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Quiet ductless air-conditioning alternative

Air-conditioning units

Ductless air conditioners are ideal for all climates

Q: Several rooms in my house are uncomfortably hot, but I don't want noisy window air conditioners and I cannot afford a central system. Will a quiet ductless system, often used with hot water heat, work for me too?

- Mike R.

A: Dear Mike: A ductless mini-split air conditioner is an excellent choice for almost any home and climate. As you indicated, these systems are also often used for whole-house cooling in homes with hot water radiant heat that do not have central hot air ductwork. Ductless heat pump models are also available for efficient heating in the winter too.

For homes with central air conditioning in which some rooms do not stay comfortably cool, adding a ductless unit is a good idea. This allows for a specific area of the house to be zone cooled for an overall electricity savings. If certain rooms are used at only certain times of the day, it makes economic sense not to keep them extremely cool when they are not being used. With computerized thermostats, ductless systems also offer this advantage.

Ductless air conditioners are called "mini-split" systems because they are similar to a regular ducted split central air conditioner, only on a smaller scale. A split system means that the compressor/condenser unit is located outdoors and "split" from the indoor cooling coils/blower. Just a small three-inch diameter hole is cut in the wall to run the tiny refrigerant lines and electric wires to the indoor cooling units.

With the compressor outdoors and an indoor cooling unit mounted high on a wall or ceiling, they are super-quiet (sounds like a "whoosh"). These units are typically even quieter than many ducted central air

James Dulley is a mechanical engineer who writes on a wide variety of energy and utility topics. His column appears in a large number of daily newspapers.
Copyright 1999 James Dulley


conditioners. In a central unit, huge amounts of air must wind through complex ducts with many bends and shape changes, all of which contribute to noise.

Mini-split ductless air-conditioners are a preferred option to trying to use several room air conditioners to cool an entire house. Window units block the window and can be a security risk. It's not terribly difficult for a thief to remove a window unit and get indoors. Also, a window unit is not located near the ceiling which is the preferred location to introduce cool air into your room.

Since these ductless units are used extensively in Europe and the Orient with their extremely high energy costs and limited space, each outdoor compressor unit is small and quiet. The typical indoor cooling units are also small, weighing 18 pounds.

For convenience and comfort, the better ductless models have hand-held remote controls that control everything - temperature, louver directions, programmed on/off times, etc. If you live in an area with high humidity, select a model with a dry mode switch setting. This adjusts the air flow and compressor for comfortable, low-humidity indoor air.

Although the efficiency ratings of ductless systems (SEER from 10 to 12) are not as high as the top-of-the-line central air conditioner (SEER up to 16), they can still be more efficient. Many old and new house duct systems have so many leaks and uneven air flow patterns that a substantial amount of the cool air never gets to the rooms where you want it. With the ductless cooling unit in the room, these transport losses are negligible.

For winter heating too, you can choose a heat pump model. If you hate that first shot of chilly air in the winter each time the furnace or heat pump blower starts, select a ductless model with a soft, slow start and a preheater for the air. For colder climates, some of the heat pump models also have backup electric resistance heat.

For very large areas, consider a model with automatic moving vanes to distribute the cool air evenly. Using a hand-held remote, the louvers can also be adjusted in a fixed right/left position to concentrate the cooling in one smaller area. Many of the heat pump models also provide an up/down louver setting to vary the air flow when heating (down) or cooling (up or level) for better efficiency.

If you have allergies, select a ductless model with built-in washable air filters. These are often more effective than a central air cleaner for removing larger allergen particles (mold, pollen, etc.) from the room air. These larger particles tend to settle back down on the carpet, furniture or in the ducts before they reach the central air cleaner.

Write for (or instantly download - Update Bulletin No. 643 - buyer's guide of nine ductless air conditioners and heat pumps listing cooling/heating outputs, efficiency ratings, comfort features, zones available, diagrams and a payback/ savings chart. Please include $3.00 and a business-size SASE to: Jim Dulley, Illinois Country Living, P.O. Box 3787, Springfield, IL 62708.


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