Q:Why put temp probe in RIMS tube?

[Jwin]

Excuse me if this is a dumb question, but...
Why is it common practice to place the temp sensor for a PID I side the rims tube?
It would seem more beneficial to place it either in the mash or on the output of the MT, pre RIMS.
I assume there is a safety aspect to it to ensure the RIMS doesn't overheat/boil/burn the wort, but I don't get the benefit of monitoring the wort temp in the tube if the mash temp is what needs to be regulated.

 

[Queequeg]

Because the PID will switch to ON until the mash temp is reached (if lower) with no regard for the temp of the wort passing over the element, meaning the wort will be boiled in the RIMS tube. The result will be burnt tasting under attenuated beer.

You want the temp sensor as close to possible to the element, so that no portion of the wort is heated above the set point.

 

[johnnysoj]

You're correct about the safety side of things. If the flow of your mash gets impeded by grain, or a pump malfunction, and the probe is in the mash tun, then your rims tube might explode.

Its also to allow for even heating. Measuring the temperature inside the tun may accidentally allow the PID to heat the wort higher than 170, and prematurely denature your enzymes.

 

[bleme]

What makes the warmer wort pumped to the top of the mash mix through?

 

[cegan09]

You're looking to hold a certain temp, right? Which means you really don't want to be above it. If you measure before the element you may be heating to above set temp with the heater. If you only measure somewhere in the kettle you're certainly going to overshoot. By measuring immediately after the heating element you control the max temp the liquid ever sees. By continuously heating to that set point you eventually get the whole liquid volume to that temp with no overshooting.

having a second probe in the mash tun isn't a bad idea, just make sure it reads the same as the RIMS probe at the same temp, otherwise you'll drive yourself insane trying to figure out why they read different.

 

[Jwin]

So, correct orientation would be inlet on the probe side, outlet on heater side?
Cegan's reply would indicate differently. My thought process is, if you are measuring the rims heat wort, you would be extending the time needed to ramp the mash temp, and I'm intending to do pretty large batches on 120v, so any unnecessary off cycles could greatly increase the time to do so.

 

[cegan09]

What makes the warmer wort pumped to the top of the mash mix through?

The fact that it's recirculating? If you're drawing off the bottom then that liquid must be replaced, and it's replaced by the liquid on top. So you have a constantly flowing liquid volume that moves through the grain bed.

So, correct orientation would be inlet on the probe side, outlet on heater side?
Cegan's reply would indicate differently. My thought process is, if you are measuring the rims heat wort, you would be extending the time needed to ramp the mash temp, and I'm intending to do pretty large batches on 120v, so any unnecessary off cycles could greatly increase the time to do so.

inlet on the element side, outlet on the probe side. That's how just about all RIMS systems are setup.

 

[Jwin]

The fact that it's recirculating? If you're drawing off the bottom then that liquid must be replaced, and it's replaced by the liquid on top. So you have a constantly flowing liquid volume that moves through the grain bed.



inlet on the element side, outlet on the probe side. That's how just about all RIMS systems are setup.

So, for the sake of my own knowledge, what keeps the probe from providing the false positive of being at target temp? Just the eventual recirculation of the non heated wort? It just seems to me that this would cause non-needed off cycling of the element, delaying the ramp temp.
I suppose this would all be variable on element power and batch size. In my case, with a lower wattage element (2k/120) and 12-18g batches, would manual mode , pump full bore in the initial ramp be the best bet?

 

[augiedoggy]

So, for the sake of my own knowledge, what keeps the probe from providing the false positive of being at target temp? Just the eventual recirculation of the non heated wort? It just seems to me that this would cause non-needed off cycling of the element, delaying the ramp temp.
I suppose this would all be variable on element power and batch size. In my case, with a lower wattage element (2k/120) and 12-18g batches, would manual mode , pump full bore in the initial ramp be the best bet?

