comfort and your energy bills. Perform air sealing and add or replace damaged insulation if needed.
  • Perform a heating/cooling load measurement of the zone (mini split), zones (multi split) or entire home (modular configuration) where each AHU is to be installed.
  • Decide where to install the outside unit. Installation may be on a small concrete slab, mounted to the home with brackets or installed on the roof. (Note: the outside unit should not be too close to venting, such as dryer vents, protruding through the home shell.)
  • Install components to interior design specifications to your satisfaction, and to manufacturer specifications to keep the warranty valid.
  • Explain basic care tips to keep your system running efficiently between professional preventive maintenance, and explain the benefits of annual maintenance agreements.

What Kind Of Maintenance Is Involved With a Ductless System?

Ductless systems require basic care, such as cleaning the air filter, by the homeowner. Check the outside unit from time to time, and remove debris, leaves and anything else that may hinder or obstruct free airflow. If you receive snow and ice in your region of the Southeast U.S., you’ll need to keep the outside unit free of these natural obstructions, too.

Your HVAC pro takes care of the technical aspects of ductless maintenance, such as checking refrigerant, inspecting electrical connections and ensuring that drainage is free of obstructions, algae and other debris.

If you still have questions about ductless heating and cooling, please contact us to be connected to an HVAC contractor near your Southeast U.S. home who is experienced with ductless systems.