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Thread: Power under soffit

  1. #1
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    Default Power under soffit

    In an effort to locate power closer to a 5v pixel roofline setup, I'm considering putting power, an F8 distro and Falcon smart receiver in an ammo box, and securing it under the soffit of the second story. Is this safe to do, and does anyone else do it? With only one Meanwell 350w PSU, in say a MTM-30 ammo can, do I need active (or passive) ventilation? During Christmas-time, load on the PSU might hit 60%, with average ambient temps < 30f. Other times of the year, PSU would be ~15% load.

    Lastly, assuming this is safe and acceptable - if anyone has any recommendations on how to secure it (siding and soffit are both vinyl), that would be helpful as well.

    Thanks for any and all insights!

    - pc

  2. #2
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    Default Re: Power under soffit

    This is a very good question.

    For me, the rub is this: Will your enclosure contain a fire?
    the primary design consideration for all electrical boxes is not to protect your stuff, but to contain a fire.
    When these items are out in the yard, it doesn't seem to be as big of an issue as when they are attached directly to your house.
    You have to assume that a fuse doesn't work and that your meanwell PS is on fire in that enclosure.

    I'm not saying I have the answers, as others will certainly chime in.
    Just saying that the plastic for a real electrical enclosure, or the metal, are made of substances to contain fire.
    Not sure about a Harbor Freight plastic ammo can.
    If it were me, I'd be using a 'real' metal electrical enclosure.

  3. #3
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    Default Re: Power under soffit

    Hmmm....when they built my house; every outlet and switch was put in a plastic box with a plastic cover,....so many potential loose terminal connections yet metal boxes are available and not used.
    In Lights Therapy

  4. #4
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    Default Re: Power under soffit

    Plastic is fine for switches, outlets and connections. The only fire hazard is the wire and such and are designed to contain that type of fire.
    But, a Power Supply can generate enormous heat very quickly, therefore, something more may be prudent if attaching it to your home.
    Quote Originally Posted by mrGrumpy View Post
    Hmmm....when they built my house; every outlet and switch was put in a plastic box with a plastic cover,....so many potential loose terminal connections yet metal boxes are available and not used.

  5. #5
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    Default Re: Power under soffit

    As far as fusing, my understanding is you fuse to protect the wire. In which case, the 120v line feeding the PSU would be protected by the houses 15a CB. Or would you put an AC fuse or other safety mechanism to limit possible amperage to the PSU even further? I would, of course, put a LV fuse block in the enclosure to protect the 5v outputs from the PSU.

    As an aside, and I'm not sure if relevant, but I was planning on feeding the box from an outdoor extension cord (16ga minimum) plugged into an outside outlet about 25' below where the box would be. Not sure if that matters, or if this makes it an even worse idea.

    As for fire containment, would something like this be better suited for the job?

    https://www.polycase.com/an-07p

    Thanks,
    - pc

  6. #6
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    Default Re: Power under soffit

    Im just asking for a project Im working on for next year, but how were you planning on mounting it? (I need to mount a snow machine under my soffit)

  7. #7
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    Default -

    Id also want to be sure that the intake and airbox/filters etc are standard.

    Does it rev OK in neutral? Only under load you have issues?

  8. #8
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    Default Re: -

    Quote Originally Posted by AntonioZep View Post
    Id also want to be sure that the intake and airbox/filters etc are standard.

    Does it rev OK in neutral? Only under load you have issues?
    Uhhh. I think you have the wrong forum. This is about Christmas light controllers lol

  9. #9
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    Default Re: Power under soffit

    Electrical enclosures are designed to house electric stuff. Plastic electrical boxes ae usually designed with types of plastic that are "self-extinguishing". That's not to say that it won't melt, or burn. But it usually burns itself out quickly and minimizes the spread of fire. NEMA is the national electrical manufacturers association. It's standards are directly applicable for electric/electronic applications. You show an aluminum NEMA enclosure in the link above. But there are plastic NEMA enclosures too.

    Ammo cans and all those other popular solutions for cheap plastic boxes aren't designed with this in mind. Ammo cans are designed to keep ammo dry, but that's about it.

    It's important to keep things in perspective. The fire rating of an enclosure is the last line of defense. It's most important to make sure you're following all the best practices for designing the circuits inside your box, and making sure to control moisture appropriately.

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