I recently replaced a ceiling light fixture with a ceiling fan with two light sockets that have a maximum rating of 9 W for LED bulbs. The bulbs in the original fixture are 10 W LED and dimmable. The bulbs that came with the fan are non-dimmable. Can I use the 10 W bulbs in the 9 W max socket? My understanding is that heat is the main reason for the wattage rating, but does 1 W make that much of a difference? That’s barely 0.01 A if I’ve done my math correctly.
Both bulbs are 60 W replacement bulbs. The 10 W is a Satco S9703. The 9 W is an Ecosmart (I think it’s this). Fan is a Hampton Bay Rothley II 52050
Best Answer
There are two completely different thermal objectives
First, don't set other stuff on fire. That's decided by the thermal insulation of the fixture (think: thick insulation in down lights) and limits the size (in actual wattage) of any bulb, but it's mainly aimed at incandescents. Incandescent bulbs love hot places and work better there.
A fixture succeeds at this goal if it has plenty of insulation and creates a little "oven" for the incandescent to burn in.
Second, let the LED keep cool. The LED cannot tolerate high temperature - neither at the LED proper or the electronic driver. Its worst worst enemy is itself: even with their good efficiency, still nearly 85% of its actual wattage is turning into heat at the LED or driver. The heat will cause premature failure of the LED.
A fixture succeeds at this goal if it provides an easy way for heat to be convected away from the bulb location.
These objectives are at best unrelated, and at worst conflicting. For instance a well-insulated, embedded-in-ceiling downlight might protect from incandescents but cook LEDs. An antiquey lamp with "lamp chimneys" might work great to convection-cool LEDs, but with incandescents, scorch the ceiling above it.
The fixture's LED limit applies to the second thermal objective. It is saying "Above 9 watts, we can't guarantee we can keep that LED cool enough for it to have a long life".