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Old 12-06-2012, 02:32 PM   #51
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The comments earlier about Herms and stratification. You would have the problem of that regardless of a HERMS coil. If the HLT water is not being mixed, it will be hotter at the top, but not by much. The real problem with a coil is that is creates at barrier around the coil that cause the strification. If you look at threads about IC coolers and Jamill tube, they discuss this regarding a "heat blanket" around the IC Coil. I do remember that when we added the tube, our cooling time improved quite a bit. That is the reason I cycle around my HERMS. If you have a COUNTER FLOW CHILLER as a HERMS, you need two pumps but you will not have any problems with that. You can also ramp the temp quicker with a counter flow vs a regular HERMS.

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Old 12-06-2012, 02:33 PM   #52
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BTW, I am thinking about switching back to my Counter Flow HERMS

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Old 12-07-2012, 12:02 AM   #53
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Default Why you need more sensors IMHO...

.... to make thing as complicated as possible.

No matter which (HERMS)-system you choose, you will always have problems with the mash temperature control, if only one probe is used.

- if the probe is in HLT only, there's no way of telling what the mash temp really is and the stratification comes a real problem. Any steps in mash temp are slow to do and overshoots are really difficult to control. If you overshoot the HLT temp it takes for ages it to cool down. It works best when the HLT has a really small amount of water in it + a powerful stirring.

- probe in the wort output only. This limits ramp times as you can't heat wort over the set mash temp without complicated control system. I also noticed that the mash temp starts to creep up over time. I think this is the best solution, if only one probe is used. With a separate small HERMS-kettle this is a good way to control the mash.

- probe in the mash only, with a careful control (PID?) of the HLT temp (or a tiny HERMS-kettle) it might be doable. Any steps in mash temps are really difficult to do without overshooting and the lag time in probe feedback makes things pretty much impossible?

My solution is to use 2 probes for the control. One in the mash and one in the wort output (I used to have 3th one in the HERMS-kettle before moving into CFC-HLT-HERMS). The control sketch in the Arduino is made so that if mash temp is way off what the set mash temp is wort can be hotter than the set mash temperature. I reduce the amount of wort "overshoot" as the set mash temp is closing in and I finally set the wort temperature same as mash. This enables fast steps (with the CFC-herms) and there's no problems with the overshoot once the settings are right.

2 point temperature control can be done also with 2 "normal controllers". I used 2 Sestos's in series before the Arduino stepped into my life. 1 was 12V output and the other one with a relay output....

One thing that comes to mind ... it's really important to check what's your free flow out from the mash tun is. It can be quite slow and if too powerful pump is used it can create suction in the mash tun and stuck mash is more that likely outcome of that (been there) especially if false bottom is in use, braided SS seems to work better. If the hoses on the input side of the pump start to jiggle, the pump sucks
I've about 3L/min flow out from mashtun with the grains in (if I remember it right). The flow also limits the temperature step times.

I just made a new version of the control sketch. I added pump on time limiter when the mash is <0.5C from the set point. The pump can run only 3000ms and can be turned on again after 10000ms break. This seems to be taking care of the overshoots when HLT temperature is much higher than the mash. I got +-0.15C accuracy with 20L water in the mash tun.

One more thing that is great with the CFC-HERMS. There's no need for powerful heating element to get the mash step time short. Just a big kettle full of thermal mass.

Edit: A short plot of the test with the new settings. It's easy with the water only to keep temperatures in check, but this looks promising:

Mash drops 0.4C from the set point and wort goes down 0.7C max (because of heat losses in HERMS line).

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Old 12-08-2012, 05:34 AM   #54
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Temp stratification isn't an issue in the HLT because its a black box system. The controller sees it needs to apply heat, it applies heat, and after given period of time, the outlet wort temp rises. The controller doesn't need to know what's going on inside the black box (i.e. the actual HLT temp.)

The tuning for a PID will vary greatly depending if the HLT is stirred or not, but that's the beauty of a PID, it can be tuned. But the moral of the story is, a properly tuned PID will account for the temp stratification. That's why it's not an issue. If you tune the PID correctly, it'll hold the out,et wort temp at the exact degree you wish.

My HERMS holds my mash temp at .0-.3* of my target mash temp (verified with a +/- .1 thermometer.)

What further level of perfection are you looking for? We're making beer, not a space ship.

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Old 12-08-2012, 06:04 AM   #55
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I agree, I'm building "a space ship" here. If that bothers you, be happy with your build, never mind my stories, just make more beer

To me the main thing is, within this thread, how powerful the "black box" is. And what I've learned from my builds is that the counterflow HERMS is the best for me. That's all.

I didn't have a plotting system when I used "herms coil in the HLT with the stirrer"-system. It would be interesting to see, if anyone has any plots of how fast their systems heat the mash?

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Old 12-10-2012, 04:16 PM   #56
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What further level of perfection are you looking for? We're making beer, not a space ship.
Maybe you're not building a space ship but I'm an engineer and that's exactly what I intend to do. Yes, I'm going to fly my brew rig to Mars. :0)
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Old 12-11-2012, 08:27 PM   #57
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Great thread! As I've been researching RIMS and HERMS and all the variations I'm still not clear on how fast of a temp change is considered a step vs a ramp. This CFC solution seems to be the fastest - am I wrong in that?

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Old 12-11-2012, 09:28 PM   #58
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Great thread! As I've been researching RIMS and HERMS and all the variations I'm still not clear on how fast of a temp change is considered a step vs a ramp. This CFC solution seems to be the fastest - am I wrong in that?
The temp change is fast but sparge temp creep seems to be the biggest demonstrated problem. Unless you keep the hlt water at the appropriate temp instead of just an arbitrary temp hot enough to get a good exchange at a fast flow.
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Old 12-12-2012, 03:18 AM   #59
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The temp change is fast but sparge temp creep seems to be the biggest demonstrated problem. Unless you keep the hlt water at the appropriate temp instead of just an arbitrary temp hot enough to get a good exchange at a fast flow.
If you are referring my plots, I'm trying to get the HLT water down when I'm heating the mash to mash off. Otherwise my sparge water would be too hot and I would get all the tannins etc. in my beer. There's absolutely no problem to maintain the HLT temp as high as you want, just dial the HLT to over 90C (200F). Other thing that can be done is to add more water into the HLT. My goal is to use as little as water as possible, I'm trying to make it so that I can use all of it to sparge. This way I'll use less water/power.

In some stage you also said that the mash temp is a couple of degrees lower than set. This is not true, maybe you were watching the wort temperature? With the CF-Herms the wort temperature will drop under the set temp when the pump is not running. Same thing happens with all Herms systems, but it's biggest with CF-Herms as the HX-coil is in air, not in water and it cools faster. Same issue can be seen too with HERMS with a very low volume (small thermal mass) heating kettle (I used as little as 1 cup in on stage). This is what makes the need of having two sensors, it's almost impossible to calculate the mash temp from wort, if it's cooling the mash some of the time. The mash temp starts to creep up, if you only measure the wort temperature.

I'm adding a "keep warm"-sketch in my Arduino software for the CF-H. The idea is to make the wort temperature more stable i.e. compensate the heat losses in hoses to pump and back to the mash tun by running the heating pump in "right" intervals. Just to keep the HX-warm, not to heat the wort. I had similar sketch on my "induction small volume HERMS" and that worked to the perfection. My mash staid under the tolerance of my sensor at it's best.
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Old 12-12-2012, 04:46 AM   #60
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Vesku, your input in this thread has been amazing. Thanks! Would you be willing to share your arduino code with us?

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