Building Reserve and Using KWH

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  • bcroe
    Solar Fanatic
    • Jan 2012
    • 5198

    Those DROK meters certainly are compact and economical, having integration over
    time (KWH) and frequency a bonus. They do draw power on the order of a watt, so
    the V leads need to be attached on the supply side of the current transformer to
    avoid becoming part of the readout. Before them I had wired this into 240VAC ckts.

    ENEmeter.png

    I expect to be using the frequency readout if I run the gen set. PF could be
    useful on big motors. Bruce Roe

    Comment

    • DanS26
      Solar Fanatic
      • Dec 2011
      • 970

      Here I use the DROKs to monitor my genset, note the frequency is the box on top. Very useful to monitor loads during an outage.

      There's a lot going on with this panel that a few readers may be interested in......

      It's a 10 position critical load panel that I modified to accept 12 positions
      An N1 switch was installed to exercise the generator under load without interrupting power to the house. See the red label.
      The item with the blue LED lights is a MidNite Solar SPD that protects the panel from high voltage surges that might emanate from a submersible pump.
      Below that is an SPD from Levitron which protects the main distribution panel.
      Next below is the DROK frequency meter.
      Next below is the DROK phase A and B load meters.

      Inside the panel are a low voltage monitor device that protects the switch mechanism from low voltage burnout and additional SPDs to protect the generator AC and DC control circuits.

      Finally the switch was wired using the Canadian code method for critical load panels. That method requires that all wiring for critical loads be removed from the main panel and routed through a junction box before landing in the critical loads panel. I went a step further and used a pass through block in the junction box rather than a mess of wire nuts.


      Monitoring.JPG

      IMG-173.jpg
      Last edited by DanS26; 12-08-2021, 12:11 PM.

      Comment

      • bcroe
        Solar Fanatic
        • Jan 2012
        • 5198

        The multiple string PV solar system here had a problem, here is my method to track
        down an array issue.

        This system is actually two complete 7.5KW inverter systems with identical panel
        arrays. On a clear midday with good sun, the outputs usually match very closely. It
        was noted, that the WEST system output was lagging the EAST system by several
        hundred watts.

        The ground mount array looked like this, all the strings operate at the same voltage
        since they are wired in parallel. Variations in power will be caused mostly by variations
        in string current. The first step was to use a clamp on DC ammeter to check the
        current of each string. This gives best results under strong sun, and STRING 6 was
        found to be lagging the others.

        StringsTest.jpg

        The normalized output of a solar cell looks like this, with about half a volt MPPT per
        cell today. These strings have 12 panels of 60 cells wired in series. With 720 cells
        in series the string MPPT total voltage is about 360V. With todays low sun and my
        poor, rather low winter elevation, the MPPT current was about 5.5A. With a series
        connection all cells in a string are forced to conduct the same current. Even with
        matched panels the precise MPPT current will vary slightly, but each cell will vary its
        voltage slightly to match the current of the others. This will normally stay pretty close
        to the broad power curve MPPT top. The problem comes when a sufficient reduction
        in voltage to match current, is far from the rated MPPT voltage. This fault condition
        might run the panel (or a portion of a panel) all the way down to zero volts without
        reaching a matching current. In that case a panel bypass diode will conduct to avoid
        much reverse voltage.

        PvMpp.png

        The shift in voltage is used here to find an under producing element. A voltmeter can
        detect the low voltage element, the rest of the string will raise its voltage to match the
        other strings, but in sliding up the voltage curve, the current (and the POWER) drop.

        My 12 panel strings looks like this, the big problem is actually connecting a voltmeter
        to the weather proof wiring. To narrow it down, I would like to measure the voltage
        across each quarter of the string, toward finding the under producer. The negative
        end is at ground potential here, so the frame can be a test point. 4 more test points
        are needed as indicated.

        StringTest.jpg

        I break apart the MC4s where indicated and insert a 3 way MC4 connector like this.
        The 3rd port will be a voltmeter access. But WAIT A MINUTE! This array can deliver
        enough power to cook 50 hot dogs at a time, and breaking any DC connection under
        load can cause awful, equipment damaging arcs. Leaving any conductors exposed
        to the weather can also cause serious damage.