The fact that the probe turns the element off once target temp is reached... thats the whole point to have it near the source so it can react faster in "real time" ... There is a couple minute difference between the time the wort passes by the element and then circulated through the grainbed and reaches the exit of the mashtun... if my probe was at the mt exit or at the rims input the temp would have way overshot the correct temp because my element would have been on the whole time.. also unless I didnt have my flow switch to kill my element in case of a stuck sparge the rims could build up pressure with a stuck flow situation and no temp probe located nearby to tell it to stop heating... The result could be like a pipe bomb. the element needs to cycle on and off quickly to remain just hot enough to maintain a temp as the liquid passes otherwise it would just keep going up or down. you want it all to be an even temp thru recirculation its not like a pot where your stirring it.

This is also why mechanical relays just dont work long in a rims application.

FYI I use an 1800w 240v (7amps) 36" long rims tube for my brewing and often brew with 11 gallons going into the fermenter. I can maintain temps and even step mash fine with my setup . I recirculate at about 1.8 gallons perminute (measured on a flowmeter) which prevents any channeling and gives the rims plenty of time to heat evenly... I average 86% efficiency and I dont even sparge traditionally... I just turn two valves to redirect flow and run 170degree water through the grainbed at the end while the kettle is filling at the same rate from the bottom of the mashtun through the rims into the BK until my preboil volume is met...

 

[cegan09]

There will be some cycling of the element when you're close to target temp. But it won't add too much delay, I'd say maybe 10 minutes for me? If you're that worried about it, take a temp reading of your mash tun when the element starts cycling, figure out the temp difference, and then make your set point that much higher. Then once you add grains drop the set point back to your desired mash temp. Doesn't take me that long to get to temp on 120V for 5 gallon batches. I use an Auber EZBoil for my controller.

You're going to have fun with 12-18gal batches on 120V. I run two separate circuits into my controller so that I can run two separate 1500W elements in the boil. It gets to a boil, just only just. I can't imagine how long it's going to take, or if you will get there on 120V with batches that large.

 

[Jwin]

I'm only using mine for RIMS/mash temp ramping. maybe for strike water for early morning stuff(turn it on, walk away and eat breakfast)
Propane elsewhere.

 

[cegan09]

I'm only using mine for RIMS/mash temp ramping. maybe for strike water for early morning stuff(turn it on, walk away and eat breakfast)
Propane elsewhere.

Ah, carry on then. You should be ok. I can't predict the speed you'll be able to change mash temp at, but maintaining mash temp will have no problem. I would suggest not running the pump full speed though. I think I've heard targeting 1/2 - 1 gal/min on the flow rate. Not sure what mine actually is, but it's certainly less than 1gpm.

 

[Bobby_M]

If the probe is in the mash and the mash is 1 degree below set point, it will fire the element until it senses setpoint temps. That's great but it will fire the element full until that happens. With a good flow rate and appropriately sized element, it may work out great. The wort exit temp at the rims may only run a few degrees above set point. Where you ruin your batch is where the pump has a problem. Flow rate stops, controller is never satisfied, wort caramelizes and burns.

With the probe at the exit of the RIMS and running at normal flow, you will learn how much offset you will typically need to maintain an average set point. In other words, you may need to run the RIMS at 2F above desired temp in order to get the mash exactly where you want it. This works fine and it's only frustrating if your mash tun bleeds heat, like if you brew outside in sub zero winds.

By the way, the Auber EZboil control module is insanely good at holding the RIMS exit at the exact temp you want.

In a perfect world, the controller would have a probe input from the RIMS exit and the middle of the mash and make decisions based on both temps. I'm not aware of such a controller and it's not really necessary.

 

[thekraken]

In a perfect world, the controller would have a probe input from the RIMS exit and the middle of the mash and make decisions based on both temps. I'm not aware of such a controller and it's not really necessary.

This is what I did. Arduinos are fun

 

[augiedoggy]

I agree the ezboil worked really well for the Time I used it ... I also jumped to the darkside with a touchscreen based arduino system now...

 

[Jwin]

If the probe is in the mash and the mash is 1 degree below set point, it will fire the element until it senses setpoint temps. That's great but it will fire the element full until that happens. With a good flow rate and appropriately sized element, it may work out great. The wort exit temp at the rims may only run a few degrees above set point. Where you ruin your batch is where the pump has a problem. Flow rate stops, controller is never satisfied, wort caramelizes and burns.

