Portable Room Air Conditioners, Selection, Use, Properties & Functions
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How to choose a portable air conditioner that fits the building and your cooling needs?
Operating properties of portable room air conditioners, FAQs
Do portable air conditioners provide outdoor fresh air intake?
How big a portable room air conditioner do I need?
Details about portable room air conditioners.

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How to choose an air conditioner for window or through-wall mounting, how much BTU capacity do you need? Also see COOLING RULES OF THUMB to guesstimate how many tons or BTUs of cooling a building needs and see RATED COOLING CAPACITY to determine the cooling capacity of existing air conditioning equipment. Our page top photo shows the front of a Haier portable room air conditioner. Not shown are condensate accumluator or ductwork/hose extending to outside.

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Portable Room Air Conditioners

Portable air conditioners - units on wheels which are plugged into an outlet but can be moved room-to-room and do not require a window for their exhaust. These cooling units are of modest cooling ability, typically around 10,000 BTUh though some producers such as Sunpentown offer units up to 14,000 BTUh. See RATED COOLING CAPACITY for an explanation of how to determine the cooling capacity of an air conditioner that is already installed at a building. There are quite a few brands of portable room air conditioners, including Fredrich, Haier, New Air, Sharp, Soleus, Supentown, SPT (shown at left). [InspectAPedia.com has no financial nor any other relationship with any brand or product discussed at this website.]

The U.S. ENERGY STAR program uses the term "Single Package" air conditioning system which is defined as follows:

Single Package: A single package unit is an ASHP or central air conditioner that combines both condenser and air handling capabilities in a single casing.[1]

In this definition, ASHP refers to an Air-Source Heat Pump (ASHP) which is further defined as follows:

Air-Source Heat Pump (ASHP): An air-source unitary heat pump model consists of one or more factory-made assemblies which normally include an indoor conditioning coil(s), compressor(s), and outdoor coil(s), including means to provide a heating function. ASHPs shall provide the function of air heating with controlled temperature, and may include the functions of air-cooling, air-circulation, air-cleaning, dehumidifying or humidifying.[1]

Question: How can I Avoid Mixing Outdoor Air Into My Room Air with a Window or Portable Air Conditioner?

Do you know of any air conditioners (besides mini split ac's) that don't mix inside air with outside air? Do you know of any ac's that have sealed compressors?

If not, do you know of a solution to not mixing inside with outside air? Do regular window ac's and dual hose portable ac's normally mix inside with outside air? - B.R.

Reply: Close the outside air intake vent on a window air conditioner unit or use a portable room air conditioner

It sounds as if you've been given some confusing information. All residential A/C compressors are sealed units, and outdoor air has no role in the internal operation of the compressor.

Room air conditioners typically have a manual control that permits mixing in outside air or shutting it off.

Central air conditioner systems do or do not have outside air supplied to the return duct system depending on the duct design, having nothing to do with the compressor you cited. Though many residential central air systems we've inspected do not provide for outside air or makeup air, it's a good component to add to the design for a very tight house where IAQ could be a worry; for maximum heating or cooling efficiency we use an air to air heat exchange where outdoor air is entering the system.

How to Close off Outside Air Intake for Window-mounted or Through-Wall Air Conditioners

If you are using a window-mounted or through-wall mounted air conditioner, it is likely to have a mechanical control, a dial or lever that opens or closes a vent that mixes or stops mixing some outside air with room air as it is circulated through the air conditioner unit.

If you don't want to introduce outdoor air (increasing the cooling and dehumidification effectiveness of the system at the expense of fresh air), just be sure that your unit's outside air control is in the "closed" position. These vents may not be perfectly air tight but in a modern air conditioner closing the vent will close off nearly all outside air intake.

Outside Air & Portable Air Conditioners

While some portable air conditioners may make use of outside air to assist in cooling their compressor and in removing condensate, at least some of the models, including dual-hose units that we read about (which is certainly not all of them) provided an outside air intake that adds outside air to the room air being cooled and dehumidified.

