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Author Topic: Frequency shift control of diversion loads  (Read 7810 times)
heatherhopper
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« Reply #30 on: June 04, 2018, 12:06:34 PM »

Tinbum - sorry to keep pestering you on this subject but I am trying to work how to add complimentary diversion to what I already have. Although our set-ups are very different in size, inputs etc (and of course the major one of grid connection) there are some common elements and I have no ambition to re-invent the wheel.

I assume from an earlier post your heatpumps are dedicated to the pool? I assume (and I have no experience with heat pumps) that their output is something up to 60c max. Do you have some idea of the diversion values (kWhs) they are adding in? Heat pump efficiency is attractive to me but it is temperature limited which reduces the potential and I am weighing up the pros and cons vs a small electric flow boiler.

You have a large buffer tank - is this exclusively fed by the boiler or do you also have diversion to that? I have some coil fed capacity in my buffer tank (thermal store, call it what you will) that I wish to divert to without cutting new pockets.

Is your Arduino control all hard wired or do you use RF or WI-FI at all? Although my primary diversions are hard wired, secondaries and any future outlets are wide spread and I am leaning towards WI-FI.

I have yet to try anything too ambitious with Arduino sketches but at least I'm over the initial befuddled state.
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Off grid AC coupled, 6kW Proven, 2.8kW PV, SMA SI/SB/WB Inverters, 4x576ah Rolls batteries @ 24v, 25kW Biomass Boiler, Wood Stoves, Spring/Well water. Sorry planet - I did try.
Tinbum
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« Reply #31 on: June 06, 2018, 09:50:54 AM »

I assume from an earlier post your heatpumps are dedicated to the pool? I assume (and I have no experience with heat pumps) that their output is something up to 60c max. Do you have some idea of the diversion values (kWhs) they are adding in? Heat pump efficiency is attractive to me but it is temperature limited which reduces the potential and I am weighing up the pros and cons vs a small electric flow boiler.

You have a large buffer tank - is this exclusively fed by the boiler or do you also have diversion to that? I have some coil fed capacity in my buffer tank (thermal store, call it what you will) that I wish to divert to without cutting new pockets.

Is your Arduino control all hard wired or do you use RF or WI-FI at all? Although my primary diversions are hard wired, secondaries and any future outlets are wide spread and I am leaning towards WI-FI.

Yes the heat pumps are for the the moment but they are to be used for the house as well in the winter when I get my finger out and get the house extension and alterations done. I'm not sure on values diverted but it a good lot. The idea of using two heat pumps is so that the system can use all available power so if there's not a lot the smaller pump comes on and then if this surplus increases the larger one come on and the small go off. Ideally an inverter type would be best but I've not seen any come up secondhand at a good price. I'm also planning on installing a GSHP to be used when the air temp is low in the winter.

The buffer tank is to be fed by the heat pumps as well. I'm going to replace most of my radiators with underfloor heating in the the refurb but if the heat pumps can supply the base load to the buffer tank to keep the water at say 40 degrees then this will reduce the load the boiler has to supply. I also have a 3 phase 9kw element in the tank so that can be switched in 3kw increments. Yes heat pumps are better at lower temps but they can supply a lot of energy.

All mine is wired with cat 6 cable. It would be possible to do it with wifi (or Bluetooth or RF) but wired is much simpler and I would think more reliable. You could use off the shelf stuff (www.denkovi.com) for that rather than writing it into the Arduino sketch. I'm learning all this Arduino stuff myself- the only computer programing I learnt was a little bit of BASIC.
« Last Edit: June 06, 2018, 09:57:11 AM by Tinbum » Logged

85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
heatherhopper
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« Reply #32 on: June 07, 2018, 11:45:09 AM »

Hmmm - small heat pump or not? Quite apart from the prices (which are still way too steep particularly for just diversion) my problems with them are the obvious off-grid limitations and the low delivery temperatures. Our system is based on buffer temperatures of up to 95c and and short run replenishment from the boiler (plus some primary diversion immersion). Once down to 60c buffer temperatures are inadequate for all the different outlets. Running a heat pump round the bottom coil would displace boiler fuel when the buffer is stratified but it would be redundant once the boiler is fired up, which is most days 6-8 months of the year. Could pipe it up as an alternative source for the underfloor part of our heating but this does not fit my needs of a secondary diversion.
More pondering required.

