Dometic AC leaking condensation into RV

[Carl Boger]

Sorry but this will be a long post to include everything.

I have 2 Dometic Penquin II 15K AC units on my 33 foot Patriot Savannah.  Both have worked great for the last 3 or so years.  A few months ago the front AC unit started leaking condensation into the RV from the return air intake side.
The rest of the area had been insulated and taped off so only room air was going through the air filter.  I had also installed a Whacko air silencer on both AC units.  Like I said both have worked correctly until a few months ago.

I first started leaking in May in Georgia during a storm that had rain going everywhere.  I thought that maybe the unit just needed to be tightened down.  I then went up on the roof  and found water inside the plastic housing where it is not supposed to collect.  Both drain holes were open.  I toweled the water out and put everything back together only to have it start leaking again with no rain but high humidity.  I took the cover off again and toweled out the water and left the filter and whacko cover off and it cooled the rv like normal and did not leak/drip condensation.

The next trip I reinstalled the filter and drove to the campsite with no leaks, but after the AC unit had been on with the filter in place for about 6 or 7 hours it started to drip again!  Took the filter out and spent about 5 days without any leaks.

When I got home I used some insulating tape around the duct work in the return air intake area and reinstalled the filter and the Whacko.  Drove about 5 hours with no leaks and set up at the campsite.  About 3 hours later it started to drip again.  Toweled out the water, removed the whacko and filter and it ran for about 3 hours before it started dripping again.

So now it is dripping with the filter removed, but not nearly as bad as when the filter is in place.  I also took out all the insulation and the taping that limited only indoor cool air to the return air intake.

One more time toweled out the water, left the filter out and thought all was good, but this morning I found that it had leaked overnight.  WTH  Filter was out it was in the low 70's last night.  Back on the roof still getting water where it's not supposed to be which is then leaking into the return air intake and into the RV. 

Toweled out all the water again, left the filter out and turned the front AC to Fan only and turned the rear AC init down to  62 degrees.  The Fan only did stop blowing at one point for maybe 30 seconds so I am not sure what that was all about, but it did happen at least one time.

Does anyone have any idea what is causing this to happen?  I can live with the rear AC unit cooling the whole coach while the front AC unit is on fan only.  I would like to use the Front AC unit on the drive home Sat, about 5 hours hoping it will not leak in that time.

I know that putting the filter on makes this problem worse.  The Rear AC unit is not leaking and it was set up just like the front unit.

The coils and condenser have been cleaned, the drains are open and not where water is collecting, this appears to be condensation as it has not rained,  the fan has been running on  high even with the ac on to keep the coils from freezing up, AC unit is working and blowing cold air, the 4 mounting bolts are snug/tight and the gasket is in good condition.  The condensation is heavy on top of the plastic housing as well as inside, see pics.  The styrofoam that covers the plastic is also in good shape and in place.

Thanks for any ideas on where to look next. 

This has been working but would like to use both AC units without either leaking

[Steve Huber]

Carl,
Check to see if you have your AC fans set to run on high. Condensation can and will form and drip into the coach from the air returns if the fan is on low or medium when in high Rh areas.
Steve

[David T. Richelderfer]

Our coach is a few years newer.  You indicated there are drain holes under the AC caps, probably under the AC units, that are there to drain the condensation catch basin.  In our coach these drain tubes run under the roof's exterior walls and above the interior walls over to the sidewalls, then down the sidewalls, again between the exterior and interior sidewalls.  Thus, the drain tubes are completely out of sight within the roof and walls and their ends exit the coach at the bottom of the sidewalls.  When our ACs are running, these drain tubes, one tube from each AC unit (we have three roof-mounted ACs), will drip condensation on the ground where they exit the bottom of the sidewalls.

Have you seen the drain tubes dripping condensation from the drain tubes when running the ACs?  If not, then mud dauber insects or the like, or road grime, may have plugged the ends of the drain tubes. Try locating the ends of the drain tubes and stick a small wire up them to clear them.

From a GOOGLE search:  "Mud daubers can clog drain tubes on RVs because their hardened dirt nests can block entire drain lines."

[Carl Boger]

Steve,

Fan is on high and has been, I have run it this way for 3 ish years and this is a new problem.

David,

My unit drains directly on the roof, there are not hoses, and the drains are in a different area of the plastic pan that is sealed off from where water is collecting.  I had thought about putting in a drain and feeding it to the area that is designed to drain, but would rather fix it properly.

This one has me baffled.

[David T. Richelderfer]

Okay, another idea I have read about.  Sometimes a RV roof gets weak and loses its convex shape where the roof-mounted ACs are setting.  If the roof has become concave or flat under the weight of an AC unit, then condensation (and rain, too, by the way) will not run away from the AC but will run under it.  After enough water collects, it will run through the hole into the coach's interior by going under, over, or through the gasket. 

[Carl Boger]

Thanks David,

I don't think that is what is going on here,  I have condensation forming inside the plastic housing and when enough puddles up the fan is picking it up and slinging it everywhere.  The question is why it is forming in the amount it is, and only on the front AC, and why has it started after 3 years.

I can say that putting the filter in exasperates the problem.  I have looked for air leaks into this "sealed" area.   The area that is designed to drain is draining fine, it is in front of where the water is in the picture. The top cover also has condensation building up in the low spots, other photo, so water is condensing in that area on both sides.  I don't know if  adding more insulation would help, it has a fitted styrofoam cover that looks like new.

I have never seen this before, and it goes from dry for about 5 hours to having a drop or two of water fall every couple of seconds.   I think I am looking for warm moist air somehow mixing with the cold indoor return air, but so far can not find it.

[Fred Brooks]

  Hi Carl,
 Any place in the air conditioner where warm moist air touches something cold you get condensate. The tray directly below the evaporator coil is designed to catch that and direct it to the drain holes in the base pan. Wacko silencer redirects the dynamics inside the return air. It is a fine balance when working correctly. Excess humidity or filter resistance could be just enough to make excess condensate to slosh over the tray edge or the drain is partially plugged in the tray. I would remove the cover up on the roof so you can access the evaporator and see the tray with the air turned off. Mix a couple drops of red food dye in a cup of water and pour it into the tray slowly and wait and see where it exits. Also the instructions from wacko tell you to remove the White insulation on the angled plenum cover: I disagree as warm return air goes past that surface.
 Make sure that condensate is not generated and dripping there. Hope this helps, Fred

[Carl Boger]

Thanks Fred,

I will have to check out the Whacko instructions again.  It is easy enough to remove the styrofoam even though that doesn't make a lot of sense to me as its insulating the warmer air.  Condensation is also flowing out on the correct side and onto the roof as normal.

I am waiting this hurricane weather out in Edisto Beach SC so this will likely have to wait for a while. 

[Carl Boger]

Fred,

I checked my instructions from wacko and their installation video and they only recommended removing a shield from underneath and not the top styrofoam cover from dometic.  They also went through the several steps to seal up the air return intake area.  Of course their opening is fairly different from mine, but basically seal off any leaks.

Thanks for keeping me on my toes though.  As a side note I had the unit start dripping again with only the fan running.  Turned the fan off and the dripping stopped.  I could also see droplets of water on the roof of the top plastic housing. 

I may try turning off the rear AC unit and running the front one when I get home to see if the rear unit is helping contribute to the moisture being formed.  That and I need to seal everything up really good again to see if that will stop it.  Thanks again for the suggestions.

[Fred Brooks]

   Stay safe Carl!