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  • PV to water heating

    Hi, with some extra thinking I have been able to free up my Aux 1 on the Midnite controller to use my WizBJr. I see at the moment my battery bank goes into float about 10am so I'll set the aux 2 to operate the SSR just below float with a time delay to deal with the voltage drop caused by pulling 36 amps from the bank.
    I would be pleased for any comments and ideas on my design which I have attached.
    Cheers,Power system Ver 15.pdf

  • #2
    Originally posted by asdex View Post
    Hi, with some extra thinking I have been able to free up my Aux 1 on the Midnite controller to use my WizBJr. I see at the moment my battery bank goes into float about 10am so I'll set the aux 2 to operate the SSR just below float with a time delay to deal with the voltage drop caused by pulling 36 amps from the bank.
    I would be pleased for any comments and ideas on my design which I have attached.
    Cheers,[ATTACH]7978[/ATTACH]
    I am not sure how a time delay will help the system deal properly with the reduction in battery terminal voltage when the heating load is turned on.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

    Comment


    • #3
      Originally posted by inetdog View Post
      I am not sure how a time delay will help the system deal properly with the reduction in battery terminal voltage when the heating load is turned on.
      The Chassic has a control for Aux 1;
      It looks like the time delay can be set for at least an hour I read but a few minutes would be fine for what I'm doing.


      Waste Not Hi
      This mode will turn Aux 1 on when the Classic gets within a certain range of the voltage set points for
      each charging stage (V High) and turn Aux 1 off when it gets to a low set point (V Low). These set points
      are user adjustable and will allow the Absorb, Float and EQ timers to continue to run. You will adjust
      these set points to negative numbers and the numbers are an offset from the voltage set point. For example
      a -0.2 would turn Aux 1 on 2 tenths of a volt below your set points. This mode will allow you maximum
      diversion while maintaining your 3 stage charging. It also allows you to set a delay time in seconds the
      Classic will wait before turning Aux 1 on after reaching the V High set point. It also allows you to set a
      hold time in seconds the Classic will wait before turning Aux 1 off after reaching the V Low set point.

      Comment


      • #4
        Originally posted by asdex View Post
        The Chassic has a control for Aux 1;
        It looks like the time delay can be set for at least an hour I read but a few minutes would be fine for what I'm doing.


        Waste Not Hi
        This mode will turn Aux 1 on when the Classic gets within a certain range of the voltage set points for
        each charging stage (V High) and turn Aux 1 off when it gets to a low set point (V Low). These set points
        are user adjustable and will allow the Absorb, Float and EQ timers to continue to run. You will adjust
        these set points to negative numbers and the numbers are an offset from the voltage set point. For example
        a -0.2 would turn Aux 1 on 2 tenths of a volt below your set points. This mode will allow you maximum
        diversion while maintaining your 3 stage charging. It also allows you to set a delay time in seconds the
        Classic will wait before turning Aux 1 on after reaching the V High set point. It also allows you to set a
        hold time in seconds the Classic will wait before turning Aux 1 off after reaching the V Low set point.
        I still do not see any purpose for the time delay (other than perhaps to accommodate the starting surge of a motor such as in a heat pump DHW supply. But that will not apply to a resistive water heater.)
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

        Comment


        • #5
          Originally posted by inetdog View Post
          I still do not see any purpose for the time delay (other than perhaps to accommodate the starting surge of a motor such as in a heat pump DHW supply. But that will not apply to a resistive water heater.)
          Ok thanks, I'll be hooking it up in a couple of weeks so will see what happens.
          Cheers,

          Comment


          • #6
            Is your wind generator unregulated into the battery bank?
            1150W, Midnite Classic 200, Cotek PSW, 8 T-605s

            Comment


            • #7
              Originally posted by thastinger View Post
              Is your wind generator unregulated into the battery bank?
              Yes it is.
              The bank will dump to either the hot water element or the wind generator resistor if the voltage becomes too high.
              Default is the resistor if the relay coil happens to burn out and the resistor is from the normally closed contact. Via the SSR of course.
              Cheers,
              Last edited by asdex; 10-28-2015, 04:02 PM. Reason: spelling mistake

              Comment


              • #8
                solar water heating

                This is exactly what I'm trying to do with my system. I would really like to hear more about how this works for you. I have a 3000 watt 48 volt system. I have bought the SSR and a 48 volt 1000 watt heating element. I was told you have to hook the wbjr. to the aux2 only. Am I understanding that you hooked it to your aux1? I presently don't have the wbjr. because I want to use the aux2 for this purpose, was I told wrong? Your first post mentions aux2 and your second your talking about aux1 time delays. I'm confused...but that's nothing new.

