PTACs vs. Room ACs

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Jan 21, 2013
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Santa Maria, CA
Hello all,

It has been a while since I've posted on this board, but as I am a little confused on this topic I figured i would come here as a source of help.

I am overseeing the installation of air conditioning units in a hotel and am trying to define them according to ASHRAE 90.1-2010. ASHRAE defines two terms - PTAC and Room air conditoners. Both can be mounted in a wall, and both can supply both cooling and heating. However, when it comes down to minimum efficiency requirements, the numbers a quite different from each other.

Is the only difference between a PTAC and a wall-mounted Room Air Conditioner the fact that a PTAC comes with a wall sleeve? As I read the definitions, that is the only distinction I see.

Thank you for any help!



Well-known member
Apr 9, 2011
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Here are my interpretations of the two terms:

PTAC - A fully self contained unit. It has the entire refrigeration unit (evaporator, condenser, and compressor). They stick out of the wall so that the condenser can give off its heat to the outdoors. Most have electric heat, but I believe some come with gas heat.

Room Air Conditioner - This seems to be a somewhat vauge term to me, but I'd guess it means that it's a split system. They'll have a fan blowing air over a cooling (evaporator) coil to provide A/C. But the condensing unit (condenser, compressor, and refrigerant piping) is located elsewhere. For apartment buildings the condensing unit is typically installed on the roof. For smaller building, they could be installed on the ground level. If it's a chilled water system, there will be a chiller somewhere outside that provides cold water to the cooling coil.

For heat they could be electric, gas, or hot water depending on how the building was designed.

PTACs are generally much less efficient. If you're in CA, I'm surprised the HVAC engineers were even able to specify PTACs. There are probably a lot of strict energy efficiency requirements in that state.