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Topic: Heat Pump running causing water to drip down through the return vents (Read 898 times) previous topic - next topic
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Heat Pump running causing water to drip down through the return vents
Our Dometic AC/Heat pump 651816 is leaking water into the RV down through the return vents.  We took the inside cover off and the little gray panel out.  The water is dripping down the front edge.  It seems there is the metal box, then inside that a black plastic box.  There is a little water in both of them at the front. 

On the outside I found two holes that seem like drain spouts.  I stuck a tie wrap up in both and nothing came out and they seemed clean.  I am not sure if this is a drain spout or not.  I cannot reach these drain spouts from the inside - if that is what they are.  They are behind a piece of plastic beside the core on the inside.

Does anyone have any ideas?

Thank you very much for any help.

Bonnie and Dave Prouty
2019 Mid Bath 27’
Bonnie & David Prouty
Full timing since August 2019 when we picked up the LD.
Re: Heat Pump running causing water to drip down through the return vents
Reply #1 –
    I had the same problem running the heat setting for several straight days while parked at our house. One day there was a 2" rainstorm creating Lake Newton up top. When I finally turned the heat pump fan off, water started dripping from the inside cover. If I turned the fan on the dripping stopped. I then placed a bucket on the floor to catch the rest of the water after turning the HP off. Then when attempting to later restart the HP nothing happened and the thermostat did not light up as though the power was off. The AC breaker was working well, as the power was at the HP, but something within the HP had disconnected.
   I was never a fan of the loud fan in the Dometic and decided to replace it with the RecPro heat pump that several other LD owners have done lately. It took about 4.5 hours to install. I filled Lake Newton with water for a leak test that went well. It was a good choice as the RecPro works as advertised with a lot quieter fan. The heating and cooling is adequate for our rear bath. 
 
2026 Coach House 27' "Casa Azul"
2010 RB "Monty"  &  2021 RB "Villa Verde"
2004 Born Free 26'
1998 Beaver Patriot 33'
1992 Barth Breakaway 28'
1982 Fleetwood Jamboree 23
Re: Heat Pump running causing water to drip down through the return vents
Reply #2 –
When does the A/C leak? When the A/C is running or when it is raining?
Big differences in potential causes.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Heat Pump running causing water to drip down through the return vents
Reply #3 –
We are still researching when it is leaking.  Not sure yet if it is rain or the heat pump.  It has only leaked when the heat pump was running.  But it did rain the day it leaked, and one other day it rained when it leaked.  We ran the heat pump a bit ago for quite a while, no water came in but there was water on the front driver side corner of the AC, on the front.  The foam under the unit was wet this morning, but there was water on the roof from the rain.  We are going to run the AC later to see if it makes it leak also.  Then our plan was to run some water on the roof and see if it leaks. 

So so far all we know is water has dripped about 3 times when the heat pump was running.  Never when it rained. (we think)  So we have no conclusive information yet.  Will post more when we run the AC, then again when we run water on the roof.

We do have the bottom off on the inside so we can look in, and the little gray door off so we can see up where the water actually dripped from.

2019 Mid Bath 27’
Bonnie & David Prouty
Full timing since August 2019 when we picked up the LD.
Re: Heat Pump running causing water to drip down through the return vents
Reply #4 –
Unlike when the A/C, is running, operating the heat pump produces no moisture.
When the leak occurs when the A/C is running,  the leak is usually caused by a plugged drain in the heat exchanger chamber..
Water that has accumulated in the chamber from previous A/C use may be blowing out now that it is cold out and you are using the heat pump, the result of the drain being plugged.
The chamber has a heat exchanger that is used for both cooling and heating.

The A/C's roof gasket may be leaking. Removing the interior cover will expose the three or four bolts that secure the A/C to the roof. Snug the bolts but don't overtighten them. Flooding the area with water, while the interior cover is removed, may help find the keak if it is coming from the roof.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Heat Pump running causing water to drip down through the return vents
Reply #5 –
The roof was dry, I ran the heat pump for an hour, no leak.  Ran the AC for an hour, no leak or water.

We tightened the 3 bolts, the 2 front ones I tightened quite a bit - maybe about 3 turns.  The back one was tighter, I tightened it about 1 turn or so.  The water seemed to be leaking from the front left side. 

I just ran water on the roof around the AC unit and so far no water coming in.

I hope tightening the 3 bolts fixed the issue.  I will post more if it leaks again.  Fingers crossed.

Thank you all so much for responding.
2019 Mid Bath 27’
Bonnie & David Prouty
Full timing since August 2019 when we picked up the LD.
Re: Heat Pump running causing water to drip down through the return vents
Reply #6 –
The heat pump dripped water again this morning.  We pulled the cover off inside as quick as we could, and there was water spatters on the inside top.  This time it dripped more water than it had in the past. 