        3wayMC4.JPG

        So here it must be PITCH BLACK to work on wiring, AC outlets at the array allow
        use of work lights. The 3rd port is not left exposed. An MC4 with no conducting
        metal is plugged in, its wire hole is plugged and the latches are ground off. The O
        ring will retain it briefly. Then wait for good noontime sun.

        Noon next day, the voltmeter reveals that three of the string sections accessed
        are running good voltage, the section nearest the POS output is low. Just making
        the measurements needs some special test leads. Long extension wires (no
        metal exposed) are connected to the voltmeter, to reach any point on the string.
        At the ends of each are both a male and a female MC4, because the 3 ways might
        have either. Again, the latches are ground off, so the plug may be removed and the
        voltmeter connected quickly without tools. The plug can be put on the unused
        voltmeter MC4. In general, MC4s are kept mated to avoid weathering.

        MC4TestPr.JPG


        Once the offending section is identified, the test points are moved into that area
        to resolve to an individual panel. WAIT FOR NIGHT AGAIN. The new locations
        are shown here, near the POS end.

        StrinSegTest.jpg

        Here is a pic of the offending section, the top 3 panels, with the test points
        already moved to bracket each one. The night work light is to the right, the
        cement mixer not involved.

        StringSegTst.JPG

        At this point one panel might stand out with way too little voltage under good sun.
        Weak sun is found to be inconclusive. HOWEVER, my situation was different. The
        first attempted fix was to replace (IN THE NIGHT) the center panel with my unused
        spare. Next day the center panel voltage was right where it should be, but those on
        either side were not good. These panels had previously been washed, which had
        no effect.

        A careful examination of the removed panel revealed a dark, rough, somewhat
        streaked surface. I remembered, for a time a pine branch had grown out above the
        3 panels, though not usually shadowing. The panels were coated with PINE SAP.
        Washing with soap did nothing, alcohol did not do it either. I took a straight blade
        from a utility knife and SCRAPED off a black powder. Fortunately the glass
        underneath was very smooth, so the blade slid smoothly across once cleaned. IN
        THE NIGHT I swapped it with the panel on the right as seen above.

        UtilitBld.JPG


        Next day, it was obvious, 2 of the 3 panels were at voltage. From the front, the
        remaining panel (now on the right) was dark, clearly affected. Sap can also be
        seen running down the edge of 2 original panels.

        3PanPineSap.JPG

        This panel was swapped with another scrapped clean panel, and all was well
        again. OK but have I removed any panel protective coating? Time will tell.
        NIGHT AGAIN, remove all the MC4 test access points.

        So why not wire test points in the day? First opening a working circuit could
        damage connectors or worse. MC4s are not so easy to separate, and slips
        could be fatal.

        Then why not open the fuse and test with no current flow? The panels need
        to be checked under load, near their MPPT point. Even a bad panel often looks
        good unloaded. Bruce Roe
        Last edited by bcroe; 12-25-2021, 11:01 PM.

        Comment

        • DanS26
          Solar Fanatic
          • Dec 2011
          • 970

          Bruce, I take a somewhat different approach when trying to find an underperforming panel. Our solar plants are very similar. As you know, I have 96 ground mount panels made up of 8 strings feeding two Fronius 7.5kW inverters. Because its a matched set any time one inverter is performing poorly I can eliminate 4 strings and concentrate on the remaining strings. With my trusty DC Amp meter I can now identify the problem string of 12 panels.

          Now here is where we differ on approach to identifying the problem panel(s).........

          1. I shut down the AC feed to the lower performing inverter. That shuts down the DC load.
          2. Next is to open the DC switch feeding the inverter.
          3. Next I open all the combiner box 15 amp touchless fuses....all 4 of them.
          4. Now that I'm sure the load is removed from the offending string which I double check to confirm no voltage, I proceed to detach all 12 panels from the string.
          5. In full sunlight I now check the voltage and short circuit amperage in each panel with my trusty Fluke multimeter.

          At this point I can usually find the problem, but if I still cannot find the panel then I have to check each panel under load.......

          6. Using a 12v car battery and a cheap charge controller, I rig up a test system with my Fluke in the middle to measure amp production for each panel under load.

          All along the way I'm also looking for poor, loose and corroded connections.

