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Oven Built: Looking to Wire. Wiring Diagram Attached for Review

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  • #16
    Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

    Purchased a new SSR the other day and replaced the old one. Ran another test and here is what happened:

    Autotune completed when I ran it at a low temperature and the oven was regulating flawlessly at 150 degrees. When I checked the input side of the SSR, it was shifting between about 20V and 0.2V respectively when it was regulating.

    Problem was when I upped the set temperature to 350, the elements start glowing as they should; also, now that autotune was completed, the PID was showing a PV (im assuming it is some indexed number on a scale of 100 about how much power the PID is outputting) that was decreasing accordingly as the actual temp neared the target temp. Even when the PV reached zero (and the input side of SSR was reading no voltage) the elements were still blazing and all regulation went back out the window.

    IM so confused by this.... Why is the SSR able to open and close at low temperatures, but as soon as the elements go full power, it seems to get stuck and won't turn the elements off? The only thing I can possibly think of at this point is that the SSR is getting too hot by the time it gets up to the higher temperatures and the heat is destroying the SSR by the time it gets up there, whereas at the low temperatures it was still working. Odd though, considering I have a fan and a huge heatsink on the SSR.

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    • #17
      Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

      I'm not very familiar with the mypid, but PV generally refers to present value as in actual temp. This should increase as the oven heats up and should even out with the SV or set temperature as that value is reached. If it isn't doing this then some pid parameter is wrong I would guess.

      As for the ssr, when you see zero voltage on the input side, have you checked the output side to see if it's reading ~240 volts AC. To be sure the pid isn't calling for heat, lower the set temp way down and then if the elements are still glowing, check the voltage across the ssr's output terminals. If the set point is below the PV or present value and the ssr is showing voltage across the outputs then the ssr is failing. If there is no voltage across the ssr output terminals and the elements are still energized then you have a wiring problem somewhere else.

      Be very careful with your troubleshooting as it may be possible that the elements are shorting to ground which would keep 120V on them constantly. If the oven is properly grounded then that should never occur but at this point most anything is possible.

      Also what ssr are you using and where did you purchase it. I know that some of the Foteks, which are good units are being falsely produced under that name in China.

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      • #18
        Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

        Originally posted by ed_denu View Post
        I'm not very familiar with the mypid, but PV generally refers to present value as in actual temp. This should increase as the oven heats up and should even out with the SV or set temperature as that value is reached. If it isn't doing this then some pid parameter is wrong I would guess.

        As for the ssr, when you see zero voltage on the input side, have you checked the output side to see if it's reading ~240 volts AC. To be sure the pid isn't calling for heat, lower the set temp way down and then if the elements are still glowing, check the voltage across the ssr's output terminals. If the set point is below the PV or present value and the ssr is showing voltage across the outputs then the ssr is failing. If there is no voltage across the ssr output terminals and the elements are still energized then you have a wiring problem somewhere else.

        Be very careful with your troubleshooting as it may be possible that the elements are shorting to ground which would keep 120V on them constantly. If the oven is properly grounded then that should never occur but at this point most anything is possible.

        Also what ssr are you using and where did you purchase it. I know that some of the Foteks, which are good units are being falsely produced under that name in China.
        When I lower the target temp beneath the current temperature in the oven, the input side of the SSR reads 0v DC. When I measure the output side, (correct me if I am doing this wrong) I switch the multimeter to 600v AC and I place the red reader on the output and the black reader on a metal ground, I get a reading of 120v (even when input side is showing 0 volts.) on both outputs 1 and 2 of the FOTEK.

        I disconnected the wire from the element-side output of the SSR (terminal 1 on fotek in image below) and plugged the oven into the wall: when I checked the voltage on that wire, it read 120v, even though it was not connected to the SSR. This would imply that there is constnatly 120v on the elements then and something is grounded incorrectly? And if that were the case, it doesn't make sense that it would have been able to regulate at the lower temperature.

        EDITED: This is the SSR I am using and it was purchased from here http://www.amazon.com/40A-SSR-Solid-...ywords=40a+ssrClick image for larger version

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        Last edited by KoreyI; 12-20-2014, 05:17 PM.