With the probe at the exit of the RIMS and running at normal flow, you will learn how much offset you will typically need to maintain an average set point. In other words, you may need to run the RIMS at 2F above desired temp in order to get the mash exactly where you want it. This works fine and it's only frustrating if your mash tun bleeds heat, like if you brew outside in sub zero winds.

By the way, the Auber EZboil control module is insanely good at holding the RIMS exit at the exact temp you want.

In a perfect world, the controller would have a probe input from the RIMS exit and the middle of the mash and make decisions based on both temps. I'm not aware of such a controller and it's not really necessary.

Thanks for chiming in Bobby. I have your 2k element and rims tube and planned on the ezboil. Which side of the tube do you recommend as the inlet?
Maybe I could install a STC style controller between the output of the ezboil and the SSR? Set it to a sub boil temp and send the rims probe to it, acting as a safety. Then send a probe mounted in the MT outlet to the ezboil? Any issues with that concept. Obviously there would be the fact of learning how much the temp would climb after the ezboil sees the target temperature, but that would be daily easy to document and recall/offset on future brews.
I am of the assumption that as long as the post rims wort is being dispersed fairly evenly, avoiding channeling, the temperature should be fairly consistent across the mash.

 

[thekraken]

Maybe I could install a STC style controller between the output of the ezboil and the SSR? Set it to a sub boil temp and send the rims probe to it, acting as a safety. Then send a probe mounted in the MT outlet to the ezboil? Any issues with that concept.

That might work. I'm not familiar with the ezboil but the description of the ezboil says it can be used for *some* mash systems, I assume it does not have PID logic. It sounds like it uses more of a thermostat logic? If that's the case that makes it good for putting the probe within the RIMS tube where temperature changes happen quickly, but *probably* not good for placing inside the mash tun where temperatures changes relatively slowly. A properly tuned PID unit might be better for what you propose... one way to find out though.

Obviously there would be the fact of learning how much the temp would climb after the ezboil sees the target temperature, but that would be daily easy to document and recall/offset on future brews.

It seems to me that if your going to go to the trouble of two controllers that it better by all hands off. At this point you might as well just do as bobby recommended and just have one controller with a probe in the RIMS tube and know from previous experience what the to offset the controller to get the right temp in the mash.

 

[Jwin]

That might work. I'm not familiar with the ezboil but the description of the ezboil says it can be used for *some* mash systems, I assume it does not have PID logic. It sounds like it uses more of a thermostat logic? If that's the case that makes it good for putting the probe within the RIMS tube where temperature changes happen quickly, but *probably* not good for placing inside the mash tun where temperatures changes relatively slowly. A properly tuned PID unit might be better for what you propose... one way to find out though.


It seems to me that if your going to go to the trouble of two controllers that it better by all hands off. At this point you might as well just do as bobby recommended and just have one controller with a probe in the RIMS tube and know from previous experience what the to offset the controller to get the right temp in the mash.

Thanks for the reply.
My concern isn't the offset, it is unnecessary off cycling of the element, delaying achieving target temp.

The ezboil has decent logic and autotype, as good as their other units afaik.

I have a spare inkbird STC style controller, so it no more trouble or cost than the wire hanging from it and a second probe, though I'm not sure if they accept the rtd pt100 probes I'm wanting to use.
Not trying to play devil's advocate here. I have a tendency, like others here, to over engineer at times. But, I only want to build this once.

A bit more about my situation:
I do 12g partygyle batches.
Usually a big beer, followed by a 5-6% brew.
I use a 30g Coleman extreme as my mash tun.
Now, that's basically results a 1bbl mash size.
220 is not an economical solution for me. So, with the limited BTU of a 2k/110 element, the desire to not have the element cycle off, I believe, is a concern.(run on much?) I don't want to wait 15-25+ minutes for a 15° ramp due to the limited heating capacity to volume ratio.
I have experimented with full bore recirculation with my setup and haven't had any issues/cavitation. I don't think scorching would be an issue with enough flow.

Now, if I'm over thinking this, please tell me so. Without having it all together, I wont know how much off cycling will occur. But, like I said, I only want to build once.

