Single Hose System

Pros: Single hose unit will have a high EER rating  then the single hose and does not draw as much power because it only has one motor and more fresh air  

Cons: A single hose cool the condenser by pulling the air from the room they are cooling, and then this air is expelled through their exhaust hose. This creates the negative pressure in the room, in which hot air is continually seeping into this room you are trying to cool from the rest of the house or building to replace the air that the portable AC expels, so that effective cooling capacity is  reduced, and slower initial cool down

Dual House System

Pros: Dual hose unit work with one hose intakes outside air to cool the condenser and another hose to expel this air A two hose unit can cool the room air quicker than a single hose unit, approximately 2~3 times faster depending upon the room size and outside temperature . Also a two hose unit can achieve energy savings since it can reduce the compressor from continually running as it circulates cool air inside the room.

Cons:

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

2) 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.

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

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