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Type: Posts; User: ggunn

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  1. Through a fixed resistance, of course. Ohm's Law:...

    Through a fixed resistance, of course. Ohm's Law: I=V/R
  2. Thread: WIFI, RF & EMF

    by ggunn
    Replies
    22$$
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    381

    PSMJ Pseudo Scientific Mumbo Jumbo There was a...

    PSMJ Pseudo Scientific Mumbo Jumbo

    There was a New Age bookstore here that had a bunch of quartz crystals laid out on black velvet at their checkout counter. If you picked one up while you were...
  3. Interesting how they just pasted the picture of...

    Interesting how they just pasted the picture of their logo onto the picture of the box.
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    Chickens are birds, right? How many chickens do...

    Chickens are birds, right? How many chickens do humans kill every year? :D
  5. It is not voltage per se that the power company...

    It is not voltage per se that the power company is concerned with, it's the power imbalance. Most utilities will allow a "small" imbalance, but you'll have to check with them as to what that limit...
  6. Replies
    48$$
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    Sometimes the market needs distorting. The "free...

    Sometimes the market needs distorting. The "free market" doesn't exist, anyway; it's already stuffed to the gills with special interest distortions. Corporations are people. Money is speech.

    War...
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    I am a bit confused by the barrage of information...

    I am a bit confused by the barrage of information here, but at first blush it appears that you are sizing the transformer for the 400A breaker. If that is what you are doing then it seems to me that...
  8. It sounds like an exam question to me.

    It sounds like an exam question to me.
  9. In some situations that would make it worth using...

    In some situations that would make it worth using even if you didn't need the higher voltage rating.
  10. In a related story... A fellow engineer...

    In a related story...

    A fellow engineer pointed out to me this morning the new in 2014 exception noted in 310.15(B)(3)(c) that exempts XHHW-2 (cross linked polyethylene) wire from the rooftop...
  11. That's what I thought upon first reading, but I...

    That's what I thought upon first reading, but I don't believe he was double derating anything.
  12. The inverter manufacturer's tech support/field...

    The inverter manufacturer's tech support/field applications engineer is your friend. Whatever you are doing they have done a bunch of; get them to spec your transformer.
  13. Thank you.

    Thank you.
  14. Replies
    11$$
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    Why wouldn't you treat it like any other...

    Why wouldn't you treat it like any other non-conductive roofing material? It seems to me that if the shingles do not conduct to each other, then each shingle you penetrate with a conductive lag bolt...
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    I am not an expert on such matters, but I am...

    I am not an expert on such matters, but I am pretty sure that one can interconnect more than one multi-cluster on the same microgrid.
  16. Just out of curiosity, can you provide an example...

    Just out of curiosity, can you provide an example of this happening? I worked a few test cases and couldn't make it happen.
  17. I think that the reason it was pulled or revised...

    I think that the reason it was pulled or revised is that the language "...shall be protected by the OCPD..." was sometimes being interpreted as requiring that the derated ampacity must be equal to or...
  18. If you use 90 degree wire but calculate the...

    If you use 90 degree wire but calculate the ampacity for wire sizing as if it were 75 degree wire because of the terminal ratings, I don't believe that can happen. When you decide if the wire is...
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    You can do it with SMA Sunny Island (battery...

    You can do it with SMA Sunny Island (battery inverters) and Sunny Boy (PV inverters). You can configure them so that as the batteries approach a 100% state of charge the SI tell the SB to dial back...
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    Under 2014 I believe you are allowed to use 125%...

    Under 2014 I believe you are allowed to use 125% of the summed rated output of the inverters to calculate the 120% rule rather than the ratings of the first OCPD's seen by the inverters.
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    Well, anything plugged into any of the outlets...

    Well, anything plugged into any of the outlets would have up to 40A of current available before tripping a breaker.

    Also, if the connection were accidental there would be a 50:50 chance that the...
  22. Grid tied PV inverters are by their nature...

    Grid tied PV inverters are by their nature current limited to their published maximum output. As for inrush current to the transformer, that can only come from the service side when the disconnect is...
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    I have done it. What are your concerns? Talk to...

    I have done it. What are your concerns? Talk to the transformer vendor and tell them what you want to do; they will tell you what model you need. FWIW, the company I dealt with told me that their...
  24. I don't remember if I mentioned it earlier, but...

    I don't remember if I mentioned it earlier, but my application was the interconnection of a bank of 480V native PV inverters with a 208V service.
  25. I will add my "don't do that" to the other...

    I will add my "don't do that" to the other responses. This will, in addition to what else has been said, defeat the GFI capability of the inverter and thereby create a significant fire hazard.
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