120/240v DC

Will resistance electrical devices such as incandescent light bulbs and radiant heaters designed for AC work with the same voltage DC?

Robert Bates wrote:

Will resistance electrical devices such as incandescent light bulbs and radiant heaters designed for AC work with the same voltage DC?
I believe so, as long as by "the same voltage" you mean the DC voltage

is the same as the RMS AC voltage.
So how's the rest of the homework going?
-- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form che...@prodigy.net.

Hi Robert;
Robert Bates wrote:

Will resistance electrical devices such as incandescent light bulbs and radiant heaters designed for AC work with the same voltage DC?

The simple answer is no. While the heater element and lamps will run just fine, the switches, and thermostats are usually not rated for DC. The contacts tend to arc severely and may have a short lifetime.
Duane
-- Home of the $35 Solar Tracker Receiver http://www.redrok.com/led3xassm.htm [*] Powered by \ \ \ //| Thermonuclear Solar Energy from the Sun / | Energy (the SUN) \ \ \ / / | Red Rock Energy \ \ / / | Duane C. Johnson Designer \ \ / \ / | 1825 Florence St Heliostat,Control,& Mounts | White Bear Lake, Minnesota === \ / \ | USA 55110-3364 === \ | (651)426-4766 use Courier New Font \ | redrok@redrok.com (my email: address) \ | http://www.redrok.com (Web site) ===

Hi Duane,
Thanks for the info. Does anyone produce DC rated switches and thermostats for 120 and 240 volts? Why invert if you don't need to.
Thanks
"Duane C. Johnson" wrote in message

Hi Robert;
Robert Bates wrote:
Will resistance electrical devices such as incandescent light bulbs and radiant heaters designed for AC work with the same voltage DC?
The simple answer is no. While the heater element and lamps will run just fine, the switches, and thermostats are usually not rated for DC. The contacts tend to arc severely and may have a short lifetime.
Duane
-- Home of the $35 Solar Tracker Receiver http://www.redrok.com/led3xassm.htm [*] Powered by \ \ \ //| Thermonuclear Solar Energy from the Sun / | Energy (the SUN) \ \ \ / / | Red Rock Energy \ \ / / | Duane C. Johnson Designer \ \ / \ / | 1825 Florence St Heliostat,Control,& Mounts | White Bear Lake, Minnesota === \ / \ | USA 55110-3364 === \ | (651)426-4766 use Courier New Font \ | redrok@redrok.com (my email: address) \ | http://www.redrok.com (Web site) ===

Perhaps this doesn't come up much because incandescent light bulbs and radiant heaters are such high wattage devices that most folks don't think to run them off batteries in the first place.
Anthony
Robert Bates wrote:

Thanks for the info. Does anyone produce DC rated switches and thermostats for 120 and 240 volts? Why invert if you don't need to.
"Duane C. Johnson" wrote in message
Robert Bates wrote:
Will resistance electrical devices such as incandescent light bulbs and radiant heaters designed for AC work with the same voltage DC?
The simple answer is no. While the heater element and lamps will run just fine, the switches, and thermostats are usually not rated for DC. The contacts tend to arc severely and may have a short lifetime.

Hi Steve;
Steve Cothran wrote:

Robert Bates wrote:
Thanks for the info. Does anyone produce DC rated switches and thermostats for 120 and 240 volts? Why invert if you don't need to.
Lots of companies make DC rated switches/breakers, for example, for DC motor drives. But unless you can get them surplus, a couple of them will cost more than a decent inverter.

They do, but generally fairly expensive especially at 240V.
However, this doesn't help the original poster because the switches and the thermostats are built into the lamp fixtures and resistance heaters. It would be difficult for these to be replaced.
Duane
-- Home of the $35 Solar Tracker Receiver http://www.redrok.com/led3xassm.htm [*] Powered by \ \ \ //| Thermonuclear Solar Energy from the Sun / | Energy (the SUN) \ \ \ / / | Red Rock Energy \ \ / / | Duane C. Johnson Designer \ \ / \ / | 1825 Florence St Heliostat,Control,& Mounts | White Bear Lake, Minnesota === \ / \ | USA 55110-3364 === \ | (651)426-4766 use Courier New Font \ | redrok@redrok.com (my email: address) \ | http://www.redrok.com (Web site) ===

Robert Bates wrote: Thanks for the info. Does anyone produce DC rated switches and thermostats for 120 and 240 volts? Why invert if you don't need to.

Lots of companies make DC rated switches/breakers, for example, for DC motor drives. But unless you can get them surplus, a couple of them will cost more than a decent inverter.

Robert Bates wrote:

Hi Duane,
Thanks for the info. Does anyone produce DC rated switches and thermostats for 120 and 240 volts? Why invert if you don't need to.
Thanks
"Duane C. Johnson" wrote in message Hi Robert;
Robert Bates wrote:
Will resistance electrical devices such as incandescent light bulbs and radiant heaters designed for AC work with the same voltage DC?
The simple answer is no. While the heater element and lamps will run just fine, the switches, and thermostats are usually not rated for DC. The contacts tend to arc severely and may have a short lifetime.
Duane
-- Home of the $35 Solar Tracker Receiver http://www.redrok.com/led3xassm.htm [*] Powered by \ \ \ //| Thermonuclear Solar Energy from the Sun / | Energy (the SUN) \ \ \ / / | Red Rock Energy \ \ / / | Duane C. Johnson Designer \ \ / \ / | 1825 Florence St Heliostat,Control,& Mounts | White Bear Lake, Minnesota === \ / \ | USA 55110-3364 === \ | (651)426-4766 use Courier New Font \ | redrok@redrok.com (my email: address) \ | http://www.redrok.com (Web site) ===

Incandescent light bulbs that are run on DC must be controlled by T rated switches. The T stands for Tungsten. The inrush current to tungsten filament light bulbs is quite high. -- Tom Horne
Well we aren't no thin blue heroes and yet we aren't no blackguards to. We're just working men and woman most remarkable like you.

Anthony Matonak wrote:

Perhaps this doesn't come up much because incandescent light bulbs and radiant heaters are such high wattage devices that most folks don't think to run them off batteries in the first place.

120 VDC isn't always from battery power. Back when I went to college, the campus had its own DC generators and used the waste heat to heat the buildings. Voltage for lighting was around 120 vdc, which couldn't be connected to the grid, and since the heating would use oil and cost just as much as as the oil used by the old generators, which supplied free power, nobody wanted to spend the money to rewire the buildings involved with the DC power system.
Not only was the power generation on the campus cheaper than Con-Ed, during the big New York blackout it was an island of light in an otherwise dark city. IIRC, the wall switches were fairly large (rotary?) switches that felt like they had a strong spring in them.
You can read about the power plant here: <http://files.asme.org/ASMEORG/Communities/History/Landmarks/5628.pdf>
I found it fascinating reading, which answered a lot of questions I had when I was there. As a bonus, the very last page of the included Scientific American article from 1888 contains an image and description of an "electric dog cart" built for the Sultan of Turkey.