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Thread: Solid State Relay - Voltage

  1. #1

    Solid State Relay - Voltage

    Anyone ever had an SSR leak voltage when not energized? I've noticed a very low level of illumination on an LED indicator light I have on my heating element circuit, so I put meter on it and sure enough, 10-12VAC. When the SSR is energized, it goes to 240vac. I measured the PID drive voltage and just to make sure, I disconnected the control voltage side of the SSR and even in open circuit control voltage I still measure 10-12vac across the load terminals. It's an 80 amp SSR that's only supporting 18 amps at 240vac.


    Best,
    Kelly
    My furnace build ----- I toil and fettle then foam turns to metal!

  2. #2
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    Yep, it happens...

    Been a while since I used SSRs but it was in industrial heat control applications and the leakage you're describing was a common occurrence.

    I've actually been bitten by some SSR heating circuits that "should have" been dead. Yet another reason for "safety nazi" approach to working on electrical equipment.

    Be careful...
    FLAME ON...!!!!

  3. #3
    Thanks Jay. I did a little web surfing and found some others that had similar remarks. I didn't know that. I'll act accordingly.

    Best,
    Kelly
    My furnace build ----- I toil and fettle then foam turns to metal!

  4. #4
    I've got a few ssr's, rather than find out they "leak" the hard way, I should check them out. Thanks for the heads up guys.

  5. #5
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    Can they "become leaky" with use and age or are they like that out of the box?

    Pete

  6. #6
    Quote Originally Posted by Petee716 View Post
    Can they "become leaky" with use and age or are they like that out of the box?Pete
    I have identical parallel circuits with SSRs and neither exhibited it initially. Somewhere along the way one did and consistently does now and for the first time the other did but doesn't do so consistently. I have an hour meter and LED status lights tied to the downstream side of the SSR and when I say "does it", I mean there is enough voltage across the SSR when it is open circuit control voltage to dimly illuminate the LED. When I measured it was 10-12vac. The coils have about 50 hours on them. That's probably 150-200hrs at temperature. How many relay cycles that equates to I cannot say but I'd guess no more than a cycle every 2-3 minutes average.

    In a way, the partially illuminated status lights are a good thing because it reminds me not to trust the relay just because the control circuit is open circuit. I still need to scrutinize the circuit and make certain there isn't another potential source of the voltage.

    Best,
    Kelly
    Last edited by kcoffield; 01-08-2018 at 07:43 PM.
    My furnace build ----- I toil and fettle then foam turns to metal!

  7. #7
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    Quote Originally Posted by Petee716 View Post
    Can they "become leaky" with use and age or are they like that out of the box?

    Pete
    Yes, and yes...

    I've seen them leak straight out of the box and have used some with zero leakage develop it over a short time.
    FLAME ON...!!!!

  8. #8
    Is there any noticeable difference (in terms of leakage) between cheap generic Chinese relays and more expensive name brand relays? Mine are Crydom relays.

  9. #9
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    I honestly couldn't say... I have zero doubt that I have ran the gambit in the quality of SSRs. Just very bothered comparing them on that level.
    FLAME ON...!!!!

  10. #10
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    Most solid state devices will "leak" a small amount of current, it's sometimes even listed in the specs as leakage current. I've had older PLC output cards with enough leakage current that when you used the output to turn a relay on, you could never turn it off. Standard answer was to add pull down resistors to the circuit, don't know if that helps or not.

    Don
    Too many irons, not enough fire,

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