Graphs from eGauge show odd power consumption.

major
major Registered Users Posts: 10
I have an eGauge2 device connected to my inverter and the graph looks unusual when the solar panels are generating power. It appears that the power *consumption* increases in the same pattern that the *generation* does.

I understand that there is loss of power with the DC > AC conversion in the inverter, but this power usage in the graphs seems really unusual. This is happening at times where our A/C system isn't running nor are any other large appliances in the house running.



In the graph above, the green line shows instantaneous energy generation (from solar) in watts. The red is power consumption, again in watts.

The large spikes are related to when I used a power-hungry appliance, like the A/C, microwave, dryer, etc. However, the baseline usage level seems to increase just as the solar generation does. That's what I'm concerned about.

Is my inverter having issues? Is this normal? I've seen this happening since the system was installed about 4.5 years ago.

Comments

  • major
    major Registered Users Posts: 10
    As an additional check, I turned off each circuit breaker one by one and saw that the power usage never dipped by much (no more than 100W when it showed 2kW of power consumption). I'm wondering if something isn't being measured correctly.
  • Horsefly
    Horsefly Registered Users Posts: 470 ✭✭✭✭
    edited July 2017 #3
    I'll admit I've had a couple of glasses of wine, but...  :)

    It looks to me like your system is operating well. I think the way the lines are plotted are a little deceptive. The way I interpret them is that when the green line (PV generation) is above the red line (inverter output), the PV array is replenishing your battery bank. When the PV array can't quite supply all the require power, the red line is above the green line (or in the case of night time, the green line is at the bottom of the red line).

    So, a couple of examples:

    1) From 10:15am to about noon, it looks like the PV array is supplying more power than the inverter needs, and it is because the CC is putting energy back into the batteries. Makes sense.

    2) At about 12:30pm, your son stuck a fork in a wall socket, which pulled about 6kW from the inverter. The PV array couldn't provide all that power, so it was pulled from the batteries. Then for about 20 minutes the PV array was again replenishing the batteries as best they could.

    So, your PV array is doing its best to keep up, and is - in sunny conditions - providing up to 3kW. In that time, some of the power is just to meet your loads, like from 1:30pm and from 2:30pm. Other times (where the green is above the red) I would interpret it that the PV array is bulk / absorb charging back into the battery bank.

    If my interpretation is correct, you are sucking up pretty much everything your PV array can give. That may be a problem, but I don't think your inverter has a problem.


    EDIT: P.S. I don't know anything about this eGauge2 thing, but it seems really cool!
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited July 2017 #4
    If you turn off all breakers so that you know there is no power draw from the inverter and the eGauge reads significant consumption, then something is very wrong.  All the sensors are on the right wires?  See figure 4 here (solar input should be on CT3):

    https://www.egauge.net/docs/egauge2b-manual.pdf

    I am available for custom hardware/firmware development

  • mike_s
    mike_s Registered Users Posts: 155 ✭✭
    The very first Google hit for egauge2 points to a pdf showing a similar graph. There, the baseline between the power draws doesn't change. 

    Are you sure the data is correct? Do you have a clamp-on ammeter to compare against? Is this egauge2 one of the devices at www.egauge.net? It looks like they only measure the AC side of things. Have you compared the wiring and configuration of your system to the examples they give in their config guide? 
  • Horsefly
    Horsefly Registered Users Posts: 470 ✭✭✭✭
    Now that I look at it again, it seems like the "baseline" of the plot is the PV production. The load consumption is then a delta from that baseline. So the red shaded spikes are showing you how much above the PV production you were consuming, and the green shaded areas are showing you when the load consumption is below the production. I guess that's an OK way to show it.

    The manual is actually of no help in understanding this graph, so I can understand why the OP is confused.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    You are definitely using a lot more power when you produce power at the PV array. That should not be happening. Only the shaded areas in red should rise, not the line itself.
  • major
    major Registered Users Posts: 10
    Thanks for all of the comments!  This gives me some ideas of where to look. I'm really wondering if something isn't being measured correctly.

    I don't have batteries, but if I take a look at my entire consumption (according to the power company), it matches my grid + PV consumption numbers. The eGauge interface is quite confusing and I see this same graph pattern on some other eGauge units while some others look very different.

    I'll keep working at it and update the thread if I come up with a solution!
  • major
    major Registered Users Posts: 10
    For what it's worth, here's my system on PVOutput: https://pvoutput.org/list.jsp?userid=59775
  • major
    major Registered Users Posts: 10
    It appears that my eGauge is set up like this:
    • CT1: Grid
    • CT2: ? (almost always shows 0)
    • CT3: Solar


    On the installation page, I see that CT1 and CT2 have a scale of 12.281 and CT3 has a scale of 24.509. I'm not entirely sure how those numbers are generated.



    I'll try to get a look inside some of the panels outside to see if I can figure anything out just by looking at it.

  • mike_s
    mike_s Registered Users Posts: 155 ✭✭
    Hard to say without knowing how everything is wired, including where the CTs are, but I do see that under "Totals and Virtual Registers", Usage is define as Grid+Solar, which would seem to explain why "Usage" goes up when solar power does.
  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    Then it should also go up when grid goes up but it doesn't.
  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    I'm with mike_s - just click the little "x" to remove Solar+ from the usage line.

