Forum Discussion

frankie32's avatar
frankie32
Explorer
Sep 06, 2016

Funnu Acting AC

I just did some mods to my ac unit swapping out ac vents in my ceiling withones that close. I have a total of 4 so no/ many areas of output. I have a Dometic 13.5 AC on my roof. Earlier I closed 2 of the 4 units and noticed after a while the AC turned off and the temp rised. Temp was set at 72 and was up to 78. I turned the unit down but nothing happened. I turned the unit off at the thermostat for a few minutes and turned it back on. This time the ac kicked on no issues. A few minutes later a loud pop and a few chunks of ice came from the 2 ducts I was using, not from the unit itself. A few minutes later it shut off again at 74 degrees (still set for 72) and would not turn on again. This time I had to run with the wife out but never checked it again. We came back to the camper this evening and it was set back to 72. I dont't know if the unit pulled itself back down or it just came down. The unit has turned on and pulled the temp back down since we have been back but am not certain if this is something I should be worried about or if I accidently froze something up. I did notice I have a every few second drip coming off the back even with the unit off.

Thoughts/ideas? Anyone else ever experience this?
  • frankie32's avatar
    frankie32
    Explorer
    Sep 06, 2016
    Good to know. Planning on leaving them open from now on. Greatly appreciate the feedback and info.
  • prichardson's avatar
    prichardson
    Explorer
    Sep 06, 2016
    On ANY A/C system, RV or otherwise, ALL registers should remain open and unrestricted. A/C and heating systems must have adequate air flow thru the system to operate properly. Most RV systems are marginal on having enough register open area to begin with so closing or blocking any is asking for trouble.
  • hohenwald48's avatar
    hohenwald48
    Explorer
    Sep 06, 2016
    As others have said, when you block air flow the evaporator will freeze up. Doesn't matter what the thermostat setting is. Once the evaporator freezes the unit will shut down due to the freeze sensor. There's a reason TT manufacturers don't put closable vents in the air conditioner system. Most of them are border line ready to freeze up even with all vents open.

    I see folks do the same with their heater ducts too. Then the furnace overheats and goes into shut down.

    It's not like your home system. Those usually have an abundance of duct cross sectional area and some vents can be closed and still leave enough air flow. RV's usually have the bare minimum of duct cross sectional area required for the unit. Some don't even have that.
  • frankie32's avatar
    frankie32
    Explorer
    Sep 06, 2016
    And this is exactly why I am here. So is there a reason I could not get the unit to adjust via the thermostat?

    And in all honesty the original plan was to put one in the bathroom for temporary shock prevention dorectly after a hot shower but the price was so good I figured four only would be good enough to swap them all. I'm getting the "of all times you listen to me" from the wife.
  • nineoaks2004's avatar
    nineoaks2004
    Explorer
    Sep 06, 2016
    Closing vents off can /will cause icing on the evap. as there is less air passing thru the coils.
  • stickdog's avatar
    stickdog
    Explorer
    Sep 06, 2016
    It's not good to block off vents, just makes the unit work harder than it was intended. HVAC guy told me that.
  • allen8106's avatar
    allen8106
    Explorer
    Sep 06, 2016
    You can't close off the air flow like that. You need all vents open and the fan on high speed. This will keep the evaporator coil from freezing the condensation, which is what happened to your unit. Low air flow causes the the refrigerant in the system to run too cold causing the freeze up. You need the air flow to keep the refrigerant at a warmer temperature, that way it doesn't get to cold freeze the condensation.

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