The balance point between maximizing the cooling ability (and reducing cooling costs) any air conditioner by closing off outside air from the system and the quality of indoor air in a tight building needs to be decided on a case-by-case basis. If your building is very tight, or has odors, stale air, or high dust or allergen levels see INDOOR AIR QUALITY IMPROVEMENT GUIDE.

FAQS & Properties of Portable Air Conditioners

One producer of portable air conditioners who provides particularly helpful description of the operating properties of these devices is Sunpentown International (SPT), a California firm. Here are some relevant FAQs that give insight to the operation and use of portable air conditioners, as well as comparing the use of single-hose and dual-hose portable room air conditioners. The photo at left shows typical flexduct and other accessories for a portable room air conditioner, in this case from Soleus.

Quoting from Sunpentown's FAQs (Quoting and paraphrasing):

Single Hose Portable Room A/C Unit

This design draws indoor air for both front cold air output as well as exhaust air (used to cool compressor).

PROS of single hose portable room air conditioners:

Fresh air is exchanged within the room.

Higher energy efficiency.

CONS of single hose portable room air conditioners:

A percentage of the air taken in is used to cool the condenser. As this air is exhaust out, it creates a negative air pressure. Air is continuously seeping in from adjacent rooms to replace the exhausted air.

Slower initial cool down.

Dual Hose - draws indoor air for front cold air output and draws outdoor air for exhaust air (used to cool compressor).

PROS of dual hose portable room air conditioners:

If outside temperature is lower than indoor temperature, compressor can be cooled down faster and produce colder front air output.

No negative pressure created within the room

Initial cool down of room is quicker than single hose.

CONS of dual hose portable room air conditioners:

Same air circulating within the room, which will decrease in oxygen and increase in carbon dioxide.

If outside temperature is high (>90°F) or when humidity is high (>80%), compressor cannot be cooled and results is increased temperature of front air output. In such cases, the second hose should not used to prevent the compressor from overheating.

Uses two internal fans and consumes more energy due to added hose.

NOTE about outdoor air: We read no indication in either design that outdoor air is added to or mixed in with room air.

How is Condensate Disposed-of for Portable Room Air Conditioners

Sunpentown Portable AC units are equipped with an advanced condensation removal system: Self-Evaporating Technology (except WA-9000E, WA-1000E & WA-1205E). When running AC mode, this technology recycles the water condensation to cool off the cooling coils, then evaporates the water out with the exhaust air.

This results in increased energy efficiency, cooling performance and reduces the need to empty the water tank. Under extreme humid conditions, the water condensation may collect faster than the unit can recycle. Should the built-in water tank becomes full, the compressor will automatically shut-off and water full indicator will blink. At this time, water should be emptied, which is a simple process.

For units with Self-Evaporating Technology, it is always suggested to not use continuous drainage in cooling mode. Allowing the water to collect and recycle helps cool down the cooling coils, which in turn produce colder air output.

More detail about how to diagnose and cure an air conditioner that is not dehumidifying can be found at Air Conditioning Dehumidification Problems.

Role of Exhaust Flex-Duct or "Hose" for Portable Room Air Conditioners

Outside air conditioning for tents (C) D Friedman

Our photo (left) shows huge portable air conditioning systems that are being used to air condition an enormous tent used for a college alumnae gathering in New York. The white flex duct you see there is blowing cool air into the tent space and the entire air conditioner is located outside the tent. This is a "total loss" system that pulls outdoor in to the unit, cools it, and blows it into the tent.

In comparison with the commercial outside portable air conditioner supply flex duct you see at left, indoor portable air conditioners provide for an exhaust duct as follows:

All portable AC units require exhaust hose installation. This is for removal of hot air which has been used to cool off the compressor. Standard installation includes venting through a sliding window or through the wall, by cutting a hole. Sunpentown AC units are supplied with the necessary accessories for either installation: flexible hose (extends up to 5'), window kit and wall adapter.

