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  1. #27
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    Quote Originally Posted by shamooooot View Post
    that's very good explanation, it actually gave me the idea of what if we use the temperature difference to tell the controller that we are in heating or in cooling mode?:

    If Tin<Tout, then follow program cool
    If Tin>Tout, then follow program heat

    Program Cool =
    If Tout - Tin=10+, then open EEV
    If Tout - Tin=10-, then close EEV

    Program Heat =
    If Tin - Tout=10+, then open EEV
    If Tin - Tout=10-, then close EEV
    There probably nothing wrong with looking at the difference. It would save an input if you needed it for something else. The command would be a little delayed while if figured out what is happening before it can start to react so that may become problematic, but I’m not convinced the delay would be significant enough to cause issues. I always prefer to reduce the thinking required by the computer and run a hard wire directly. There’s no confusion, it has a clear on or off command, and it can respond immediately right from the very beginning. I’m not sure what the refresh rate would be on your program though so maybe it’s really not an issue at all.

    I made a quick sketch ... sigh, I should label the sensors according to how we’ve previously discussed... I’ll draw a new one up when I get the chance.


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  3. #28
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    So if you were to use 4 thermistors then you would use T1, T2, T3, T4

    If you use only three thermistors then you would need T2, T4, T5


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  5. #29
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    Quote Originally Posted by thatguy View Post


    So if you were to use 4 thermistors then you would use T1, T2, T3, T4

    If you use only three thermistors then you would need T2, T4, T5


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    Thank you for all your efforts!

    Can you walk me through your sketch?, I am a bit confused with it.

    The outdoor unit has its own system and its own expansion valve. Is it safe to say that I can use the T1out and the T2in only, as my inputs ?

  6. #30
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    Electronic Expansion Valves

    Quote Originally Posted by shamooooot View Post
    Thank you for all your efforts!

    Can you walk me through your sketch?, I am a bit confused with it.

    The outdoor unit has its own system and its own expansion valve. Is it safe to say that I can use the T1out and the T2in only, as my inputs ?
    Does this help?



    I drew it in heating mode because I mentioned previously in my example that Reversing valve input would be heat when Unenergized.

    Simply swap the hot gas out and the suction in through the reversing valve to change to cooling mode. I had drawn the little slider inside of it to indicate the path of the suction gas on the first picture. That slider is true to life as to how they work. Slide that over to connect the middle and right pipes (instead of the middle and left pipes) and you will be in cooling mode.

    You will see that your thermistor is not in the right spot to measure superheat when you switch to cooling mode so if you want both heat and cooling then you need to add at least one more thermistor. So you can monitor the refrigerant temperature at the outlet of the EEV after the refrigerant changes direction.

    Let me know if you still have questions.


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  8. #31
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    We install walk in freezer and coolers that use a 5V DC EEV, the EEV will open proportionally to the strength of the signal between 0 and 5V, if they all are like that then an Arduino would be perfect for them
    https://www.heatcraftrpd.com/QRC/res/pdf/H-IM-QRC.pdf

    thats the link to the manual for the control module, should help you get an understanding of how to program the arduino at least on the cooling side, it has part numbers for the EEVs/sensors towards the end you could probably find a manual on those or something similar but for heat pumps that will help you get a base for what parameters you are going to want to use

  9. #32
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    Quote Originally Posted by KittySwampAss View Post
    We install walk in freezer and coolers that use a 5V DC EEV, the EEV will open proportionally to the strength of the signal between 0 and 5V, if they all are like that then an Arduino would be perfect for them
    https://www.heatcraftrpd.com/QRC/res/pdf/H-IM-QRC.pdf

    thats the link to the manual for the control module, should help you get an understanding of how to program the arduino at least on the cooling side, it has part numbers for the EEVs/sensors towards the end you could probably find a manual on those or something similar but for heat pumps that will help you get a base for what parameters you are going to want to use
    Hmm interesting so there's no stepper motor power head on those eev's? Do you have a pic of the eev?

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  10. #33
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    Quote Originally Posted by JayMan7 View Post
    Hmm interesting so there's no stepper motor power head on those eev's? Do you have a pic of the eev?

    Sent from my SM-G960U using Tapatalk
    It sounds to me like it is a control board that has a 0-5v DC signal input from the pressure transducer , the control board converts that to a equivalent number of steps output to the EEV.

    “The expansion valve position can be monitored from the LED display pressing the “MONITOR” button and scrolling to ESP. This will indicate the number of steps the valve is open.

    This can also be checked by using the EXV test pins on the board. This is indicated by a 0 to 5 volts DC signal. At 0 volts the valve is closed and at 5 volts the valve is fully open. At values between 0 and 5 volts, the valve will be opened proportionately.”

    It says it’s a “bipolar motor with two windings” controlling the EEV.... sounds like a stepper to me.



    I haven’t read the whole thing, just skimmed some parts of the manual hat looked like it would include this info, so I may have missed something here but looks like a normal stepper to me, however it also looks fairly easily replicated with some programming and an Arduino


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  12. #34
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    True 0-5VDC would make more sense as a signal circuit and not as the actual driver of the eev

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