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Thread: Metal Halide In-Rush Current

  1. #1
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    Richland, WA, Benton County
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    Metal Halide In-Rush Current

    We have several Lithonia LV1000M-GP6 lamps installed for truck yard lighting. They are operated via a lighting contactor and each circuit is fused ahead of the contactor. We are having recurring blown fuse issues. Does anyone have a rule of thumb for the in-rush current for these lamps? Any other ideas on why this happening?

  2. #2
    Join Date
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    Placerville, CA, USA
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    What type of fuse are you using? You want one with a long thermal time constant in the range of the inrush current.

  3. #3
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    The rule of thumb is you don't put more load on a circuit than it's sized for.

    How do you know it's inrush blowing the fuse? If it is then something needs to be rewired or reevaluated at least.
    Once in a while you get shown the light
    In the strangest of places if you look at it right. Robert Hunter

  4. #4
    Join Date
    Jun 2003
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    6,677
    It somewhat depends on the type of ballast. Many ballasts have a crest factor of 1.7 or 1.8. I believe that means the momentary current could be almost 2x the current calculated from the rated ballast wattage.

    Interestingly, one of the tables I have for MH ballasts state that on many types of ballasts the maximum input current occurs during a momentary power outage, and not on the initial startup.

  5. #5
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    Thanks for the feedback Guys, we are using Littelfuse CCMR 30A fuses. It is interesting to note that the ballast manufacturer lists an operating current of 2.35A but recommends a 6A fuse. If you can share your table(s) on MH ballasts that would be great.

  6. #6
    Join Date
    Jun 2010
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    Quote Originally Posted by GotShocked View Post
    Thanks for the feedback Guys, we are using Littelfuse CCMR 30A fuses. It is interesting to note that the ballast manufacturer lists an operating current of 2.35A but recommends a 6A fuse. If you can share your table(s) on MH ballasts that would be great.
    individual fuse is to identify the fault location and to prevent a fault at one fixture from pulling everything else down

  7. #7
    Join Date
    Jun 2010
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    There's a move towards LED in everything to trim down on wattage but many threads are coming up asking about 1,000W HIDs. I have no idea what's going on.

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