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        • #19
          Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

          Originally posted by KoreyI View Post
          When I lower the target temp beneath the current temperature in the oven, the input side of the SSR reads 0v DC. When I measure the output side, (correct me if I am doing this wrong) I switch the multimeter to 600v AC and I place the red reader on the output and the black reader on a metal ground, I get a reading of 120v (even when input side is showing 0 volts.) on both outputs 1 and 2 of the FOTEK. That would indicate the ssr output relay is closed and not working properly if the input is showing 0 volts DC. Could the pid be giving the ssr too high a voltage and causing the problem.

          I disconnected the wire from the element-side output of the SSR (terminal 1 on fotek in image below) and plugged the oven into the wall: when I checked the voltage on that wire, it read 120v, even though it was not connected to the SSR. This would imply that there is constnatly 120v on the elements then and something is grounded incorrectly? And if that were the case, it doesn't make sense that it would have been able to regulate at the lower temperature. No, the voltage is AC, so what you are reading is 1/2 the normal voltage coming through the element from the side directly connected to the source. Only one of the hot feeds(phase) is being switched. The element is getting 2 hot feeds, each phase 180 degrees apart in the sine wave, so when one feed is positive, the other is negative and serves as the return path for the current. This occurs 60 times a second, referred to as 60hz.

          EDITED: This is the SSR I am using and it was purchased from here Amazon.com: 40A SSR Solid State Relay: Everything Else[ATTACH=CONFIG]4376[/ATTACH]
          I will give this some thought and comment more later.

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          • #20
            Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

            Originally posted by ed_denu View Post
            I will give this some thought and comment more later.
            Thanks - when the pid i sending power to the inputs i get a dc reading of 24 volts and the ssr is supposed to be rated up to 32 volts, so i dont think that is the issue. I was considering purchasing an 80A ssr and larger heatsink directly from Auber instruments website but id hate to end up spending that and running into same issue :/

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            • #21
              Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

              Originally posted by ed_denu View Post
              I will give this some thought and comment more later.
              Thanks - when the pid is sending power to the inputs i get a dc reading of 24 volts and the ssr is supposed to be rated up to 32 volts, so i dont think that is the issue. I was considering purchasing an 80A ssr and larger heatsink directly from Auber instruments website but id hate to end up spending that and running into same issue :/

              Comment


              • #22
                Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

                Originally posted by ed_denu View Post
                I will give this some thought and comment more later.
                Ed, correct me if I am wrong because I have more experience with contactors than with pid.

                with zero voltage on inlet side of the ssr I would think it is normal that you get 120 v reading on either side of out put side of ssr
                when checking one terminal with ground because one side is coming directly from power source so a meter connected to that terminal and a ground should read 120 v,the other power wire is going directly to element and then comes back to the other side of ssr so a meter connected there and to a ground should read 120 v.

                in the first test that the op is doing both wires are connected to the output of the ssr , I think the black wire coming from the element should be disconnected to do the test.with that wire disconnected and zero voltage on inlet side he should check voltage between the two outlet terminals and if ssr is ok he should get a zero v reading .
                http://www.peintureenpoudrepb.com
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                baz

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                • #23
                  Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

                  Originally posted by baz View Post
                  Ed, correct me if I am wrong because I have more experience with contactors than with pid.

                  with zero voltage on inlet side of the ssr I would think it is normal that you get 120 v reading on either side of out put side of ssr
                  when checking one terminal with ground because one side is coming directly from power source so a meter connected to that terminal and a ground should read 120 v,the other power wire is going directly to element and then comes back to the other side of ssr so a meter connected there and to a ground should read 120 v.

                  in the first test that the op is doing both wires are connected to the output of the ssr , I think the black wire coming from the element should be disconnected to do the test.with that wire disconnected and zero voltage on inlet side he should check voltage between the two outlet terminals and if ssr is ok he should get a zero v reading .
                  Baz, You're absolutely correct. With single phase and two hot feeds from different phases there is no way of determining which phase you are getting a voltage reading from going to ground and phase to phase will always read 240V. Disconnecting the wire either at the ssr or element would work, but the problem with disconnecting the wire is that he is doing this test after a noted failure so all wiring is still hot. I believe if he shuts down the oven controls and then tests again all symptoms change. There actually may be an easier way. That is to check voltage across both of the element terminals if you have easy access and you should get a 240 volt reading if the ssr output side relay is closed. If you only see 120V then it would appear that there is a short to ground somewhere.

