A/C not cold

Discussion in 'General Camping Discussion Forum' started by Birdwoman26, May 12, 2016.

  1. Birdwoman26

    Birdwoman26 New Member

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    First time out in NTU Aliner Expedition. Tried out the air conditioner. 78 degrees out but humid. It ran okay but never got cold. Any ideas?
     
  2. 94-D2

    94-D2 Happy Campin'

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    Are you sure the compressor was running and not just the fan. If it is not getting cold, I suspect the compressor is not running. I have had a condition where the capacitor does not fire off and start the compressor. Usually after an on and off situation. Turn it on and see if you hear a secondary motor run that has a load on it. It should be apparent. The fan will sound higher and free running with no load basically. If it isn't Getting cold you have a problem.
     
  3. daschnoz

    daschnoz Active Member

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    I didn't stay at a Holiday Inn Express last night, but I do work for an HVAC company. I'm the guy that writes the equipment selection software that our sales force and building design engineers use to size and configure our equipment.
    http://www.poolpak.com/

    We had the same problem with our PUP last year.

    Low temperature (relatively speaking), high humidity - assuming that you don't have an electrical or mechanical problem with the A/C/ - I bet your A/C coil is freezing up. Most "quality" A/C systems have a mechanism that monitors the surface temperature of the cold coil. When the temperature gets below 33°F, it shuts down the compressor for a period of time to allow the temperature to come back up. BUT, these are not "quality" systems; they're made as inexpensively as possible and this is not an absolutely necessary feature to make the system function.

    Try running the heat while you run the A/C. It sounds counter-intuitive, but it will help keep the coil from freezing.




    If you're a nerd and want to know why, read on.

    The key with refrigeration systems is to follow the heat. Once I figured this part out, the function of refrigeration systems made perfect sense.

    A/C units do not cool the air. Instead, the air gives its heat energy to the cold side (evaporator coil) of the A/C. That heat is then given back to the air that blows through the coil on the hot side (condenser coil).


    There are 2 types of cooling loads that an A/C unit will see - latent and sensible. Sensible load is the measured air temperature that triggers the thermostat. Latent load is the heat energy that is stored in water vapor (felt as humidity).

    We all know that cold air holds less water vapor than hot air (this is why it is so dry during the winter). <-- This is important to the next part

    An A/C system needs a certain amount of heat input from the air (on the evap. coil) to function correctly. When the air is cool and humid, the available sensible heat energy is low, but the latent heat energy is high. As the air passes through the evaporator coil, water vapor condenses into liquid water on the surface of the coil. In a low temperature, high humidity condition, that condensed water vapor then gives its heat energy to the evaporator coil. The result - ice on the evaporator coil. The ice will block the airflow and give the illusion that the A/C is broken.

    Dehimidification is a side effect of refrigeration systems, and this is why. By running the heat with the A/C, you're adding more sensible heat energy to the air and giving the A/C more energy to pull from the air itself. It will still pull energy from the condensed liquid water, but since there is more sensible energy in the air, the coil will not freeze.
     
  4. drosengrant

    drosengrant One Day at a Time

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    Daschnoz Interesting but thanks for the headache [:D] [:D] [:D] [:D] [:D]
     
  5. 94-D2

    94-D2 Happy Campin'

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    That is exactly what I meant. [A]
     
  6. daschnoz

    daschnoz Active Member

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    You're welcome. I did give fair warning.
     
  7. bols2Dawall

    bols2Dawall S.W. Ontario

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    Are you saying the A/C unit was blowing cold air but the PUP never got cool , or ............?
     
  8. Birdwoman26

    Birdwoman26 New Member

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    The air was a little cool but it never cooled down the camper. We let it run a long time. Maybe it needs charged? It's an L G . the fantastic fan felt cooler.

    Sent from my Nexus 7 using Tapatalk
     
  9. bols2Dawall

    bols2Dawall S.W. Ontario

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    Eliminate any simple causes 1st , make sure the rear of the unit isn't obstructed , make sure the fins are clean and straight
     
  10. Dirtydozn

    Dirtydozn New Member

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    I have been an ac tech for 15 years. more than likely if the pup has been sitting for a while it is the capacitor. the cap is the most commonly replaced part on an a/c a lot of caps can dry up just like a car battery. you would know if it is working the air would be cold. take the cap out and test it if you can if not set it on a table if the bottom does not sit perfectly flush on the table its bad same goes for the top those systems are very simple. if you have a meter with an amp clamp put it on one of the main wires coming into the unit if the compressor is running you will have a higher amp draw if not it will probably read around a couple amps and that means compressor is not running bad cap. if it is running then its low on Freon. I would bet a thousand dollars it s the cap espescially if it has sat for a while any questions ask there is no ac I cant fix from industrial to residential
     

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