asr t1_j2pfg4c wrote on January 3, 2023 at 12:59 AM

Reply to comment by velifer in How many of these recessed lights can I use on a dimmer switch? by notscammed

Sorry, but it's you that is wrong. No one uses rheostat dimmers, they would radiate a ridiculous amount of heat - basically the entire heat load of a lamp, inside a tiny box.

/u/Riegel_Haribo is correct.

Maybe you are confused because they look like rheostats, but they are not.

velifer t1_j2psnxx wrote on January 3, 2023 at 2:28 AM

If you don't think the multi-wound rheostat dimmer for home lighting and fans was ever a thing, then I'm sorry that facts are hard for you. Yes they sucked. Yes, they could get hot. Yes, they absolutely were used in houses and in a form factor that fit into standard work boxes.

asr t1_j2q5rr4 wrote on January 3, 2023 at 4:02 AM

No they were not. Sorry, but rheostat dimmers simply get too hot to be placed inside electrical boxes on the wall.

You are just mistaken about this. They can only be used in specialized applications with the load exactly matched to the rheostat.

They were never used for general purpose lighting in homes.

I don't even get how you think they were supposed to work - the rheostat has to match the load exactly, how exactly would you even install them in a home where the homeowner can change the light bulb?

(Fans are a different story.)

EliminateTimeZones t1_j2qafne wrote on January 3, 2023 at 4:39 AM

Variable autotransformers do not need such close load matching and definitely have been used in residential applications. Bigger than your standard wall switch, but sold in a form factor to be installed in a standard 2x4 studwall

TrainerNaive t1_j2r5rl7 wrote on January 3, 2023 at 10:46 AM

Your house would soon be on fire if you fitted a simple rheostat in a regular wall box and used it to control more than a few watts.

The other folks are right, the earliest domestic lighting dimmers (late 60s onward) used semiconductor switches. Commercial premises, school halls and theatres had rheostat dimmers before that but they were in huge cabinets and dissipated huge amounts of heat.

Very low power fans might have been controlled by rheostat. More likely rotary variacs (variable auto transformers).

I am a chartered electrical and electronics engineer with over 50 years' experience.