air conditioner

[Don Meyer]

In a car you are recirculating interior air if set that way & it cools better than cooling hotter outside air........to duplicate this in the Scamp it
would seem that you should bring cabin air into the side & top of the a/c unit.

This could be done by putting a vent in the side of the closet next to the a/c unit to pull interior air in thus, recirculating cabin air.

Would this work???

Thanks Don

[ericw]

Originally Posted by Don Meyer

In a car you are recirculating interior air if set that way & it cools better than cooling hotter outside air........to duplicate this in the Scamp it
would seem that you should bring cabin air into the side & top of the a/c unit.

This could be done by putting a vent in the side of the closet next to the a/c unit to pull interior air in thus, recirculating cabin air.

Would this work???

Thanks Don

Simple answer: No, it would not work and I would not recommend it.

Longer answer: When cars recirculate they take most of the air from the inside, cool it more, and put it back into the cabin. But even in recirculate the hot end of the AC is taking cool OUTSIDE air, transferring heat to it, and keeping it OUTSIDE.

When properly setup your trailer will also work like your car in recirculate mode. The trailer's cool air will come in the bottom front of the AC and exit the top front just like your car takes cabin air, cools it even more, and sends it back into the cabin.

You must have normal temperature OUTSIDE air that comes in the sides and top, gets warmed up and then exhausted out the back of the AC to the OUTSIDE.

If you do what you suggested the AC will work hard and not cool off the trailer. The reason is that the fan will be taking "kind of cool" air from the trailer through the sides and top and to the outside. Air from somewhere will have to replace that air that just left the trailer. Every little leak in your trailer will let in a little air to replace that air. That air is warm so your trailer warms up instead of cools down and you end up with a battle of the AC trying to cool it, but warm air coming in trying to warm it and the whole thing doesn't work well.

Thanks to Frederick Simson for the picture below showing the air flow how it should be.

[Don Meyer]

Okay...that clears it up - thank you!! The previous owner had it installed wrong. I will install a separate vent to bring outside air in.

Now for the drain....I will install the a/c on a cookie sheet with a drain hose
going thru the floor, if there is a better way please let me know.

This forum is GREAT.....Don

[ericw]

Originally Posted by Don Meyer

Okay...that clears it up - thank you!! The previous owner had it installed wrong. I will install a separate vent to bring outside air in.

Now for the drain....I will install the a/c on a cookie sheet with a drain hose
going thru the floor, if there is a better way please let me know.

This forum is GREAT.....Don

I'm glad it was helpful. I also have learned a lot from people on here.

I'll tell you my experience with draining water. To test it, I ran it outside in my driveway in fairly humid weather. The bottom filled with water and then there was enough water that the fan splashed the water a little bit and it over flowed and poured out. I ended up drilling a hole in the bottom to make sure I knew where the water would come out.

My point is that make sure your cookie sheet is plenty big even when your trailer is at slightly different angles and check where the water goes in humid conditions. I actually tilted my trailer different ways just to make sure my drainage system worked.

Good luck. Post pictures when you are done.

[Don Meyer]

thanks Eric.......Don

[floyd]

Below is an example of that same A/C unit installed through the outside wall of a completely different camper. My point is to show how much vent really needs to be outside in order to work efficiently. The rest of the side and top vents were sealed prior to the install. You can measure your's but I think you are looking at something less than 6" sticking outside.

I also have some pictures of an early Scamp factory install The condenser was sealed to the assist fan which exhausted through the floor.
A vent on the outside drew fresh outside air to cool the condenser.
The front of the unit was sealed to the face of the bench.

[Don Meyer]

Based on the recommendations above ...this is what I have done.

1 cut a 5" x 5" hole in the floor under the door side seat to pull air in
2 cut a 2" x 12" opening in the rear of the closet(seat side) to allow
air in to the closet (where the a/c in mounted) from the floor vent.

Next I will install the a/c in the closet & seal the front to the cabin &
the rear to the outside thru vent installed in the side of the camper.

Hope this is correct....comments please

Don

[Bob Miller]

Hmmmm... A hole in the floor might not be the best idea for at least these reasons:

1. Road dirt will get in while driving.
2. Water splash can get in and/or damage the flooring and subflooring.
3. Unless covered (reducing it's effective area), critters can gain entry.

Unless you want to use an outside vent, most small wall mounted a/c's recycle inside air for maximum cooling. Pulling in hot outside air will only reduce the cooling effectiveness of the unit.

