Fire Hazard? Expanding Foam - Electric Boxes

Discussion in 'Electrical Forum discussion & Blog' started by molo, May 8, 2009.

  1. molo

    molo Member

    Messages:
    844
    Location:
    cold new york
    Is there a fire hazard created when you put expanding foam around electric boxes? What, if anything, is safe when using the foam around a box?

    Thanks for any replies:)
  2. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    996
    Location:
    NY State, USA
    Supposedly foam is fine around boxes. Just make sure all holes are sealed so the foam does not enter the boxes.
  3. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    In that case heat dissipation from the box due to I²R loss and bad wirenutting/connections depends on heat conduction through the copper and the cover plate being at room temp. I guess the NEC has already figured the boxes would be insulated with no air flow around them.
  4. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    996
    Location:
    NY State, USA
    I have never heard of "heat dissipation" around electrical enclosures being an issue.
    A failed connection just need to be contained for safety.

    I would say the NEC definitely has considered this assuming many boxes and enclosures are on exterior walls and ceilings.
  5. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    I guess that means that enclosures have, or the air in them has, never gotten to 120 °C :D
    "Wood slowly chars [at] 120°-150°"
    but failed connections certainly have
    "Electrical arcing [up to] to 3750°[C]

    I guess air is pretty good thermal insulator.
    Last edited: May 9, 2009
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