 

[cegan09]

I think you're just looking for reasons to over-complicate things. Put the temp probe in the outlet of the RIMS and brew. If you're really using propane to get to strike temp then your concerns about it cycling early are basically voided.

Do a water only test if you're worried. Heat to strike temp, then set the RIMS for that temp and see what it does. If the mash tun happens to settle to a degree or two below the RIMS set point then move the set point and just do that for all future brews.

I can tell you that my EzBoil controlled RIMS setup holds mash temps dead nuts on. I heat to strike temp, add grains, adjust my set point to mash temp and walk away for an hour. An hour later it's all still dead on, both measuring in the RIMS and taking readings inside the mash tun.

 

[PlexVector]

Thanks for the reply.
My concern isn't the offset, it is unnecessary off cycling of the element, delaying achieving target temp.

The ezboil has decent logic and autotype, as good as their other units afaik.

I have a spare inkbird STC style controller, so it no more trouble or cost than the wire hanging from it and a second probe, though I'm not sure if they accept the rtd pt100 probes I'm wanting to use.
Not trying to play devil's advocate here. I have a tendency, like others here, to over engineer at times. But, I only want to build this once.

A bit more about my situation:
I do 12g partygyle batches.
Usually a big beer, followed by a 5-6% brew.
I use a 30g Coleman extreme as my mash tun.
Now, that's basically results a 1bbl mash size.
220 is not an economical solution for me. So, with the limited BTU of a 2k/110 element, the desire to not have the element cycle off, I believe, is a concern.(run on much?) I don't want to wait 15-25+ minutes for a 15° ramp due to the limited heating capacity to volume ratio.
I have experimented with full bore recirculation with my setup and haven't had any issues/cavitation. I don't think scorching would be an issue with enough flow.

Now, if I'm over thinking this, please tell me so. Without having it all together, I wont know how much off cycling will occur. But, like I said, I only want to build once.

Let's look at your problem from a different position.

Your goal is to heat 30 gal as quickly as possible. Per the laws of thermodynamics for a fixed mass to shorten the time you need a greater delta in temperature. With a rims you are heating a small mass and adding it to a greater mass, so the quicker you can heat that small mass and add it to the larger mass will decrease your time. so, your limiting factors are what temperature are you willing to heat the small mass in your RIMs. Too high and you will scorch it, so you need to move the mass more quickly through the RIMs, but you have limited power to heat the small mass to add to the large mass at the flow rate required to heat the large mass in a shorter period of time.

So the problem is not that the probe sitting at the RIMs output cutting on and off. You just don't have the power to heat the mass in the time you would like to see with the system you have.

This is what I do with a similar system as yours, but smaller scale. I heat the strike water in the kettle as quickly as I can with a propane burner and use the rims to maintain the mash temp in my cooler. That way the 110V RIMs system only needs to maintain the difference in heat loss of the system. For me I set the RIMs PID 2F above mash temp. Even with a 220V RIMs this method is quicker than trying to heat to strike with the RIMS.

 

[Wizard_of_Frobozz]

My concern isn't the offset, it is unnecessary off cycling of the element, delaying achieving target temp.

In my system the temperature probe is right at the exit of the RIMS tube. When I am ramping up from one rest to another, the element stays on 100% until the temperature gets within a degree or two of the new setpoint. It only starts to cycle off once it's it's there, so there really isn't any excessive "off" time. For reference, I have a 3500W 240V element in my RIMS chamber.

I've found that having a decent recirculation rate is at least as important as the power of your heater element when it comes to ramp times. As long as the fluid is moving sufficiently (and your controller is tuned properly), it will heat the wort as fast as it can until you reach your higher temperature. That's basically the end of your your ramp up anyway, so you haven't lost any time.

 

[thekraken]

In my system the temperature probe is right at the exit of the RIMS tube. When I am ramping up from one rest to another, the element stays on 100% until the temperature gets within a degree or two of the new setpoint. It only starts to cycle off once it's it's there, so there really isn't any excessive "off" time. For reference, I have a 3500W 240V element in my RIMS chamber.

