HERMS Temp Probe Location

SAMPLER said:

Good point but i don't see this helping the chances of overshooting possible sparge temps. Too bad the second PID couldn't over ride the first and shut off the element before it over shoots the temp.

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Set first PID in HLT to your desired mash out temp. Second PID is reading your mash temps and when they drop it turns on and recirculates through the herms. Problem here is you'd want the temp probe buried in the center of your mash so it didn't shut off immediately as the hot wort flows through the coil.

MX1 said:

again, you dont need 2.

I will not be using 2, just 1, all about choices....

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This thread got all over the place quickly (I'm probably at least partially at fault for that), but I do remember the OP saying he/she was planning on using two PIDs.

Fwiw I use one PID too. I'm just trying to see if there's any real advantage we are missing by adding a second.

of course, to operate with a pid i THINK you need a termo.

i i have two and use one as a dummy thermometer on my MLT when mashing and the others been tuned in my HLT (recirculating).

at boil, i disconnect from MLT and plug into BK and boil off the previous dummy pid while i start breaking down the rest of my gear

kpr121 said:

This thread got all over the place quickly (I'm probably at least partially at fault for that), but I do remember the OP saying he/she was planning on using two PIDs.

Fwiw I use one PID too. I'm just trying to see if there's any real advantage we are missing by adding a second.

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You don't really need two, but the second works as a digital thermometer. All it really does is reduce overshoot by limiting HLT temps.

A digital thermometer, or even a bi-metal thermometer at that, costs about 40-50. That's as much as a PID anyways. Basically the difference is the cost of a temp probe... Not bad.

Something that hasn't come up yet is if you have the capability to run two elements at once you can do double batches easier. First PID manages mash/sparge while second runs the BK. The second can be used as a dummy during the first batches mashing.

Can one PID operate both an element and pump for recirculating through the herms?

kpr121 said:

Something that hasn't come up yet is if you have the capability to run two elements at once you can do double batches easier. First PID manages mash/sparge while second runs the BK. The second can be used as a dummy during the first batches mashing.

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This for the win.

Although I run propane and a BCS-460. Same cost as 4 PIDS plus I can data log.

I would never run less than 2 PIDs. One for the Hex-O and one for the HLT.

I suspect that there are more Kal clones out there than any other type of e-HERMS system (although I have no data, and may be wrong). They use one PID at the exit of the HLT to control the HLT element, and another as a thermometer to monitor the mash temperature at the exit of the MLT. Given the success with that system, I don't see the need for more than one PID to control the temperature in HLT.

Perhaps there are ways to improve upon that, but that method appears to be more than adequate. I would be very interested to hear what Kal or someone who runs a Kal clone has to say on the matter.

With a Kal clone, that's still 2 PIDs.

Functionally speaking, with a 5 or 10g setup, you *might* be able to get away with one pid, and swap it back and forth as needed (although that defeats the purpose of a PID as they learn over time).

With my 2bbl system that's simply not an option. The lag between my HEX and my HLT is 4* (Defined as if my HLT is set to 172* and has been stabilized, my HEX is spitting out 168* once it too has been stabilized.) so when I ramp up my mash temp say 10* my HLT would end up 10-20* over temp before my HEX-O (mash) temp read the right temp 5-10 minutes AFTER my HLT has hit the correct set point.

Or to put it another way:
By the time my HEX-O, or my MT-O is reading the right temp in a step mash, it's too late. My HLT is already 10-20* over temp and the HEX is following lock-step. Killing the heat won't fix it. I've got a 30g bath over temp.

The only way to fix that is to shut down my recirc pump, close the valves, drain a third or so of the HLT, fill with cold water, and then reheat to the correct temp.

2 pids are cheaper over the long run, if anything, use the second to monitor the mash and shut the pump down if it goes over temp.

luhrks said:

Functionally speaking, with a 5 or 10g setup, you *might* be able to get away with one pid, and swap it back and forth as needed (although that defeats the purpose of a PID as they learn over time).

