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I have a length of exposed metal conduit on my plywood ceiling with several boxes for light fixtures along it's length. I'd like to install a ceiling fan in one of these boxes. I understand that I can use a wiremount box or another ceiling fan rated box and then install the ceiling fan on that box. But I think the box would then be visible and I'd rather have the electrical box be hidden beneath the canopy of the fan. Is this possible?

  • How thick is the plywood and how is it attached to the joists above? – Jim Stewart Jul 28 '18 at 21:30
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    The plywood is is 5/8" oriented strand board (not sure if that's technically considered plywood). It is attached to joists using construction adhesive and 12D ringshank nails every 6". On top of that, the ceiling is lined with 1/4" birch ply attached with construction adhesive and 3/4" finishing nails – buildtiny Jul 28 '18 at 22:07
  • The screw holding ability for pull-out may be less for OSB than for plywood, but it is still probably enough for wood screws to hold a modern standard ceiling fan. These are maybe 30 lb. – Jim Stewart Jul 28 '18 at 22:17
  • Oh good! I was hoping so. The ceiling fan we plan to install is 22 lb. – buildtiny Jul 28 '18 at 22:41
  • How high is the ceiling above the floor? Do you have access to the area above the ceiling? You have said that you want to locate the fan at one of the boxes. Is there a joist at the location of the box? Or is the box between two joists? – Jim Stewart Jul 29 '18 at 20:06
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If the current box is rated for a light fixture, then you can use it for a fan, if there is structure behind the box to attach the fan bracket to. You could use long wood screws to clamp the fan bracket to the box and the screws would go through holes in the box or beside the box and screw into a suitable wooden member in the ceiling or just in the OSB if it is thick enough.

You could not use small bolts into threaded holes in the box designed for a cover or for a light-weight light fixture. The new Hunter fans come with fairly long wood screws which are designed to hold the fan bracket in ceiling joists, but check that they are long enough. The instructions will state how much thread of these screws must be in solid wood.

You might have to build a split ring out of plywood or solid wood, place it around the electrical box and screw that to the OSB ceiling. Then the fan bracket would be secured to the ring with the special wood screws supplied with the fan. Modern fans have a large shroud which would obscure the ring. There would be a larger gap than usual between the top of the shroud and the ceiling, but I don't think it would look bad.

  • Thanks so much! Do you think 1/2" ply would be sufficient for the ring? Assuming that the shroud completely covers the ring, I guess I would then just cut holes in the shroud to allow the conduit lines to run through? – buildtiny Jul 28 '18 at 22:59
  • You might have to have the ring thicker than 1/2". It might have to come out flush with the edge of the box so it might have to be 1.5 inches thick.It could be cut from a scrap of 2x8 or two pieces of 3/4" plywood (real plywood not OSB) fastened together. If the latter, the piece of 3/4" plywood on the room side could probably be a whole ring; the plywood on the ceiling side would be two pieces (to let the conduit through. – Jim Stewart Jul 29 '18 at 19:51
  • How high is the ceiling above the floor? If this is a low ceiling room (8 ft or less), then having the fan mounted 1.5 inches below the ceiling would be a negative. In that case one might think about alternatives. – Jim Stewart Jul 29 '18 at 19:57
  • What is the make and model of the fan? Will it have a light that hangs below the fan? Could you send a picture of the box? – Jim Stewart Jul 29 '18 at 20:00

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