I've found that having a decent recirculation rate is at least as important as the power of your heater element when it comes to ramp times. As long as the fluid is moving sufficiently (and your controller is tuned properly), it will heat the wort as fast as it can until you reach your higher temperature. That's basically the end of your your ramp up anyway, so you haven't lost any time.

I think the point OP is trying to make is that while ramping when your RIMS output gets to setpoint it starts cycling but the grainbed is still lagging behind. With a perfect world RIMS controller it would ramp the fastest by heating the liquid in the tube well past setpoint to reach equilibrium at the setpoint within the grainbed. (That's not to say there is anything at all wrong with your system, again just thinking about perfect world here)

 

[Wizard_of_Frobozz]

I think the point OP is trying to make is that when your RIMS output gets to setpoint it starts cycling but the grainbed is still lagging behind. With a perfect world RIMS controller it would ramp the fastest by heating the liquid in the tube well past setpoint to reach equilibrium in the grainbed at the setpoint. (That's not to say there is anything at all wrong with your system, again just thinking about perfect world here)

Yeah, that would be a method to achieve a faster ramp time, if you could effectively control it. It would mean you end up heating some of your wort above your target rest temperature. Not sure that really would be an issue - after all, a decoction mash boils a portion of your wort to achieve the same thing, and that's a time honored technique.

However, I do think there are some practical limitations to being able to hit the perfect world that make it very hard to achieve in real life. I've had issues with heating too fast, and boiling inside the RIMS tube, which causes my pump to start pulsing, and the flow rate into the mash tun drops off a lot. I've tuned my controller so that doesn't happen anymore, but as I was learning the system, I found that the best overall results were from setting my target rest temperature, and letting the controller turn on and off to keep the output of the RIMS tube at that temperature.

So many things can affect your system performance - pump, piping, mash tun, heater power, etc. In the end, you have to experiment with your system and see what works best for you. It would be interesting if you could make a RIMS system perform like a decoction mash. We'd need a new acronym - RDMS doesn't seem right, for some reason

 

[golfindia]

Maybe it could be accomplished by running 2 back to back RIMS tubes and writing some arduino code to adjust between the output of the two. I'm not smart or motivated enough to think about it beyond that point, though.

 

[augiedoggy]

I think the point OP is trying to make is that while ramping when your RIMS output gets to setpoint it starts cycling but the grainbed is still lagging behind. With a perfect world RIMS controller it would ramp the fastest by heating the liquid in the tube well past setpoint to reach equilibrium at the setpoint within the grainbed. (That's not to say there is anything at all wrong with your system, again just thinking about perfect world here)

If it did heat past the setpoint its also converting differently too right? it wont magically and instantly mix and stabilize with all the grain in the grainbed and become a lower temp.. it will start out as a very high possibly denaturing temp as it hits the grainbed... I just dont see the point? the rims is supposed to maintain and increase for step mashing its not for what I'm understanding the OP wants to do which is almost instantly correct for low strike temps or otherwise.. The only percise way to use the rims with the least amount of overshoot or possible disaster is to mount the probe at the rims exit. Other ways might work but they are less than ideal for a rims function.

 

[thekraken]

If it did heat past the setpoint its also converting differently too right? ... it will start out as a very high possibly denaturing temp as it hits the grainbed

I don't know, will it? The tube is only heating a relatively small volume of liquid at a time. I've thought about the denaturing problem too but come back to "well, it works for decoctions"... The point is with a purpose made control you'd set limits and find a balance. For example: If I remember correctly I programed mine to never exceed 10F, or was it 8F, above setpoint at the output of the RIMS.

the rims is supposed to maintain and increase for step mashing its not for what I'm understanding the OP wants to do which is almost instantly correct for low strike temps or otherwise..

He's just talking about maximizing ramp speed I think.

The only percise way to use the rims with the least amount of overshoot or possible disaster is to mount the probe at the rims exit. Other ways might work but they are less than ideal for a rims function.

Well that's just being closed minded! I agree that's the best way with off the shelf parts.

All that said we're steering off track for OP's thread here. I don't get the impression he is up for making his own custom controller.