Keep the exhaust hose as short and straight as possible.
Heat is emitted back into the room as hot air travels through the hose, try insulating the hose.
If unit is to be operated throughout the day, turn on the unit early, before the noon heat hits.
If unit is to be operated at night and outdoor temperature is lower than room temperature, first open windows to allow air exchange. After 15/20 minutes, close windows.
When unit is turned on, set fan on High to allow air circulation. After 30 minutes, set fan to Low. In low fan, air is allowed to pass through the cooling coils over a longer period of time, thus the air output will be colder than High fan.

[End of quote, paraphrase]

Portable, window, or through-wall air conditioners are typically described by their manufacturer as suited for:

Single Room Air Conditioner Capacity - typically for rooms up to 20' x 20' or 400 sq.ft. in area. BTUs in this product range are typically from 6,000 BTUh to 10,000 BTUh.
Portable room air conditioners - 7,500 to 14,000 BTUH, portable, using one or in some cases two flexible ducts to move heat from the room, through cooling coil and the compressor, to outdoors

Multiple Room Air Conditioner Capacity - typically for a total area of up to 800 sq.ft. BTUs in this product range are typically from 10,000 BTUh to 16,000 BTUh.
Large Capacity Air Conditioner Capacity - typically for multiple rooms or very large rooms up to a total area from 900 sq. ft. to 2,000 sq.ft. BTUs in this product range are typically from 16,000 to 28,000 BTUh.
Central Air Conditioning - typically to cool an entire floor or multiple floors in a home. Also see A/C TYPES, ENERGY SOURCES
Commercial grade portable air conditioner units for outdoor use - such as air conditioning a large tent (see our photo above)

To determine the BTUs needed to cool a given space follow this procedure:

Calculate the total square feet to be cooled: Measure the size of the room (or rooms) to be cooled, to obtain total square feet. Multiply room length by width for each room and if there are multiple rooms, add the room areas together to get a single number.
Read the Base BTUs needed from Table 1 below
Add additional BTUs for these factors:

+ 4,000 BTUs for each room below a ceiling or roof which is not insulated
+ 4,000 BTUs for a home or residential kitchen included in the cooled area
+ 1,500 BTUs for each window which receives significant daily sunshine
+ 1,500 BTUs for a room over a kitchen or boiler room IF the kitchen or boiler room is actively producing heat during the cooling period
+ 600 BTUs per person over two, if more than two occupants will be occupying the room during the cooling period

Subtract BTUs from the total required if these factors are present:

- 1,000 BTUs if the room is on the shaded side of the building

Calculate the final total BTUh needed from the above steps. This should place you in the right range of cooling capacity needed. Review the warning below about buying an oversized air conditioner.

The Air Conditioner BTU Recommendation table found at AIR CONDITIONER BTU CHART gives recommended air conditioning BTU's necessary to cool a single room. The data in the table assumes that the ceiling over the room is insulated and that the room is not over or is not itself a special heat-producing area such as a kitchen or boiler room. Do not buy an air conditioner which is oversized (too many BTUh) for the area you need to cool. You may think that bigger is better, but not in the case of air conditioning.

To make a room comfortable the air conditioner needs to both cool the room air AND dehumidify the room air.

If the air conditioner is too large for the space to be cooled, the temperature will drop quickly and the A/C unit will shut off before the air has become adequately dry.

The room will be either too cold or too humid for comfort.

How Much Cooling Capacity do we need Per Square Foot of Building Area? How Much Space can a Ton of Cooling Capacity Serve?

Maybe 450 sq.ft. to 1000 sq.ft. of a typical home can be cooled per ton of cooling capacity: that is, one ton (or 12,000 btuh) of air conditioning can cool about 500 sq.ft. of space. Sketch courtesy of Carson Dunlop

But the real answer is, it depends. Some of the factors that affect the ability of an air conditioner to cool a space need to be considered besides just the number of square feet. These include at least the following questions about air conditioning load and cooling requirements:

What are the sun and heat characteristics of the geographic area where the building is located (southern U.S. vs. northern U.S. or Canada, for example)?
How much direct sunlight is falling on the building?
Is it bright hot sun or only partly sunny?
What are the exterior colors of surfaces on which sunlight is falling?
How well the building is insulated?
How drafty is the building?
How many occupants are in the building?
What other heat sources (or cooling sources) are in the building?
How high are the interior ceilings?
How does air circulate within the occupied spaces?
What defects in the air conditioning system need to be overcome, such as duct system errors or damage, dirty filters, blocked cooling coils, etc. ?

