AC--- Is this do-able?

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AC--- Is this do-able?

Postby tinksdad » Wed Nov 19, 2008 5:38 pm

I have been working at the design for the next build. I've redesigned several times trying to stay within the initial concept for "The Paddy Wagon". I'm not buying one stick of wood for the trailer until I work out the bugaboos in the design.

Using the charts and all the other information available, I come up with a weight of 925 pounds including the mattress, battery and a/c unit. That 50 pounds for the a/c is giving me fits . I've been trying to keep it high and in the front; but that weight basically over the tongue is really messing up my tongue weight percentage (especially since the area below the a/c would end being used as a tongue box and more weight will be added when loaded). I either have to have a 6 foot tongue or move the axle so far forward that it interferes with the door location.

Unless I want to give up the a/c, the only other option I see is to move it to the rear and give up some galley space. I did some work up drawings of something I think I could live with; but I'd like some opinions on whether it will work or if I'm overlooking something. I am thinking that I might be able to mount it sideways in a enclosed compartment under the galley counter through the side wall, build a shroud and add some duct work to the cabin area. A similar compartment would be put on the other side of the galley to house the battery, shore power and other electrical components to balance the weight load side to side. Both compartments would have matching vented access door in the side walls. The drawings have the front face left off under the galley counter for clarity sake.

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Since I don't really want to have to go outside to turn it on and off or adjust the temp, if it's possible, I am also going to try to rewire the control panel and mount it inside near the vent.

Will this configuration work? Do I need to add additional fans to move the air around inside the compartment? Any thing else I'm overlooking?
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Postby caseydog » Wed Nov 19, 2008 7:10 pm

I see one problem right away. The intake area for the condenser fan is on the sides and top of the unit -- about the last six inches.

You will need to separate that area from your conditioned air side or you will be sucking conditioned air to blow through the condenser, in effect, creating a vacuum in your teardrop.

So, either you need to have six inches of AC unit sticking out the side of the TD, or you need a wall in your AC enclosure to separate conditioned air from the condenser cooling air, which needs to come from outside.

There are some other similar, but simpler designs on the forum. If I can find them, I'll post a link.
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Postby john » Wed Nov 19, 2008 8:19 pm

I like it. :thumbsup: :thumbsup:

I agree you need to do something about the intake for the condenser.

I would suggest you duct the cold air feed to the cabin only. The return could be accomplished through a grill visible from inside the tear. Placing it high above the mattress is a good idea.

There are pics of mine in the links below. It is mounted in the rear also. There may be some ideas for you there. Also check out 2bits' build.

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Postby tinksdad » Wed Nov 19, 2008 10:48 pm

:? :?

I appreciate the input. I just spent several hours searching past threads on a/c installs and I think I'm starting to get a handle on what needs to be done. Liberal application of copious amounts of :beer: may help!! This may call for a trip to the box store with my tape measure and actually seeing where and how big all the vents are and where they are placed on the unit. Maybe even see if I can find some of the instruction manuals on-line to read before I commit to anything in particular.


Since I don't have a heated work space; I have plenty of time to work out the major concerns before I actually start building this one. That's one nice thing about Sketchup.... I can try all kinds of configurations without cutting any plywood into many small pieces of scrap!!!
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Postby tinksdad » Wed Nov 19, 2008 11:40 pm

So..... it's just a generic ac unit I found on Sketchup; but to my understanding thus far, there are four distinct air flow zones that need to be addressed (separated by the blue dash lines). And the amount of air flow and their respective separation in each zone is important to efficient operation.

Am I close so far??

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Postby planovet » Wed Nov 19, 2008 11:49 pm

That's pretty much it. Here is a better picture: http://home.howstuffworks.com/ac2.htm

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Postby Miriam C. » Thu Nov 20, 2008 12:08 am

I cut extra vents on the side of mine for intake. It worked fine but at 90* it could have done better. Now it does. There is a board between the two vents and another vent on the galley side. Lined it with bubble insul. to keep things from getting too hot. It also vents the heat to the bottom.

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Postby caseydog » Thu Nov 20, 2008 2:13 pm

I boxed in the back of the AC unit, and the condenser fan forces hot air out through some dryer vent hose.

Intake air for the condenser fan comes from the galley, which is vented to the outside.

