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Kill-a-watt meter

Discussion in 'Off Grid Living' started by rsbhunter, Jan 10, 2012.

  1. rsbhunter

    rsbhunter Monkey+

    Ok, just ordered a kill-a-watt meter so that i can start the planning of my solar system for off grid, and now want to get a good multi meter...I don't want a $150.00 meter, but i do want one that will last, be accurate, and do what is needed in setting up my system....Also, if i put my panel array on a pole, what height is at the upper limit for cable length and strength, wind and weight....is 4" sch 40 steel pipe enough, or ???? I'm sure it depends on the weight, and height of the panels and framing. I am looking at 8-10 Kryocera 200-235 watt panels (46 lbs ea.), can do 2 pole mounts if required......and will use guy wires to help with the stability.....Any suggestions, hints, advice would be a big help....Hows Nadja doing with the snow situation? Thanks, Russell
  2. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Look at the posts by TnAndy... His system is right up your alley....
  3. VisuTrac

    VisuTrac Ваша мать носит военные ботинки Site Supporter+++


    That Kill-a-watt meter is worth it's weight in savings.

    found a lot of phantom loads in the house. like TV's and stereos that don't really turn off just power down waiting for you to beacon with the remote. (fixed with power strips that turn everything connected off)

    and energy hogs like the standalone dehumidifier in the basement (fixed by lighting a fire in the fireplace insert when it feels damp in the spring , early humid summer)

    Every watt you can conserve is cheaper than increasing your array size.

    TnAndy likes this.
  4. strunk

    strunk Monkey+

    Regarding multimeters, I've been happy with this one.
    Last edited by a moderator: Apr 25, 2016
  5. TnAndy

    TnAndy Senior Member Founding Member

    Don't buy, and waste money, on a meter unless it can measure DC amps with a clamp on feature ( MAKE SURE it says DC amps, not just AC ).

    This is one that won't break the budget:
    Amazon.com: Auto ranging AC/DC Digital Clamp Meter: Home Improvement

    Just measuring volts won't cut it when it comes to troubleshooting your system...you can show full voltage on a line, and yet have almost NO amps. I was showing 1500w on one charge controller from one array, and 1350 on the other controller, same size array....WTF ? What I finally traced it down to was a bad MC4 connector off the end of one pair of panels....it would connect enough to pass voltage, but not the amps the pair of panels would produce, and a clamp on amp meter was the only way to find that.
    Last edited by a moderator: Apr 25, 2016
  6. TnAndy

    TnAndy Senior Member Founding Member

    Nobody but a structural engineer can tell you exactly, but my seat of the pants guess is 4" won't cut it unless you DO use guy wires. I used 6" on my initial two arrays of 10x175w, and 8" on the most recent of 10x245w.....both sunk in large blocks of concrete (4x4x4, then 5x5x5 )....and I have basically no wind where I'm tucked under the eastern side of a mountain.

    As to cable size from the array to your charge controller, the closer you can mount the array, the better, of course, but you can also do things like connect the panels in sets of 2 or 3, (or more) depending on the panel voltage ( probably mid 30v range for the ones you're looking at ) and what charge controller you pick.

    For example, I ran all my panels in series sets of 2....which raises the voltage to around mid 70 range. My charge controllers ( Outback 60 and 80 ) will accept up to about 130-135v in ( with de-rating to allow for max cold condition ), so I actually could have gone in sets of 3, except that would have limited me to 9 panels on my arrays, where 10 maxed out the amount of watts the CC would handle.

    By raising voltage from the array to the CC, you lessen the voltage drop ( use a DC voltage drop calculator, google one ), and thus can use smaller wire.

    Midnite has charge controllers out now that will take up to 250v on the input side.....meaning you can string 6-7 panels together, getting your voltage from the array in the 200+v range, and REALLY lower your wire size......BUT......be aware that now you're in the voltage range that can really zap your a$$ if you don't know what you're doing ( whereas 70v and below is fairly safe stuff to work with ), AND if you do get any shading on any of the panels in a string, the whole string goes WAY down in production....just a slight shade from something on one panels pretty much kills the whole string. So make DANG sure there are no trees/etc, to shade early/late, or you'll kill an hour or more of production off a string.

    Good read on charge controllers, by the way, if you haven't seen it, from AZ Sun/Wind ( and good folks to buy from, IMHO.....they know their stuff )

    Maximum Power Point Tracking Charge Controller
    dataman19, hank2222 and BTPost like this.
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