          Comment

          • bcroe
            Solar Fanatic
            • Jan 2012
            • 5198

            Dan, your method is much more expedient than mine. That is pretty
            much what I did, the first time working on the array wiring. But panels
            have no power switch, so daytime work requires a lot of care. These
            days I just do not like shutting anything down in daylight.

            I recommend the DC disconnect switch to the inverter breaks both wires.
            My installer used one switch, 2 poles breaking the POS hot lead on the
            2 systems. This had the obvious disadvantage that one system could
            not be disconnected while the other was running. When it first operated,
            the installer had left me some unacceptable wiring mangement (or lack of).

            While I was DC disconnected and rerouting a wire, apparently it brushed
            the frame and blew the inverter ground fault fuse. This caused some panic
            and took a while to figure out. These problems go away with 2 DC
            disconnect switches, each breaking both the POS and NEG leads of a system.

            Living on the property, I am not in a hurry to solve a problem, if the losses
            are small. The price is setting up night lights, and another day for each
            setup change. But I do not need to disconnect every panel. My first stage
            test would find wiring problems, completed once by following the wire to a
            burned out MC4. The next stage (day) is to identify individual panels. Can
            take extra days if strong sun goes away.

            My tests are made with the panels connected, with MPPT loading. My
            experience with a disconnect panel is that voltage tests will not find much,
            and short circuit current will not reveal part of a panel being bypassed. I
            need to see all sections work together without any bypassing, hard to be
            sure of when disconnected.

            When I first connected 40 no name panels (purchased at different times),
            I found 3 that sometimes would partially bypass. While I might still find a
            use for these under producers, swapping in others put this array at peak
            efficiency. Getting this good a match would be difficult, doing MPPT
            testing of individual panels, under a less than stable sun. A similar thing
            happened with the pine sap coating, the degraded panels would drift in
            and out of bypassing. When the worst offender was cleaned, another
            became an offender.

            All the same panels are still in service today, 8.5 years later. Most of the
            several hundred MC4 connectors have been apart and together at some
            point, for testing and rewiring the snow resistant arrangement. From the
            quality seen, I sort of expect each time, some fraction of the MC4s might
            need replacement, this time using NoOx on contacts. I am leaving them
            alone for now. Bruce Roe

            Comment

            • DanS26
              Solar Fanatic
              • Dec 2011
              • 970

              I have never had a single MC4 failed connection in over 10 years...(knock on wood)....I use silver conductive grease sparingly on every connection and make sure the connection is torqued each the same. I also make sure every connection is away from the rain and at the the high point of a drip loop.

              Silver conductive grease I believe is the secret sauce, but never use too much since it could cause a short in the connection if it oozes. Some people confuse it with di-electric grease which will have an opposite effect. Silver conductive grease is expensive but I think worth every penny.........


              Comment

              • bcroe
                Solar Fanatic
                • Jan 2012
                • 5198

                Another Net Metering year, the weather only gave me 29,000 KWh, still
                about 7% more than I consumed. 1st net metering month April was just
                terrible, unseasonably cold used a lot of energy, so many clouds limited
                energy collected. Still got thru with 500KWh surplus, no buying energy.
                That array can usually break even under clouds, but it really delivers
                under sun.

                I was promised the availability of a heat pump that can attach to any
                water heater, for the 3rd year it did not materialize. Have been thinking
                of some kind of dual mode setup, using inside summer air to help AC
                and dehumidify in summer, some other heat source in winter.

                Meantime energy sources have been running wild, Mon I put a re
                conditioned 24 gallon tank on the 77, and the pump shut off at a $100
                limit before it was full. Good thing my coast to cost travels are way down.

                Both the connect fees and the energy charges continue to escalate,
                my crazy idea to not connect to the gas line, and generate all property
                energy with solar, is starting to look not so crazy. Bruce Roe
                Last edited by bcroe; 05-04-2022, 11:26 PM.

                Comment

                • bcroe
                  Solar Fanatic
                  • Jan 2012
                  • 5198

                  Originally posted by DanS26
                  I use a Nyle system. I only run it during late spring, summer and early fall. It is also on a timer so that it only operates during daylight hours. In the warm months it will use ~50 to 60 kWh per month and generate most of our hot water requirements.

