Cooling problem with 2001 2720 trailmanor

[trailmanorkids]

We are restoring a 2001 2720 trailmanor and have the biggest air conditioner that will fit (this is before roof air). We are having problems in the Texas heat with the a/c not being able to keep the trailor cool. Any suggestions on how to fix this problem would be appreciated.

[Shane826]

If the A/C is working the next step is to work on filling any gaps between panels. The TM walls themselves are actually quite good for insulation. But if you have gaps, you’re gonna lose the HVAC battle. Pool noodles seem to be the favorite gap filler.

[Larryjb]

The side AC is never going to cool as well as rooftop AC. I'm also stuck with a side AC unit and here's what I do:
1) use a roof vent with the fan to exhaust hot air.
2) Use a fan to distribute the cold air to the ends of the trailer.
3) I have blackout blinds to keep the sunlight from heating through the windows.

I haven't taken our trailer into Texas, but when it's in the mid-90's, I can only get the trailer down to about 80°F

Shane is right though, that the insulating of the cabinet around the AC unit is very poor. It may help to add some Sytrofoam and aluminum foil where you can to the inside walls of the AC cabinet. Also, if your current AC unit is a window mount type (they have outside air vents on the sides), this will also work against you. You want a through wall style AC unit. It's my understanding that makes a big difference. I believe some people have taped off the side vents, but I don't know what effect that could have on the cooling capabilities or longevity of the AC unit.

[Bill]

Originally Posted by Larryjb

The side AC is never going to cool as well as rooftop AC. [If] your current AC unit is a window mount type (they have outside air vents on the sides), this will also work against you. You want a through wall style AC unit. It's my understanding that makes a big difference.

Larry - you have described the biggest problem with window-type AC units in this application.

It is important to understand that an air-conditioner not only pulls heat out of the room, but also generates a lot of its own heat as part of its operation. It has to get rid of all this heat somewhere, somehow. It does it by using it to heat up a "working fluid", circulating that hot fluid through a radiator similar to a car radiator, then sucking in warm outside air, blowing it across that radiator, and pushing that extra-hot air back outside. Meanwhile, indoor air is blown across a second radiator, where the cooling takes place, and blown back indoors. These two air streams - outdoor air heated and blown back outdoors, and indoor air cooled and blown back indoors, must be kept strictly separate. If they are allowed to mix, the overall cooling effect is reduced.

Back when the Forum was new, one of our members described his efforts to form some sheet metal panels that would keep the two streams separate. Because the entire air conditioner was inside the camper, he had to figure out where the super-hot air flowed, and make sure that all of it was exhausted outside and kept separate from the indoor air stream. It was a pain to form the sheet metal structure and fit it behind the air conditioner body, but he reported that it made quite a difference. I've looked for his post, but I think it disappeared when the forum was rebuilt in 2004 or so.

I believe some people have taped off the side vents, but I don't know what effect that could have on the cooling capabilities or longevity of the AC unit.

Not quite right, but the right idea.

Bill

[Bill]

Originally Posted by Bill

Back when the Forum was new, one of our members described his efforts to form some sheet metal walls that would keep the two streams separate. Because the entire air conditioner was inside the camper, he had to figure out where the super-hot air flowed, and make sure that all of it was exhausted outside and kept separate from the indoor air stream. It was a pain to form the sheet metal structure and fit it behind the air conditioner body, but he reported that it made quite a difference. I've looked for his post, but I think it disappeared when the forum was rebuilt in 2004 or so.

For the life of me, I couldn't find the posts I mentioned, but Tim Cassel came through. Thanks, Tim! The member's username was HarveyRV. The original posts and their pictures are missing, but there was a lot of follow-up. Some of those posts are here
https://www.trailmanorowners.com/for...ead.php?t=7477
and here
http://www.trailmanorowners.com/foru...ead.php?t=6335
In these threads, the "sheet metal structure" I referred to is called a "shroud". The shroud doesn't have to be perfect, but the more it can keep the really hot exhaust air separate from the inside cooler air, the happier you'll be.

Bill

[Larryjb]

I read through the links that Bill posted to see what I could get from them without pictures. harveyrv from the first link I believe had the solution if you're looking to get ideas. However, if you have an air conditioner with side vents, you cannot simply cover the side vents up.

A quick lesson first. To cool the air, you first have to compress it, then let it expand. If you make a small "o" with your lips and blow gently on your hand, the air feels cool. When the air is allowed to expand it cools, and this is why the air feels cooler when you blow this way. If you leave your lips in a large "O", you get little or no cooling effect because the air coming out is not expanding.

So, if you take some air that has been compressed, it will get warmer than the ambient air around. If you blow the ambient air over the compressed warm air, it will cool the compressed air back to the ambient temperature. Then if you let that compressed air expand, it will get cold.