                  KoreyI, if you can test between the element end connections that would be one test but even that doesn't rule out bad wiring(or a short to ground). I would go back to testing the ssr with no load on the output side. To do this you would test continuity(ohms resistance) between the ssr's output terminals when the pid is calling for heat and when it's not. I've never seen or heard of an ssr that fails closed and then opens again when every thing is reset.

                  Baz, The only thing I would question is your last sentence. With the load side of the ssr output disconnected and doing a voltage check between the ssr's output terminals I believe the reading would always be zero volts as there would be no return current path regardless of the ssr's output relay state.

                  Bottom line is I would test the ssr without load on the output side by doing the resistance check. If the relay opens and closes correctly when input voltage is supplied then the ssr isn't at fault and I would look closely at the wiring and possible short conditions.
                  Last edited by ed_denu; 12-21-2014, 01:38 PM.

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                  • #24
                    Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

                    Just to clarify my above post and as baz has observed, you cannot check voltages at the ssr output side to perform any troubleshooting. Reason being is the the line side of the ssr is always hot with one phase and the load side is back feeding from the other phase that's going into the elements and back to the ssr. So any reading between the ssr's output terminals is always going to read 240V regardless of the relay's contact state and any reading from either terminal to ground is always going to read 120V.

                    So the two methods to test would be to check the elements terminals for 204V or test the ssr with no load as I mentioned above. The best method however would be to use a clamp meter. You could then determine if the ssr relay is open or closed by doing an amperage reading. This latter method would be my first choice.
                    Last edited by ed_denu; 12-21-2014, 03:50 PM.

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                    • #25
                      Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

                      Originally posted by ed_denu View Post
                      Baz, You're absolutely correct. With single phase and two hot feeds from different phases there is no way of determining which phase you are getting a voltage reading from going to ground and phase to phase will always read 240V. Disconnecting the wire either at the ssr or element would work, but the problem with disconnecting the wire is that he is doing this test after a noted failure so all wiring is still hot. I believe if he shuts down the oven controls and then tests again all symptoms change. There actually may be an easier way. That is to check voltage across both of the element terminals if you have easy access and you should get a 240 volt reading if the ssr output side relay is closed. If you only see 120V then it would appear that there is a short to ground somewhere.

                      KoreyI, if you can test between the element end connections that would be one test but even that doesn't rule out bad wiring(or a short to ground). I would go back to testing the ssr with no load on the output side. To do this you would test continuity(ohms resistance) between the ssr's output terminals when the pid is calling for heat and when it's not. I've never seen or heard of an ssr that fails closed and then opens again when every thing is reset.

                      Baz, The only thing I would question is your last sentence. With the load side of the ssr output disconnected and doing a voltage check between the ssr's output terminals I believe the reading would always be zero volts as there would be no return current path regardless of the ssr's output relay state.
                      You are correct i probably had one of my brain wires shorted for a minute, thanks for pointing that out


                      Bottom line is I would test the ssr without load on the output side by doing the resistance check. If the relay opens and closes correctly when input voltage is supplied then the ssr isn't at fault and I would look closely at the wiring and possible short conditions.
                      The methods you suggest in your next post will tell if the ssr is working properly.
                      http://www.peintureenpoudrepb.com
                      http://www.polissagepb.com
                      http://www.powdercoatpb.com
                      baz

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                      • #26
                        Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

                        Thanks again - I am going to check both tests as you've suggested. To check the voltage across the element terminals I will have to make some sort of access panel as I sealed that up with the sheet metal during construction (didn't think I'd really need to get at it again.) And with regards to testing the Ohm resistance without the load connected, can you suggest what sort of reading I should be looking for with voltage being applied/not applied on input side?