    I am available for custom hardware/firmware development

  • mike_s
    mike_s Registered Users Posts: 155 ✭✭
    edited July 2017 #14
    Solray said:
    Then it should also go up when grid goes up but it doesn't.
    Huh? What then are the red spikes in the graph at night when there's no solar?
  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    I think those are spikes in the peaks not the baseline.
  • mike_s
    mike_s Registered Users Posts: 155 ✭✭
    edited July 2017 #16
    Solray said:
    I think those are spikes in the peaks not the baseline.
    Those are spikes in Utilization, cause by spikes in Grid. So it should be obvious that when Grid goes up, so does Utilization, contrary to what you said.

    As I pointed out, Utilization is defined as Grid+Solar. At night, Solar is 0, so you only see Grid. During the day, the apparent "baseline" rises, because the Solar component is added to Grid. 

    Of course, without knowing how it's wired, and where the sensors are, it's all just conjecture.
  • major
    major Registered Users Posts: 10
    edited July 2017 #17
    I started to come to the same conclusion that the math was wrong in the eGauge interface. After looking at things a little more, I realized I misunderstood how the registers worked. ;)

    I verified that CT1 is the grid and CT3 is the solar inverter. What I didn't realize is that CT1 would be negative and positive:
    • If CT1 is positive, it means I'm pushing power into the grid. The solar panels are making more energy than I'm consuming.
    • If CT1 is negative, it means I'm pulling power from the grid. The solar panels are not making enough energy to meet my consumption. (This happens all night long.)
    The consumption calculation seems like it should be: solar power generation minus grid reading. As an example, if my solar panels are producing 2,000W and my grid register shows 500W, then I'm consuming 1,500W at that moment. If the solar panels are producing 2,000W and the grid register shows -1,000W, then I'm consuming 3,000W.

    Is this a standard setup where CT1 flips between being negative and positive? I'm still seeing a rise in consumption as the panels generate more energy, but I'm thinking that might be including some of the DC > AC inverter power loss.  Since I'm getting a penalty for that conversion, it shows up as "power consumption" in the readings.

    Here is how the eGauge looks now:



    My fridge, dishwasher, and A/C are running right now, so 3.9kW of consumption seems quite reasonable. Hey, it's Texas in the middle of summer and it's almost 100F (38C) outside. ;)
  • major
    major Registered Users Posts: 10
    Well, that's still not right. I'm still getting some very strange graphs.

    I did a lot of reading on residential AC wiring and split-phase power, and it seems like I may have a measurement problem on L2. I see lots of current on my L1 (10-15A when the air conditioner is on) all day long.  However, I only see a tiny amount of current (almost always under 0.1-0.2A) on my L2.  The L2 measurement remains low even when 240V appliances are running.

    Could this mean that the current transformer attached to my L2 has disconnected or has some kind of problem? Could it be possible that my CT2 (which should be on L2) is on the neutral wire?
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    If the CT were on the neutral it would  read the unbalanced load current, which should be low on a ballanced system, could you not check and see if it is on a white wire? Some CT's have jumpers to set the range, could have a jumper across the wrong  pins, or missing, have no idea what you have but some thoughts.
    Is the air conditioner 240v or 120V ?
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • major
    major Registered Users Posts: 10
    I had assumed my air conditioner is 240V, but I could be wrong. However, I know my clothes dryer and oven are 240V for sure, and I'm not seeing an amperage over 0.02A on L2 when those are running (even though I see significant amperage flowing on L1 at that time).

    I'm wondering if my current transformer on the L2 is broken or not attached correctly. CT1 (Grid L1) and CT3 (solar inverter) are showing totally reasonable amounts of amperage, but CT2 (L2) is way off.

    I guess I'll need to tinker in the breaker box to see what's happening. I don't have much experience there and I certainly don't want to hurt myself. ;)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    A "true" current transformer is something to "respect". If the output is not connected to a load (such as resistor), the output voltage of an unconnected CT can reach several hundred volts (or more). And it could damage the current transformer (arc/puncture the insulation in the windings).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • major
    major Registered Users Posts: 10
    Thanks for that, Bill. I might call an electrician to give this a look.

    I'm still reading about harmonic distortion and the eGauge gives me data on that for each CT.  CT1 (L1) and CT3 (solar inverter) seem to stay under 20 at all times, but CT2 (on L2) is anywhere from 300-1000. Is that a sign of a possible electrical problem?
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Find an electrican with motor control experience, they will be more familiar with current transformers, not all electricans have such experience. 
    If the circuit breaker for the air conditioning is a 2 pole then it would be 240v.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • major
    major Registered Users Posts: 10
    It's not fixed yet, but the eGauge folks took a look remotely and they're pretty sure that CT2 is damaged or has fallen off the wire in the breaker box. I've ordered a replacement CT and I have an electrician coming out next week to help me with the replacement.

    Thanks for all of the suggestions, everyone! :)
  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    Glad that you got it figured out, that was very odd behavior indeed.