Fuel for Thought

APU Success

We have gone from Auxiliary Power to New APU Pt. 1 and New Apu Pt. 2, and now we move on to the final blog in the installation series.

Wiring. Use the appropriate size wire for the task at hand. For my needs, I used 12/3 wire. It is thicker than the average extension cord (most are 16/3 or 14/3) and 10/3 wire seemed to be overkill for this project. This wire can be found at most any Lowe’s or Home depot on spools. Just have them cut the length you need.

If you use a Thermoking or Carrier APU, it will usually be installed to also charge the truck batteries. An easy addition to this setup is to add a converter. An inverter takes 12 volt and changes it into 120 volt current. A converter does the opposite, it takes 120 volt current and converts it to 12 volt. This then connects to the truck for charging the batteries. Some other generators, usually larger ones, will have a 12 volt outlet on them that can be used for this purpose. A converter will run anywhere from $130 - $200.

What about shore power? You can also add a transfer switch to automatically switch between generator and shore power. A 30 amp transfer switch can be had for as little as $70 - $80.

If you are not comfortable or knowledgeable with electrical connections, hire a professional to do the work. Once installed correctly, the generator will literally just plug into the system.

As noted in previous blogs, there have been some unaccounted for benefits of this type of truck APU. 

First, fuel. Yes, you will have to fill the gas tank as needed and it will be an extra trip to the front of the truck stop or a large gas station for tractor trailers, but straight trucks can easily gas up just about anywhere. Here’s the benefit, IFTA taxes. If you run your diesel generator from your truck fuel tanks, it reduces your IFTA mileage, which results in higher fuel taxes. This may not be a significant amount (depending on how much you use your diesel generator), but over time it can add up. Unless you have a separate fuel tank for your generator, you are using IFTA taxed fuel in your diesel generator. Suppose you put 5000 hours on a Carrier Comfort Pro. That is roughly 2000 gallons of fuel @ .4 gallons per hour. That is 2000 gallons of fuel the truck did not use, but IFTA taxes were paid on these gallons. 

Second, fuel cost. We all know how expensive diesel fuel is these days. Well, a gasoline generator uses less expensive fuel and uses less of it than a diesel generator. You will see fuel savings just on fuel cost per gallon.

Third, an inverter generator, like the GenMax that I chose to use, it can eliminate the need for a separate inverter. It produces clean power just like your inverters. 

Fourth, cost. This benefit, although not unforeseen, is definitely noteworthy. If you have priced new or used diesel APUs recently (if you can find one in stock), then you know you would spend in excess of $10,000 easily, more likely over $12,000 for a new one. This setup, even if you have to add a rooftop heat pump, mini split A/C, or under-bunk heat pump can still be had for a fraction of the cost. In the unlikely event that you had to do so, you could feasibly replace this entire setup 3 - 5 times before approaching the cost of a new diesel APU. More likely is the fact that you will only need to replace the generator after excessive run hours accumulate, but again the rest of the system is already in place and all you will have to do is replace the generator and plug it in.

If you have any questions regarding this setup, installation or improvements, feel free to contact me. I tried to cover all the basics, but if I missed any, please let me know.

Happiness lies in the joy of achievement and the thrill of creative effort. 

- Franklin D. Roosevelt

See you down the road,

Greg