Folks,
While using propane a propane gas valve with burner under recirculation conditions, I was getting +- 1 degree mash temperatures for an hour.
I changed over to an electric Rims Tube and I am seeing +- 4 degrees. I have two temperature probes in use for the Rims Tube system. The first probe is where the wort enters the rims tube. The second probe is where the wort is returned to the kettle. The temperature is controlled from the temperature probe where the wort first enters the rims tube. I moved it to the other probe initially but didn't see much difference between the two. My thought was I wanted to heat the wort based off the temperature of the wort coming out of the kettle.
Under system settings on the BCS460 control, the differential swing for this output shows 3 degrees. I was targeting 154 degrees for my latest mash and was seeing 150 degrees and 157/158 degrees. I guess you could call this "chasing" the temperature a bit.
When the element was on, it seemed the different between input and output temperature was around 15 degrees.
Rims Tube - Temperature Swing
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BCS Portland
- Posts: 68
- Joined: Mon May 04, 2009 7:30 pm
Re: Rims Tube - Temperature Swing
I've got a temp probe @ Rims tube exit and one in the mash. The Rims tube probe controls the heat and I usually set my temps 1 degree higher than I want the mash to be at. That is the one part of my system that seems to be finally settled.
Re: Rims Tube - Temperature Swing
Be careful, the Differential Swing setting is only used for outputs under Differential Control. I'm guessing that you're using PID control, which uses the PID algorithm and tuning coefficients instead.
'Chasing' the temperature is usually the result of temp probe placement and PID tuning. Placing the probe directly after the element is usually recommended, as it simplifies the control system and hence the PID tuning (usually defaults work well).
You also have the option to use a probe placed further downstream, however this complicates the control system because it adds a variety of variables into the mix, such as grain/water thermal mass, heat loss, and pump speed, which are all system dependent. These variables can be overcome with a well tuned PID, but it will take some manual tuning to get there. The best way to get a feel for the PID algorithm is to see it in action with the PID Controller Display, which prints out each term and its effect on the system interactively.
I think the 15 degree differential can be explained mostly by pump speed. When you turn on the element, it takes significant time for the heated wort to return to the RIMS input. And, unless you have a theoretically perfect system, it will always be less than the RIMS output due to thermal loss to the environment (less than perfect insulation)
'Chasing' the temperature is usually the result of temp probe placement and PID tuning. Placing the probe directly after the element is usually recommended, as it simplifies the control system and hence the PID tuning (usually defaults work well).
You also have the option to use a probe placed further downstream, however this complicates the control system because it adds a variety of variables into the mix, such as grain/water thermal mass, heat loss, and pump speed, which are all system dependent. These variables can be overcome with a well tuned PID, but it will take some manual tuning to get there. The best way to get a feel for the PID algorithm is to see it in action with the PID Controller Display, which prints out each term and its effect on the system interactively.
I think the 15 degree differential can be explained mostly by pump speed. When you turn on the element, it takes significant time for the heated wort to return to the RIMS input. And, unless you have a theoretically perfect system, it will always be less than the RIMS output due to thermal loss to the environment (less than perfect insulation)
Re: Rims Tube - Temperature Swing
Thanks for the great information. When I ran the test with simple water, the probe placement didn't seem to matter much. I will switch the placement of my probes on my next batch and see what happens. It makes sense.
My thought was that I was heating based off of the temperature of the wort coming out of the kettle instead of the temperature of the wort returning to the kettle.
My thought was that I was heating based off of the temperature of the wort coming out of the kettle instead of the temperature of the wort returning to the kettle.
Re: Rims Tube - Temperature Swing
Think of it that you are returning wort to the MT at the correct temp regardless of the temp coming out.gbrewer wrote:Thanks for the great information. When I ran the test with simple water, the probe placement didn't seem to matter much. I will switch the placement of my probes on my next batch and see what happens. It makes sense.
My thought was that I was heating based off of the temperature of the wort coming out of the kettle instead of the temperature of the wort returning to the kettle.
With the probe in the RIMs output, you should never superheat the wort.
I have a probe in the RIMs output controlling the element and a probe in the MT just to monitor mash temp.
Ed
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missing_link
- Posts: 45
- Joined: Sat Dec 20, 2008 2:44 pm
Re: Rims Tube - Temperature Swing
I've been using an electric rims tube for a few years now.
I initially placed my control sensor at the exit of the mash. In this setting, the system calls for heat and begins to heat the return wort. It keeps heating until the exiting wort is at the set temp. Then your eyes bulge in horror as you watch the mash temp continue to climb to 170!!!
With the control sensor at the return, you just need to learn if you need to be 1 or 2 degrees over the set temp and the mash will hold perfectly the whole time. When testing with water and no grain, your system will heat and cycle quite a bit different than it does with grain.
Linc
I initially placed my control sensor at the exit of the mash. In this setting, the system calls for heat and begins to heat the return wort. It keeps heating until the exiting wort is at the set temp. Then your eyes bulge in horror as you watch the mash temp continue to climb to 170!!!
With the control sensor at the return, you just need to learn if you need to be 1 or 2 degrees over the set temp and the mash will hold perfectly the whole time. When testing with water and no grain, your system will heat and cycle quite a bit different than it does with grain.
Linc