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Oven Temp continues to rise

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  • Oven Temp continues to rise

    I'm running a MYPIN TA4-SNR PID, 2 40amp SSRs with 3 elements. My oven runs on 220 with double 40amp breaker. I think my elements are 2000 watts, and 2 3500 watts. I've got one 3500 element connected to one SSR and the 2000 and other 3500 watt elements connected to the other SSR. My oven heats up to 400 degrees in about 15 min. Once it reaches my set temperature the little red light on the MYPIN PID goes out and one of the 3500 watt element turns off. The other two elements stay red hot. My rising temperature slows, but continues to rise. I would have thought that all three would reduce heat to maintain my set temperature. What should I check? Do I have a faulty SSR? Suggestions.
    Thanks,
    David
    Last edited by david9h; 09-16-2017, 08:31 PM.

  • #2
    Incorrect wiring or bad SSR... Check the wiring carefully. I would start by checking the SSR input wires and make sure they're doing what they should... Best starting point other than a good visual inspection of wiring. It's even easier to just disconnect one of the input wires to see if the SSR in question
    shuts off the other two elements.
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    • #3
      Ok, I'll check the wiring. This is the first time I'm running two elements off one SSR. I previously had a one for one set up. If my one of my two elements were more wattage than I calculated would that cause my SSR to fail like this?

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      • #4
        SSR's can fail for a variety of reasons and in a variety of ways... I ran one SSR per Element in my build. I could easily see running as many as 3 lower wattage Elements on a single Higher amperage rated SSR... Basically... That should not be your problem unless you've created a higher load than the SSR was rated for. Since you haven't shared numbers, this is all that can be offered really.
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        • #5
          I checked my wiring and it all appears correct and all connections are tight. Quick test tonight. Both SSRs blinking in unison. Both red lights go out when the oven temp is 15 degrees over the set temperature. one element turns off. The other two stay on. i'll disconnect wires tomorrow to make sure which SSR is operating which elements.
          Scott, what other numbers would be helpful. i tried to provide numbers in my first post, but must have missed something important.

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          • #6
            Disconnected one SSR and found that the SSR that has two elements connected is the culprit as expected. I currently have two Fotek SSRs that are 3-32VDC input and 24-330VAC output. I have a backup Fotek SSR that is 3-32VDC and 90-480 VAC output. I think this will work fine as a replacement, but thought I would put it out there to see anyone thinks differently.
            Thanks.

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            • #7
              Current carrying capability of the SSR's would be helpful in working out issues... but it seems like You may have found your issue... Let me know how it goes.
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              • #8
                If you have a multi-meter then testing the ssr(s) can be fairly straight forward if you have a basic understanding of ssr's. Since ssr's only switch one leg of the 240V circuit you need to understand that even with the ssr in an open position, which is the state when the pid is not calling for heat you will get a reading of 240 volts across the ssrs' output terminals. With the pid calling for heat and checking voltage across the outputs the reading will be zero volts.

                Another method is to disconnect both output side connections and do a continuity check. Be sure to wire nut off both leads as the one back feeding from the element will also be hot. If you have an ssr you wish to check that isn't installed you can easily bench test it using any 12VDC battery.

                You don't mention heatsinks, but the most common cause of ssr failure is excessive heat buildup so ensure you have a good connection between the ssr and sink using a dialectic grease between them.
                Last edited by ed_denu; 09-18-2017, 10:55 AM.

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                • #9
                  Thanks for the follow-up. I had found the bench test method and found my SSR to have failed. I've got heat sinks and dialectic grease between both SSRs. I've been checking the temps in my box and haven't found anything more than warm, 80-90 degrees. What temp is excessive?

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                  • #10
                    There area lot of illicit Fotek's around, so search and verify that the ones you have are legitimate. The Foteks manufactured in Taiwan were very good and reliable ssr's, then someone started making knock-offs that were very unreliable. Assuming you have legitimate products then I would only be guessing as to why one failed assuming a proper heatsink. The two elements you're running should be fine for a 40A version of the ssr.

                    80-90F should not be excessive so I don't believe that's your problem. How long did the oven operate before the ssr failed? It's possible even with name brand products to get a defective one now and then.

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                    • #11
                      I had run my oven intermittently for about 5 years on the two Foteks. I think both were legit Foteks, but I'll have to refresh my "fake" knowledge again before I buy any more.

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