DC electrical switches ? What do you use for DC ?

[scanzel]

In my conversion I am hoping to do all led 12/24v dc lighting. I would like to know what type of switches to use especially if you want to do a 3 way location. Ac switches are not apprved for dc so what does everyone use. The marine switches made by Carling switch are great but very expensive. So what is the suggestion ? Thank you.

[belfert]

I don't have any three way switches in my bus, but I just used Carling or Carling style switches in my bus.  I don't have all that many switches so the cost wasn't too bad in the overall scheme of things.

[robertglines1]

You are correct : many won't agree but a ac switch has a small amount of feed back  (electrical circuit draw) as I don't know correct term. I know your job lets you have a little more insight than most of us.  I stick with the bus switches and when I run out get the ones used in RV 12 volt Dc systems or go to local elect supply house and get dc rated rocker switches.  Good Question.!!   Really don't understand the mechanics of the AC switch  current draw when used on DC but learned that one the hard way.     Bob

[Sam 4106]

One way to switch a light from more than one location is to use latching relays. They work by sending a momentary low voltage signal the the relay from any of as many switch locations as you want. You can switch 12, 24, or 120 volt lighting with latching relays with the appropriate contact rating using 12 volts for the relay coils. Our bus lighting is wired that way with 1 relay for each lighting circuit. One circuit each for main living room, ceiling mirror, kitchen, dinette, bathroom, and two in bedroom. We can turn any light circuit on or off from 5 different locations. The switches have small neon lights above them so you can tell which lights are on. This was the way the bus was when we got it, and we like it.

Good luck, Sam

[Sean]

In my conversion I am hoping to do all led 12/24v dc lighting. I would like to know what type of switches to use especially if you want to do a 3 way location. Ac switches are not apprved for dc so what does everyone use. The marine switches made by Carling switch are great but very expensive. So what is the suggestion ? Thank you.

I bought my DC switches on eBay, where lots of surplus stuff ends up.  I paid maybe ten bucks for 50 switches, and they were SPDT, which means they can be used either as On/Off or three-way.  I paid dearly later, though, when I had to have the switch plates custom made.  I wanted stainless plates; it would have been much cheaper in plastic.

You can buy single- and multiple-gang DC switches with plates at many surplus stores such as Northwest RV Surplus in Eugene.

All that said, for very low-current (a few amps for lights), 12-volt applications, many household AC switches will work fine.  They will not be stamped on the package, but if you call the manufacturer, they can often tell you the DC rating of their standard AC switches.  You want the positive snap-action style with no illumination or other features.

The reason why DC ratings are much lower than AC ratings (and why some models can not be used with DC at all) is arcing.  AC voltage passes through zero 120 times per second, so any arc that forms while the switch contacts are opening is extinguished in a maximum of 8.34 milliseconds.  DC voltage is constant, and so any arc that forms will not be extinguished until the contacts move far enough apart to do so.   Arcing can pit and erode the contacts, and/or cover them in carbon deposits, all of which increases the resistance of the switch.  This ultimately leads to ohmic heating, which can be hazardous.

Opening a 12-volt circuit carrying just a few amps poses very little risk of arcing, and most standard, snap-action AC house switches will work fine.  Again, contact the manufacturer and ask what the DC rating of the switch would be.

If you want illuminated switches or other special features, you will need to stick with purpose-built DC switches rated for the voltage you are using.

-Sean
http://OurOdyssey.BlogSpot.com

[HB of CJ]

Crown Supercoach.  Never happened as old age got into the way.  Don't delay your dreams!  The chassis would have remained 12 volts DC OEM stock with perhaps some bulb updates and the House would have been all 110 VAC A/C running thru one (1) or two (2) sine wave inverters.  There would have been little or no interconnection between the two.  Hope this helps.  HB of CJ (old coot...now busless)

[luvrbus]

I was told the same as Sean is telling you guys years ago by my friend Dave Galey who is a electrical engineer from OK State U that a snap type household type would work for DC either the rocker type or the old standard flip  

I had some 2 ways and 3 ways in Matts Eagle and they never where a problem heck I broke one and replaced it the silent thinking when it quit I would replace it 6 years ago and it never has gave up it could be the marine wiring lol  

[robertglines1]

Guys : listen to the engineers! just passing on a personal bad experience. I will error on the side of making sure it is dc rated.  don't need to understand. Lots of things I don't understand.  Women for sure!!!!!    Bob

[HB of CJ]

Tulsa and Edison duked it out over this.  Nothing new here.  It has to do with arc breaking and supression and the amperage going through the low voltage DC switches.  Yep...be sure to understand your switches are appropriately DC rated.  Burning up hurts.  HB of CJ (old coot)  (did that poor engineer guy in the Titanic movie really get zapped when he fell against that huge old breaker/fuse panel?)  AUGHHHH!

[luvrbus]

I have taken a Blue Sea single pole ac/dc breaker (contrary to some they do make a AC/DC breaker)and a regular single pole Square D breaker apart and there was no difference in the 2 except the Blue Sea was sealed for moisture fwiw and cost 20 bucks

good luck

[Sean]

I have taken a Blue Sea single pole ac/dc breaker (contrary to some they do make a AC/DC breaker)and a regular single pole Square D breaker apart and there was no difference in the 2 except the Blue Sea was sealed for moisture fwiw and cost 20 bucks

I find that odd, because most Blue Sea marine breakers (the ones with the rounded and knurled handles with holes in them) are the magnetic-hydraulic type, whereas the typical Square-D breaker would be thermal-magnetic.  BTW, Square-D QO series breakers are rated for both AC and DC.

That said, Blue Sea does market some standard thermal-magnetic breakers, and Schneider Electric (Square-D and other brand names) also makes hyrdraulic-magnetic breakers, so it's possible you disassembled two of the same type.

The hydraulic mechanism is encapsulated, so it also may have appeared quite similar to the fixed-core mechanism of a thermal-magnetic breaker.

BTW, AirPax makes most of those marine-style breakers, and almost everyone who sells them OEMs them from AirPax.  The form-factor is standardized, so anyone's brand will fit anyone else's panel.  If you have a Blue Sea panel, no need to buy their breakers for additions or replacements.  I like the Blue Sea stuff, but they charge a premium for their products that is, IMO, unwarranted.  Paneltronics makes panels nearly as pretty for less money.

-Sean
http://OurOdyssey.BlogSpot.com

[Lee Bradley]

I am using latching relays at the main panel for each light circuit with push button grounds. You can add as many push buttons as you want/need per relay and use very light signal wire to the push button. Master panel for all circuits by my bed with LEDs to show energized circuits.

[Oonrahnjay]

  I am using latching relays at the main panel for each light circuit with push button grounds. You can add as many push buttons as you want/need per relay and use very light signal wire to the push button. Master panel for all circuits by my bed with LEDs to show energized circuits. 

     Can you provide Brand Name or website for your latching relays, Lee?  Thanks,   BruceH   NC   USA