 

[augiedoggy]

I don't know, will it? The tube is only heating a relatively small volume of liquid at a time. I've thought about the denaturing problem too but come back to "well, it works for decoctions"... The point is with a purpose made control you'd set limits and find a balance. For example: If I remember correctly I programed mine to never exceed 10F, or was it 8F, above setpoint at the output of the RIMS.


He's just talking about maximizing ramp speed I think.



Well that's just being closed minded! I agree that's the best way with off the shelf parts.

All that said we're steering off track for OP's thread here. I don't get the impression he is up for making his own custom controller.

Im talking about a standard rims here... sure you could make a very complicated system that does more faster but a person could argue that overcomplicating something when a simple basic design works perfectly well (and with less to go wrong) is not really "Best"... I am up for hearing how a temp probe placed elsewhere in the system would work better and still offer the same benefits? I know there are folks here who have them at the MT inlet or output and some even stick them in the MT sidewall and pray they never get poor flow in that area but those methods will all produce some degree of overshooting the way I understand it and from the tests Ive done.

 

[thekraken]

Im talking about a standard rims here...

To be fair in the context of the posts to which you replied weren't about standard rims.

sure you could make a very complicated system that does more faster but a person could argue that overcomplicating something when a simple basic design works perfectly well (and with less to go wrong) is not really "Best"...

Why do we go from very basic to very complicated? Why can't it be in a middle ground, something a little different than usual that may get a little better performance? It's nothing so complicated.

If Auber tomorrow came out with a compact, purpose built, plug-n-play RIMS controller that utilized two probes instead of one would that be such a complicated thing that you would dismiss it? (Assuming you were in the market and the price point wasn't stupid)

If we are all so worried about complicating things a little bit then why bother with DIY rims/herms in the first place?

 

[augiedoggy]

To be fair in the context of the posts to which you replied weren't about standard rims.



Why do we go from very basic to very complicated? Why can't it be in a middle ground, something a little different than usual that may get a little better performance? It's nothing so complicated.

If Auber tomorrow came out with a compact, purpose built, plug-n-play RIMS controller that utilized two probes instead of one would that be such a complicated thing that you would dismiss it? (Assuming you were in the market and the price point wasn't stupid)

If we are all so worried about complicating things a little bit then why bother with DIY rims/herms in the first place?

But why use two when one hold exact temps fine?

 

[thekraken]

For all the reasons we've discussed on this thread. Optimized ramping and the ability to control the temp of the grain bed directly.

I'm not saying there is anything so wrong with the traditional approach, just that it might could be improved. These were controllers in a "perfect world" scenario that we were describing.

 

[Wizard_of_Frobozz]

But why use two when one hold exact temps fine?

If your only goal is to maintain temps then I agree with you. I'm a big believer in KISS. However, the OP stated their goal was to maximize ramp times.

How you measure performance depends on what your objective is: a Ferrari is the "best" car if you want to hit zero to 60 in 4 seconds. A Prius is "best" if you want maximum fuel efficiency and range (just an example - not trying to turn this into a car debate!)

The industrial control systems I've worked with do exactly what the OP is looking for by using a PID loop and one or more probes but they can get very complicated. I would think you would need some sort of mixer in your Mash tun to get the higher temperature from the RIMS tube to mix quicker than just recirculating in order to avoid overshooting your rest temps in the mash tun. Might not be worth the extra complexity but that depends on how important the ramp times are to the OP.

 

[augiedoggy]

fair enough,
But I would just use a larger rims with a faster flow rate if I wanted faster temp ramps my self because I do think putting the temp probe elsewhere will cause temp overshoots. while it would be better at ramping it wouldnt be as good at maintaining and it wouldnt be as stable while ramping I believe. a person could make a dual probe temp controlller like the kraken and figure out some way to make it work im sure but then I think we are off topic from the OP's original question.

 

[Wizard_of_Frobozz]

Yeah, I think we've answered the OP's question pretty thoroughly now: Precise temp control and avoiding overshoots is why the probe is usually placed at the RIMS tube outlet.