If you compress and expand regular air in an air conditioner, you will get some cooling, but not a lot. So, air conditioners fill some pipes with a different gas (ice rinks use ammonia, automobiles use R134a, and I believe even that is getting replaced with something less harmful to the ozone layer). This gas stays inside the pipes. So, when this gas in the pipes is compressed it gets warm. The air conditioner blows the ambient air over the pipes (actually a condenser which looks almost exactly like a mini radiator) to make the compressed gas in the pipes the same as the ambient temperature. The gas in the pipes is then allowed to expand into an "evaporator", which looks like another type of radiator. The gas in the evaporator is now extremely cold, and can get cold enough to freeze water. This is why AC units can freeze up in humid environments. Regular air is blown over this cold evaporator which has the effect of cooling the room air.

Hopefully you are still with me now.

If we go back to the condenser side, which is the back of the AC unit, facing the outer wall. I took a peek at the airflow (from an online drawing) and saw that window mounted air conditioners take ambient air in through the sides and circulate it out the back. In the side mounted AC Trailmanors, you are getting 1/3 or at best 1/2 of the desired airflow going over the condenser. Thus, my suggestion of covering up these vents would be detrimental to cooling. Even the AC units that advertise that they can be installed in a wall, if you look closely they still need the side vents clear.

Because HarveyRV was installing an AC unit where there had been none, I suspect he placed it so that the side vents on both sides were clear. The baffle he installed must have been a vertical piece to prevent the hot air coming directly from the back of the AC from mixing from the ambient air entering the sides of the unit.

HarveyRV has given me some ideas, but I have a few other important tasks to take care of first, like a powered potty vent.

[Bill]

That's a great explanation, Larry. Let me add one practical thought for someone who is going to install a unit for the first time, or replace an existing unit. From the point of view of airflow paths, there are two different designs. Either one will work, but you have to know which one you have.

1. In some units, ambient air (meaning outdoor air) enters the unit from the side, passes over the radiator for the compressor where it picks up its heat load, and is exhausted out the back of the unit. Meanwhile, indoor air enters the unit from an area of the front, passes over radiator for the evaporator where it is cooled, and is expelled back into the room through a different area of the front.

2. Outdoor air enters the unit from a part of the rear face, passes over the radiator for the compressor where it picks up its heat load, and is expelled back outdoors through a different area of the rear face. Meanwhile, indoor air enters the unit from the sides, passes over the radiator for the evaporator where it is cooled, and is expelled back into the room through the front.

You can tell which one you have by simply setting it on a table, starting it up, and passing a strip of paper or Kleenex around the unit to see where air enters and where it leaves. Either way works, but you have to know which one you have in order to setup the baffles (shrouds) that keep the air streams separate.

Bill

[Bill]

By the way, a related question often comes up, and this is a good place to address it. Specifically, what about a portable roll-around air conditioner? Is this a good solution?

A portable unit is one that rides around on wheels, with one or two hoses that are pointed out a window during use. Besides price, what is the difference between a one-hose unit and a two-hose unit?

As discussed in the two posts above, any air conditioner needs a flow of air to remove heat from the compressor, and needs to blow that heated air outside. A two-hose air conditioner brings in outdoor air through one hose, and blows it back outdoors through the other. But a one-hose unit has no source of outside air, so it uses some of the previously-cooled indoor air to cool the compressor, and then blows it outside through the single hose. In other words, it works hard to cool the indoor air, then uses some of that cool air to cool the compressor, and blows it outside. What a waste!

You can guess which one works better, delivering the full BTU rating to the inside of the trailer. You can also guess which costs more. But in my mind, anyway, a two-hose unit is the only one to consider.

Bill

[Larryjb]

Originally Posted by Bill

By the way, a related question often comes up, and this is a good place to address it. Specifically, what about a portable roll-around air conditioner? Is this a good solution?

A portable unit is one that rides around on wheels, with one or two hoses that are pointed out a window during use. Besides price, what is the difference between a one-hose unit and a two-hose unit?

As discussed in the two posts above, any air conditioner needs a flow of air to remove heat from the compressor, and needs to blow that heated air outside. A two-hose air conditioner brings in outdoor air through one hose, and blows it back outdoors through the other. But a one-hose unit has no source of outside air, so it uses some of the previously-cooled indoor air to cool the compressor, and then blows it outside through the single hose. In other words, it works hard to cool the indoor air, then uses some of that cool air to cool the compressor, and blows it outside. What a waste!

You can guess which one works better, delivering the full BTU rating to the inside of the trailer. You can also guess which costs more. But in my mind, anyway, a two-hose unit is the only one to consider.

Bill

I have found that hot air leaking from the exhaust hose, and the use of a non-insulated exhaust hose is far more detrimental to efficiency. I wrap our exhaust hose with some flexible silvered insulating mat material, and tape every joint. This makes the hose non-flexible, but I believe that makes the greatest improvement to efficiency on the portable units.

For those with the side mounted AC units, if we switch to a true in-wall unit that has no side vents, one could remodel the cabinet and square off the opening to make a little more space. Because they require a sleeve, the drip pan concept would have to be redesigned a little, but that shouldn't be too difficult.

[trailmanorkids]

Thanks to every one who commented on our problem and offered suggestions. We will see what works best for us. Again thanks for your help.
Trailmanorkids.