Fan rated boxes

[jmellc]

Sounds like another case where the NEC has become a design manual.
This provides for a "what if" and contradicts 90.1(B)

The thinking there is that a provision is already being made for a future fan. It stands to reason that if you provide a spare wire, why not provide a fan rated box? Replacing a box later is costly and sometimes damages the surfaces around it.

 

[jmellc]

I saw 1 situation where a fan box had been provided on a sloped ceiling that would not accommodate the fan being installed. The screw eyes would only allow the bracket to mount 1 way; it would not allow the ball hanger of the fan to be at the right angle. I had to dig the box out & replace with a different one. It was a pancake box. I forget the details, but rotating the box did not help. I should remember the details but they have slipped away. I remember thinking the manufacturers should think of such things.

 

[jmellc]

The fan he has, like most, mount to the box. I don't think independent support is in the instructions, but when I see the fan I'll check just to be sure.

And even if it were, who gets to build something to support the fan from? Usually the boxes are in between studs and hung with a piece of furring strip.

The easiest way to assure safety and compliance is to demo the old box and put in the kind with spreaders. If we are replacing a pancake box nailed to the bottom of a stud things get trickier. Hole relocation is usually the only option.

On edit: I have used saddle boxes that were fan rated to replace pancake boxes. I forgot about them.

Even concealed work boxes with spreaders are not trouble free in every case. I've had a few installs with 24" joists where the spreader had a bit of give & would allow the fan to pull the box out of the ceiling a little. Not dangerous, but not desirable either. I had to cut shims from a 2x4 to slide in and hold spreader, or tie wire it to wood subfloor above if there was any. Notice on some of those boxes too, that 16" joists allow greater weight load than 24" joists. A few fans out there may exceed limit with these.

I have worked with several fans that have a large hanger that can reach to joists, some to both sides. And if the box is side mounted to a joist, most of these brackets can mount with both sides to the same joist.