Can the contacts of a "DC" specified relay handle "115ac"?

Question

I'm looking for a mechanical relay with a 12vdc coil.  Many of the cheaper ones out there are automotive. A couple list their contacts at 40amps at 14vdc or 20 amps at 14vdc.  Couldn't I still run 115ac through the contacts?  Most of the relays I have now I run  both ac and dc through (the contacts not the coil).  I know I wouldn't get the full amps listed at 14vdc but sheesh  I only need less than one amp. Thanks

? · Accepted Answer

The relay contacts are not rated for 115 Volt ac and while 115 volts is not a very high potential it could possibly arc over the low voltage dc contacts if you turn the relay off with an inductive load connected. Better to find a relay with ac contacts. You might want to checkout  this Radio shack relay it has a 12 volt dc coil 120 volt 10 amp contacts Catalog #275 - 248.

billrussell42 · Answer

you are probably OK, as long as the current is low. 

But if I were designing a product, and I wanted reliability, I'd get a relay that was rated for AC make and break. 


edit, I forgot about the insulation. I'd NOT use these relays for high voltage AC. The contacts are only insulated for 12 volts, not the 200 volts required for AC operation.

.

Technobuff · Answer

Don't use auto relays, use relays with contacts specified for 115 AC or better at your desired current switching. 1A is nothing!
Auto relays probably don't have adequate insulation (if any, sometimes!) to isolate the higher voltage. Too dangerous.

Anonymous · Answer

You could.  I wouldnt suggest more than an Amp tho, being as you are running it so much higher than its ratings.

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Can the contacts of a "DC" specified relay handle "115ac"?

4 Answers