Just a thought...

[Thinh]

Originally Posted by Bob Miller

Hmmmm... A hole in the floor might not be the best idea for at least these reasons:

1. Road dirt will get in while driving.
2. Water splash can get in and/or damage the flooring and subflooring.
3. Unless covered (reducing it's effective area), critters can gain entry.

Unless you want to use an outside vent, most small wall mounted a/c's recycle inside air for maximum cooling. Pulling in hot outside air will only reduce the cooling effectiveness of the unit.

Just a thought...

...IMO, when making a floor vent, one shouldn't make it straight down ward, but down and bend rear ward instead. On top of that, the vent should be covered by a grid at opening. That way when the trailer is on the move, no dirt could come in, no water splash could get in and no bugs entered either. Just my thought....

[floyd]

The hole in the floor shown in the above pictures is factory... and 30+ years old when the picture was taken upon disassembly prior to restoration. The floor was in good shape. Also the round black spot shown(inside) has a tube running out the bottom to drain excess condensation. (Shown next to the exhaust vent viewed from below the floor.)

[BOBco.]

I'm working on the Ac installation on my Scamp 13. For the external vents I bought a couple of boat hatches off of eBay. The Intake is down in the floor and exhaust out the side. When AC is not in use the doors can be shut and no water, dirt bugs or critters can enter. I'm putting the AC in the kitchen cabinet so there is some dead space behind the AC. With the hatch door I can use the space for storage of the electrical cord or water hose when on the road.

[Whs]

Just read through all of the posts.
I installed a 6000 but unit under front bunk of my 1996 scamp 16' layout 4.
It exhausts down through the floor and draws air from outside, in other words, it's set up properly. I also have a diverter that makes tithe air blow upward as well as a fan blowing forward.
The unit is blowing plenty cold (59-61 at vent). But it just doesn't cool the trailer in the heat. It was 89 in Vegas today and the scamp only got down to 78. I can only imagine what it's 105!

Here's my question, would upgrading to an 8000btu help?

[ericw]

Originally Posted by Whs

Just read through all of the posts.
I installed a 6000 but unit under front bunk of my 1996 scamp 16' layout 4.
It exhausts down through the floor and draws air from outside, in other words, it's set up properly. I also have a diverter that makes tithe air blow upward as well as a fan blowing forward.
The unit is blowing plenty cold (59-61 at vent). But it just doesn't cool the trailer in the heat. It was 89 in Vegas today and the scamp only got down to 78. I can only imagine what it's 105!

Here's my question, would upgrading to an 8000btu help?

Will, I did something very similar in my scamp 13' and 5000 BTU's was more than enough (IMO). Here are a few thoughts that others may add to. First, I noticed that my floor was cold enough, but the ceiling was too warm for me. I added a fan on the floor pointed up to circulate the air through the trailer and that made a big difference. Second, you have to make sure the air is actually doing what you think it is doing. I had sealed the exhaust portion of the AC with a fan to help blow it out and that I was confident in. I checked the temperature coming out of this and it confirmed what I thought. However, I was using entire under front bunk area as the chamber for the cool outside air into the back of the AC and hoping most of the air came through the exterior hole I had made to let air in. It turns out I was only mostly right and some air was coming from the living area back into that chamber and through the AC. That is bad! I don't like losing my cool air in the trailer. So I had to seal off around the front of the AC and everywhere else (fiberglass to wall, etc...) to make sure all of the air going into the back of the AC was from the outside. Third, you have to make sure you have enough air flow through the back of the AC. There is a fan in the AC unit, but I also added a fan to make sure I got enough air through the back of the AC unit. Obviously, if you don't get enough air through the back of AC unit it does not cool near as well. I move a lot of air and the air coming out is still fairly warm. Fourth, you have to make sure the warm air going out the trailer from the warm side of the AC unit is not turning around and coming back into the trailer again. This also would lower the efficiency and cooling.

All of my comments are subjective. It could be that my setup works worse than yours but it is just good enough for me . What we all should do (as you have started to do) is measure air temperatures at:
(1) vent into trailer for the back of the AC
(2) vent out of trailer (warm air)
(3) temp out of front of the AC into the trailer living area
(4) warmest temperature in the trailer near the ceiling
(5) nominal outside temperature

Unfortunately, it is only in the 70's today where I am which doesn't make for a great test.

Hopefully, some of these ideas were helpful. Good luck and keep us posted on what you find so we can learn also.