The engineering geek in me likes trying to figure out how to meet the goal of rapid ramp times within the limitations that the OP gave (specifically using 120v, which in turn, limits heater size). I'm with you - I'd probably go for two heaters on different circuits and a larger pump before trying to add the complexity of rapid mixing of hotter wort with the mash tun.

I would say this kind of debate is what leads to new innovations within our community, and it's one of the main reasons I stopped lurking and started contributing here.

 

[Jwin]

For all the reasons we've discussed on this thread. Optimized ramping and the ability to control the temp of the grain bed directly.

More so even, just optimization of the ramping. If monitoring the grain bed helps with that, then so be it. I'm not worried about denaturing. The flow rate required will avoid overheating and the mass of wort should avoid significant denaturing. Again, I have experimented with recirculation at full bore pump speed. Works fine. Remember also, I am gyle brewing, so we're talking pretty thin mashes here.

Now, all this could be in vain. With significant flow, and proper reintroduction of the wort in the tun, the controller may work fine.
But adding 3 wires and a single stc-PID as a loop between the existing PID and SSR would be pretty easy.

Now, as far as the debate on overshooting, BIABers basically do what I any to do with a larger element, no? Monitor the mash directly while recirculating and heating...

Now as far as the debate of temp probe inlet v outlet, I have seen RIMS tubes mounted both horizontal and vertical. Perhaps that is the origin of different opinions?

To further p*ss on the fire, what would be the downside of pulling wort through the rims over pushing it through. seems that could be safer, with proper implemention. May need a bleeder valve.
Now, one could argue that biab has better though flow than a cooler tun.

Thank you to everyone for their replies. Who knows, maybe we'll figure out a better way
Advancement comes though debate.

 

[Wizard_of_Frobozz]

To further p*ss on the fire, what would be the downside of pulling wort through the rims over pushing it through. seems that could be safer, with proper implemention.

You want to minimize any flow restrictions on the inlet side of your pump. A pump needs a minimum "Net Positive Suction Head", which is a fancy way of saying it needs a minimum pressure at it's inlet. Any flow restrictions (such as a RIMS tube) on the suction side of the pump reduces the pressure into the pump suction. This in turn, leads to cavitation, which causes flow reduction and eventually damage to your pump. Cavitation is basically boiling inside the pump because the pressure in the pump impeller drops below the boiling point of the liquid. Hotter liquids are closer to their boiling points, so it's a very real concern with our setups.

 

[Jwin]

So, my original question has been answered. I was in assumption that the most prominent reason for the probe in the tube is mostly safety. Now, it is utilized also to regulate temperature. I was just reading a white page on PID loops. I don't think that the RIMS probe is the best placement for temperature regulation.
There are PIDs out there that accept multiple probes, but hey are quite costly. RPi would probably be the most cost effective way to do this, but I have no experience with them. So, I think I'll look into designing a system with 3 controllers in a loop.
The probe in the RIMS acting as a safety to one controller. Two probes in the mash. Essentially running the two mash pids in parallel, followed by a PID in series to them(rims safety), then the SSR. Probe placement would be pretty critical. I think one in the mash and one on the MT output would be sound. That way, if channeling occurs, it will trip the MT output and let the mass of the mash catch up.
The rims PID could be set to ~10° below boiling, and then lowered once the target step temperature is close.
Now, all this is based on the assumption that PIDs have a resistance on their output, and seeing live DC voltage on the output wouldn't damage them. Otherwise, I guess I could wire a resistor into the picture.
Any opinions on this? I'm sure a diagram would be better, but I'm about to head to work and don't have the time...

Thanks all.

 

[augiedoggy]

theoretically having the probe at the inlet of the mt would just allow for very little overshooting and you may very likely get closer MT temps to the setpoint... The other thing to consider here is with a 120v element the reality is you would get better performance and more utilization out of it if you circulate SLOWER to give it more contact time to heat the wort per pass... This is a reason I used a long narrow rims tube with a long element... the wort exiting my rims IS fully and eaqually heated to the desired setpoint I set my temp co0ntroller at... the only practical realized variable here is the time delay between the wort exiting the rims and the time it takes to make it through the grainbed long enough to ramp it up to the desired temp..

