Class C roof top air

[Ron Dittmer]

Originally Posted by Josephls

30 foot rig needs 2 ac units if you travel in the summer. Ours is 28’ and one is not enough when the temps are in the mid 90’s and up. Which is a majority of the country in the summer.
A new ac won’t make any difference . I installed a new unit to get one that’s quiet and the newer units don’t cool anymore than older units which is to be expected.

I’ll never own another rig of this size without 50 amp and 2 ac units. For me this was Lesson learned.

You have a very common complaint. The length, width, height, and quantity of slide outs influence the volume of air you are trying to cool, so even some mid-length rigs have cooling issues with one a/c unit.

Keep in mind for next time (if there is a next time for you) and as a warning to others, just because you have two a/c units and 50 amp service, does not mean you can run both a/c units with the generator. Most require being plugged into 50 amp service to run that second air conditioner. So when you boondock, it's still just one a/c unit. The RV manufactures don't wire that second a/c unit to the generator, so you can't even try running both off it.

The standard Onan 4000 generator cannot support two a/c units and the class-C manufactures won't install a bigger generator. I have read that a few people are finding success in running two a/c units with an Onan 4000 by adding soft start units inside each (and changing the wiring to run both). The soft-start units eliminate the spike in amperage during start-up which prevents the main breaker from tripping. But don't take my word on it. Do your research on whether this really works.

[Josephls]

Ron, I’m aware that you can’t run 2 ac units on a Onan 4000. I’d be surprised to find many that aren’t aware of that. When it’s hot as in close to or triple digit temps I’m not boon docking ,I’m in a camp ground with electric service. Even with only one ac it’s no fun to run that noisy gen all night to keep the ac going.

[SteveNSue]

You can find portable 15,000 BTU AC units at Lowe's or Depot for about $600. They run on 110 VAC and just use an exhaust tube you can stick out a window. Cut some cardboard to block the screen with the vent hose ported thru it. We use one in our house for hot rooms and find it works great and is much less than reworking the RV interior.

[frank1018]

Got it home from shop. Did think to gen up and be sure it turned on after servicing. We have had nothing but storms, wind and rain here since. I am going to check around the ceiling ducts to be sure nothing separated and no spaces in the rooftop as soon as the weather clears. Buying insulating window shades for cab and bedroom windows since there are 3. I will see if the cleaning helped any.

[jjrbus]

A long time ago in a land far away I put 2 ducted roof airs on a bus conversion. By dumb luck I had a how to guide on designing RV duct work.



Move ahead a couple decades and doing some AC work on a house in Florida I found there is a Manual D for designing home duct work. Obviously the people that put the duct in my house never heard of the manual D and it all needed to be redone! I opted for mini spits instead and would do so in my RV but have no room for interior units.



Makes me wonder if duct work is put in RV without consulting the instructions??

[bladerunner4]

Originally Posted by frank1018

You are right. The one time I took it out in fall after I bought it, it was quite warm and all the air units were humming in rv park. I never thought about it. It is a 13500 unit with duct. I am not sure of brand because unit is being serviced and manuals are in it. A guy told me they only last about 5 years and this is 6 years old. Wondering if there is any truth to this. Made me start to wonder before I go on month long trip of course in August out west. I will invest in the reflective windshield stuff and maybe for windows too. I know this is not a top of the line unit either so I am guessing not insulated that well. Thanks for the tips. I appreciate it.

I have a ducted 15K btu a/c in my 29 mv. I just did a modification on my unit that boosted the airflow and cooling throughout the unit tremendously. Here is the video on it.

https://www.youtube.com/watch?v=V9rEQb05Qv4

. That said, i didn't buy the device they are using in the video. I built one on my 3d printer it works on the same principle. I just finished installing it and what a difference. I had installed a second 13k unit in the back since i live in south Florida, and the standard design of the front unit just wouldn't cool the back. With this upgrade i wouldn't have needed a second a/c. Oh well when i go to sell it it will add value. Also clean to coils that will add cooling efficiency.