My last house was built in 1947. It has an unusual low voltage sytem in which relays are actuated by a low voltage circuit. Its kind of neat, becaue the relay is placed near the load, and doorbell wire is from from the switch. Therefore, you can have a switch activating a light or device 10 feet away or 100 feet away without having to run full current handling cable. The wall switches are momentary contact rockers. The parts are rather hard to find, and very few electricians have ever even seems these systems.

I'm familiar with those. My wife's grandmother's "new" house (1948) in Clarksville, TN is wired with those - and you're right, parts are hard to come by. There are superficially similar lighting controls available nowadays, but I only encounter them in high-end commercial buildings, usually for 277 volt lights.

The supply wiring for the loads is conventional, of course.

To a point, higher voltage is more "efficient" than low voltage. Power is a product of voltage and amperage and to supply the same amount of power (or light), the amperage must go up a commensurate amount. What takes 1 amp at 120v takes 10 amps at 12v and so on. When the current goes up, so must the conductor size, also in a commensurate fashion. A wire rated for 10 amps will have about 10 times the effective cross section of a wire rated for 1 amp.

It's a little more involved comparing 12v DC to 120v AC when the discussion is power, but the principle applies AC to AC or DC to DC - lower voltage requires higher amperage for an equal amount of power (motor size, amount of light produced, heating element, etc)

TANSTAAFL.

Tom

You are correct. My house was designed & built by O'Neil Ford. He was very heavily into the housing for the masses movement post-WWII. He was the principle architect for the 1968 Hemisfair here. Among the other oddities of my house was that it was originally heated and cooled with central plant usiong ammonia coolant. There were 4 seperate air handlers located in different parts of the house. The central plant was about the size of a VW bug. I have no idea how efficient is was, as the house was retrofitted with conventional HVAC long before I got it. It is a flat roofed house with 4' eaves all around. Despite having huge windows, it has very little sun load.