I've recently installed an X10 dimmer switch (WS12A) in my HT according to the instructions. Today, while working in the HT, I noticed the switch was very warm--not hot. The lights controlled by the switch were on during this time.

My question is do you think this is something to be concerned about?
Could it be an indication of something being wrong?

Thanks.

It's normal.

It's normal for most dimmers to heat up as they are providing resistance to the load.

It's normal, if it becomes an issue you could install a dimming relay, placing the high wattage load on that as opposed to on the wallbox dimmer. Useful if you have someone using the space that dosen't understand that is normal operation.

It's normal for most dimmers to heat up as they are providing resistance to the load.

I haven't seen a resistance dimmer....ever.

The heat is due to the small voltage drop across the Triac.

Targus, that small voltage drop is a "resistance" ie: inefficiency. You're both right.

It's a 'resistance' whose voltage drop, doesn't change with current....also known as a PN junction drop....I wouldn't call it a resistor, you can if you want to though. ;)