Another Air Conditioner Question - Fiberglass RV


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Old 06-07-2015, 05:41 PM   #1
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Name: Huck
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Another Air Conditioner Question

Correct me if my understanding is wrong. I don't know much about ac's, but just watched a video so I'm dangerous.

On a window AC, outside air is sucked in on the top and sides and blown over the coil and exhausts out the back.

If my understanding is correct, I don't see how the ac in my trailer would ever cool very well. It seems to me it would either suck in air from the trailer, wasting my cool air, or it would suck in the hot air that was coming out the back.

Wouldn't it be much more efficient if the outside air sucked in to cool the coil didn't mix with the hot air being pushed out? To get isolation between the inside air and outside air, it seems it should be an enclosed system. What I mean is, on a window ac in a house, the cool air is blown into the house and re-cooled inside the house and the outside air intake and exhaust are outside the house. The window is the barrier between inside and outside air.

Would baffles help? Or is there already a baffle? It's been a while since I had mine out.
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Old 06-07-2015, 05:58 PM   #2
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Another Air Conditioner Question

Outside air is not "sucked in" to the trailer. Outside air is separated from inside air with a baffle, and they don't meet. Outside air is brought in from outside and exhausted back outside. That's the hot side. Inside air is brought in to the unit and sent back inside, as drier cooler air. That's the cool side. Here's a good basic explanation:

http://www.brighthubengineering.com/...tioner-works/#


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Old 06-08-2015, 10:31 AM   #3
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By inside the trailer, I mean it is being sucked into the ac compartment inside the trailer.

I think I see the problem with why mine doesn't cool as well as it should. It looks to me like it is using inside trailer air to cool the coil. The ac is also crammed into a small space with severely restricted air flow, so I don't think there is enough air circulation over the coil.

Again, the little I know about ac's is what I learned on the web.

In below picture, at the top is the back of the ac and where the hot air is exhausted. In the middle is a vent that has less than 1/2" clearance when the lid is closed. On both sides, the clearance is minimal and the only air that can be sucked into the ac for cooling the coil comes from inside the trailer. So the air being used to cool the coil is cooled air instead of outside air.



I'm going by a standard window ac where the window is the divider. Inside, the ac cools air that is already in the room. Outside, the ac pulls in outside air, blows it over the coil, and exhausts to the outside.

If I am correct and that is how it works, how can I fix my problem?
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Old 06-08-2015, 12:58 PM   #4
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Originally Posted by Huck View Post
If I am correct and that is how it works, how can I fix my problem?
The factory "fixed" the problem by putting the unit on the roof. Of course that is not really an option ($$$$$$$$$) for you. I added a small fan behind the side-mount A/C on my Scamp to help exhaust the really hot exhaust air, but that did not do much for the incoming air except maybe throw the hot air out a little farther and perhaps create some draw on the intake side. There is a good 3 1/2" inches above the A/C in my Scamp but only 3/4" on one side and 1 1/2" on the other. I would prefer some more clearance on the sides and have recently considered cutting a hole through the side of the cabinet under the sink and adding some ducting down and through the floor to really find the coolest air for the intake. I may do so in the future if/when I swap the 6K unit for an 8K that I assume will need more flow.

All that said, it certainly looks like you need more flow. That can be mechanical with a fan (or fans) or just by providing more area. It looks like you are tight on the top and that is a shame as I think the top is where most of the intake louvers are (at least on my window units). I think any of these type installations can be improved with a little more engineering. Whether it is enough to get you where you need to be cool-wise I can’t say. Good luck!

Edit: You asked about baffles. I did add a horizontail baffle to help seperate the hot exhaust air from the incoming cool air. But the Scamp actually has a seperate little grill above the A/C in this area that makes this possible.
I have considered adding another little intake fan to this area to help "pressurize” the intake side but have not done in yet. What I have seems to be working so far, but could be better. I say play with what you have, little 12V fans, duct tape (the aluminum kind) and thin Styrofoam are all cheap and easy to work with.
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Old 06-09-2015, 04:12 PM   #5
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I did some testing today to see if my theory on why the ac doesn't adequately cool the trailer was right. I think the tests show it was.

The below picture shows the temps at different spots on ac. Just from looking at the picture it is obvious whenever you turn on the ac, you get both hot and cool air dumped into the trailer.

