My new 2009 Dutch Star came with two 13,500 btu roof mounted ac units. I live in SW Florida where the temp is pretty much low to mid 90s every day in the summer. I have not been able to get he coach cooled below 80 during the day unless it rains. The units have been checked out and found to be working as designed. Am I expecting too much?

Yes and no. Living in Florida you know requires as much AC as possible(obviously their is a limit of no return). We opted for a third 13.5 in addition to the two optional 15s(total of 43.5). Works fine to whatever temp we need without having to cover up windows, vents, etc.

One of the disadvantages to the ducted return is some inefficiency, however having the silence of the truly ducted system is great.

I also have 2-13.5 A/C's. Even on the hottest days, you could hang meat in our bedroom. It is always cool. The living room/kitchen is different.

There are a few factors.
1. Direction your coach is facing. If it is getting direction sunlight through the front windshield in the afternoon, then it will heat up fast. We have a sun screen that helps a lot, plus I keep the drapes closed.
2. If getting sun on passenger side, having your awning out helps keep the sun off of your coach.
3. Start early in the morning making sure that the inside of your coach is cooled down. If it ever gets hot inside, my A/C never seems to catch up.

The dealership I bought my coach from said that in our climate they won't order anything over 36 feet long without 3 A/C units. They were just adamant that at 39' or more 2 units just weren't adequate in a hot climate. They had just taken in a 40' DSDP on trade with only 2 units, and they were already chopping the roof up for the 3rd unit.
My old 36 footer had two A/C's, and as Ben & Bonita said the rear bedroom was fine, the living area was much tougher in the summer.

Scottsdale gave you some good advice. We have 2 of the 15K units and never have a problem. We keep it at 72 on the front AC and drop it to 68 at night (like sleeping in cool). However, if the coach gets hot, it is harder to cool down. We put out awnings to shade from the sun and pull down shades. We also have Prompt sun shades for the front windshield that helps a LOT. You might consider exterior sun shades for other windows to help with heat transfer.

On our old motor home we made inserts for each window of that bubble/aluminum insulation that you can get at Lowes or HD. It kept it quite comfortable when it was parked in the drive at our house without AC on.

I know you won't want to be inside not looking out, but it is an example that the barrier does block heat. So do some experimenting.

I agree with the others about sun screens, awnings, and the direction you are facing.

I have 2 15K AC's.

Newmar added 1 more outlet and 1 more return all the way up front, and moved the front thermistor near the door.

All of these things help, and you should be able to get comfortable.

One other item. We have a Fantastic Fan in the LR/Kitchen area. A lot of sunlight was coming through there generating heat. We got a type of pillow that fits the hole from CW and it keeps the sunlight out during hot weather.

As every one has already stated, heat gain from the sun is enemy # 1

My 05 DSDP doubles as a guest house for my wife's parents on their visits from FL (they are out their as we speak).
My coach sits inside our shop with full hookups. Inside shop temps in the mid 90's are common in the summer. They set the front ac on 72 and the rear temp on 74 (bedroom can double as a meat locker).During the heat of that day while I piddle in the shop the ac's are off more than on.

We insulate the front windshield and close the windshield drapes. Even in the shop you could fell the windshield radiating heat

You mentioned that your ac's checked out, did they tell you the difference between inlet and outlet temperatures ?

I have a 37' MA gas with 2 slides with 2 15k AC roof mounted AC's. I live 24x7x365 in the rig and have it inside a uninsulated 40'x75' metal building.

The temps here in Texas have been running in the high 90's to 100. I checked the roof temps yesterday during the hot part of the day and the were over 110 degrees. If you are suspecting a 30+ degree differential temp drop with 2 13.5's it ain't going to happen. 20+ degrees maybe.

I did a AC tune up this spring and 1 thing I did was cover the suction lines with foam. My AC exit temps dropped about 4 degrees just from that. The exit temps are 40 degrees the last time I used my IR temp gage. I also cleaned the the dust and dirt from the squirrel cage and cleaned the condenser fins. Also, be sure to clean your filters in the return air.

Here are some other tips.
1) Try adding sun screens on all your windows.
2) Window awnings also help. The big side awning will keep a lot of heat out.
3) I also have a small floor fan sitting in the bedroom pushing the cold air out to the living area.
4) I covered my vents with the large Maxx Air covers that I painted to match the coach.

Bottom line, learn to be comfortable at 78 degrees or add a 3 unit.

This message has been edited. Last edited by: oemtech,

Roger oemtech assessments. Window awnings, and windshield covers/screens will make a tremendous difference in the performance of your AC's. Just pulling your front windshield curtains will help, remember the front windshield is not dual pane like your other windows, therefore a large heat transfer surface. The other thing is start early in your efforts to cool, don't wait until the coach is 80 degrees inside before you turn your AC's on, turn them on first thing in the morning. This keeps the interior at a relatively even (lower) ambient temp, therefore allowing AC's to compensate for outside temp increases.

Spike