Certainly hard wired is best and my primary diversions will remain as such and standalone. Running cable to less well placed locations is a pain though. I have had a Wi-Fi relay on test for a while now with no hiccups so this will probably be the route I take. I don't trust Bluetooth and have found RF a bit finicky. Initially I think I will continue to just use the Arduino for simple serial output to the central data broker and process responses from there. Doesn't really utilise the potential I know but if I add AC frequency measurement to it's DC voltage measurement it will give me a nearly complete data set to work with and will have been worth the minimal cost.
I continue to plod forward from complete ignorance to miniscule understanding regards this programming lark.
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Off grid AC coupled, 6kW Proven, 2.8kW PV, SMA SI/SB/WB Inverters, 4x576ah Rolls batteries @ 24v, 25kW Biomass Boiler, Wood Stoves, Spring/Well water. Sorry planet - I did try.
heatherhopper
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« Reply #33 on: July 19, 2018, 11:12:16 AM »

Tinbum
When setting up your frequency measurement with the Arduino have you ever tried the simple pulse counting method? I have a small discrepancy (0.29 or thereabouts) between the frequency values returned by the Arduino and the SI. The difference is consistent throughout the range.
I have just applied a software offset to the Arduino value in later processing to align the two so it is not really a problem for my needs. All this programming stuff is still largely gibberish to me so it is probably be an error in the sketch. Multimeter has chosen this moment to expire so I can't poke around the actual grid and check the SI value. Any similar experience?
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Off grid AC coupled, 6kW Proven, 2.8kW PV, SMA SI/SB/WB Inverters, 4x576ah Rolls batteries @ 24v, 25kW Biomass Boiler, Wood Stoves, Spring/Well water. Sorry planet - I did try.
Tinbum
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« Reply #34 on: July 19, 2018, 11:39:33 AM »

I'm doing this and you will see i have a calibration value in there. This varies from Arduino to Arduino.

void loop()
{
  if (FreqMeasure.available())
  {
    // average several reading together
    sum = sum + FreqMeasure.read();
    count = count + 1;

    if (timer0 > interval0)
    {
      if (x == 1) // to ignore first result
      {
        timer0 -= interval0; //reset the timer
        float frequency = FreqMeasure.countToFrequency(sum / count);
        frequency = frequency - 0.055; //calibration
        z = z + 1;

        if (z == 5) // to reduce display changes
        {
          if (frequency > 40 && frequency < 60)
          {
            lcd.setCursor(0, 1); //Start at character 10 on line 2
            lcd.print("FREQUENCY");
            lcd.setCursor(10, 1); //Start at character 16 on line 2
            lcd.print(frequency);
          }
        }

it's based on https://www.pjrc.com/teensy/td_libs_FreqMeasure.html but i don't use his circuit. On my mega I simply have the output of a bell transformer connected to ground and pin 49 with a resistor in series.
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85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
heatherhopper
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« Reply #35 on: July 19, 2018, 02:18:16 PM »

I went with a diode/resistor/optocoupler circuit and a very simple pulse counting sketch combined with battery voltage - all just measurement at the moment as I can control from elsewhere and all very stable for a while now. I did see that teensy example but the brain cell started to wobble so I went looking for something more staightforward (to my way of thinking anyway). I will have to add the calibration into the sketch if I start using the thing for direct control purposes.

Relieved to know that a calibration is generally required but the number I have is relatively quite large and surprised me. Maybe I need some filltering or something. How did you arrive at your calibration number?

I think I will await the arrival of a new multimeter and investigate from there.
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Off grid AC coupled, 6kW Proven, 2.8kW PV, SMA SI/SB/WB Inverters, 4x576ah Rolls batteries @ 24v, 25kW Biomass Boiler, Wood Stoves, Spring/Well water. Sorry planet - I did try.
Tinbum
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« Reply #36 on: July 19, 2018, 06:54:00 PM »

For the calibration I just compared the value calculated to that shown on a G59 relay I have. The value is small but does change depending on the Arduino used. I guess its due to the crystals used in them and their tolerances.

Very very occasionally I get a rogue value hence the line;

if (frequency > 40 && frequency < 60)

and i always discard the first value as that is always way out;

if (x == 1) // to ignore first result

I tried a few different circuits for measuring the frequency and found them all very similar in result so went with the easiest.


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85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
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