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  1. #40
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    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
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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
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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.
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  4. #43
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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
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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
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    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
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    Post how it works for us...


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  9. #47
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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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  10. #48
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    Quote Originally Posted by danielthechskid View Post
    OK, parish, please if you are going to do this:

    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

    This sounds like a fun project, have at it and let us know how it goes.
    Sorry for the long delay. I finely got back to this project and the statements above actually make a little more sense to me. I do have lots to report and a few new questions. Sorry for the long post.

    I went with the pre made stage 2 kit from the heat exchanger people. I was considering my own so I could put the extra condensers where I wanted. This kit just stacks the extra condenser. The kit also came with some extra insulation and a larger suction line. In the end I don’t think that extra condenser is doing much for me.

    I got this kit all hooked up. The chiller set up really kicks ass getting the fluid chilled. It will cool 6 gallons of fluid from 72deg down to 30deg in just 15 minutes with the car at idle. This I am thrilled with.

    To get from 30deg to bottoming out at 26deg takes another 20-30min. Clearly by the time it gets down to 30deg it is approaching a limit of something. I think it is the lack of suction mentioned above. Here is some data and observations that I have.

    When the fluid is warm the outlet temp of the 1st condenser is about 10deg above ambient suggesting the 2nd condenser is helping. The high pressure is 110-130 and the low pressure is about 20psi.

    Once the fluid is down to below 30deg the outlet of the 1st condenser is ambient suggesting the 2nd condenser is doing nothing. Even the inlet to the 1st condenser isn’t very hot. The pressures are now 80-90psi high side and 16psi low side. Pressure with the car off is something like 67psi so that compressor isn’t being asked to do much.

    It seems to me like the lack of suction from this type of pump is going to stop me from getting much colder. It seems the extra condenser maybe got me a touch of faster recovery time but not any colder min temp.

    Is my thinking correct?

    I do have a question. Is there any reason the heat exchanger can’t be in the back of the car with longer freon lines? It is about 15lbs right at the nose of the car.

  11. #49
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    If you move the coil , be careful where you put it

    You need plenty of air flowing through it

    different parts of the vehicle have positive and negative air pressure

    Take a pick-up truck for instance .... it operates perfectly while driving down the highway ...UNTIL you add a snow plow

    Ive seen plenty of trucks overheat sitting on the side of the road

    Its crazy but that snow plow will block enough air to starve the radiator ... and the plow is 3 feet away

    But anyhow ... the air flow is probly different at the rear of a vehicle , especially since you have tons of metal ahead of it ....but you wont know until you try !
    Last edited by Snapperhead; 05-27-2020 at 06:33 AM.

  12. #50
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    Quote Originally Posted by Snapperhead View Post
    If you move the coil , be careful where you put it

    You need plenty of air flowing through it

    different parts of the vehicle have positive and negative air pressure

    Take a pick-up truck for instance .... it operates perfectly while driving down the highway ...UNTIL you add a snow plow

    Ive seen plenty of trucks overheat sitting on the side of the road

    Its crazy but that snow plow will block enough air to starve the radiator ... and the plow is 3 feet away

    But anyhow ... the air flow is probly different at the rear of a vehicle , especially since you have tons of metal ahead of it ....but you wont know until you try !
    I am talking about moving what I guess is the evaporator. The condenser would still be right at the front of the car. Right now it is all at the front of the car and the freon lines are very short. Is there any reason the freon lines couldn’t be 20’ long and snake under the car?

  13. #51
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    When I say snake I mean it will change elevations a couple of times. I am not sure if freon lines care about that.

  14. #52
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    Quote Originally Posted by parish8 View Post
    When I say snake I mean it will change elevations a couple of times. I am not sure if freon lines care about that.
    It depends on the type of refrigerant and oil in the systems. Some systems don’t like it while others don’t care so much.

    I can’t speak for automotive, they do things a little different from the rest of the industry, but with residential, commercial, and industrial, the lines are sized to maintain refrigerant velocity through the pipes to help with the return of oil to the compressor. With non automotive equipment we don’t typically care about elevation change until it exceeds 3 feet, but we also strive to produce a finished product where the suction line slopes towards the compressor and minimizes the snaking through spaces.


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