Cooling takes place in front half of ac, so 68 toward the front and then getting hotter (94) toward the rear makes sense. Still, it would be helpful to block that 94 degrees from heating up the trailer.



The temperature at the outside exhaust vent was 113, the same as what is seen on the top rear of the ac. I pushed some insulation in the gap between ac and edge of the opening in fiberglass opening, but as you can see, it still reads 113. I think that's the main reason these ac's are not adequately cooling the trailer. Too much heat from the ac exhaust is venting into the trailer instead of out the vent to the outside.

At the top of the picture is the top of the fiberglass enclosure for the ac. Notice how hot that area is. If I can figure out how to get into it, I plan on insulating the enclosure to prevent the hot air from getting into the trailer.

I also think the ac will work more efficiently with the ac compartment lid open. Since it is using inside air to cool the coil, might as well make sure the airflow is adequate.

This is on a Parkliner. They could have built the ac enclosure a little bigger for better air flow, better isolated inside air from outside air, and insulated the exhaust area, and I think a 5000 BTU ac would cool the trailer down just fine.
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Old 06-09-2015, 04:23 PM   #6
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You should have vents on the sides and back along with the top. The A/C doesn't care where the air comes from since there is a shroud at the fan to direct the air through the coil and out the back.
You could remove the case and cut out the entire right side so that the air is unrestricted from that side and cover the top vents.
There has to be a place for the intake air to come from and often the floor or the side has a vent there or a vent through the side wall.
You could cut an opening in the floor and install a mesh screen to keep some of the critters out. Some have put louvered vents with the openings to the rear to help keep water out while traveling.
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Old 06-09-2015, 04:40 PM   #7
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You should have vents on the sides and back along with the top. The A/C doesn't care where the air comes from since there is a shroud at the fan to direct the air through the coil and out the back.
You could remove the case and cut out the entire right side so that the air is unrestricted from that side and cover the top vents.
There has to be a place for the intake air to come from and often the floor or the side has a vent there or a vent through the side wall.
You could cut an opening in the floor and install a mesh screen to keep some of the critters out. Some have put louvered vents with the openings to the rear to help keep water out while traveling.
The way it is wedged in, there is little airspace on either side or the top (when the lid is closed). I'm thinking with air flow restricted so much, the coil isn't be cooled down as much as it should be resulting in the ac running hot and more heat buildup at the rear.

That does give me an idea. The ac is under a seating area for the small 2 person table. I could cut out the fiberglass adjacent to the left side ac vents and install a vent there.
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Old 06-09-2015, 07:49 PM   #8
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I have seen a photo somewhere of a small trailer that had a small a/c that was mounted on a sliding tray. The outside of the trailer had a louvered vent cover that had hinges on top and a latch on the bottom. When a/c was needed the outside cover would be lifted up and the a/c unit slid outward so the back was completely exposed to the outside for proper flow and a seal kept the front inside the trailer.
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Old 06-09-2015, 08:44 PM   #9
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Anything installed that crooked seems like it might be a prior owner modification. Parkliner is supposedly a premium brand, that looks like an owner hack-and whack job to get it into a space too small.
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Old 06-09-2015, 09:48 PM   #10
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Anything installed that crooked seems like it might be a prior owner modification. Parkliner is supposedly a premium brand, that looks like an owner hack-and whack job to get it into a space too small.
Factory installed.
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Old 06-10-2015, 12:01 AM   #11
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Bummer then........
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Old 06-10-2015, 11:18 PM   #12
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Huck, I too own a Parkliner and would like to utilize the existing AC unit but figure out a way to cool better without a floor fan. Currently, that is my solution. Just wondering, did you ever test the theory of keeping the bench top open for more air flow and if so did it make a significant difference? Thank Kevin


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Old 06-11-2015, 09:12 PM   #13
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Here is how I did mine so that it sucks in "fresh" outside air and exhausts it away from the camper.

I'm adding air conditioning to my Scamp.
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Old 06-13-2015, 10:23 AM   #14
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Here is how I did mine so that it sucks in "fresh" outside air and exhausts it away from the camper.

I'm adding air conditioning to my Scamp.
Thanks Bryan. That's very close to what I had in mind as a solution. The biggest problem I have is, there is not enough space in the ac "cabinet" in a Parkliner to implement it. Plus the only way the ac fits into the cabinet is at a slant. I think the idea of the slant was to make it easier to get to the controls. I wish it had a remote control and then I could just shove it all the way back.
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