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I'm trying to install a ceiling fan, however I'm not sure if the electrical box is rated for a ceiling fan. There are no screws available in the box. Am I supposed to use the screws through the box ears and then into holes at the end? The holes at the end only seem to have 2-3 threads, would they be enough to hold the weight of fan? The fan I'm trying to install needs at least 35 lbs weight (actual weight of fan is around 15 lbs). Do I use 10-32 screws or 10-24, and what length?enter image description here

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  • Can you figure out the brand name on the box? In metal boxes it’s often stamped into the metal on the inside, sometimes you can see it through paint, but that paint does look thick. If you can find the brand, I’m sure we can help you find the screw specs. – Tyson Jul 27 '18 at 16:00
  • It is a Harbor Breeze fan from Lowe's. @Tyson I tried scratching the paint but it is really thick, any tips on removing paint? – Jay M Jul 27 '18 at 18:41
  • I flipped thru google images hoping to get lucky but that’s didn’t help. My guess would be 10-32, length wise measure the depth of the box and add about a 1/4 or so. – Tyson Jul 27 '18 at 18:49
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    @Tyson I could find a similar looking box at coronadazecharters.com/electrical-box-for-ceiling-fan-support if that helps – Jay M Jul 28 '18 at 0:22
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    @Tyson Your advice worked! I removed the paint and found some details. The specs are here – Jay M Jul 28 '18 at 5:26
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The label says so, so yeah, it's fan rated

You can see a partially painted over label there that says it can handle a 70-pound fan or fixture when attached to joists that are 24" on center, so yeah, it's a fan rated box alright. However, it appears to use a metal hanger bar running across a joist bay (instead of mounting to a joist directly in the fashion a pancake or saddle box does).

As to what screws to use....

I would use 10-32 screws, about 3/4" longer than the depth of the box (so 2.5" or 3" long) and screw them into the holes in the back of the box that lie behind the cover-plate mounting ears -- they need to engage into the hanger bar behind the box in order to mount the fan correctly, it appears, in your case.

  • Is there any way to check if the screw will engage in to hanger bar also, or just the end of box. My original confusion was, if it's just the box there may not be as many threads to engage. Are the holes in middle same spec as the outer mount screws - I mean can I use them to test a screw without damaging the mount screw hole threads? – Jay M Jul 28 '18 at 0:31
  • @JayM -- I am not sure how you would tell how far the screw's engaging – ThreePhaseEel Jul 28 '18 at 0:52
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    You would go by length of the screw as you threaded it in. You will not damage the threads by testing if you are careful and don't force it or cross thread it. – Jim Stewart Jul 28 '18 at 1:14
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    Thanks all, @JimStewart I found out that it is an Arlington FBRS415. The depth of box is 1.5" and I could insert additional 1" without any issues. The box says "use only screws provided #10-32 with locking means". Would it be okay to get 10-32 2" screws with hex-head? Any ideas of what is meant by locking means, and do I need to go longer than 2.5" to hit the hanger bar? – Jay M Jul 28 '18 at 5:32
  • You want the screws to go into the mounting plate behind the top of the box, and some way past the mounting plate, but not contact the top of the mounting bar. The "locking means" would be a lock washer which impedes loosening of the screw from vibration. Some screws have a captive lock washer, but an added lock washer would do. – Jim Stewart Jul 28 '18 at 10:37
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Study this installation instruction sheet: Arlington FBRS415 pdf . There were two screws that were originally "parked" in the box to secure the fan bracket to the "ears" and those screws have been removed and lost. Contact the mfgr and get some new screws, if you want the exact type originally supplied. You could buy a complete new box of this type and remove the screws from it, but there are fastener outlets from which you can purchase specially rated screws.

But for the light weight fan that you are installing I believe any sufficiently long screws of the right diameter and thread pitch would suffice. However, if later someone wanted to put in a very heavy fan, then ordinary screws might fail. The rating of the box surely depends on having the mfgr supplied screws or equivalent.

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