                        And last question: The new SSR that I purchased literally got so hot that the plastic part of it started to melt, which is again the reason I think this may be coming down to the SSR failing due to heat. My intention is to replace this SSR in the long run with one that isn't melted -- and on that note, would either of you suggest any particular SSR/heatsink combo that is known to be particularly good? I am willing to pay for the non-cheap stuff if it is known to be better quality: I was looking at the following:
                        80A SSR [MGR-1D4880] - $32.00 : auberins.com, Temperature control solutions for home and industry with this: Heat Sink for 80A SSR, Single Phase or 3 Phase [HS80] - $49.95 : auberins.com, Temperature control solutions for home and industry

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                        • #27
                          Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

                          Originally posted by KoreyI View Post
                          Thanks again - I am going to check both tests as you've suggested. To check the voltage across the element terminals I will have to make some sort of access panel as I sealed that up with the sheet metal during construction (didn't think I'd really need to get at it again.) I wouldn't do that, just look at the other methods of testing. Do you have or have access to a clamp meter?And with regards to testing the Ohm resistance without the load connected, can you suggest what sort of reading I should be looking for with voltage being applied/not applied on input side?Reading should be one(open) or zero(closed)

                          And last question: The new SSR that I purchased literally got so hot that the plastic part of it started to melt, which is again the reason I think this may be coming down to the SSR failing due to heat. If that's the case then I don't think there's any doubt about the problem. An ssr should never get that hot. Did you use a heat compound between the ssr and sink? My intention is to replace this SSR in the long run with one that isn't melted -- and on that note, would either of you suggest any particular SSR/heatsink combo that is known to be particularly good? How many elements/watts are you using?I am willing to pay for the non-cheap stuff if it is known to be better quality: I was looking at the following:
                          80A SSR [MGR-1D4880] - $32.00 : auberins.com, Temperature control solutions for home and industry with this: Heat Sink for 80A SSR, Single Phase or 3 Phase [HS80] - $49.95 : auberins.com, Temperature control solutions for home and industry
                          I personally do not have a favorable view of the Auber components. Rather than pay that for a heatsink/fan you might look to a salvaged computer cpu heatsink/fan combination. All desktops have them these days and they can be salvaged for probably nothing.
                          Last edited by ed_denu; 12-22-2014, 10:12 AM.

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                          • #28
                            Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

                            Thinking about this yet again here is probably the easiest way to test the ssr. Disconnect the ssr's output load side(going to the element). Wire nut it off as it will be hot when you power on the oven. Power on the oven. Then with a multimeter check the load side of the ssr that you just disconnected to ground. If the ssr relay is closed then you should see a 120 volt reading. If the ssr relay is open then zero voltage. With the pids SV value above the PV then the relay should be closed and you should see voltage. With the SV less than the PV then zero voltage, unless the ssr is failed close.

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                            • #29
                              Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

                              I unfortunately don't have a clamp meter. I checked ssr as per your final suggestion and it read 120 at all times with load disconnected -- so that's definitely stuck closed.

                              That leaves me with two defective ssr's and I highly doubt the chances if getting two DOA ones so the heat has to be ruining them.
                              I have three oven elements at 2600 watts each. The person who made the wiring diagram suggested to me that based on that total wattage a 40A ssr would be sufficient but I'm now starting to think I'd be safer with a 60A or 80A ssr with a larger heatsink. And, on the first two ssr's I wasn't using thermal compound but I just dug some out of my PC junk drawer and will certainly use it next time. The only concern I have about using a CPU heatsink and fan is that the contact point on the CPU heat sink I just dug up is not large enough to make full connect with ssr surface. I'll have to see if I can find someone else with some junk PC I can rip apart.
                              Last edited by KoreyI; 12-23-2014, 02:17 AM.

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                              • #30
                                Re: Oven Built: Looking to Wire. Wiring Diagram Attached for Review

                                With the ssr melted and reading 120V at all times then it's definitely toast. The 40A ssr for your load would be marginal, but the lack of using a thermal compound probably contributed to the failure. I'm pretty sure if you go with a larger ssr and heatsink with compound you will be fine. If you don't find a decent cpu combination then blowing most any fan over a heatsink would certainly improve upon cooling.

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