DC Arc Fault Protection

peakbaggerpeakbagger Solar Expert Posts: 341 ✭✭✭
My 2 KW install was just about ready and I ran into the 2011 NEC requirement for either a seperate DC arc Fault protection device or an inverter equipped with one. Luckily i hadnt bouhgt the inverter. The local building inspector is not electrically oriented and is requiring me to have master electrician sign off on the install. There are no electrician in the area with solar background so I basically have to prove that the install meets NEC chapter and verse. Ultimately if I need a AHJ to sign off on not installing one, he will be the state fire marshall and is not known to be very accomodating.

To date I havent found any external devices for this but have seen some discussion by midnight solar and eaton corp but no product yet. Sunny Boy does have two 3 KW inverters, one is equipped with it and the other has it as an option but they are both 3 KW. I realize that the microinverters dont require them as the DC panel voltage is less than 50 volts but would prefer not to go that way.

Anyone know of any other inverters of components that meet the intent of the code? Most of the references I see to this requirement is to have the AHJ waive it as product doesnt exist. It is surprising that the other inverter firms would walk away from this market as about half the states are NEC 2011 states.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: DC Arc Fault Protection

    This is the kind of situation that gets me riled. I usually tell them to supply me with exactly the make & model of the equipment they want installed and where to get it. They never can. They write the rules and tell you to comply but don't have a clue as to even if it is possible to do so.

    What do you do? Stuff some AC arc-fault breakers in a box and wire 'em in, then take them out after inspection? All well and good to tell people what they have to do when you have no idea what you're talking about. Most of these 'inspectors' have zero qualifications to analyze any work done in any field.

    Sorry. I'm ranting again.

    If anyone does know of a source for these mythical DC arc-fault breakers speak up! :D
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: DC Arc Fault Protection
    peakbagger wrote: »
    Sunny Boy does have two 3 KW inverters, one is equipped with it and the other has it as an option but they are both 3 KW. I realize that the microinverters dont require them as the DC panel voltage is less than 50 volts but would prefer not to go that way.

    Anyone know of any other inverters of components that meet the intent of the code?

    The brand new TL3000/4000/5000-us from SMA do have integrated DC AFCI (not optional) and also offer their new 12A 120 Volt AC "emergency power" output driven directly from the panel DC when the grid goes down. Nobody has any real experience with them yet, but the SMA Platinum dealers have gotten their initial shipments already.

    Coot: no indication whether they make the AFCIs themselves (and won't sell them) or get them from another manufacturer.
    Once you are on the 2011 code, it does get miserable.
    SMA SB 3000, old BP panels.
  • boBboB Solar Expert Posts: 953 ✭✭✭✭
    Re: DC Arc Fault Protection

    >>>>Ultimately if I need a AHJ to sign off on not installing one, he will be the state fire marshall and is not known to be very accomodating.<<<<

    Sorry, I don't follow what that means, exactly.

    Yes, the whole DC arc fault requirements are kinda confusing now.

    Midnite Solar will have a small external AF mitigation solution eventually but for now the SMA has their
    11000TL-US-12 240VAC inverter and Inetdog mentioned others.

    In the US, an AHJ is usually the one who has to sign off on the install. There may be
    some additional city requirements or fire marshals may start to demand extra PV disconnects.

    NEC 690.11 is just starting to be required as these products only recently start to be available.

    BTW, the magic voltage at the moment is 80 VDC.

    boB
  • jaggedbenjaggedben Solar Expert Posts: 230 ✭✭
    Re: DC Arc Fault Protection

    Fronius has announced AFCI in its newest inverters ("IG Plus Advanced") but I'm not sure they're on shelves yet or that they'll have one smaller than 3kW.

    The code section that allows waiving a requirement for this situation is 90.4. Your basic argument is that this is a newer requirement and that products are not yet available that are suitable for the system you are installing.

    Ultimately, if it has to go to the state fire marshal, and he wants to be a hardass, then I guess it will come down to whether the 3kW inverter will actually function with your system design, and whether, if it does he will require you to buy too-large an inverter or recognize that that is an undue financial burden. If the specs of the 2kW and 3kW are different enough that you'd have to change other equipment in system (i.e. number of panels) to make it work, then you have a stronger argument against him requiring it. Otherwise 90.4 really leaves it up to him. That would be the solution: buy an inverter that's too big. Heck, at least you could probably add more panels later if you wanted to.

    BTW, California, by far the biggest market in the US, and keeper of lists that some other states use, goes on (its version of) the 2011 NEC at the beginning of next year. So that pretty much explains why the inverter companies are getting around to this at the current time.
Sign In or Register to comment.