Switch DC equivalent rating?

[drummerdimitri]

I'd like to buy some switches for a project but since they are rated for AC current and I need them for DC, what would be a good approximation of their DC ratings?

They're rated for AC 125V/6A or 250V/3A. I need them for 8A DC is that too much to ask or will it not go into thermal runaway?

[ejeffrey]

Yes, that is probably too much.  DC rating depends on the voltage even more than the current.  Switches typically have much lower voltage ratings at DC than AC due to the arc extinguishing properties of AC waveforms.  The load is another factor: an inductive load (such as a motor or relay coil) will tend to sustain the arc and needs snubber capacitors or diodes.

Maybe your switch could handle 8A DC at a very low voltage (5-10 V) that produces little arcing, but trying to operate at (say) 48 VDC would almost certainly destroy it.

[drummerdimitri]

Yes, that is probably too much.  DC rating depends on the voltage even more than the current.  Switches typically have much lower voltage ratings at DC than AC due to the arc extinguishing properties of AC waveforms.  The load is another factor: an inductive load (such as a motor or relay coil) will tend to sustain the arc and needs snubber capacitors or diodes.

Maybe your switch could handle 8A DC at a very low voltage (5-10 V) that produces little arcing, but trying to operate at (say) 48 VDC would almost certainly destroy it.

It will be used on a 5V circuit so it should be fine I guess 

[Nominal Animal]

Consider looking at automotive switches.  Cars use 12VDC or 24VDC, and the switches are usually marked with 12VDC current rating (10A is common).

Just a couple of days ago, I was looking at additional switches for switching ~12V LEDs, and automotive switches fit that bill perfectly.

[ejeffrey]

It will be used on a 5V circuit so it should be fine I guess 

Maybe?  As long as it isn't thermally limited (8A will produce ~70% more heat than 6A) it is probably OK.  But I agree with Nominal Animal: try looking at automotive switches to find one that has an actual low voltage DC rating.

[drummerdimitri]

It will be used on a 5V circuit so it should be fine I guess 

Maybe?  As long as it isn't thermally limited (8A will produce ~70% more heat than 6A) it is probably OK.  But I agree with Nominal Animal: try looking at automotive switches to find one that has an actual low voltage DC rating.

I have a Flir thermal imager, what would be a safe max temperature as I will test it before inserting it into the circuit. Does 60C sound reasonable?