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Type: Posts; User: ggunn

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    7$$
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    229

    Isn't it a code violation to pull a bare Cu ECG...

    Isn't it a code violation to pull a bare Cu ECG through a metallic raceway?
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    56$$
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    765

    Backing away from the issue itself a little... ...

    Backing away from the issue itself a little...

    What this points out to me is that the code surrounding PV is not yet written well enough. Anything that is a commonly encountered situation should...
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    5$$
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    My code book (NEC2011) does not have a 690.9(F)....

    My code book (NEC2011) does not have a 690.9(F). The exception to 690.9(B) indicates to me that no OCPD is needed (the transformer is rated at greater than the maximum output current of the...
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    5$$
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    Step down transformer protection

    I am assisting a colleague with a design incorporating a 480VAC inverter interconnecting with a 208V service through a step down transformer. What, if any, disco/OCPD does he need between the...
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    7$$
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    One thing you need to consider with any voltage...

    One thing you need to consider with any voltage divider is that the load resistance also contributes to the network and therefore influences the voltage at the center node. Also, a ten ohm resistance...
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    5$$
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    But whether it is available as a panel main...

    But whether it is available as a panel main breaker is another question. I have no idea, but the OP expressed a doubt.
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    5$$
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    If you can't find one you will have to, I dunno,...

    If you can't find one you will have to, I dunno, do something else. If the engineer put something in the design that doesn't exist it is his problem to fix. It's his responsibility to design...
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    1$$
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    As far as I know there is no problem with running...

    As far as I know there is no problem with running your USE-2 into the disco.
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    56$$
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    765

    It's because you size the conductors to handle...

    It's because you size the conductors to handle the maximum current the inverter can produce so that the inverter could not possibly endanger them. Any fault current in excess of the rating of the...
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    56$$
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    A couple of things… Why are we discussing...

    A couple of things…


    Why are we discussing the load breakers? The size of the load breakers does not figure into the 120% rule in the panel.

    Also, OCPD for an inverter feed needs to be at the...
  11. Transformer on the DC side? Surely that isn't...

    Transformer on the DC side? Surely that isn't what you mean.

    And don't call me Shirley. :D
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    1$$
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    150

    I am pretty sure that you cannot run DC through a...

    I am pretty sure that you cannot run DC through a building without it being in conduit. You also may need a DC disco on the array side of the building.
  13. If you ground the neutral of the transformer but...

    If you ground the neutral of the transformer but the inverter does not connect to it, the inverter still has a floating neutral.
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    12$$
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    (10.43A)(1.25) = 13A. Glass automotive fuses are...

    (10.43A)(1.25) = 13A. Glass automotive fuses are rated to 250VDC, and 15A is a common size. Could it be that simple?
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    12$$
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    Well, I'm in Austin, you know. :D

    Well, I'm in Austin, you know. :D
  16. I believe you need to bond X0 to a ground rod at...

    I believe you need to bond X0 to a ground rod at the transformer if you want any loads to connect to it.
  17. Thread: 110.21(B)

    by ggunn
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    3$$
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    175

    You would void the NEMA rating, at any rate.

    You would void the NEMA rating, at any rate.
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    13$$
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    357

    The busbar rating should be a non-issue, but the...

    The busbar rating should be a non-issue, but the conductors you will be tapping are subject to the 120% rule.
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    12$$
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    273

    Unless the DC conductors enter the building,...

    Unless the DC conductors enter the building, right?
  20. Thread: Inverter max VOC

    by ggunn
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    45$$
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    929

    So, what's wrong with the design practice of...

    So, what's wrong with the design practice of sizing strings such that excessive/damaging/uncompliant Voc won't ever be reached?
  21. Thread: Inverter max VOC

    by ggunn
    Replies
    45$$
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    929

    I'm not going to split hairs over the meaning of...

    I'm not going to split hairs over the meaning of the word "virtual"; you can assume whatever risk you feel comfortable with when designing a system. Keep in mind, however, that some inverter...
  22. Thread: Inverter max VOC

    by ggunn
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    45$$
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    929

    I am aware of that. Did you miss the "virtually"...

    I am aware of that. Did you miss the "virtually" in my statement?
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    6$$
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    Some of them don't even have a maximum voltage...

    Some of them don't even have a maximum voltage tolerance of 600V.
  24. Thread: Inverter max VOC

    by ggunn
    Replies
    45$$
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    929

    Voltage has virtually nothing to do with...

    Voltage has virtually nothing to do with irradiance. When the first rays of the sun hit the modules in the morning, the voltage goes to Voc for whatever temperature the modules are at the time, which...
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    6$$
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    One thing to be careful of is the actual max DC...

    One thing to be careful of is the actual max DC voltage tolerable by the inverter. I have seen inverters with "600" in the product name that will only tolerate 500VDC.
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