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Old 04-30-2007, 11:37 AM   #1
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Does anyone have any ideas of ways to prevent ac condensation? I have a frigiking roof unit in my RV and it works great, but drips when it's been on for about 3 or 4 hours. I just put all new beautiful carpet in the Amigo and now I have to keep a bucket in the middle What can I do to help this situation out. I have cleaned the outside coils and inside coils. But after that I am clueless as to what I can do. I am perfectly capable of tearing it apart if anyone has any extreme suggestions.

Thanks in advance,
Nate
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Old 04-30-2007, 11:37 AM   #2
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Does anyone have any ideas of ways to prevent ac condensation? I have a frigiking roof unit in my RV and it works great, but drips when it's been on for about 3 or 4 hours. I just put all new beautiful carpet in the Amigo and now I have to keep a bucket in the middle What can I do to help this situation out. I have cleaned the outside coils and inside coils. But after that I am clueless as to what I can do. I am perfectly capable of tearing it apart if anyone has any extreme suggestions.

Thanks in advance,
Nate
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Old 04-30-2007, 11:39 AM   #3
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One other thing I wanted to add is that the indoor outdoor thermometer that I have says that it is at 49% humidity inside. Is that too high? Would a dehumidifier alleviate this problem?
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Old 04-30-2007, 02:37 PM   #4
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Hi Nate,
Can you tell us what diagnostics you have done to ensure draining of the condensate is being taken care of properly? Every A/C unit I have had, had a way to drain the condensate.
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Old 04-30-2007, 04:53 PM   #5
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well, like I said, I cleaned the condenser coils inside and outside, but that's about it. Let me take a picture up on the roof real quick and maybe I can acquaint you more with this specific unit.

One thing that I can add is now that the temperature outside has dropped about 10 degrees, it no longer is doing it. The humidity inside has stayed around 50% and still is, however, the unit is not working as hard.

Please keep the ideas coming until I post a picture. I have a life or death situation with a John Deere tractor right now that needs to be fixed by morning. Anyone know anything about Diesels? Please PM me if you do

Thanks,
Nate
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Old 04-30-2007, 05:09 PM   #6
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It is perfectly normal for an A/C to have condensate. You can not stop the condensation. It just needs to be kept where it belongs...on the outside. It runs off the evaporator coil and into a pan that drains onto the roof. (Evaporator is the cold coil that cools the air and the condenser is the warm coil on the roof that rejects the heat.) If the water is coming inside the trailer, you either have a drain pan that is cracked or has a pin hole or the gasket between the roof and the A/C unit is leaking.

To replace the gasket, you will need to remove the inside cover and there are 4 bolts which clamp the unit to the roof. You should be able to see the joint between the roof and the A/C unit. You will need to disconnect the power wiring and get some help to lift the unit up. The new gasket is a square and looks like closed cell foam rubber. Set the unit carefully back onto the gasket and the opening. Use NO cement of sealant on the gasket. Tighten it down until it is good and firm and the unit does not wiggle.

If this is not the problem, operate the unit with the inside cover off and see if you can track the location of the leak.

The humidity at 49% is not too high and a dehumidifier will not do much good. The reason the condensate forms is that the coil temperature is below the dew point of the air and the moisture in the air condenses on the cold surface. This cooling process is actually dehumidification.

Best of luck.

Ken
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Old 04-30-2007, 05:47 PM   #7
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here is a pic of the outside



and a picture of the unit from the inside...


I don't think those really help, but anyway. I'm not quite sure I am understanding what you are saying. Are you saying that even if I fix that seal there is a good chance the condensation is still going to happen via the inside coils? This can't be normal or okay. I am probably misunderstanding you. Shouldn't all the condensation be forming on the outside coils only? Technically the dew point inside would always be high enough for the coils to produce condensation since they are always cooler than the indoor temp.

I am lost. Not an unusual situation
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Old 04-30-2007, 06:42 PM   #8
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Normally your velocity over the evaporator coil is no more than 500 fpm (feet per minute). Over that and there is a great possibility that the water droplets will carry over. You will always have condensation on the coil when you have the coil temperature below the air dew point. Cooling the air over the coil will bring the air close to saturation and pull the excess moisture from the air. There is a possibility that the unit is not performing correctly and by over cooling the air, it can create a cold spot in the outlet duct/damper and additional condensation will form at that point.

