Standard wall switches with a DC rating

yosemitebillMay 8, 2011

It seems like several years back I used to see standard wall switches that had both an AC and DC rating, but have looked everywhere and can't come with any at all. They were the "old fashioned noisy click style".

I want to replace some of the wall mount rocker switches in our motorhome with a traditional home type switch that you can find and just feels right in the dark. This is for the standard 12 volt lighting circuit.

I understand the DC arc issue of contacts fusing but tried some off the shelf 120 VAC switches thinking that the 1156 lights bulbs drawing only 2.1 amps might be OK. I mounted one in a nice looking surface mount box to try but instead found the arc burns the contacts enough to actually prevent current flow after several uses.

Does anybody know of any of these older type style switches that are still available?

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Try this useful link. Note it doesn't say ac OR dc. I have removed these several times, and as far as I can remember, they Are 'snappy'. Maybe not exactly what you want, but it's th first modern thing that came to mind.

Here is a link that might be useful: Useful link

    Bookmark   May 8, 2011 at 10:14PM
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DC switches do not have the convenience of the current going through zero twice a cycle like AC switches.
This tend to extinguish any arc that forms whan th eswitch opens.

DC switches need a strong snap action opening ht contacts and a wider contact gap when open.

If you look at switches that ARE rated for both, you will notice the DC voltage rating is far smaller than the AC rating.

Low voltage switches also need higher quality contacts and even use gold in some cases.
Using one of these switches for even a few cycles on 120 V AC removes enough gold (it is thinly plated) to prevent the switch from operating on low voltage DC.

You may have to change to toggle switches that do not look the same as typical AC snap switches.
They are easily available with up to 48 VDC ratings, but watch the current capacity.
At 12 V even a 20 W bulb is almost 2 amps (and may draw that much or more briefly when turning on).

    Bookmark   May 9, 2011 at 9:21AM
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Thank you for the replies and ideas.

You know, I have actually seen that Leviton switch, and also some round ones, at the hardware store in town. I'll have to look at the ratings actually stamped on it.

I guess the last time I did this in the early 90's, T-rated switches which appears to be the proper term of what I am looking for, were AC/DC rated and were still fairly easy to find. I also found info that shows the old mercury wall switches had a 10amp DC rating.

The idea of toggle switches always left me wondering on how to make it look a little nicer but I just thought now of maybe using empty CATV wall plates, or drilling out nylon plates, for the toggle switch.

The other thing that just came to mind was to maybe try the 1156 LED replacement that typically only draw about 100mA, with modern AC only wall switches.

    Bookmark   May 9, 2011 at 4:05PM
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I think you will find that the actual lumen output of those LED replacements is quite low. They are fine for brake lights and tail lights, where their high brightness is fine for being seen. But brightness is not the same as luminous flux.

I doubt that 12v compact fluorescent will help either. I haven't used one, but I'd expect them to have built in switching supplies with a fairly high starting inrush.

    Bookmark   May 12, 2011 at 12:15AM
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