Gen use and roof air for over the road A/C

[TomC]

Just got back (Tues) from the Rally in Albuquerque, NM with 2700 other RV's.  Met Melbo and his wife Billie, and Bob Evans and Marilyn-both delightful couples-went to dinner together.  Learned much about Internet on the road and how to run a business from the road (gearing up to that in a few years).
I was in the dry camping section and had to run the generator everyday for batteries since my refer is all electric (Norcold 6.3 12v/120v compressor type).  I also filled the tank before going to the Balloon Fiesta Park.  With taking off the fuel burned to and from the truck stop, I burned 8 gallons with the generator sitting for 5 days-not bad.
Also, coming back to L.A., on Tuesday, had to kick on the roof A/C (my only A/C) from Kingman to L.A. with the heat wave we were having.  At first I had all three on, but my wife complained it was too cold, so with 102 degree weather, ran on the front two with the interior being right at 70 degrees.  I was a little warm with the sun in my face driving west, but with my dash fan blowing at me, managed to keep from sweating. 
I still maintain with a well insulated bus, the expensive to up keep over the road A/C system is not necessary.  You can't beat the maintenance I've done on my three 13,500btu/hr Coleman roof airs-and that is zero except for yearly cleaning of the filters (and that's over a 14 year period).  Good Luck, TomC

[Utahclaimjumper]

I have the same result with my two 15Ks behind a 12.5 diesel gen.>>>Dan

[Lin]

Using roof air for OTR is not the best, but it can be acceptable.  Fortunately for us, we do not generally like it too cold.  We only cool our house down to about 78, so if we can approach that while driving, we are okay.  Since I bought the bus already converted, I did not choose where the AC units are.  The front unit should be much further forward than it is.  If the unit was almost above the driver area, we would have no problem at all.  As is we have to try different methods to make it work.  Last summer, we put a curtain across the bus just behind the unit, and that helped quite a bit.  I could have just run both units instead, but chose not to.

I have seen it suggested here and elsewhere to cut a duct-size hole in the bottom of the rooftop unit, and let the air blow straight down.  The design of the rooftop really sacrifices effeciency for compactness.  In mine, the air is forced into a 10" wide, 2" deep plenum through a 4" by 8" blower duct (these are approximate measurements).  The air is forced through the back and front louvers by the pressure in the plenum.  I would assume that a huge amount of air flow is lost.  I am planning on doing an adaption of the dump-hole-on-the-bottom concept.  I am opening a large hole on the bottom of the unit and will put an flap over it that can be left closed for normal use, or opened to between a 30 to 45 degree angle so that the dumped air will be blown up front when driving.  I think that that, plus a dash fan, should be a nice improvement.

[John316]

Tom,

Thanks for the post. I am glad for the confirmation. We just decided to chuck our OTR air. Too much money spent on it already, and who knows how much more to get it going (already spent 5k).

We have five 15K roof airs, but only 1.5 inches of foam on the walls, and roughly 3 on the roof. So even though we don't have as much isnsulation as you do, we should keep cool.

Thanks again for the post.

God bless,

John

[Singing Land Cruiser]

We don't know alot about OTR A/C But we did read alot of Pros and Cons on the matter. We have ripped out the OTR because we don't want to re-learn what you guys taught have alraedy learned. OTR A/C = $$$ if/when it stops working. We will start with 2 Roofs and see what happens. All the Best, M&C

[gus]

Lin,

I cut a hole in mine two years ago and the difference is amazing. Since my AC is also too far aft I use a small fan to blow air on me while underway.

I blocked the side vents internally with foam board so there is absolutely no air loss to the side. I couldn't see any reason to ever need the side vents and haven't in two years.

However, the main reason I did it is to keep the boss happy and her seat is aft of mine and right where the cold air hits in the aisle right next to her seat so she keeps very comfortable.

It is not cool enough for me in the driver's seat but it is not uncomfortable. I thought about mounting the AC in the next forward roof space but decided I really don't want another hole in the roof so I will live with it.

[Lin]

Gus, I also have considered another unit further up front, but have no immediate plans for that.  I did just get back in the house from installing the prototype of the flap door I mentioned.  I am sure that the craftsman among you will be impressed by the genuine black duct tape hinge and the paper clip/S-hook flap holder.

[luvrbus]

I'll take the 32000btu Red Dot dash air with a engine driven compressor any day over a roof air why burn fuel in 2 engines.  
If you guys lived here in AZ that 13,000 BTU roof air would be of no good to you      

good luck

[Lin]

Clifford,
   You are certainly right about what is better, but I am only looking for good-enough right now.  It's not like I drive an Eagle!  What is the cost of the Red Dot system including installation?

[Melbo]

I run my roof air (front only) from my inverter and battery bank while driving

We have it ducted to the front seats

We have always been comfortable even in 100 plus heat

So no need to run two engines and still use the roof top air

Melbo

[gus]

Lin,

Your clever innovations don't show in the photos. More please!

lbus and Melbo,

We travel more than camp and my theory is that my gen would not get enough use to keep it in good condition if I didn't use it for AC underway. I doubt that I will live long enough to wear it out!!

This way I eliminate the inefficient inverter and the huge battery banks. Simple is better to me.

[Lin]

Gus,

In the picture, you can see the rectangular hole cut in the housing below the blower.  The plastic flap, which will probably get a real hinge was just attached with duct tape, which does not show here, to see how it would work.  I tried to find the best angle to set it, and found that the opening as it appears in the pictures was just enough that no air was coming from the louvers.  From where it is, the more it is closed, the more air is forced through the original louvers.  It seems to work better with the opening than without it.  From here, I will just put a latch of some type to close it and a chain or something to limit how far it drops open.  The whole thing is a bit tacky I suppose, and not at all of the caliber of work that some here do in their rolling works of genius, skill and art.  However, I like a certain amount of idiosyncrasy.

Melbo,

I would like the option of running the AC off the inverter.  I have a 2500 watt Trace, so I think it could push one.  However, it is a 12 volter,  so I will have to come up with a way to supply the current on the road before that is a possibility.  I know some have put 12volt alternators on the engine, and maybe I'll get to that in the future.  Anyway, since we mostly stop at campgrounds, the only time we get the use the generator is for running the air on the road.

[niles500]

Lin - the only improvement I can see are some "sides" made of  some type of accordian type material that will insure that the air flows in a forward direction (no lateral dispersion) - FWIW

[busnut104]

I have two means, I can run the front roof unite off the inverter and I also have a welsh unite for the dash, witch is a small eng. driven compressor and piped to the org. dash unite.

[gus]

Lin,

I didn't see the photo horizontal scroll bar, that was the reason I couldn't see anything!!

I think the S hook is especially classy!!