A few thoughts and observations...
Like many here, we have found that the heat load on our 2004 Horizon 40AD is more than the Winnie supplied basement air can handle. As many have suggested, in various ways, preventing additional heat gain is the least expensive and easiest way to improve a/c efficiency. Less to cool IS less to cool.
However, with our awnings deployed, shades on, systems operating properly, ducting in order, etc, we cant muster more than 79 on a hot day. (We are not willing to put reflective foil in the windows of our coach, we don't care for the look, and at close to $300K, we feel we shouldn't have to)
While many may find that acceptable, we do not. Comfort is somewhat of a personal decision. Too warm is just too warm, no matter the number it happens at for you. We think it not unreasonable to expect that the cooling system be designed to have sufficient capacity to cool the coach to at least 76, and easily keep it there.
I think Winnie did what they could in terms of basic design, and may well have known that there was a deficit in their design or heat load calculations. But think about it. They tout the basement air as the answer! If they had to admit, by offering an optional third a/c unit on the roof (like most large mid to high-line manufacturers do) they would seem to contradict their own marketing. I get that. I also understand that they inexplicably omit insulation in areas that are easy and inexpensive to insulate, and would seemingly not pose any issues in terms of serviceability, etc. The cabinet over the front of the coach is a great example. It's totally uninsulated! Such foolishness... We insulated ours and it helped tremendously. Then there is the roof roll area, where the walls join the roof structure. Surely they could make a foam extrusion that laid in that space and at least helped thermal efficiency. There are countless other areas. We have addressed as many of them as we can.
But in the end, we installed a Carrier low-profile, high-efficiency roof air unit in the kitchen last year. At only 7.5 inches tall, and considerably lighter than any other model we could find, it does the trick. We can now keep the interior comfortable regardless of the exterior temp. Contrary to the person that expressed concerns about amp load, etc we have had no trouble with overloading or circuit breaker tripping. We carefully monitor incoming voltage via our inverter (we replaced ours with a Prosine the day we took delivery) and have a unique cord setup. Our "third" roof unit is wired back to the circuit breaker box through the electrical cord bay. We have installed a disconnect point there, allowing us to choose if the power for the third unit comes from the coach or we can attach a twist on "shore cord" allowing us to run it to the pedestal and plug it in to the 20 amp outlet. This way, if we only have 30 amp service, we can put the extra load on the pedestal and not on the coach (which wouldn't work anyway) As many of you know, most pedestals are not fused at 30 amps, but rather have separate 20 and 30 amp breakers, and are part of a larger buss. The extra load on the pedestal works out just fine this way. To date, we have not had any problems with this configuration.
Now... on to the real monster. Try cooling the coach while going down the road on a hot day! Not going to happen. We have a torrent of hot air that erupts from under the bed while we are driving at highway speeds. No manner of intervention from Winnie has been able to slow it to the point that the A/C can keep up. As best as I can understand, there is a gap somewhere in the firewall or the substructure that allows hot engine warmed air to be "sucked in" as the coach goes down the road. The only way we can minimize this effect is to keep the dash air on full speed, in the "normal" setting, which "pressurizes" the coach and slows it a bit. Sometime soon, I am going to redesign the upper bulkhead area of the electrical cord compartment, and create a seal there, and see if that is part of the problem. I should mention that we also put foam in our outdoor vent openings (dryer and kitchen micro fan) to help lessen the vacuum effect.
All in all, our Winnie is still built and engineered better than anything else we can find in this price range. Sure, there are shortcomings, (some of them maddening!) but overall, we still love it.
I guess I can get off of my soap box now...
