AC versus DC switches

[wopachop]

Hardware store sells a $0.99 switch and also a $2.50 switch for residential AC application.
Was reading on this forum that its not safe pulling DC current through AC switches.
I currently have 4a worth of LEDs on a $2.50 AC switch. Is that unsafe?

 

[400bird]

It's not a great idea. What is your DC voltage? You'll probably have better success at lower voltages.
Is there a fuse or some circuit protection before the switch?

 

[wopachop]

Sorry its a trailer running 12v. The circuit has its own 10 or 15a fuse.

 

[400bird]

It's making and breaking the connection where this is most likely to become an issue. AC voltage and current pass through 0 many times per second, so it's easy to break the current. DC doesn't have the same 0 crossing, so it's much more difficult to break the connection. 12v is less likely to have issues when compared to 48 volts or higher.

 

[mikefitz]

4a worth of LEDs on a $2.50 AC switch. Is that unsafe?

No, not at 4A and 12 volts. Worst case, that's very unlikely, is the contacts fail.

 

[zanydroid]

I believe a lot of 120VAC switches are also listed for lower DC voltages. 12VDC is probably no big deal.

If you want it be risk averse you can confirm the Dc rating of your switches or use LED controllers with dry contact inputs to a control switch. Then the switch only needs to interrupt a control level signal (like less than a milliamp)

 

[Hedges]

You can also make contacts more resistant to DC arcing with a "snubber", such as capacitor and resistor in series, placed across the terminals. Or for inductive loads, a reverse-biased diode. Same thing we do in circuit designs to protect transistors.