A/C condensation problem

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jscottt

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Question about condensation on an indoor unit. So I was working on a unit the problem was water was leaking onto their roof. I checked the drain/drain pan and verified that it was working. I come to find out that air is blowing the condensation off the evaporator onto the plenum. What’s the solution?
 

Gary RV_Wizard

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RV roof a/c units do not mix outside air with interior, so condensation inside occurs easily when cooking, showering, doors open in humid weather, etc. It collects on the heat exchange evaporator if air flow volume is too low or leakage around the intake/outflow allows the air to remix. The close proximity in an RV food unit intake/output duct makes this a fairly common problem. Sometimes the ducting is so poorly designed that it is impossible to totally eliminate in high humidity environments. Water just collects in the ducting and drips after awhile.
 

John From Detroit

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Question about condensation on an indoor unit. So I was working on a unit the problem was water was leaking onto their roof. I checked the drain/drain pan and verified that it was working. I come to find out that air is blowing the condensation off the evaporator onto the plenum. What’s the solution?
Water leakind ONTO the roof or is not a problem that's working as designed, it is supposed to drain ONTO the roof (Unless you have a ducted drain to ground most do not)

Now water leaking INSIDE.. that's kind of what you described... Trying to recall all the causes.
1: Nose down RV (Front lower than rear)
2: Dirty intake filter (Creates vacuum inside the intake plenum and does exactly what you describe)
3: Iced evaporator (Freezing) when it thaws.
 

Kirk

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Trying to recall all the causes.
The drain from the cooling coils drip pan can be plugged, or partially plugged and that will cause the pan to overflow and drip inside of the RV. If so it should be cleaned and flushed using a chlorine bleach mixture to kill any growing mold and such that does develop when the air conditioner is used for extended periods.
 

gwinger

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Remove the cover on the inside of the trailer. Make sure all the gaps and between the supply and return air are sealed.
As said above, water on the roof is normal.
 

Henry J Fate

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Question about condensation on an indoor unit. So I was working on a unit the problem was water was leaking onto their roof. I checked the drain/drain pan and verified that it was working. I come to find out that air is blowing the condensation off the evaporator onto the plenum. What’s the solution?

The evaporator core is in the plenum. The evaporator has 2 functions. It removes heat from the air passing through it and will also remove humidity which is removed in the form of H2O. The water (H2O) that accumulates on the evaporator core is designed to find its way to the bottom of the evaporator core and into a drip tray which in turn drains the water onto the roof. This assumes that no drain from the roof unit to the ground exists.

If water is being blown off of the evaporator and into the return air to the living space, this can happen with a dirty evaporator coil, an iced up coil or from a dirty/clogged drip pan under the evaporator coil or all of the above. This assumes that the unit is stock for example a change in the stock fan motor could alter the air flow.

Clean the coil thoroughly, clean the drip pan, use a clean correct air filter and go from there. There should also be a freeze stat mounted near the center of the evaporator coil. The freeze stat prevents the evaporator coil from icing over. Make sure it is there. Replacing it would be a good idea if the unit is found to be icing up.
 

jscottt

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RV roof a/c units do not mix outside air with interior, so condensation inside occurs easily when cooking, showering, doors open in humid weather, etc. service area It collects on the heat exchange evaporator if air flow volume is too low or leakage around the intake/outflow allows the air to remix. The close proximity in an RV food unit intake/output duct makes this a fairly common problem. Sometimes the ducting is so poorly designed that it is impossible to totally eliminate in high humidity environments. Water just collects in the ducting and drips after awhile.
thank you for the advice roofing Annandale, VA
 

Ex-Calif

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Water leakind ONTO the roof or is not a problem that's working as designed, it is supposed to drain ONTO the roof (Unless you have a ducted drain to ground most do not)

Now water leaking INSIDE.. that's kind of what you described... Trying to recall all the causes.
1: Nose down RV (Front lower than rear)
2: Dirty intake filter (Creates vacuum inside the intake plenum and does exactly what you describe)
3: Iced evaporator (Freezing) when it thaws.
Mine has to be level or slightly nose down or it leaks inside. I looked at it before and the weep holes on the pan are tiny. One day when I am back on the roof I plan to open the drain holes a bit.

Florida summer overwhelmed it several times and a towel on the floor was the only recourse...
 

John From Detroit

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Another source of "Leaks" inside is high humidity.. the air inside the RV is loaded with moisture.
When the AC runs the outlet vents get ...relative to the air around 'em. VERY COLD so the warm. moisture laden air, inside the RV chills and it rains. (Moisture condenses out)

The only cure I know for that one is Arid-zona (Move to a dryer zone)
 

SRGuy

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Jun 9, 2021
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Austin, TX
My AC was dripping onto the floor, at the main unit. As always, when I get into a problem with an RV, I am stunned by how terrible construction errors are.

In my case, the insulation around the unit was almost nonexistent, and the framing moron had used a ducting frame piece instead of a solid piece to finish the framing. I Imagine he/she ran out of solid pieces, and was too lazy to refill the station. The frame had two ducting pieces, wood with a hole to hook up the duct work. So, my AC was blowing cold air into the space between my roof and ceiling! I sealed the extra hole, put new insulation and much better foil tape around the unit, closed it up and my problem was solved. I also treated the returns in a similar fashion. Their insulation was also a joke!
 
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