Making my own APU

You never want to use jumper cables with an inverter that large,....it will eventually destroy the inverter at best or cause a fire at worst. I thought about installing the inverter in the thermoking cabinet, but then you have to deal with insulating it from the weather,...venting for cooling,...besides, there is already tons of heat in the cabinet to begin with. Take your time and do it up right the first time out..you won't be sorry!...Good luck with your project!

 

I use to use one of those portable A/C's and in 100 degree weather it just could not keep up, I now have a 8000 BTU window A/C that I put in my passenger window and when its over 100 outside it will keep it in the low 70's in the truck. The portable A/C tube and having to keep a window cracked to draw air for the air it is exhausting are to much heat for it to overcome IMHO. $250 gen at harbor freight with 2 year replacement warranty and $225 for the A/C and $15 for a ceramic heater. Less than $500 for my redneck APU and I'm good all night on 2 gallons of gas. I also have had several level 1 Insp. and the gen has never been a issue.

 

wow, to much heat from the portable unit, didnt think it would be that bad, next idea, what about those units they put on top of those tour bus's that singers have and R.V bus's, we that work

 

xxxlcj, I think I don't understand something. Can u please make a bit light for me ? So the portable unit is cooling but also is heating in the same time, or I didn't get the ideea corectly ?
I've seen in someone truck a portable unit (8000 BTU) and was cooling so nice. No heat liberated at all. And the flexible pipe on the window was fitted to a lexan stripe and no heat from outside was coming inside. Around the unit was no heat at all.

 

I have been thinking about building my own APU quite a bit as well, one thing I do see is that many use the Kubota 3 banger Diesel. I really dont see any reason why a guy couldnt get this thing to run a gennerator and an AC pump. The rest of the setup is pretty simple. If I do it on my next truck I think I will disconnect the sleeper from the rest of the trucks AC and heat system, and I will reroute everything through the APU, This way I am gaining as little weight as possible, the controls are already in the sleeper, and all I have to add is the control for the engine.

Here is my wishlist of things for the unit to do.

1. Break apart the battery bank on the truck so you have all 4 batts for starting the truck, but you have 1 that is soley rigged to start the APU, and the other 3 will be isloated to power the truck chasis, but they can all be charged at once.

The reason for this is if you pull in somwhere and leave your lights on and your batteries die, you can fire up your APU charge up your batts and still start your truck.

For controls a simple off and on switch and a push button start, with an indicator light for the glowplugs would keep it simple and easy. A timer would be a good idea as well so you could tell the unit when to turn off and when to turn back on.

I had also thought about a "courtesy start" switch that could be located on the unit its self so a friend could start it for you with out having to accsess your truck.

Something you would want to have though would be a key on the unit its self that would allow you to disable the unit when you are serviceing it so as that the ole lady didnt try starting it when you had your hands stuffed in it.

I would also like it much better if the unit could be mounted in the passenger side step box, it would make the truck look cleaner, save on weight, and keep the noise as far away from my pillow as possible.

Even if the unit had to have a radiator that was mounted behind the sleeper or between the frame rails, keeping the engine away from the sleeper would make it much better.

It would also be slick if you could tap the exhaust for the unit into your existing truck exhaust. This way you know the exhaust isnt pooling in and around your sleeper, instead it is going up and out the stack.

I had also considered using solenoids to divert the flow of the AC lines and Water lines between the APU and the truck, this would allow the bunk heater to be run on either.

 

In my experience there was just to much heat coming off the exhaust tube and because you had to leave a window cracked to have air to replace the air being exhausted it did not cool that good. Now the window A/C has all the heat outside and just keeps pulling and recirculating the air inside so it is alot more efficient. I thought long and hard about the roof A/C like the RV's but didn't want to give up my wing and the extra m.p.g. that it gives me pulling the reefer now that the flat bed has been parked. I have a friend that has a roof mounted A/C on a black Pete and he says it will freeze him out in Vegas in the summer so they do work good.

 

I found that the heat coming off the exhaust tube and coming in from the window that needed to be cracked open was just to much for the portable A/C to over come. It would keep it about 10 to 15 deg cooler than outside which is not bad when its only 80 or so but in the south in 100 plus not so good. I had a lexan window adapter I made and even tried to cover the exhaust tube with some insulation but still was not ideal for 90 degree plus days IMHO That's just what I found maybe others had better luck, I don't know. I do know that the 8000 BTU window A/C I recently got does alot better job for me.

 

I have thought about doing the same thing but am a little worried it might sound a little pingie with such a small about of noise and exhaust going though such a big system. The gen I have now is pretty quite and I make sure I park into the wind if I know I'm going to be running it and so far I haven't had any problems with exhaust fumes.

 

I'm squeezing my brains how to build an APU by myself to save money and a friend of mine just bought a TriPac second hand with 3000 $. That "pissed" me off how some people have such luck. We both start laughing about me envying him and his luck.
The unit is running so smooth and has no glitches at all.
That's what I call blind luck.

 

One thing that most people don't realize is that an a/c system is a heat pump and nothing more. You have to look at it like this... the system is pumping HEAT out of the cab/sleeper....NOT pumping cool air into these areas. At that point you quickly become aware of the importance of INSULATION!!!!!! Just check out the wall thickness of a reefer unit designed (not just capable) to haul subzero frozen. You will find that they are much more substantial compared to a standard refrigerated trailer. So, invest your time in insulating your truck, then you could run one of those portable units if thats what your shooting for.....Window shades...block the sun, prevent it from heating surfaces that you are trying to cool. To the poster with the wishlist...You may want to think about isolating your sleeper system from the truck system as this could make for a hot cab on hot days. This would be different with different trucks of course, but I run a classic and it would be a sweatbox without the sleeper a/c....even with the curtains pulled you would have great heat build-up in the rear that would be radiated into the cab space (dark blue paint...not cool friendly!).