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General: PV compatible domestic energy monitor...

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    • CommentAuthorSprocket
    • CommentTimeJun 13th 2012 edited
     
    I got a price for the Elkor Wattson 1100 3-pase modbus thing.
    One-off is $347 (US dollars, not Canadian) so just over £220
    And they have some recommended precision calibrated solid CTs. (< 0.2%) at $22 each.
    I think that sounds pretty good (*). I'm very tempted.

    * For what it does and the potential, assumming it works as well as it promises.
    I still like the idea of the Open Energy Monitor though. Might do both.
    • CommentAuthorjms452
    • CommentTimeJun 15th 2012
     
    The Wattson solar plus with easyfit seems to work fairly well but even with a modern sunny boy 3600TL-20 inverter shows ~+80W phantom generation. The wattson fix is to show less than 90W generation as zero which works surprisingly well.

    Is also slightly garish compared with the understated OWL but I'm sure I 'll get used
    to it.
    • CommentAuthorSprocket
    • CommentTimeJun 15th 2012 edited
     
    Do you think it is a general error of +/- 80W (which doesn't sound that unreasonable) or a problem with zero?

    What about calibration? Is it all preset or is there anything to adjust?

    How is it getting it's import export numbers?
    The CT sensor layout in the manual looks a little unconventional (2 CT sensors on a Y cable?)
    How many CT sensors did you have to install and where are they?

    Ta
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 15th 2012
     
    Any data that it can generate is gratefully received for analysis as well :bigsmile:
    • CommentAuthorjms452
    • CommentTimeJun 15th 2012
     
    I believe that it is plus 80 due to phase shit induced by capacitor banks on the output of the inverter (presumably to smooth the output)

    wiring is exactly as the easifit diagram:
    http://www.diykyoto.com/uk/holmes/easifit-installation
    • CommentAuthorSprocket
    • CommentTimeJun 15th 2012
     
    Hi JMS, the inverter output is AC. The inverter will have used some fancy electronics to adjust the phase of it's output so it is (hopefully) precisely in-phase with your mains AC power.

    Any other electrical types watching? (OK, thats a silly question)
    How do folks think the two CTs on the Y are arranged?
    Presumably the load resistor is inside the WattsOn, not in the clamp?
    So the two CTs could just be in series (with one backwards)... so one subtracts from the other?

    Does that sound likely?
    And if so, then if they are not precisely matched could this account for the +80?

    JMS, is the CT wiring such that is possible to swap over the CTs? Or are they hardwired so that one is specifically for import and the other for export? I wonder if swapping them would change the +80 to a -80.
    • CommentAuthorjms452
    • CommentTimeJun 18th 2012
     
    its a known issue that the wattson generates a bit less than 90W phantom generation so I doubt I can fix it with something so simple (defeatist I know). I'll try your suggestiosn before (and if) I splash out £50 on the TXact but at risk of sounding lame the trunking is a real pain to get off the wires under the generation meter :shamed:
    • CommentAuthorEd Davies
    • CommentTimeJun 18th 2012 edited
     
    Posted By: jms452I believe that it is plus 80 due to phase shit induced by capacitor banks on the output of the inverter (presumably to smooth the output)

    Posted By: SprocketHi JMS, the inverter output is AC. The inverter will have used some fancy electronics to adjust the phase of it's output so it is (hopefully) precisely in-phase with your mains AC power.

    As I understand it (Gavin or another adult will probably be along in a minute) inverters have a fairly large amount of capacitance in their output stages which is related to sensing whether there's a proper low impedance grid connected. It's so you don't have a grid failure but lines staying live because two neighbours' PV on the same phase are both generating and each thinks the other is the grid so their anti-islanding protection doesn't cut in.

    Consequently an inverter will draw a reasonable amount of current (though very little real power) even when it's not generating.
    • CommentAuthorjms452
    • CommentTimeJun 27th 2012
     
    Just playing with the Wattson PV with some actual data.

    The accuracy is as I'd expect from a clip on meter (indicative but a bit off) but the logging combined with the software is fairly powerfull.

    Attached is a standard graph for Monday with generation in green and use in blue.
      untitled.JPG
    • CommentAuthorSprocket
    • CommentTimeJun 27th 2012
     
    Interesting.
    Well, you can certainly see what I presume is the kettle :-)
    And some clouds.

    I've been looking into (expecting to implement shortly) overall import/export measured at the meter.
    I had thought that would be all I would need.
    But there is something nice about seeing consumption independent of generation.
    I'll have to see what I can do. My Panels and generation meter are quite along way from my meter and are in another building that also consumes power so it could be a bit tricky.
    • CommentAuthorjms452
    • CommentTimeJun 28th 2012
     
    Posted By: SprocketInteresting.
    Well, you can certainly see what I presume is the kettle :-)


    Yes - That's the kettle it is on for a sufficiently short amount of time it is averaged from 2kW down to ~1kW.

    you can also see the washing machine in the late morning which uses less power than I'd have expected.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 28th 2012
     
    How much water is in it :wink:

    I am always surprised about my washing machine. Uses less that a kWh on some washes.
    •  
      CommentAuthorDamonHD
    • CommentTimeJun 28th 2012
     
    Ours uses 0.16kWh on a cold wash!

    Rgds

    Damon

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