Other types of portable or individual-area air conditioners

Heating & Cooling units - capable of both cooling or heating a room using electricity. Basically these units are small heat pumps that are mounted in a building window or wall. Heating/Cooling units will give two different BTUh figures, one for cooling and one for heating.

These figures will differ, for example, producing 18,000 BTUh in cooling mode but only 12,000 BTUh in heating mode. The difference between heating and cooling, and the amount of heat actually available will depend also on the outdoor temperatures when in heating mode (as with any heat pump system, the unit cannot provide heat below certain temperatures.)
Slider or Casement Window units - narrow tall cooling systems which are designed to fit into the narrow space provided by casement or slider windows.
Through-wall air conditioners - air conditioning units which are designed to be installed into a metal sleeve which is then itself installed in an opening cut into the building wall, leaving windows unobstructed, or perhaps for use in a room without a suitable window in which an air conditioner could be placed. BTU output is typically a bit more than the smallest window air conditioners but otherwise is similar in range.
Portable air conditioners - units on wheels which are plugged into an outlet but can be moved room-to-room and do not require a window for their exhaust. These cooling units are of modest cooling ability, typically around 10,000 BTUh though some producers such as Sunpentown offer units up to 14,000 BTUh. See PORTABLE ROOM AIR CONDITIONERS for details about portable room air conditioners.

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PORTABLE ROOM AIR CONDITIONERS

Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects" section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and home inspection educator.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Thanks to various industry and air conditioner sales publications and consumer pamphlets including Sears Kenmore(R) air conditioning sales
Sunpentown International (SPT), 21415 Baker Parkway, City of Industry, CA 91789, 800-330-0388 / 909-468-5288, produces portable room air conditioners. Web search 12/31/2010. FAQ for portable room air conditioners: http://www.sunpentown.com/learnmore.html
[1] U.S. Government EnergyStar Program, ENERGY STAR Program Requirements for ASHPs and Central Air Conditioners – FINAL DRAFT, found at http://www.energystar.gov/ia/partners/prod_development/revisions
/downloads/ac_ashp/Final_Draft_CAC_ASHP_Eligibility_Criteria.pdf
Air-Conditioning and Refrigeration Institute. Standard 210/240 “2003 Standard for Unitary Air-Conditioning and Air-Source Heat Pump Equipment.”

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
Air Conditioning Inspection, Diagnosis, Repair, Efficiency all the basics for home owners, inspectors, new repairmen
Air Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
Asbestos HVAC Ducts and Flues field identification photos and guide
Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation
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Portable Room Air Conditioners

Question: How can I Avoid Mixing Outdoor Air Into My Room Air with a Window or Portable Air Conditioner?

Reply: Close the outside air intake vent on a window air conditioner unit or use a portable room air conditioner

How to Close off Outside Air Intake for Window-mounted or Through-Wall Air Conditioners

Outside Air & Portable Air Conditioners

FAQS & Properties of Portable Air Conditioners

Single Hose Portable Room A/C Unit

PROS of single hose portable room air conditioners:

CONS of single hose portable room air conditioners:

Dual Hose - draws indoor air for front cold air output and draws outdoor air for exhaust air (used to cool compressor).

PROS of dual hose portable room air conditioners:

CONS of dual hose portable room air conditioners:

How is Condensate Disposed-of for Portable Room Air Conditioners

Role of Exhaust Flex-Duct or "Hose" for Portable Room Air Conditioners

Portable, window, or through-wall air conditioners are typically described by their manufacturer as suited for:

To determine the BTUs needed to cool a given space follow this procedure:

How Much Cooling Capacity do we need Per Square Foot of Building Area? How Much Space can a Ton of Cooling Capacity Serve?

Other types of portable or individual-area air conditioners

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair