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  1. #40
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    Feb 2019
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    Thread Starter
    Quote Originally Posted by Core_d View Post
    Cant measure air temp with an ir....


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    Thought I was measuring the outlet fitting on the condenser and comparing that to ambient.

  2. #41
    Join Date
    Dec 2012
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    columbus, OH
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    Quote Originally Posted by parish8 View Post
    Thought I was measuring the outlet fitting on the condenser and comparing that to ambient.
    That is true, the ambient air temp going into the coil. Get as accurate a measurement as you can on both. Probably atleast 6” away from the coil is best for both measurements.


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  3. #42
    Join Date
    Jul 2002
    Location
    Chariton, Iowa
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    OK, parish, please if you are going to do this:

    LEARN, LEARN, LEARN. Learn about HVAC and MVAC theory of operation, terminology, and history until you can pass the prior years versions of the EPA section 608 (all 3 types) and 609 practice tests with a closed book, then keep learning even more. Bonus points if you get your 608 universal certification and become a pro member on this very site.

    Don't know what a POA (pilot operated absolute pressure) valve is? LEARN Hint: It has the same function as an ORIT (opens on rise of inlet) or EPR (evaporator pressure regulator) valve.

    You said it is a GM variable displacement compressor, that means it is either the V5, V7, or CVC. These have a control valve that reduces the stroke by sending discharge pressure to the crankcase to prevent the pistons from reaching bottom dead center, which is possible because the angle pivot of the swash plate is spring loaded so the pistons are directly forced up but are only pulled back by said spring. The control valve responds to the suction pressure. Hint 2: variable displacement compressors replaced the POA/ORIT/EPR valve.

    Because of this your suction pressure and hence saturation temperature can never go lower than the control valve set point.

    Some CVC models had a PWM solenoid instead of the control valve so that the PCM can control the stroke and thus suction pressure instead.

    If you really want to go colder you are going to have to use a compressor with that solenoid and a standalone controller to operate it, or switch to a fixed displacement compressor.

    Second, R134a refrigerant which was a Suva not a Freon until Chemours bought DuPont, LOVES parallel flow heat exchangers. You want as much parallel as you can get NOT series. This is why parallel flow condensers replaced serial flow tube and fin and serpentine types.

    Use a liquid receiver, or better yet use condensers that have them and a subcooling section built in so that you have 2.



    Use a real TXV not an automotive style H block and definitely not a fixed orifice.

    This sounds like a fun project, have at it and let us know how it goes.
    To get the degree symbol ° on Windows hold down the Alt key and type 0176 or 248 on the keyboard number pad. It is also available via the character map, and on Windows 8.1 devices with a touchscreen via the on screen keyboard.

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  4. #43
    Join Date
    Jul 2002
    Location
    Chariton, Iowa
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    Oh, and you can't use an IR thermometer on shiny metal, the emissivity is wrong as it reflects surrounding IR instead of emitting its own. you have to at the very least aim the thermometer at a sticker applied to the metal, preferably a matte black one.

    A clamp on thermocouple probe is easier.

  5. #44
    Join Date
    Dec 2012
    Location
    columbus, OH
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    I believe section 609 is the epa cert you want for automotive ac. It would be better if you got a pro status here and had this thread moved. Im sure the mods are more lenient giving the fact its automotive ac but not sure how far this thread can go. You already have enough posts and I believe a section 609 can be had on googler pretty cheap.

    I was going to spare you the rant about IR Thermometers but its true they can often be inaccurate. A k-type thermocouple would really come in handy on this project. Im sure you can get it also pretty cheap on googler.

    Let us know...


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  6. #45
    Join Date
    Feb 2019
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    16
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    Thread Starter
    Quote Originally Posted by danielthechskid View Post
    OK, parish, please if you are going to do this:

    LEARN, LEARN, LEARN. Learn about HVAC and MVAC theory of operation, terminology, and history until you can pass the prior years versions of the EPA section 608 (all 3 types) and 609 practice tests with a closed book, then keep learning even more. Bonus points if you get your 608 universal certification and become a pro member on this very site.

    Don't know what a POA (pilot operated absolute pressure) valve is? LEARN Hint: It has the same function as an ORIT (opens on rise of inlet) or EPR (evaporator pressure regulator) valve.

    You said it is a GM variable displacement compressor, that means it is either the V5, V7, or CVC. These have a control valve that reduces the stroke by sending discharge pressure to the crankcase to prevent the pistons from reaching bottom dead center, which is possible because the angle pivot of the swash plate is spring loaded so the pistons are directly forced up but are only pulled back by said spring. The control valve responds to the suction pressure. Hint 2: variable displacement compressors replaced the POA/ORIT/EPR valve.

    Because of this your suction pressure and hence saturation temperature can never go lower than the control valve set point.

    Some CVC models had a PWM solenoid instead of the control valve so that the PCM can control the stroke and thus suction pressure instead.

    If you really want to go colder you are going to have to use a compressor with that solenoid and a standalone controller to operate it, or switch to a fixed displacement compressor.

    Second, R134a refrigerant which was a Suva not a Freon until Chemours bought DuPont, LOVES parallel flow heat exchangers. You want as much parallel as you can get NOT series. This is why parallel flow condensers replaced serial flow tube and fin and serpentine types.

    Use a liquid receiver, or better yet use condensers that have them and a subcooling section built in so that you have 2.



    Use a real TXV not an automotive style H block and definitely not a fixed orifice.

    This sounds like a fun project, have at it and let us know how it goes.
    mmmm, I am not going to do any of that(the becoming an hvac expert part). if that is what is required to improve on this system I will run it as is and work on perfecting the car in other ways.

    I will work on getting an accurate temp on the condenser outlet and of the air entering the grill of the car. if there is a large difference then I will try running water over the condenser to get that temp down and see if it has an effect of antifreeze temp. if that gets me the desired results then I will attempt to add more condenser.

    I appreciate all the help. I now have a plan.

  7. Likes Core_d liked this post
  8. #46
    Join Date
    Dec 2012
    Location
    columbus, OH
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    Post how it works for us...


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  9. #47
    Join Date
    Dec 2012
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    columbus, OH
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    Is this man out there somewhere 8degrees off and perfectly happy? None the less i think my “accurate temperature” speech may have done a little good;”:-)

    Poor soul.


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