RIMS Tube Flow Rate and System Functionality

HomeBrewTalk.com - Beer, Wine, Mead, & Cider Brewing Discussion Community.

Help Support Homebrew Talk:

reuliss

Well-Known Member
Joined
Dec 29, 2012
Messages
458
Reaction score
41
I recently build a rims system using a tube and a 1500W element, auber pid/ssr, etc. Over the past few brews, my system kept malfunctioning, where the pid controller was blowing past my target temps the second I hit the "on' switch for my heating element. I couldn't figure out what the issue was.

Then I went back to the drawing board, took my control box apart, etc. and found nothing wrong, really leaving me to scratch my head. I did another test run with plain water, redid the autotune for the PID, and STILL I was blowing past temp when I was actually brewing.

On a whim, I decided to increase my flow rate through the RIMS tube, and voila! Suddenly, the system worked perfectly maintaining temp. In several ways, I don't understand why flow rate should matter, since I would assume that with a slower flow rate the element would simply fire less often, but the proof is in the pudding, as they say.

Has anyone else made a similar observation? Similarly, anyone have any clue why my system is acting this way? Ideally, I'd like to use a slower flow rate if at all possible.
 

phreaky

Well-Known Member
Joined
Dec 20, 2010
Messages
177
Reaction score
90
Location
Kansas City
Your flow rate through the tube will affect how quickly the pid notices the temp changes, so it definitely is a key part of the calculations. You should always try to flow through the tube at the same speed, so that your pid settings don't need to be changed with each batch.

Once you determine the speed you wish it to flow at, then run another autotune, and it will calibrate it at that flow rate. From that point on, try to hit the same flow rate for each batch, and you're in business.
 
OP
R

reuliss

Well-Known Member
Joined
Dec 29, 2012
Messages
458
Reaction score
41
Your flow rate through the tube will affect how quickly the pid notices the temp changes, so it definitely is a key part of the calculations. You should always try to flow through the tube at the same speed, so that your pid settings don't need to be changed with each batch.

Once you determine the speed you wish it to flow at, then run another autotune, and it will calibrate it at that flow rate. From that point on, try to hit the same flow rate for each batch, and you're in business.
That makes a ton of sense. Thank you! If only I knew that before! I would have saved myself a lot of frustration! At least I know now :ban:
 

muhteeus

Well-Known Member
Joined
Sep 5, 2012
Messages
310
Reaction score
41
Location
Trophy Club
As someone about to build a system like this. Real world test-data is priceless.

With control you have to remember that any change to a variable affects your control loop. One small adjustment can be the difference between bounded and unstable.
 
OP
R

reuliss

Well-Known Member
Joined
Dec 29, 2012
Messages
458
Reaction score
41
phreaky said:
Your flow rate through the tube will affect how quickly the pid notices the temp changes, so it definitely is a key part of the calculations. You should always try to flow through the tube at the same speed, so that your pid settings don't need to be changed with each batch.

Once you determine the speed you wish it to flow at, then run another autotune, and it will calibrate it at that flow rate. From that point on, try to hit the same flow rate for each batch, and you're in business.
So I have an interesting update on this. I tried to re-auto tune but at a slower, more desirable flow rate. To my surprise I've learned that the PID becomes less precise. At a faster flow rate, after an autotune, the system will keep the temp at EXACTLY the right temp. At a slower flow rate, even after an autotune at that rate, the actual temp goes +\- 3 or so degrees and goes up and down continuously. After seeing that, I opted for the quicker flow rate but more consistent temps.
 

phreaky

Well-Known Member
Joined
Dec 20, 2010
Messages
177
Reaction score
90
Location
Kansas City
Any particular reason you want a slower rate? I've always felt the highest rate you can get without a stuck sparge is the best. It allows for quicker steps and steadier temps like you've noticed.

On my system with a full false bottom, and .5-1 lb rice hulls in every batch, wheat or not, I can almost run the pump wide open for the full hour of recirculation. Knock on wood, but have yet to get a stuck batch do far like this.
 

Rootsman NL

Member
Joined
Mar 1, 2021
Messages
13
Reaction score
0
Im experimenting with my flow rate as I had a scorched wort/burned element with my first use of my rims installation.
i tried another batch yesterday with a slower flow rate and it did not scorch this time. When I use a lower flow rate my PID controller is telling my element to use less power and is turning the element off more often. I used a flow of 3L/min (0,8 gallon/min). I have also learned that mashing at lower temperatures (protein rest) is causing scorching problems.

cheers Ruud
 
Top