Switch ratings

Discussion in 'General Electronics Chat' started by shortbus, Aug 14, 2011.

  1. shortbus

    Thread Starter AAC Fanatic!

    Sep 30, 2009
    Probably a dumb question, but can't find an answer to it. Will AC switches and relays work for DC - IF - they are not switched while powered?

    I know what your saying, but, How about using a DPDT for reversing only when the power is off to the switch or relay? There will be no arc because power is off, and the actual contacts are of a large enough size to handle the current, so why not?

    Before I started to know enough, I did it quite often (used AC switches on DC) with out problems. Just want to know if its OK to do.
  2. Pencil

    Senior Member

    Dec 8, 2009
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
  4. SgtWookie


    Jul 17, 2007
    You can get into trouble with the coils of relays and solenoids.
    DC coils generally have more turns and higher resistance than coils made for AC do, so if you try to use a relay with a coil rated for AC voltage on the same DC voltage, you may overheat the coil.
  5. shortbus

    Thread Starter AAC Fanatic!

    Sep 30, 2009
    Thanks every one for the answers.

    @Pencil- thats the type of answers I was finding.

    @KJ6EAD- Thats the way I've always looked at the ratings. As long as the circuit was not powered at switching, the switch should handle the current.

    @SgtWookie- I knew about the relay coils, but some easily found relays have DC coils but AC contacts.