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Unfortunately, this is a pretty common misconception (I shared it for a while). The PID does not learn anything. The only time it will adjust the P/I/D settings is if you set it to AutoTune. We had a big discussion on this a few months ago and got Auber to comment.

So if you only had 1 PID, you're going to have to either re-tune each time you switch probes, or leave it set to one keggle and sacrifice performance on the other keggle...

The more you know... <=nestar:

BadNewsBrewery said:

Unfortunately, this is a pretty common misconception (I shared it for a while). The PID does not learn anything. The only time it will adjust the P/I/D settings is if you set it to AutoTune. We had a big discussion on this a few months ago and got Auber to comment.

So if you only had 1 PID, you're going to have to either re-tune each time you switch probes, or leave it set to one keggle and sacrifice performance on the other keggle...

The more you know... <=nestar:

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You're right. My bad.

luhrks said:

There will always be a difference between the HLT water temp and what comes out of your HERMS. In fact, the greater the delta, the faster your mash temp rises.

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I'm not sure if I understand this. If your HLT temp rises quickly and your HEX out does not rise quickly (what you said), which is a big delta, doesn't that mean that your mash temp is not rising quickly because the HEX is not getting heated by the HLT?

Unless you're recirculating too fast, won't the HEX out temp be equal to the HLT temp as long as your HLT water is recircing or being agitated and the HEX is long enough? Is this a known number of feet? Obviously the HEX material, wall thickness, and delta will also come into play. I would think that the smaller the delta the quicker the mash temp will rise, which is the exact opposite of what you said (provided that you have good heat transfer to the HEX).

the issue is cooling off 10 gallons of water in the hlt. it will be at 190 when you have set it to 170 (for example) and continue to rise.

jeffmeh said:

I should also add that there is one advantage the PID in manual mode has over the potentiometer for the boil kettle. You can set the setpoint to 208F or thereabouts and walk away without worrying about a boilover, then when the alarm sounds or before, go back and set it to 100% manual, then lower the manual % when you reach a boil.

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+1.

The other big advantage is it that helps when doing extended hop stands that seem to be coming all the rage: This is where you soak hops after the boil at a specific temperature.

I did a 30+50 minute stand recently where the stand that started 30 minutes in was done at 170F for the last 50 minutes. I set the boil PID to 170F and it held the wort at that temp for the duration.

As an aside: In the past we've all done 60 -> 0 min hop additions to the boil. I get a feeling that the next ~5 years is going to start to see a lot of interesting post boil hop additions done at various times at varying temps over that time at the homebrew level (some craft brewers are already doing it).

You can't do that with a PWM boil control dial as it doesn't understand the concept of temperature. Another plus for PID.

EDIT: +1 to what BadNewsBrewery said about using a single PID different ways. You can't really do that without doing a 20-40 min auto-tune and changing the temp probe offset every time you switch. Not really plausible. If you need 2 PIDs, buy 2 PIDs.

Kal

kal said:

+1.
EDIT: +1 to what BadNewsBrewery said about using a single PID different ways. You can't really do that without doing a 20-40 min auto-tune and changing the temp probe offset every time you switch. Not really plausible. If you need 2 PIDs, buy 2 PIDs.

Kal

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I suppose if you were REALLY on a budget, you could run an auto-tune and record the parameters for each configuration. Then just set the values manually when you switch. It seems like a lot of effort, paperwork, and room for error compared to a $40 PID and some wire, but a notepad and manually entered values should get you there.

-Kevin

Good point - yes - you could write them down and reuse them. Agreed that it's a big pain for a savings of $40. It would grow tiring very fast.

Kal

kevink said:

I'm not sure if I understand this. If your HLT temp rises quickly and your HEX out does not rise quickly (what you said), which is a big delta, doesn't that mean that your mash temp is not rising quickly because the HEX is not getting heated by the HLT?

