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PID problems runaway temp

ctryboy88

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Joined Sep 18, 2013
Just finishing up PID and smokehouse build and gave it a test run today. I used SMD200 PID and ssr from auber. It's controlling a 240v element. The problem I'm having is that it seems the element isnt shutting off even though the indicator on the PID and on the ssr are showing they are cycling. I've double checked my wiring which was done according to the diagram in the manual and it seems to be correct. I'm not sure where to start trouble shooting. Is it possible the PID is bad? It displays as though it's working properly but the temp keeps going up. Thanks.
 

tallbm

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Just finishing up PID and smokehouse build and gave it a test run today. I used SMD200 PID and ssr from auber. It's controlling a 240v element. The problem I'm having is that it seems the element isnt shutting off even though the indicator on the PID and on the ssr are showing they are cycling. I've double checked my wiring which was done according to the diagram in the manual and it seems to be correct. I'm not sure where to start trouble shooting. Is it possible the PID is bad? It displays as though it's working properly but the temp keeps going up. Thanks.
I would guess that if anything was going bad it would be the SSR being stuck in the On/closed position.  This would cause electricity to always flow through the SSR to the heating element.

If you have a multi meter you can always check this by checking to see if electricity is making it to the heating element when the SSR is suppose to be cycled off there by cutting the electricity from the SSR to the heating element.

I hope this info makes sense and helps :)
 

clearprop

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You would have to check the DC leads going from the PID to the SSR, if they are HOT/CLOSED when they shouldn't be, the PID is at fault somehow. If the are not HOT/CLOSED, then you need to check the 240v line side of the SSR (Wire between the SSR and the ELEMENT), if that like is HOT/indicating 120v, then the SSR isleaking power/failed in CLOSED state.

I am in the process of building a PID and am trying to figure out the best FAIL SAFE OVER RIDE set up to protect against an SSR that failed in a closed state---and better yet---- protecting for not only the SSR, but protecting for a fail PID that is stuck giving voltage to the SSR...... any ideas?
 

masonsjax

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I recently finished an Auber SMD-200 build. The Auber SSR was dead on arrival. It took me some time to track down where the problem was. I assumed I had a wire crossed somewhere, but the SSR would not close even though the led would cycle. I removed the SSR and tested with a 9v battery and a 120v lamp and could not get the lamp to turn on. Auber sent me a new SSR without arguing, but it happened on a Friday and I had a replacement SSR delivered, installed, and working successfully on Sunday afternoon (from Amazon), before Auber even acknowledged my first email.

BTW, the Auber PID has an adjustable high (and low) temp alarm. I don't think it will shut off, but at least it will complain audibly when things potentially get out of control.
 
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tallbm

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I am in the process of building a PID and am trying to figure out the best FAIL SAFE OVER RIDE set up to protect against an SSR that failed in a closed state---and better yet---- protecting for not only the SSR, but protecting for a fail PID that is stuck giving voltage to the SSR...... any ideas?
I would follow the MES strategy and use this Goodman Amana B1370154 Flame Rollout Switch 350° OEM


After the SSR you wire that guy in and have it fastened into the smoker.  Should the temp exceed 350F then the switch would open and cut off juice to the element.  Again, this is what the MES does but I believe they use a one time switch at a lower temp rather than this resetable one at a higher temp :)
 
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clearprop

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A manual reset thermal limit switch does solve the problem if 350 is the highest temp you will use, but what if you were to want to use your electric smoker to smoke/bake a pizza at 425* etc? A second pid can be set and have the values changed to to 30 degrees (or whatever you wanted to consider an overheat temp) over any temperature you have your element controlling PID set to. I guess when doing LONG smokes (when you likely won't be around to personally monitor the smoke the whole time) the temp isn't going to be much above 220 degrees; therefore, a thermal limit switch would work good. Then when you are using HIGHER temperatures, it will be for a shorter time period when you will be around to monitor the smoke/cook and then you can just JUMP the thermal limit switch out of the circuit and reset it when done.

If the contractor hooked up to the overheat/run-away PID was installed after it's own PID, but BEFORE the smokers element PID, it would  turn off the smoker's element PID, and it's SSR and obviously the ELEMENT too.... that is where my theory ends...

Then I assume that when the temps drop below the overheat/run-away set point, the contractor will close the circuit and turn the other PID back on.... so would that PID resume where it left off and go back into an overheat state to then just get turned off until it cools down again and repeat? or when power is reapplied to the PID will it just sit idle?

I copied and changed the schematic below to add a secondary PID to control run-away over heat, not sure how it will work. Sorry this isn't with the SMD200, but the SYL-2352P, although it would shut it down the same (if it works?)


I'm guessing this is where a thermal limit switch COULD go? The SSR would still remain active from being failed in a CLOSED state, and then the temperatures would evenually fall, the PID would then send DC voltage to the FAILED SSR. Would the SSR keep getting hotter and eventually physically melt/start fire in this instance even though the circuit AFTER the SSR is OPEN from the thermal limit switch?

 
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ctryboy88

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Joined Sep 18, 2013
I found the problem, I shorted out the ssr and it's staying closed.I may add the thermal limit switch as I really don't want to add another PID to figure out how to program. I may have to have my 9 year old set the one I already have lol. Thanks everyone for the help.
 

tallbm

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I found the problem, I shorted out the ssr and it's staying closed.I may add the thermal limit switch as I really don't want to add another PID to figure out how to program. I may have to have my 9 year old set the one I already have lol. Thanks everyone for the help.
I'm glad you found your issue.

As for your idea of wiring in the rollout limit switch and then bypassing it with a switch (lets just pretend its a toggle switch) for hot cooks that would work and be simpler than a dual competing PID type setup, but there is one thing to consider.

The rollout limit switch would be tripped every time you did a hot cook above 350F because it is attached to the interior of the smoker at all times. 

Every time you flipped back from doing a high heat cook to a low slow cook you would need to make sure and hit the reset button on the rollout switch to reset it or else you will get no heat :)

Also double check what the upper temp limit of the rollout switch is so it doesn't get burned out from a high heat cook.

I guess you could always rig up some sort of insulated cover for the rollout switch so on hot cooks it doesn't trip and then remove the cover for low and slow cooks.  This would make life a bit easier on this kind of setup :)

If you take those factors into consideration and make it easy to reset the switch then you would technically be good to go :)
 
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clearprop

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Joined Jan 10, 2014
I'll try to come up with a way to make the thermal switch easily removable. I would image they aren't designed to be overheated and tripped that many times before they fail themselves or loose their tolerance. That way it can be swapable with one that is in a range/oven (has a higher over temp rating). Or have two of them: a higher temp and a lower temp that can be removable. Then again, they use then in furnaces to cycle on and off between operating ranges multiple times, but that is also considering it is operating within its temperature specs and not over shooting by hundreds of degrees.


I would recommend installing the thermal switches regardless. But having more precise control over the over temp with PID doesn't seem like it would be too big a of a pain to program, you would just have the change the one temperature setting on it's once set up.

Here is what I came up with so far (note this is for a 240v element and does not use a neutral)

The contactor can be placed between the element and the SSR if you didn't want it to shut the power off to the controlling PID.

 
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