AC Activated Relay Problems

Discussion in 'The Projects Forum' started by leonhart88, May 1, 2013.

  1. leonhart88

    Thread Starter Senior Member

    Feb 23, 2007
    118
    1
    Hi All,

    I have a AC activated relay (Crydom A2425-10) which doesn't seem to be working properly, or I am misunderstanding something.

    I'm wiring it appropriately (120VAC live to pin 4, and 120VAC neutral to pin 3). I'm then connecting one end of the load to 120VAC live (pin 2) and probing pin 1.

    I notice that even when I remove the 120VAC live on pin 4, pin 1 is still reading 120VAC. I expect removing the 120VAC on the relay input would close it and I would read 0VAC on pin 1.

    Anyone have any thoughts on this?
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    Pin 1 NO contact ?
    Pin 2 NO contact ?
    Pin 4 Coil hot ?
    Pin 3 coil neutral ?
    Pin 2 is not hot unless connected to pin 4; load , one side to pin 2, other end floating.
    Can you hear relay click when power is applied?
    Maybe if you connect pin 2 to pin 4, load to pin1, & measure V between other end of load to pin 3; or better conect load directly to AC so that coil can be turned on & off.
     
  3. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
    If I understand correctly, you do not have a load connected to the relay?
    If not what you are probably reading is leakage through the SSR. I think if you connect your load (or a light bulb) to the relay, the voltage you are seeing will be gone.
     
  4. #12

    Expert

    Nov 30, 2010
    16,246
    6,738
    Trying to do this without a drawing makes my head spin. Maybe making a drawing would organize this in your head, leonhart. It won't hurt. It won't make you more confused. I promise.
     
  5. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304

    Bernard..I had to go and look it up, it's a solid state relay...no coil.
     
  6. leonhart88

    Thread Starter Senior Member

    Feb 23, 2007
    118
    1
    Thanks for all your replies. I should attach the datasheet next time so you guys have a better idea of what I'm trying to do. The relay is a SSR, so you won't hear a click.

    Correct, I was testing it without a load. I investigated further and noticed the relay uses a SCR output. I read that sometimes you need a bleeder resistor in parallel with your load in order for it to work properly. I'm going to attach the load and give it a try, but if I recall correctly, it still was not working (I'm using a cartridge heater, 100W, 120VAC, so roughly 150 ohms). It does seem to work properly when I attach a 10K ohm resistor in parallel though.
     
  7. leonhart88

    Thread Starter Senior Member

    Feb 23, 2007
    118
    1
    I take what I just said back. I removed my bleeder resistor, and plugged in my cartridge heater and it worked. I had an inkling it might be related to having no load but I was a bit scared to plug it in because it didn't seem to be working properly.

    I'm going to do a bit of research on my own, but I'm curious as to why this happens with AC activated relays, but not DC activated relays? I have a similar set up with a DC activated relay and it works fine without a load. I'm guessing it has something to do with SCRs...
     
  8. crutschow

    Expert

    Mar 14, 2008
    12,972
    3,219
    SCRs require AC to work properly in an AC SSR.
     
  9. leonhart88

    Thread Starter Senior Member

    Feb 23, 2007
    118
    1
    So after doing some research it does have to do with SCRs/TRIACs and leakage current as gerty mentioned.

    Also, the DC activated AC relay (which has SCR outputs as well) I was testing had a LED in it, which I'm guessing acts as a load, thus why I can't replicate the original problem with it. If there was no LED, I would expect it to behave the same since they both use SCRs.

    Thanks for the help!
     
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