I would argue that a 5500w rims flowing at 5gpm still wont work as well as my 42" long rims with a 36" long 1800w element and 1/4" space all the way around the element between it and the rims tube wall.. Just my opinion but I feel I have taken the possibility of scorching out of the equation as well as denaturing enzymes (if it is a real concern) as well as eliminated any safety concerns.. I get the advantages of a herms with the advantages of a rims. I can still increase my mash temps quite quickly for step mashing when brewing an 11 gallon batch

 

[Wizard_of_Frobozz]

I would argue that a 5500w rims flowing at 5gpm still wont work as well as my 42" long rims with a 36" long 1800w element and 1/4" space all the way around the element between it and the rims tube wall

Augie, where did you find that 1800W element? That's a pretty unusual element. I completely agree with you on contact time - that's something a lot of people miss when designing systems. Just because you have 5500W on your element doesn't mean you are actually transferring all of that heat into the the wort. Heat exchange takes time. Dwell time is a very important factor in heat exchanger performance but it gets missed because the normal heat transfer equation (Q=mCp∆T) doesn't involve time; it assumes 100% transfer. If you put 5500 watts into the heater, and there isn't sufficient flow to remove 100% of that energy, the element will heat up to push up that ∆T, and potentially scorch your wort.

 

[thekraken]

Now as far as the debate of temp probe inlet v outlet, I have seen RIMS tubes mounted both horizontal and vertical. Perhaps that is the origin of different opinions?

I was more under the impression that horizontal vs vertical is about either convenience of mounting or mounting such that you don't get air bubbles in the tube. Either way the probe is typically on the output.

So, my original question has been answered. I was in assumption that the most prominent reason for the probe in the tube is mostly safety. Now, it is utilized also to regulate temperature.

Ehhh I still feel if you are going to use an off the shelf PID controller it is the best place to put the probe at the output. I think it is more than an afterthought.

So, I think I'll look into designing a system with 3 controllers in a loop.
The probe in the RIMS acting as a safety to one controller. Two probes in the mash. Essentially running the two mash pids in parallel, followed by a PID in series to them(rims safety), then the SSR. Probe placement would be pretty critical. I think one in the mash and one on the MT output would be sound. That way, if channeling occurs, it will trip the MT output and let the mass of the mash catch up.
The rims PID could be set to ~10° below boiling, and then lowered once the target step temperature is close.
Now, all this is based on the assumption that PIDs have a resistance on their output, and seeing live DC voltage on the output wouldn't damage them. Otherwise, I guess I could wire a resistor into the picture.
Any opinions on this? I'm sure a diagram would be better, but I'm about to head to work and don't have the time...

Thanks all.

Woof.. that makes my head hurt! I know I'm being a complete hypocrite here but... man that sounds complicated and expensive. Just for the record I was talking about an imaginary controller that does these great things in a single neat little purpose built package. As you mentioned a rpi or microcontroller would be the cleanest DIY solution. But I understand that the software side of things isn't for everyone.

Good luck with your build I'll be curious to see how it works.

 

[mabrungard]

The only temperature that matters in a RIMS is the peak temperature of the wort downstream of the heating element. Remember, all the enzymes are in the wort...not only the grain bed. If you overheat the wort, you will prematurely denature those enzymes. Monitoring that wort temp at the RIMS tube exit is the ONLY thing that the PID needs to see.

I agree that reaching the desired temperature in the grain bed is also desirable, but there is no way around the physics and thermodynamics of the system. The only way to add heat to the system is via the wort flow and it takes time to get that fully heated wort through the bed and bring the bed to that desired equilibrium temperature. I monitor temperatures via regular electronic thermometers mounted in the mash tun inlet and outlet pipes along with the PID sensor in the RIMS tube. I can tell you that it takes several minutes for that heat wave to travel through the tun after a temperature step. I don't care that the temps in the bed aren't up to temp instantly, but my RIMS element does have enough power to bring that discharged wort to my intended temp step immediately. That's what really counts. So don't worry so much about incorporating a multi-sensor control system into a RIMS, one sensor will do.