This is not brewing related although it looks like it could be. I wonder how that happened?
Here is the setup. The heat comes from two cheap 1500W hot plates. The intent is for the kettles to batch out oil and lye for soapmaking. So the initial heating could vary between three and seven batches. They are 5 and 10 gallon kettles. Soon to be both 10. *edit* Goal temperature is around 125.
The problem I am having is getting the controller to cope with the thermal mass of the cast iron hot plate. It is causing crazy overshoot.
I started with PID's. I autotuned several times (full volume and single batch) and could not get the results I was looking for. I did not get into manual tuning yet.
I figured that before I spent too much time on the PID's, I would try the DSPR120. I just swapped one of those in yesterday. I heated the oil kettle in mash mode with only one batch in it and overshot 50 degrees. I set the offset and tried again. It worked the second time but I wasn't crazy how the dspr handled it. It seemed to just limit the power to the element for the entire heating. That seems like it is not fully utilizing the heat source and will add a lot of time to heating.
In short, if any of you folks would care to offer some advice:
- What controller would you use for this situation?
- should the system be tuned to a full kettle, smallest batch volume or somewhere else?
- how best to tune?
Thank you for having a look and any help you can offer.
Here is the setup. The heat comes from two cheap 1500W hot plates. The intent is for the kettles to batch out oil and lye for soapmaking. So the initial heating could vary between three and seven batches. They are 5 and 10 gallon kettles. Soon to be both 10. *edit* Goal temperature is around 125.
The problem I am having is getting the controller to cope with the thermal mass of the cast iron hot plate. It is causing crazy overshoot.
I started with PID's. I autotuned several times (full volume and single batch) and could not get the results I was looking for. I did not get into manual tuning yet.
I figured that before I spent too much time on the PID's, I would try the DSPR120. I just swapped one of those in yesterday. I heated the oil kettle in mash mode with only one batch in it and overshot 50 degrees. I set the offset and tried again. It worked the second time but I wasn't crazy how the dspr handled it. It seemed to just limit the power to the element for the entire heating. That seems like it is not fully utilizing the heat source and will add a lot of time to heating.
In short, if any of you folks would care to offer some advice:
- What controller would you use for this situation?
- should the system be tuned to a full kettle, smallest batch volume or somewhere else?
- how best to tune?
Thank you for having a look and any help you can offer.
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