OC protection question

hillbilly
hillbilly Solar Expert Posts: 334 ✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
I'm wanting to make sure that I'm not missing something here, I am planning to wire an Iota charger via it's own dedicated AC circuit. The very short (2' or less) DC + conductor would tie into the Batt+ buss, as would the PV output, and the inverter DC+ input (inverter is not a charger). I think I've kind of got things mostly figured but I'm not sure if I need an additional breaker between the Iota charger and the buss (I am pretty sure that I would). The PV output would have just come from it's own breaker, and the inverter DC in would have a breaker directly downstream of this buss bar. The Iota has it's own breaker on the AC side, but I'm thinking that I probably need a CB for the DC connection.

Thanks,
HB
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Comments

  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #2
    Re: OC protection question

    Yes you will need an appropriately sized breaker on the dc + side of the iota
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #3
    Re: OC protection question

    Maybe it is not needed:
    PROTECTION FEATURES
The IOTA Power Converters/Battery Chargers are de- signed with high quality
 components to help ensure years of continuous use. The unit is protected by 
multiple protec- tion features for a long, trouble-free life.

 1) Reverse Battery Polarity Protection.
 2) Brown-Out Input Protection.
 3) Over-Current Protection - cycle by cycle peak limiting as well as rated 
     current limiting to maximize the life of the converter.
 4) Over-Temperature Protection. In addi- tion, it is designed with a unique 
     “proportional” fan control circuit. Fan speed is directly proportional to the
     converter’s internal ambient temperature. This enables the fan to turn on
     and off very slowly, minimizing unwanted fan-starting noise.
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #4
    Re: OC protection question

    it would be required by code if nothing else. but I for one would not want any wires leaving my battery bank and traveling to a device with no protection talk about a fir waiting to happen.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #5
    Re: OC protection question

    Never depend on electronics for protecting the wiring, the cycle by cycle over current current check only works when the Transistors or FET are functional, if they short out ( common failure mode ) you have a direct short.
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  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    #6
    Re: OC protection question

    Thanks, the more I looked at the wiring plan the more obvious it started to be that there would be a direct path from the battery to the charger. I think the only thing that even had me wondering in the first place was the short distance of wire (the buss will be in a big baby box, and the charger would be mounted right beside the box). An additional breaker is no biggie, so we'll just add that in.

    This does raise another question: in trying to protect all positive conductors that connect to the battery bank it would seem best to have that protection as close as possible to the power source. So in this case we're looking into a wire of about 10' from the battery terminal to the battery buss bars, these wires would carry either charging (PV and Iota), or discharging currents. In other words there are power sources at either end of this wire run, do I need to have protection at each end of it or would it be ok for the wire to run about 10' from the battery terminal to it's first breaker? I need to have breakers at that specific location (ie, can't move the boxes closer to the battery), but I could mount a fuse at the battery terminal itself if needed.
    Thanks for the help, I'll likely have a few more questions as I'm helping some friends on a small RV system.
    HB
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  • peterako
    peterako Solar Expert Posts: 144 ✭✭
    #7
    Re: OC protection question

    Allways put a fuse on the battery direct. the current from a sort close by the battery will burn/fry everithing .
    A simple dropt tool or a rat biting the cables is enough or when you fast are changing cable connection on your and mix up . always try to be faster the murpys law.

    Greetings from Greece
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  • Robin Gudgel
    Robin Gudgel Registered Users, Solar Expert Posts: 58 ✭✭
    #8
    Re: OC protection question

    The DC output circuits of chargers are normally pretty short. Ten feet or less. You can put the breaker anywhere along that length. It is normally not practicle to put the breaker right next to the battery although that would be the best. Not a big deal though. Just make sure it is a DC breaker and that it has an interrupt rating adequate for the fault current that could develop if the charger goes South.
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