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Air Conditioning & APU's

Discussion in 'Questions To Truckers From The General Public' started by tumblin dice, Jun 26, 2014.

  1. Jun 26, 2014 #1
    tumblin dice

    tumblin dice Light Load Member

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    Apr 18, 2014
    Jacksonville, FL
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    On a car the A/C compressor is driven by the serpentine belt. The condenser is mounted in front of the radiator and the evaporator is mounted under the dash in the venting system. I presume that on a Class 8 truck the A/C works in the same manner. I read about APU's used to power the A/C in the truck when parked. I don't understand how the APU can drive the A/C since the compressor is belt driven by the engine. Is there an auxiliary A/C for the sleeper that is driven by the APU? Is it a 110 VAC unit? I've never had an opportunity to inspect a modern day class 8 rig. Can anyone enlighten me?
     
    tumblin dice, Jun 26, 2014
    tumblin dice, Jun 26, 2014
    #1
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  3. Jun 26, 2014 #2
    STexan

    STexan Road Train Member

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    Longview, TX
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    An APU has it own engine that runs an alternator as well as it's own condenser, evaporator, compressor, dryer, etc. It is "plumbed" into the existing sleeper vent duct work. Typically they do not provide cooled air to the cab area vent system, only to the sleeper area. They can only run when the truck engine is off.
     
    STexan, Jun 26, 2014
    STexan, Jun 26, 2014
    #2
    tumblin dice Thanks this.
  4. Jun 26, 2014 #3
    Chris50

    Chris50 Medium Load Member

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    Jun 21, 2010
    Florida
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    A tripac APU can run while the truck engine is on but i dont think its recommended.. Ive forgotten to cut my apu off a few times and ran the truck for a few minutes.. There is a setting in the control module `EPS` for external power source you can switch to `no` and it wont cut off when you turn the ignition on.
     
    Chris50, Jun 26, 2014
    Chris50, Jun 26, 2014
    #3
  5. Jun 26, 2014 #4
    STexan

    STexan Road Train Member

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    Longview, TX
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    I suspected there probably was a setting to allow it to run manually, apart from truck engine state, but our tri-pacs are all set to shut off on key-on, then will resume in [battery maintenance] standby mode on key-off (you will then have to turn on ac or heat manually)
     
    STexan, Jun 26, 2014
    STexan, Jun 26, 2014
    #4
  7. Jul 4, 2014 #5
    PackRatTDI

    PackRatTDI Licensed to Ill

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    El Chuco, Tejas
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    Trivia time. Some of the GMC buses greyhound and Trailways used had a separate small engine to run the air conditioning compressor. The engineers felt that the 238 Jimmy engine (6-71) lacked the power to run the large capacity compressor (a bus ac compressor is a behemoth!). Odd thing though, they used a small gasoline engine instead of diesel. Meaning the driver had to monitor two fuel levels.

    This lasted until the end of the PD3104 coach model. When the PD3106 was released in the mid 60s, it was powered by the "318" (8V71) which the engineers decided would be able to drive the ac system and the separate engine was phased out.
     
    PackRatTDI, Jul 4, 2014
    PackRatTDI, Jul 4, 2014
    #5
  8. Jul 4, 2014 #6
    tumblin dice

    tumblin dice Light Load Member

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    Apr 18, 2014
    Jacksonville, FL
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    That's interesting indeed.....had to smile at the mention of the old 238!
     
    tumblin dice, Jul 4, 2014
    tumblin dice, Jul 4, 2014
    #6
  9. Jul 4, 2014 #7
    Studebaker Hawk

    Studebaker Hawk Road Train Member

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    NW Indiana
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    Many drivers have an APU that is a generator only, powering a self contained 120v air conditioner. You even see them sticking out the passenger window, one of those $120 Haier units from home depot. Very sophisticated.
     
    Studebaker Hawk, Jul 4, 2014
    Studebaker Hawk, Jul 4, 2014
    #7
  10. Jul 5, 2014 #8
    tumblin dice

    tumblin dice Light Load Member

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    Apr 18, 2014
    Jacksonville, FL
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    Yeah I saw an O/O who cut a hole in the back of his sleeper and had a home window unit mounted in there! Hillbilly Engineering at it's finest!
     
    tumblin dice, Jul 5, 2014
    tumblin dice, Jul 5, 2014
    #8
  11. Jul 6, 2014 #9
    browndawg

    browndawg Medium Load Member

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    Dec 20, 2013
    Rock Island, IL
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    i don't know about everyone else but that darn fan on the back of my sleeper is annoying kicking on and off all the time
     
    browndawg, Jul 6, 2014
    browndawg, Jul 6, 2014
    #9
  12. Aug 18, 2014 #10
    Excorcist1

    Excorcist1 Light Load Member

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    Jan 11, 2012
    Chestertown, MD
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    I had the fan on the back of a frtl. but not with the unit installed in the Pete. I'm trying to figure out what type of unit I actually have.
     
    Excorcist1, Aug 18, 2014
    Excorcist1, Aug 18, 2014
    #10
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