Portable Air Conditioners:
Why is a Dual Hose Design Better?


Using a dual hose (two air duct hoses) portable air conditioner design will allow the same size system to provide 40% to 70% or more cooling using the same amount of electricity compared to a single hose model.


1. Single Air Duct Hose

Depending on outdoor temperature, up to 67% of the cooling capacity of a single-hose unit is lost due to hot air drawn in from the outside. If air is exhausted to the outside, the laws of physics demand that an equal amount of air must somehow replace it. Below, red arrows show hot outdoor air pulled into the indoors through tiny leaks and cracks, joints, etc. called microleaks. Blue arrows show cooled indoor air. The "hose" is the hot exhaust air duct hose.


As indoor air is blown outdoors through the exhaust air duct hose, indoor air pressure drops slightly, causing replacement air, called "make up air" or "infiltration air" to be drawn in from the outdoors through microleaks.


2. Dual Air Duct Hoses

Below you can see how a dual hose system uses no indoor air to cool the condenser, and draws in no make up air from the outdoors. No hot air from the outside is drawn inside the structure that is being cooled. The condenser section gets its air flow from the outdoors.  No cooling capacity is lost due to discarded cool air, or to hot outdoor air being drawn inside.


In the dual hose model, there are two air duct hoses, the inlet hose brings outdoor air into the condenser section of the air conditioner where it blows across the hot coil, the exhaust air duct hose exhausts the hot air to the outdoors. Outdoor air and indoor are not mixed in any way.


drawing shows infiltration air of portable air conditioner with single hose


      drawing shows portable air conditioner dual hose, no air infiltration

Below is a diagram of how an air conditioner works. The top half of the drawing shows components that are typically located outdoors, the bottom half shows components located indoors. In a portable air conditioner, all of the components are located inside a single unit, which is indoors.


A portable air conditioner of one ton size (12,000 BTU) requires a minimum of 250 CFM air flow across the condenser. On a single hose portable AC, the amount of hot infiltration air is equal to the condenser air flow. At 250 CFM, for each 1F temperature difference, 270 BTU of capacity is lost.


diagram of how an air conditioner works   chart shows capacity loss of single hose portable air conditioner due to infiltration air

When outdoor air is warmer than indoor air, at 250 CFM, capacity loss equals at least 270 BTU per each degree F of temperature difference. Power utilization is unchanged, so as capacity declines and power use remains constant, efficiency drops. For more details on how capacity and efficiency is calculated, click here.

Above left you can see the normal design of an air conditioner. Note that the top half is typically located outdoors in the ODU (Outdoor Unit). The bottom half of the system is located indoors, called the IDU.  Note that both IDU and ODU each have their own fan. The indoor fan blows room air across the cold evaporator coil to cool the room air and return it to the room. The operation of an air conditioner is such that heat is absorbed by the indoor coil as indoor air flows across it, cooling the air. Outdoors, the heat is released as outdoor air flows across the hot outdoor condenser coil, warming the air and cooling the coil.


Air Conditioners are rated based on how much cooling is done by the IDU, when the outdoor air temperature is at the AHRI standard test condition of 95F. With a portable air conditioner, all of the components are located in a single unit indoors. Nearly all portable air conditioners use a single hose, however using a dual hose design is far more efficient and increases cooling capacity.


Climax offers a 12,000 BTU dual hose DC Inverter portable air conditioner that fully delivers its rated capacity. Combining the variable capacity and high efficiency of a DC Inverter compressor with a dual hose design provides the most efficient possible portable air conditioner, capable of using 67% less total power to perform the same amount of cooling, or providing more than twice as much cooling for the same power usage. DC Inverter Portable AC Brochure



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