How would a home unit be properly vented in a bus bay? Are they using the type of home unit that has the condensor and evaporator in the same housing?
They used to use the "Home" type with just the condensing unit downstairs. The ones Luvrbus was talking about houses both "units" if you will or a "package unit"
On the "home" condenser only types, the air comes in all around the sides of the unit and a fan blows it out the top. Outdoors this works great.
The way I have seen them vented is they put them close to a bay door. The bay door has a vent or screen covering most all of the door. They then put a piece of sheet metal that touches the bay door on one side of it, then attach the other end to the top of the condensing unit. They then use a second sheet going from the top rear of the unit bent so it forces the air out the top half of the bay door vent. The air comes in from the bottom half of the bay door and usually there is another vent for incoming air on the bay floor.
I have also seen them use wood to do the same thing. I first doubted that they would be able to shed enough heat that way but after driving several of them they cool fine.
Some buses have 2 units. One on each side. I have also seen them mounted where the condenser coil for the bus air normally goes on an Eagle.
The "package units" that Luvrbus spoke of vent as above or they draw air in one side and blow it out the other side. (at least the ones I have seen)
The old "Memphisaire" condensing units I remember took air from inside the bay and blew it out a vent in the door. The fan motors could be reversed and I have seen some that suck air IN the bay door then into bay and out through the generator vent, radiator for generator or however they were set up.
My 10 Eagle has an old 3 ton "Baird" brand unit, I believe. It sucks air in from the bay door and blows it out the bottom of the bay. I really like it. The coil stays clean and other than a contactor, it has been trouble free from day one (1988).
I have the same problem as you with heat building up in the front. The way the unit is ducted it basically pressurizes the area between two "inner" walls of both sides of the bus. They then put 4" round vents in the front area, back area, and each of the 9 bunks. The bunks stay nice and cool, I just need help up front. I really wanted to keep the roof clean and stay away from the noise of a non ducted roof unit if possible. I really like the idea of a mini-split or another basement type unit for the front.
My basement air needs 240V to work and although I have the generator capacity available, I would like the front unit to be 120V in case I stay in a campground with 30A service. I know it wouldn't cool the whole bus, but it might be able to take the edge off in a mild climate.
If I was not so stubborn I could put 2 roof units on the bus and solve all of my problems.......
I too would be interested in why the mini-splits do not pull as much moisture from the air.
Sorry for the long post and for the topic drift gang.