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For your application, you could aim the evaporator side of the AC right into the sleeping cabin, and duct the condenser air out the side of the TD. You could draw condenser air from a second vent in the side, or from the galley, as long as the galley is vented to allow fresh air in.

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Postby brian_bp » Thu Nov 20, 2008 4:59 pm

A member of FiberglassRV (Per Walthinsen) built a similar A/C unit into his small trailer with added ducting like this, and it works... but due to the resistance to air flow through the restrictive ducting it needed a booster fan. It is descrbed in the topic A/C in Fiberglass Trailers, Cool your egg the efficient, cheap and easy way..
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Postby caseydog » Thu Nov 20, 2008 5:15 pm

brian_bp wrote:A member of FiberglassRV (Per Walthinsen) built a similar A/C unit into his small trailer with added ducting like this, and it works... but due to the resistance to air flow through the restrictive ducting it needed a booster fan. It is descrbed in the topic A/C in Fiberglass Trailers, Cool your egg the efficient, cheap and easy way..


On mine, the built in condenser fan pushed enough air on its own. I guess some AC units are different than others. I used a standard Dryer vent -- four inches, IIRC.
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Postby tinksdad » Thu Nov 20, 2008 8:03 pm

Again.... I need to say "Thanks" for all the input!! After using "search" and following about 40 or 50 threads on A/C installs last night, I went to bed with a headache. Sometime during the night, I had an epiphany.....K.I.S.S. !! By trying to shave a few inches and add a shroud with duct work, I was making the unit the same depth (or larger) than the width. As long as I was going to remove the front face plate anyways to access the control panel; just cut some holes and butt it up against the galley/cabin wall. Start with smaller holes and expand as necessary. The rest just sort of fell in place after that. Today's response postings, after I woke up, tended to confirm that!!

Knocked out some quick sketches so this addled brain won't forget by the time it comes for installation; but I think I have the concept down. It may take some experimentation, and I think I can raise the whole thing a couple more inches because I think my galley counter-top may be a couple inches low. I'll know that for sure once I get the floor on the frame and before I start laying out the sidewall framing.

For your entertainment.....
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Postby McTeardrops » Thu Nov 20, 2008 9:37 pm

With the supply and return as close together as shown, air flow will be out one grill and in the other. (short circuit) I used my rear shelf to provide separation, but the vaned diffusers from the unit might also work. Ideally, for AC, the supply should be below the return. The thermostat sensor should be as far from the unit as possible, but the easiest location would be in the return air duct.
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Postby john » Thu Nov 20, 2008 9:49 pm

Wow :shock:

You've been thinking.


You might want to consider increasing the size of the vent on the side of the tear. Ideally it should come as close as possible to the same size area as the intakes on the sides and top of the AC unit combined.


good work :applause: :applause: :thumbsup:
Build I -- Scenic ---
http://www.flickr.com/photos/8121727@N04/
Goto the Tear Build file

Build II -- Scenic II ---
viewtopic.php?t=29603

Build III -- Scenic Solo---
viewtopic.php?f=50&t=50324

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http://polifrogblog.blogspot.com/2009/0 ... -2009.html

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Postby tinksdad » Fri Nov 21, 2008 10:56 am

McTeardrops wrote:With the supply and return as close together as shown, air flow will be out one grill and in the other. (short circuit) I used my rear shelf to provide separation, but the vaned diffusers from the unit might also work. Ideally, for AC, the supply should be below the return. The thermostat sensor should be as far from the unit as possible, but the easiest location would be in the return air duct.


When I actually start the build, I am going to try to duct the a/c cold coming into the cabin as close to the ceiling as possible. There will be cabinets on that wall above the air conditioner, so I may be able to work it out. Right now, I'm just trying to work out the basic concept so I don't make an expensive mistake later. I'm still thinking about a PetCool; but currently can't justify the price difference.
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Postby tinksdad » Fri Nov 21, 2008 11:01 am

john wrote:Wow :shock:

You've been thinking.


You might want to consider increasing the size of the vent on the side of the tear. Ideally it should come as close as possible to the same size area as the intakes on the sides and top of the AC unit combined.


good work :applause: :applause: :thumbsup:


That's also something I was thinking about. A larger vent could be disguised as an access door to the battery compartment on the other side of the trailer and both sides would match.

I rushed through my first build "Itty-Bitty". This one I am taking my time and planning it all out ahead of time. The trailer frame in the back yard keeps calling me.... "Build me!! Build me!!"
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