APU question

Discussion in 'Questions From New Drivers' started by Sisqscott, Jul 16, 2019.

  1. Sisqscott

    Sisqscott Bobtail Member

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    Hello all....I have a couple of questions about APU's. Is an APU essentially a diesel generator that charges batteries to power an inverter?
     
  2. Moose1958

    Moose1958 Road Train Member

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    An APU is a small Diesel Engine that powers an AC system and an alternator that provides power to the batteries and the cab.
     
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  3. stwik

    stwik Road Train Member

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  4. mhyn

    mhyn Road Train Member

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    Carrier APU- Diesel GENERATOR that gives 120v power and run HVAC system (located under bed). It has alternator too for battery charging.
    Tripac APU- Diesel ENGINE that runs A/C compressor and alternator. Alternator charges batteries and supply power to inverter. Inverter makes 120V. Also it has separate heater for cab heating(diesel fired).
     
    Last edited: Jul 16, 2019
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  5. I glide 47

    I glide 47 Road Train Member

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    Air conditioning !, heat for winter 110 power for whatever also makes your bed ,
     
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  6. Sisqscott

    Sisqscott Bobtail Member

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    Thanks for the replies!
    So the APU powers a separate A/C system from the engine powered one?
    Does it have its own battery bank that it charges?
     
  7. mitrucker

    mitrucker Road Train Member

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    No. It charges the truck batteries.
     
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  8. Moose1958

    Moose1958 Road Train Member

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    I have not driven a Truck since Dec of 2012. Also, I do not wish to engage in a flame tossing contest. I am just going to ask a question. I have seen some comments in this thread that seem to say the APU is providing regular household voltages. Is this something new? I actually was under the impression that an APU only provided power to the truck's batteries, and it was the batteries that powered the truck's electrical system (inverter) when the main engine was off. If my understanding of this is wrong please correct me.
     
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  9. lovesthedrive

    lovesthedrive Is here to help

    It really depends on what you get for an APU. There are some that not only keep the batteries topped off. Yet they also run the air conditioner in the summer as well as the bunk heater for colder winter. APU's are not just diesel. APU's are usually for what ever fuel the truck runs on. Average horse power on a APU is about seven horse power. The idea is that it is only a pint an hour to run a APU over the engine at one gallon of fuel per hour.
     
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  10. Moose1958

    Moose1958 Road Train Member

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    Yes, I know about the 2nd AC system. However, I was not aware the bunk heater was part of the APU I had several trucks with APU's and I never remember any that put out heat. Only that the APU kept the batteries charged as the trucks electrical system kept the air circulating. I also understand that an APU will be fueled by whatever fuel the vehicle's main engine uses, that is just common sense.

    I was only asking about the comment's that seem to leave the impression the APU is putting out regular House voltages and current. Because if today's APU's are doing this it is new to me.
     
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