                  Very efficient and quiet. Since it is also rated as a one ton AC I have it connected to the cold return duct work but as you see I also installed a louver to redirect the cold air during late spring and early fall when the house is too cool for additional AC.
                  So another year, Nyle periodically says the unit will be available,
                  but once again failed to deliver it. Bruce Roe

                  Comment

                  • DanS26
                    Solar Fanatic
                    • Dec 2011
                    • 970

                    Installed my Nyle in April 2012...so over 10 years of excellent service. Replaced a relay about 5 years ago was the the only time I had to touch it. The unit is well built...I expect at least a 20 year life. My only ding is that it uses neutral switching to control the unit instead of power phase switching. I talked to their engineers about that design and they stated the new unit would not have neutral switching on their 120v systems. I added an extra thermostat control on the input side of things because I don't trust neutral switching in that type of device. Cut in set for 95* and cut out at 125*. Very quiet and efficient......I do not know if it's running unless I'm standing right next to it.

                    Don't know why the delay in the new E8 product......but the marketing and specs look good.......

                    Comment

                    • bcroe
                      Solar Fanatic
                      • Jan 2012
                      • 5198

                      Thanks to the weather this has been my worst solar production
                      year ever. Usually I have some 11,500KWh of energy in reserve
                      on this date, to be consumed over the winter. I only see
                      10,300KWh on the spinning disc meter. The system is working
                      very well, but the clouds are so common, and I may also be losing
                      to the smoke from the left coast. But I think it will be enough.

                      I took a shot at measuring net metering inverter efficiency, waiting
                      for stable strong sun to give clipping. If I believe the inverter
                      display of voltage and current, input and output, the efficiency of
                      each is near 93%. Maybe the readout errs, the efficiency was rated
                      95%. I doubt it has dropped that much, which would cause a lot
                      more heating. Or is it a hint they are getting old?

                      I continue to be bombarded with ads for Smart Thermostats. The
                      price listed is astronomical, which then allows these supposedly
                      generous rebates. I will just continue to use my little round, tilting
                      mercury tube thermostat, which will last a lifetime with no batteries
                      and no maintenance.

                      Seems natural gas price has tripled in 3 years, electricity is way up
                      too, propane is probably doing the same. Not buying any here.
                      Every year the solar science experiment looks like a better investment.

                      The energy use situation here has hardly changed in 2 years, I do
                      now have a pretty small attic vent fan with heat/humidity control,
                      runs a lot of the year. I am told it will help my energy situation,
                      but that is minimized by good insulation. A complete measurement
                      would be need to be made for the entire year.

                      The percent clipping meter did not get built this year.

                      I have shown an output graph of keeping my inverters in clipping 8
                      hours straight in good sun. That over the majority of months. BUT
                      the time never increases, even on the longest day of the year. My
                      observation of the cause, is the sun rising and setting so far to the
                      north, trees are shading the panels. One cure might be build a
                      different array, another is my chain saw. The snow rejection of
                      the older sections could be improved. We shall see.

                      The last, variable tilt, snow rejection array construction has been
                      superior. But increasingly expensive to construct, with the price of
                      materials. I realized it could easily be built as double sided, with
                      minimal additional construction cost. So mounting twice as many
                      PV panels on it would be more economical, with panels so cheap.
                      Of course this wants to face E-W, at an angle better for snow rejection.

                      Bruce Roe

                      Comment

                      • DanS26
                        Solar Fanatic
                        • Dec 2011
                        • 970

                        Bruce I hope you have a grandfathered contract that is forever renewed.

                        Some REMC POCOs are run by good old boy board of directors that have no clue or business sense. The deal you have is absolute economic nonsense. Good for you!

                        You better keep that contract in a safe because it's worth its weight in gold.

                        Comment

                        • bcroe
                          Solar Fanatic
                          • Jan 2012
                          • 5198

                          A paramont way to manage on less energy here, is to avoid
                          wasting it. Any electrical loads continuously on, are subject
                          to periodic review. Those located outside the living space are
                          especially of interest, since the energy they waste as heat does
                          not even contribute (at a low COP) to keeping me warm. These
                          include GFIs, gas detector alarms, security devices such as motion
                          detector lights, cameras and controls, central vacuum, garage door
                          opener controls, TV etc remote control receivers, computer DC
                          conversion power packs, and battery maintainers for infrequently
                          used IC engines. Some of these were addressed by plugging into
                          room circuits that were only on with the lights. Many were hugely
                          improved with the purchase of Energy Star appliances. Of those
                          remaining, any Wall Wart powered device aquired is suspect.

