While installing boxes and wires for fixtures can be reasonably straightforward, what happens if we want to install a ceiling fan in a room? Does it use the same type of box? While standard ceiling boxes are reasonably sturdy and can hold the weight of a standard light fixture, as electricians we are required to use a box that is rated for the application of what we are installing.
What is a fan-rated box? A fan-rated box can look much like a normal round/octagonal box, but there are a few differences. Probably the biggest difference is that they are rated to hold more weight than a standard ceiling-mounted electrical box. NEC 314.27(A) states that ceiling boxes are required to support a luminaire weighing 50 pounds. NEC 314.27(C) states that fan-rated boxes must be marked as suitable by the manufacturer, and shall not support fans that weigh more than 70 pounds. If they are designed to support more than a 35-pound fan, the required marking shall include the maximum weight to be supported.
Another distinct difference between a standard ceiling box and a fan-rated box is the attachment screws needed to support the fixture or fan from the box. While a standard ceiling box uses 8-32 screws, a standard wall outlet box uses 6-32 screws. A ceiling fan-rated box can use both 8-32 and 10-32 screws. It has these larger screws so that the boxes can support more weight than the standard ceiling box, and be able to better withstand the vibration/movement of a ceiling fan.
Ceiling fan-rated boxes come in both metallic and non-metallic variants. They are available in several different depths and configurations for almost any application you can think of.
When are we required to use them? During installation, we must adhere to NEC 314.27(C) regarding boxes mounted in the ceilings of habitable rooms of dwelling occupancies in a location acceptable for the installation of ceiling fans. These boxes should either be listed for the sole support of ceiling fans or provide access to structural framing capable of supporting ceiling fans. This is for ALL habitable rooms in a dwelling. We, as electricians, have no idea what kind of fixtures a homeowner or tenant might attempt to put up in a room in the future, so we must plan for the fact that someone WILL install one.
Ceiling fan-rated boxes do come in a few different styles. If you are installing a fan rated box in a new ceiling and are intent on mounting between two joists, you can get a standard depth round or octagonal box that mounts to a bar as seen below:
If you want to mount directly to the joist (as in the center of a room), you can use a pancake-style round box as seen below:
You could also use the above box to mount between two joists and span that distance with a piece of lumber. You would just have to make sure that it is capable of holding the weight of the fan. If you are in a remodeling scenario, you will first have to remove the existing box. This will leave you with a hole in the drywall where you can use a remodeling ceiling fan rated box as shown below:
These remodeling boxes are relatively easy to install, and can even be installed from below without the need to get into the attic (or between floors!!). The feet sit on the drywall while you screw the bar to make it longer, which forces it into the joist so it will carry the weight of the fan. Then just install the box, insert the wire and install the fan!
Where can you get them? You can find ceiling fan-rated boxes at any home supply center, electrical supply, or most local hardware stores, and they are available in all states. They are sold by companies like Raco, Arlington, Steel City, and Carlon just to name a few. They range in price from $5 or so up to $25. While pricing isn’t ALWAYS indicative of quality, just make sure that the box you are purchasing and installing is listed and labeled as rated for ceiling fan use. The last thing you want coming down on your head is a spinning fan!