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Old 03-17-2013, 07:58 PM   #1
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Default Single PID / Pump employment

So if you have read my other threads here, you know where I am in the rebuild process.

Main project R%D is the eHERMS control Box. Understanding that a 2 PID setup would be ideal, I would like to discuss a single PID, single element, 2 pump set up.

I have this....Boil Kettle Control

My question is this;
A. do I set the wort to recirq continually, and the pid controls the temp of the HLT?

B. Set the PID to just recrq the wort at temp drop?

C. I know the PID needs to moniter the mash temp, so how do I set the HLT water temp?

I plane on using mt 2nd pump to recirq the HLT water to maintain even temp throughout.

Just need a little help "seeing" the process i guess.

Thx

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Old 03-17-2013, 09:04 PM   #2
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You should be continuously recirculating.

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Old 03-17-2013, 10:50 PM   #3
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You should be continuously recirculating.
I kinda figured this, so how do i affect change in the system?

So I use a temp probe at the exit of the herms coil the mash, to cycle the element in the HLT I assume. Then is my set point is the Mash temp I need to hit, other than on or off how to i keep the water in the HLT in the taret range?

I am sure it is simple, i just cant see it....

Tim
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Old 03-17-2013, 11:10 PM   #4
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when i get a second pump and third pid, i'll modify my plan. however, until then i plan to take the temp as it leaves my herms coil. since the temp i want will be directly influenced by the element in the hlt, i'll affect the change there.

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Old 03-18-2013, 01:42 AM   #5
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Originally Posted by MX1 View Post
I kinda figured this, so how do i affect change in the system?

So I use a temp probe at the exit of the herms coil the mash, to cycle the element in the HLT I assume. Then is my set point is the Mash temp I need to hit, other than on or off how to i keep the water in the HLT in the taret range?

I am sure it is simple, i just cant see it....

Tim
I have RIMS, not HERMS & my sensor is at the output of my RIMS tube. I'd have to assume the same for HERMS - maybe someone who has an electric HERMS will comment.
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Old 03-18-2013, 11:56 AM   #6
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So I have it set up where the PID monitors the temperature of the water in the HLT and maintains that. One pump recirculates the wort through the HERMS coil, the second pump recirculates the water in the HLT. I do monitor the temperature at the inlet to the HERMS coil, but just for my situational awareness.

You could definitely measure the temperature of the wort, and use that to fire the element in the HLT. My suggestion would be to have it measure the temperature at the inlet to the coil (or the outlet from your MLT). Here's why - you're not concerned about the temperature of the small amount of wort exiting the HERMS coil - you're concerned about the overall temperature of the grain bed and the wort in the MLT, a much larger volume. Measuring the temperature at the outlet of the MLT will give you the overall temperature of the mash, given that the wort will have difused through the grain and the temperatures will have stabilized. The temperature of the wort exiting the HERMS coil will be much higher than that.

So, if I were you and had a single PID, I'd measure the temperature of the wort as it exits the MLT and use that to control the temperature of the HLT. Make sure to run the auto-tune because you could suffer some serious lag and ramping on a setup like that.

-Kevin

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Old 03-18-2013, 01:42 PM   #7
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You could definitely measure the temperature of the wort, and use that to fire the element in the HLT. My suggestion would be to have it measure the temperature at the inlet to the coil (or the outlet from your MLT). Here's why - you're not concerned about the temperature of the small amount of wort exiting the HERMS coil - you're concerned about the overall temperature of the grain bed and the wort in the MLT, a much larger volume. Measuring the temperature at the outlet of the MLT will give you the overall temperature of the mash, given that the wort will have difused through the grain and the temperatures will have stabilized. The temperature of the wort exiting the HERMS coil will be much higher than that.
I do HERMS, and I measure at the output of the coil.

When I was building my system and trying to decide where to put the probe, I came on there and posted a poll to see what people use and why. The overwhelming response was that the output of the coil was the way to go. (in fact, many people had originally had their probes in other locations and ultimately MOVED them to the coil output for better behavior.)

The reasoning was, ironically, the same reasoning you used, but in reverse.

If you are measuring at the inlet to the coil and your mash is too cool, the heat in the HLT is going to turn on, but it will stay on until it starts to detect "at temp" wort entering the coil. When that finally happens, you potentially have a lot of very hot water in the HLT and wort coming out of the coil (and at the top of your MLT) that is way over your desired temp.

By measuring at the output of the coil, you are ensuring that the wort that goes back into the MLT is never going to be over your set-temp. The mash holds temps pretty well, so you will settle on your set temp pretty easily.

Other internet research at the time I was building turned up a few places that were suggested to never use, and the inlet to the coil (or outlet of the MLT) was the top one that was suggested to avoid because of temp over shoots.

Anyway... just my $0.02. I do measure at coil output and when I was first using it, I had several thermometers in place. One at the bottom of the MLT, one in the middle of the grain bed, and then the one at the coil output. The variation between these three probes was never more than 1*F.
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Old 03-18-2013, 02:54 PM   #8
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Interesting logic... I think it would take longer for the mash to get up to temperature measuring at the outlet, but also reduce the risk of overshoot. Come to think of it, if you assume a near 100% efficient transfer of a 50' SS coil in the HLT with 10 or so gallons of water in it, then the output temperature of the HEX would be the same as the temperature of the water in the HLT which is what I measure so I guess I'm doing it the same as you.

I think the Kal setup (which I copied) is honestly the best of both worlds. I have learned that I can set my HLT (and thus wort output from the HEX) temp about 10* above my target temperature, and then start to ramp that temperature down to my target temperature, and I'll see a much faster change in the mash temperature overall. I'm just curious if the 'fuzzy logic' feature of the PID could do all this for us by measuring at the MLT output - ramp nice and fast, and then slow down to get to your ideal temperature... If it worked without overshoot, it would be a much faster heating operation than measuring at the HEX outlet.

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2014:
5gal Scottish Wee Heavy
5gal Saison
15gal American Pale Ale
20gal Belgian Wit (10 dumped)


Keg 1: Apfelwein
Keg 2: Belgian Wit (Failure)
Keg 3: American Pale Ale
Fermenting: Belgian Wit (Take 2)
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Old 03-18-2013, 03:06 PM   #9
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Quote:
Originally Posted by BadNewsBrewery View Post
if you assume a near 100% efficient transfer of a 50' SS coil in the HLT with 10 or so gallons of water in it, then the output temperature of the HEX would be the same as the temperature of the water in the HLT which is what I measure so I guess I'm doing it the same as you.
Right. If the heat transfer was perfect, coil output and HLT contents would be the same.

I have only 10' of 1/2" OD copper for my coil, but I pump at a relatively slow rate compared to what my pump can actually do, so heat transfer should be pretty good.

But, I honestly have no idea what temp my HLT sits at when I am mashing. It's probably a couple of degrees warmer, but I've never measured it. I am not particularly concerned with what temp the HLT is and am just interested in the temp of my mash.
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Old 03-18-2013, 03:56 PM   #10
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I will be using 50ft od 1/2 ss for my coil.

So end state, measure at HEX outlet, let the MLT run at whatever temp it needs to to maintainthe mash temp.

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