                          There are about 6 Battery Maintainers serving here, for electric
                          start IC engines. Recently I went thru the maintainers, noting that
                          they tended to draw maximum over 4W, and not much less even
                          when battery current was far less power.

                          It is not so easy to build a really efficient, economical, line frequency,
                          small line isolation/conversion transformer. There is technology to
                          get around this using high frequency switching. These may be
                          recognized by their heft, or rather lack of it.

                          SwitchMaint.png

                          I bought a couple of 12V battery maintainers using this technology.
                          They were set up with my standrd 12V maintainer EC3 connectors,
                          mating to the EC3 connectors on all my IC engine batteries which
                          are battery current protected by fusable links. These cannot be
                          connected backwards or easily come loose, I do not normally use
                          the supplied clip leads.

                          CAR WIRE 2.JPGCAR WIRE 1.JPG

                          This is the battery end wiring with pins ready to insert into the EC3
                          connector. Note the fusible link in the hot, red positivs lead. For
                          some wire strain relief a big piece of heat shrink tubing can be used.
                          I usually make a dummy mating dust cap.

                          I plugged the new tech maintainer into my Kill-A-Watt, and the no
                          load draw was 0.0 Watt! My maintainer test unit showed, drain was
                          very minimal, tracking needed battery current. Voltage regulation was
                          very good, around 13.85 VDC. Looks like this ap might save me a
                          couple hundred KWhours a year.

                          So I will be checking these units for reliability and EMI. If they prove
                          out over time, all the rest of the control transformers here will get
                          another look. Bruce Roe

                          Comment

                          • bcroe
                            Solar Fanatic
                            • Jan 2012
                            • 5198

                            I am entering into my 5th winter of using 6 air to air mini
                            split heat pumps, to avoid any fossile fuel use, for 2 buildings.
                            I plan to report on the experience about fall 23, of a lot of
                            details you will not find on YouTu-e. Service incidents have
                            been very minimal, less than annual, essentailly all related
                            to installer lack of experience. However this DIYer has
                            saved a fortune on the work. Bruce Roe
                            OcHpN.JPG

                            Comment

                            • bcroe
                              Solar Fanatic
                              • Jan 2012
                              • 5198

                              Although energy reserve built up was not very high this net metering
                              year, warmer weather and some sun allowed it hold for several weeks
                              past the usual 1 Nov starting decline. I am hopeful to make it thru with
                              some to spare again this winter. This week weather has been really
                              tough for the country. This area usually dodges most of that, but we
                              did get hit with -10F temps and wind giving a chill of -30F (how much
                              of that applies to buildings?). This does take a slug of energy, with
                              my HVAC COP not much better than 1.

                              One consequence, for my first memory in northern IL, the PoCo ask
                              nicely that customers in a dozen states from the E coast to IL try to
                              conserve electricity. I do not see much I can do to help. All the
                              appliances we should avoid using, are not being used just now. With
                              the all electric conversion, almost all my KWh go to heating these
                              winter months. But today we did get some real sun, unusual here in
                              Dec, so I did clear the panels and contributed some 60KWh to the
                              situation.

                              With the nuke plant doing nicely, within sight of the property, I doubt
                              we will get hit with a rolling blackout. If we do, I will be burning fossil
                              fuels in the gen set and the propane furnace to get by, not very green.
                              Bruce Roe

                              Comment

                              • Mike 134
                                Solar Fanatic
                                • Jan 2022
                                • 385

                                Originally posted by bcroe
                                This area usually dodges most of that, but we
                                did get hit with -10F temps and wind giving a chill of -30F (how much
                                of that applies to buildings?). This does take a slug of energy, with
                                my HVAC COP not much better than 1.


                                Bruce Roe
                                The strong winds remove heat faster from an object outdoors, but the final temperature still is -10.
                                Same with your building, if it's fairly airtight the winds won't find ever crack and crevasse to leak in. A tent can feel ok at -10 outside with no wind disturbing the trapped air but have some 30 mph winds pushing into it and it gets pretty cold inside.

                                Comment

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