We then ran quite a bit of water all around on the roof watching for a leak which we never found one.  We ran the heat pump while we ran water on the roof.  We covered part of the intake with cardboard hoping to get some suction like it must have when the heat pump is running. 
2019 Mid Bath 27’
Bonnie & David Prouty
Full timing since August 2019 when we picked up the LD.
Re: Heat Pump running causing water to drip down through the return vents
Reply #7 –
Hi Bonnie;  I don't know where you are located, are you running the heat pump (still just a type of air conditioner, that conditions the air to your liking) for heat?   If so, then the unit has internal valves that reverse the flow of freon and the external 'condenser' gets cold and the internal 'evaporator' gets hot.  There is still a drain pan under the internal coils that would drain water outside onto the roof in normal chilling mode.  The external heat exchanger, normally quite dry would be condensing liquid outside. When running the (now colder) external heat exchanger, has a fan blowing any accumulated moisture all over outside. If there was frozen chunks on the outside coils they might melt and drain outside onto the roof through those two small drains you mentioned earlier.
    I'm guessing you have hydraulic levelers, I might tip the entire motorhome just a little lower on the front left to see if you can get the water to drain away from the heat pump location. The refrigerator can handle slightly off level operation. (If you are needing heat, it probably isn't working hard, anyway.)
    Mike did the extreme fix and replaced his whole unit with the Rec-Pro. A call to Dometic may not help much.
    The Airstream Forum did have comments about dripping water from a heat pump A/C:  Dometic Heat Pump Dripping Water through Ceiling Grill - Airstream Forums  , and a google search did show up a few comments also.   RonB

  edit: my experience is only with older Dometic 13.5k BTUH air conditioners, no heat pumps.
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Heat Pump running causing water to drip down through the return vents
Reply #8 –
Quote from: RonB  - 
unit has internal valves that reverse the flow of freon and the external 'condenser' gets cold and the internal 'evaporator' gets hot.  There is still a drain pan under the internal coils that would drain water outside onto the roof in normal chilling mode.  The external heat exchanger, normally quite dry would be condensing liquid outside.

Removing the A/C's cover, up on the roof, would be my next move to see if the tray's drain holes are plugged, allowing the coil's condensate to build up and somehow flow back into the interior through the interior outlet.
Filling the tray with water would be a good test.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Heat Pump running causing water to drip down through the return vents
Reply #9 –
I think I have figured out where the water is coming from.  It is leaking in between the big air conditioner pan, and the plastic box that has the heat exchanger and fan.  If I squirt water in the big pan it goes under the plastic into the grove where I have my finger in the picture.  It builds up enough water and gets sucked up then drops down into the inside.

I am considering doing two things.  Drill a hole or two in front of the plastic pan, in the big metal pan to make another drain hole in the front.  The two drain holes on each side are working fine, I think the water can just seep in at the front before it can drain out the existing drain holes.  The existing drain holes are draining properly.  We try to keep the rig real level.  The other thing I am considering is putting a little sealant between the plastic piece and the metal pan where it seeps in.  I did tighten the screws that hold the plastic pan to the metal pan but that did not help any. 

Does anyone have any thoughts on drilling a hole or two in front of the plastic pan, and putting sealant around the plastic pan?  I will put something metal down between the roof and ac pan to be sure I do not accidentally hit the roof when drilling the hole. 

Thank you so much in advance for your thoughts,
Bonnie and Dave
2019 Mid Bath 27’
Bonnie & David Prouty
Full timing since August 2019 when we picked up the LD.
Re: Heat Pump running causing water to drip down through the return vents
Reply #10 –
I just called Dometic and they said they are not technical and cannot help further than what I have already checked that they can only send me to a service center. 

I attached the diagram and marked with red the two pans with red, and the screws I tightened in blue.

Thanks for any thoughts.
2019 Mid Bath 27’
Bonnie & David Prouty
Full timing since August 2019 when we picked up the LD.
Re: Heat Pump running causing water to drip down through the return vents
Reply #11 –
We have never had the problem with the heat pump, but we did have a problem with the a/c running in high humidity.  It was condensation between the return air and the air flow.  We put some a/c insulated tape on the area where this happened.  It improved the situation, but did not eliminate it until we moved to a less humid area. 
Ross Taylor
2017 MB
Re: Heat Pump running causing water to drip down through the return vents
Reply #12 –
Without seeing your A/C, I would suggest drilling the holes where they can be sealed if doing this turns out to be a mistake.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
 
Re: Heat Pump running causing water to drip down through the return vents
Reply #13 –
I did drill 4 holes in the metal part.  I can easily seal them with sealant if needed. 
I also put sealant where the water was leaking in between the metal box and the plastic box.  I just finished this today.  We will see how it goes from here.  If it drips again I will give an update.

Thank you all for your input. 
2019 Mid Bath 27’
Bonnie & David Prouty
Full timing since August 2019 when we picked up the LD.