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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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Renewable Energy: Preventing grid supply in a FITs situation

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    • CommentAuthorGBP-Keith
    • CommentTimeApr 28th 2012 edited
     
    You are all starting to wander from the subject with your Freudian theories regarding the 'mentality of man'. Just for the record, I'm not trying to deny others some of the electricity that I generate and I'm with DamonHD on this. For the record, I believe that a high percentage of what I produce from my 8.7kW array will go onto the grid because I just don't have the need for it. So please keep that discussion for another thread please guys.

    I have another theoretical / technical question though that someone may be able to answer and help save me some time. Does anyone think that the signal from the relay switch could be sent down a cable some distance to switch the contactor remotely? Let's say 50 metres of cable?
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 28th 2012
     
    50 meters is not far and contractors require little current and some work on low voltage.
    Find an online cable volt drop calculator and plug in the relevant numbers and see what comes out.
    • CommentAuthorSeret
    • CommentTimeApr 29th 2012
     
    Really depends on your control voltage Keith. As ST says, figure out your voltage drop and if it's still good for what your switching gear is rated for then you're on.

    PS: I did start another thread for all the philosophising yesterday :wink:
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 29th 2012 edited
     
    To select your contactor use this page:
    http://asiaexport.rs-online.com/web/c/automation-control-gear/contactors/contactors/?sra=p
    not sure how your PV is wired but you can easily get one that would cover the total peak output.
    The thing to keep an eye on is the coil voltage (230V AC) and if the contactor is normally open or normally closed. You want normally open (NO)

    And use this volt drop calculator
    http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

    So if you want to have the contactor 50m from your inverter relay (and I have chosen a ridiculous installation method as a worse case scenario) and assumed that the load is 10W (quite hefty for a contactor) and using 1mm2 twin and earth.
    You will get a volt drop of 0.042V at 230V.

    So really nothing to worry about apart from safety.
    • CommentAuthorGBP-Keith
    • CommentTimeMay 1st 2012
     
    I think I'm going to plump for the Hager ES220. it seems able to run a heating load of up to 4.4 kw and is normally off (open). Not sure about the coil status.

    Has anyone used this particular contactor with the SMA inverters with success? If so I would love to know.
    • CommentAuthorGavin_A
    • CommentTimeMay 1st 2012
     
    pretty sure they're the ones we use, and they work fine with SMA.

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