[Bob Miller]

Quote, "it's set up properly."


Well.... not exactly.
These a/c units (hopefully) draw little, if any, air from outside into the cooling circuit. That air is recirculating the inside air that it is already cooling. Now, even in Vegas, where the odds of otherwise are readily available, heat rises and cold settles, this means that none of the hottest air in the top of the trailer is recirculated and the cold air at the floor is doing just fine. It's just not enough to blow the cold air UP, ya gotta pull that warm air into the unit to cool it.


Window a/c are designed for just that, mounting at window height, not at floor level. The laws of thermal dynamics can be a harsh mistress....


Adding BTU's will help, but it may not "Do the job" you are attempting to do.

[Darral T.]

This may be a dumb question since I'm not a HVAC guy... but if you blow the cold air to the ceiling....where is the warm air going?

Originally Posted by Bob Miller

Quote, "it's set up properly."


Well.... not exactly.
These a/c units (hopefully) draw little, if any, air from outside into the cooling circuit. That air is recirculating from the inside air that it is already cooling. Now, even in Vegas, where the odds of otherwise are readily available, heat rises and cold settles, this means that none of the hottest air in the top of the trailer is recirculated and the cold air at the floor is doing just fine. It's just not enough to blow the cold air UP, ya gotta pull that warm air into the unit to cool it.


Window a/c are designed for just that, mounting at window height, not at floor level. The laws of thermal dynamics can be a harsh mistress....


Adding BTU's will help, but it may not "Do the job" you are attempting to do.

[Bob Miller]

Originally Posted by Darral T.

This may be a dumb question since I'm not a HVAC guy... but if you blow the cold air to the ceiling....where is the warm air going?

Basically, that cold air becomes warm air long before it gets to the ceiling.

With a fan blowing up, if you measure the temperature of the airstream you will find that it rises in temp very quickly.The cold air out of the a/c has no desire to rise and, unless it is ducted to the ceiling, it will never get there. and never cool what's trapped at the top of the trailer. Add to that, the ceiling in an RV is the place with the hottest exterior surfaces. This is one of the reasons why standard RV a/c's are located on the roof, even when there are ducted, and why wall mounted RV ac units have never proved popular.

Look at a home central heating and cooling system. It pumps cool air in through the ceiling vents (not floor vents I hope) that cools the warmest air first, it then continues to settle to the floor, cooling the cooler part of the air space.. Then most a/c systems draw recirculating air from the ceiling return vent, so it re-cools the warmest air. not what's at the floor level.

[Darral T.]

Our central unit has been blowing from the floor (crawl space) vents for the past 27 yrs! To me, since it's more expensive to heat a house than cool it, I'd rather have the warm air blowing up from the floor. Just speaking from experience with OUR unit.

Either way, our house has ran very efficiently with this setup. I dont care for ceiling vents from what I've heard others describe int he winter. I have my roof-mounted A/C with a heat unit. I dont like the "feel" when the heat strip kicks on (cold on the floor). I dont notice this at home (with A/C) but then again- MUCH larger volume of air very unlike the small quarters of the Scamp.

Originally Posted by Bob Miller

Basically, that cold air becomes warm air long before it gets to the ceiling.

Look at a home central heating and cooling system. It pumps cool air in through the ceiling vents (not floor vents I hope) that cools the warmest air first, it then continues to settle to the floor, cooling the cooler part of the air space.. Then most a/c systems draw recirculating air from the ceiling return vent, so it re-cools the warmest air. not what's at the floor level.

[Bob Miller]

More expensive to heat???
I guess that depends on the type of heat you have. My winter gas/electric bills runs about $120, my summer gas/electric bill runs about $300.
Hopefully your return vents are in the ceiling.


I do recall being in a house cooled from the floor and they depended on ceiling fans to circulate the air.

[Darral T.]

At the height for winter/summer, my heat/cooling bills never surpass the $180 range. My central furnace uses natural gas. My return vent is 21x21 and is located in our hallway at floor level.

Feel free to come by and check it out sometime...

Originally Posted by Bob Miller

More expensive to heat???
I guess that depends on the type of heat you have. My winter gas/electric bills runs about $120, my summer gas/electric bill runs about $300.
Hopefully your return vents are in the ceiling.


I do recall being in a house cooled from the floor and they depended on ceiling fans to circulate the air.

[Bob Miller]

Sounds like our annual bills are about the same then.