Dating back at least as far as WWII, APUs are found in every jet plane and in many military vehicles. The proliferation of anti-idling laws prompted their adoption by the trucking industry. A typical APU for an OTR truck consists of a small diesel engine (often 2 cylinder, around 12 hp, Kubota and Perkins seem popular, but other brands in the mix), a high capacity alternator (output might be 12 or 28v dc or 110v ac), an air conditioning compressor and a heat exchanger. I found a few with hydraulic pumps instead of AC.
Compact package mounted on the truck chassis. Usually the AC compressor and the APU engine coolant are routed to blower coils in the sleeper. Sometimes AC and electric are routed to a reefer box or trailer. Sometimes APU coolant is routed through the trucks cooling system. That way, the main engine is warm when the driver awakes.
Bottom line for me is that, after doing all that work refurbing my Kohler 4500 watt generator, now I'm not even gonna use it. Before another winter hits this part of the world, I will have an APU in my bus. As an old friend and dairy farmer used to say, "Even if I have to sell a cow." (I don't actually have a cow to sell, but maybe I could steal one.)
Apparently these things are available used in the "well under a grand" category. I think I can get more than that for my Kohler. An APU in this price range would likely need work, but I'm not afraid of a project.
Here's what I have in mind: Reading Rob Gray's build thread in 2010 is what convinced me that a bus for full timers can operate on a solar budget. Even he, however, has a small backup generator. (And recently bought a much larger generator to use at the home place.) In that thought process, I gave up the idea of two large roof air units and an 8K diesel generator. We lived through the last two summers with just fans, but it was not always pleasant.
Since we got the Gillig, I've been planning to cut a hole high in the rear bulkhead and mount the smallest room AC unit I can find above our bed. With the rear of the bus well insulated and shut off from the main living area, I believe we could cool bedroom/bath/laundry area with such a small unit AND not have to run a generator to do it. As of now, I'm still planning to do exactly that, BUT, now I'm also planning to put an APU where the generator was going to sit.
I'll mount a blower coil in the bedroom and maybe a small radiator on each side of the bed. That way we can be warm or cool with only that tiny diesel running AND charge the batteries at the same time. While I'm at it, I'll probably run lines to the AC blower in the dash and include selector valves in the system. We could have cabin AC when we're traveling without having to add another compressor to the prime mover. No, I'm not thinking of getting rid of the wood stove, but an APU will make a far better backup heating system than would radiant propane heaters. What's more, not using my generator will mean that I don't have to carry gasoline — petrol to the rest of the world. I like that idea.
Words cannot express my excitement at this development. Starting today, the hunt is on.
Here are a few shots of the generator with my homemade exhaust manifold in place:
And have you seen my '85 square body? Scottsdale trim, 4x4, 3/4 ton. I like it:
It is however on the main highway so it's on the way to all the stuff people normally want to visit in Queensland. If you want to try a spot of camping in the Oz bush, watch the wallabies and shoot the shit around a campfire feel free to drop into our place if you get down here.
. Long story short. The lamp was two wire and when I got my hand grip around the bare wires, I, in my shorts and bare feet on the wet grass became the perfect ground. I still remember the burst capillary beds in my legs and one arm from the experience.. A fuse finally blue in the house or I guess I wouldn't be telling this story. I'm now very careful about grounds. I read every article I find and I have come to the conclusion that ground needs to go back to its source. If you are using battery power, the ground needs to go back to the battery. If you are using a genny, the ground needs to go back to it only. If you are using shore power, the ground needs to go back to it only. I'm not talking about neutral or common--just ground.