On a nice warm day, start the a/c and let it run for 10 or 15 minutes. Using a calibrated pair of thermometers or just one, get the temperature of the leaving the unit and also the air entering the unit. The leaving air temperature (dry bulb)should be about 20 dF lower than the inlet air. If it is a lot greater than 20 dF you have a problem.

Is the unit ever trying to form ice on the evaporator coil? Are you getting condensation draining out of the unit on the exterior? Have you pulled the inside cover to check the condition of the coil? It should be shiny clean aluminum and no dirt or dust. Is the filter clean?

The "inside" coil is the cold one and the outside coil is the hot one. The cold coil will have condensation and the amount depends on the humidity of the air. The cold coil will have a drain to drain the water that collects to the outside. If you can not find water running out of the RV, you have a plugged drain line. They will get plugged with algae at times and have to be blown or brushed out.

You may wind up having to pull the unit completely out of the Rv and setting it on a work bench to se if you can find the drain.

From the photo of the top, I am a bit lost. Is this unit setting in a recess on the RV?

Ken
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Old 04-30-2007, 07:03 PM   #9
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Thanks for the great information. I live in the lovely dry state of Colorado, there is very little humidity here right now and there is hardly any runoff happening on the outside. There is no icing going on with the evaporator coil. I CAN tell you now that the outlet temperature will definitely be more than 20 degrees cooler than the inlet, especially if I were to do it, say when the indoor temp is 80. It feels about as cold as the air inside of a fridge. Probably 35-45 degrees. It is COLD! If I understand you correctly would more circulation around the evaporator coil improve the problem at hand? Also, where can I get a better thermostat than what is currently in the unit. I would like to add a remote thermostat. I am quite electric savvy, I just can't seem to find anything asthetically and operationally pleasing. Also, the air noises that it makes are very loud. Would it be wise to wire it so that the fan only came on when the unit was cooling, versus running all the time? I know this is a million questions, but I am taking a 34 year old RV and modernizing it. These small things are what really count in the functionality of it. Replacing carpet then developing a water stain in the middle of your floor, quite frankly SUCKS!

Thanks so much for trying to help. Do you feel that the first place to really start with this issue would be the inside/outside gasket?

-Nate
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Old 04-30-2007, 07:45 PM   #10
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Nate, looking at your pics the unit looks like it is recessed into the roof, there should be a drain tube off the drip pan where it collects the water off evaporator coil. When you run it leave cover off roof opening to see where water is collecting and look for a drain hole. There is a piece of paper or sealent in lower right hand corner what is it.
On AC's mounted on roof deck the water wep holes would plug up and the fan would blow the water out of full drip pan down into ceiling vents below in coach you maybe having same problem with the blower blowing water out of drip pan because your drain hole is plugged as someone has already said.
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Old 04-30-2007, 08:44 PM   #11
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that must be a bad picture, it sticks out of the roof like a sore thumb, lol

I am going to remove the two drain hoses, clean them out and refit them, hopefully that will fix the problem. Probably won't get to it right away, but I will fill you all in with the outcome.

Thanks,
Nate
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Old 05-01-2007, 06:59 AM   #12
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In that outside picture, are we looking down into a box that contains the compressor and such? And that box projects above the roof line of the RV? If so, I'm guessing the a/c itself is sitting on the roof rather than recessed down into it. And that looks like a residential a/c in the box rather than the usual RV type in its sleek plastic shroud. Is this some sort of home made installation? Just trying to understand what we are dealing with here...

At any rate, condensation is normal and unavoidable, so you have to arrange proper drainage and sealing to keep it out of the interior. Check those drain lines. It is unusual to get inside condensation except in high humidity situations and even then it is usually minimal. Wonder if you might be pulling some moist outside air into the air return somehow (air leak)? I've seen a/cs do odd things when air leaks back to the intake side from either the output side or the exterior. Freeze ups is one common symptom of that, but inside water condensation is the forerunner of that.
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Old 05-01-2007, 07:36 AM   #13
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It is definitely an RV unit. Remember it is probably 20-30 years old. I haven't gotten around to cleaning them today, but I will soon.
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Old 05-01-2007, 05:40 PM   #14
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I can tell on the photos, that the unit is elevated over the roof and it appears that the sides are plywood. Looks like a homemade A/C cover. You need to check the temperature difference across the unit. If it is too cool there, run the furnace and warm up the RV and leave it running to keep a heat load on the A/C.

As old as the unit is, I would not bother to have taps put in to check the refrigerant. It would be beter to just replace the unit.

Ken
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