                Comment


                • #9
                  Originally posted by mb4859 View Post
                  This is exactly what I'm trying to do with my system. I would really like to hear more about how this works for you. I have a 3000 watt 48 volt system. I have bought the SSR and a 48 volt 1000 watt heating element. I was told you have to hook the wbjr. to the aux2 only. Am I understanding that you hooked it to your aux1? I presently don't have the wbjr. because I want to use the aux2 for this purpose, was I told wrong? Your first post mentions aux2 and your second your talking about aux1 time delays. I'm confused...but that's nothing new.
                  Hi, I have just got my system running now. The water heating element (1000w@24v) runs from a SSR which is controller by a 24volt relay. This relay is turned on from Aux 1 when the SOC is 99% and off at 98%. I'm going to change that to Waste Not Hi function. I used the relay rather than control the SSR directly from Aux 1 as when the water gets hot and the thermostat open, it drops the relay off and the normally closed contact will operate another SSR to dump the battery bank to a dump resister. This is for when I have my wind generator connected up.
                  So far the system is working well. At about 10am the batteries float and power goes to the hot water. The element draws 26 amps so even with cloud, the PV/charge controller system is supplying that easily.
                  I am setting up some pictures on Google Photos but this is an ongoing thing as I'm having trouble getting them to be seen by everyone. You can Google "Gactrx Online" photos. I'll add more soon plus my circuit diagram. I use Aux for my WzBJr.
                  Cheers,

                  Comment


                  • #10
                    if your heater thermostat is switching off, you are going to have a problem when you add the wind gen, you will be relying on the load bank then.
                    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                    solar: http://tinyurl.com/LMR-Solar
                    gen: http://tinyurl.com/LMR-Lister

                    Comment


                    • #11
                      Originally posted by Mike90250 View Post
                      if your heater thermostat is switching off, you are going to have a problem when you add the wind gen, you will be relying on the load bank then.
                      Yes that's quite normal for a wind generator. It can't be disconnected as it will overspeed. It needs to be either diverted to a load resistor or the overcurrent going to the batteries drawn off. The load resistor came with the wind generator so is sized correctly.In decided to attach the generator to the battery bank to keep the voltage at a steady 24 or so.
                      Cheers,

                      Comment


                      • #12
                        I got my system all wired up on aux 2 waste not hi. I am going to drain the water heater in the morning and install the 48 volt 1000 watt element in the bottom space of my water tank. I'll set the element on it to 150 degrees and the top one to 120 and see what happens. I'll let you know how mine works out.

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                        • #13
                          I have my system up and running with mixed results. I used the aux2 to turn on my SSR hooked up to my 48 volt 1000 watt water heater element in the bottom of my water heater. I could see the aux2 output cycling on and off but I would never stay on. I have it set at -0.2 volts on and when I was 1 volt over the set point it kept PW Modulating on and off, being off most of the time. I turned it on manually and it seemed to be working fine and not pulling down my voltage, but when I would turn it back to AUTO it would start pulsing on and off. I may have to try aux1 waste not Hi.

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                          • #14
                            As I have a WzBJr I decided to use Aux one for the water heating. It works fine and as it's either on or off I can see the performance better. I don't see the use of PWM Aux 2 has in this situation anyway. I tried SOC setting first and it worked well but I think I missed out on quite a bit of water heating potential. I switched to Waste Not Hi but haven't played with the voltage settings much yet and I wanted to get the monitoring app going first. I'll do some fine turning this coming weekend. I also have a Amp Hr meter which I'll put in the water heating circuit to see how things are going.
                            Cheers

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                            • #15
                              I also have Midnite Classic. I tried the PWM diversion but could not get it work reliably. I put in the WBJr and configured the Aux 1 waste not Hi as follows:
                              VLow = -.8
                              VHi = -.3
                              Delay = 450 sec
                              hold = 25 sec

                              So what happens? When the voltage gets within -.V of absorb voltage the delay time starts. The controller goes to absorb. After 450 sec the relay closes. If the voltage drops more to more than -.8 V below absorb the hold timer starts. It the voltage is not above -.8 V when the hold timer times out the relay opens and the delay timer starts again. I found this logic worked pretty well for me. The size of your element is important because if it is too big you will never divert consistently or too small you will not get as much power as you might. An element size around 1/2 or less of your array size should work ok. Depending on the time of year the Aux 1 may try 3 or 4 times before there is enough power available to run your diversion load.If your panel tilt is set for max power in the winter you will be able to support a larger load for a shorter period of time in the winter than the summer. In the summer it will take more tries to divert with the same size load as winter.

                              This worked for me but I could see there was still more power to be had. Also sun - cloud - sun days meant the aux 1 spent most of its time in delay. Consider checking out the Midnite Forum - Arduino. PID PWM diversion gets you every watt of power to had automatically with the batteries within .1V of setpoints.

                              Will

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