Wall switch is very warm

Depends what you mean by "very warm". If it is uncomfortable to hold your fingers on the switch for any length of time then there's probably something wrong somewhere - perhaps the dimmer switch is incorrectly specified for the load? What are you dimming, and what is the specification of the switch?

On the other hand, if you just mean that it is "obviously warmer" than the ordinary switch, especially if the temperature drops when the light isn't dimming (i.e. is at full brightness) then it's probably normal. Check the documentation that came with the switch, it might tell you what to expect.

E&OE :-)

HTH

Hwyl!

M.

Yes. Dimmers always drop a volt or two in use - at say an amp for a mild

If its got complex electronics in it as well it may even be more.

We have the exact same problem, we bought our swtiches from homebase, the dimmer switches are definetly warm. We have just assumed that its warmer than the plastic ones before becasue the metal face plate conducts heat better. Husband is an electrician and had to double check the wiring was OK becasue of it, but its all fine!

Assuming all the heat goes outwards through the plate rather than into the wall, the outside temperature will be the same independent of it being plastic/ metal or whatever.

Yes, but your assumption is false. The lower the heat flow through the front plate the higher the ambient temperature in the box and thus more heat dissipated through the box and into the wall.

As heat is energy reducing it through the front plate obviously means the deficit goes somewhere else ...ie out the back!

Thermal conductivity of plastics can range from 0.2 to 500 W/mK (specialistic plastics) so I'll stick with my assumption of ignoring the % that goes into the wall, especially as most walls are insulated! So a quick calc with convection, conduction thermal resistances and ignoring contact resistances....

At steady state conditions are reached the convection from the outside of the plate to the air in the room will dominate the heat dissipation.

Stuff the coat, I'll get me annorac

wel it doesn't necessarily do that. Heat takes the 'shortest (most thermally conductive) route to a cold place. If thats a solid brick wall, so be it, if its a metal plate...then it will get warmer.

Thanks to all. I think I can safely assume the heat is normal : )