Unless you're recirculating too fast, won't the HEX out temp be equal to the HLT temp as long as your HLT water is recircing or being agitated and the HEX is long enough? Is this a known number of feet? Obviously the HEX material, wall thickness, and delta will also come into play. I would think that the smaller the delta the quicker the mash temp will rise, which is the exact opposite of what you said (provided that you have good heat transfer to the HEX).

Click to expand...

The larger the delta, the faster the mash temp will rise.

Q=m*cp*deltaT
(Q is rate of heat transfer, m is wort flow rate, cp is the heat capacity of wort, delta T is the different between HLT and wort temp).

The larger the difference in the HLT temp and wort temp, the greater the heat exchange. Likewise, the higher the wort flow rate, the faster the heat exchange. If your wort is at 140F, and your target is 152F, you want your HLT temp to be greater than 152F, because it will make the wort heat up faster.

There will always be a temp difference between the wort in the HEX and the HLT, because the HEX coil is impeding heat transfer (introducing lag).

JayMac said:

The larger the delta, the faster the mash temp will rise.

Q=m*cp*deltaT
(Q is rate of heat transfer, m is wort flow rate, cp is the heat capacity of wort, delta T is the different between HLT and wort temp).

The larger the difference in the HLT temp and wort temp, the greater the heat exchange. Likewise, the higher the wort flow rate, the faster the heat exchange. If your wort is at 140F, and your target is 152F, you want your HLT temp to be greater than 152F, because it will make the wort heat up faster.

There will always be a temp difference between the wort in the HEX and the HLT, because the HEX coil is impeding heat transfer (introducing lag).

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Yay! sciencey type person.

to put it in perspective, the closer you get to the set point of the HLT, the slower the temp in the coil adjusts.

If you have your MT at 140 and the HLT at 170 then turn the pump on, your fluid out of the HEX at flow rate X will be 170- (a few degrees). As the mass of your MT rises to temp, the slower the change in temp in the HEX until you get to a point where you've hit the "lag point" (HEX-O temp is a degree or 3 below the HLT temp, and will not rise further).

For practical intents and purposes, the lag point in my 2bbl system is 4* ergo to mash at 152* I set my HLT to 165* and I monitor both the HEX-O and HLT to confirm. I also run a 3rd off the bottom of the MT as a "reality check"

BadNewsBrewery said:

Unfortunately, this is a pretty common misconception (I shared it for a while). The PID does not learn anything. The only time it will adjust the P/I/D settings is if you set it to AutoTune. We had a big discussion on this a few months ago and got Auber to comment.

Click to expand...

You wouldn't happen to have a link to that thread, would you? I'd like to read it.

JayMac said:

The larger the delta, the faster the mash temp will rise.

Q=m*cp*deltaT
(Q is rate of heat transfer, m is wort flow rate, cp is the heat capacity of wort, delta T is the different between HLT and wort temp).

The larger the difference in the HLT temp and wort temp, the greater the heat exchange. Likewise, the higher the wort flow rate, the faster the heat exchange. If your wort is at 140F, and your target is 152F, you want your HLT temp to be greater than 152F, because it will make the wort heat up faster.

There will always be a temp difference between the wort in the HEX and the HLT, because the HEX coil is impeding heat transfer (introducing lag).

Click to expand...

OK, delta between HLT and MT, not HLT and HEX out. I don't know why I was thinking delta between HLT and HEX out. That makes sense.

JayMac said:

If your wort is at 140F, and your target is 152F, you want your HLT temp to be greater than 152F, because it will make the wort heat up faster.

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In your example, how much longer will it take to heat the wort if you set the HLT temp to 152 (plus a few degrees for loss from hex out to MT)? Does it add that much more time? I realize that it depends on a lot of variables, but are we talking minutes here or an hour?

kevink said:

You wouldn't happen to have a link to that thread, would you? I'd like to read it.

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Here you go. https://www.homebrewtalk.com/f170/does-turning-off-contactor-cause-pid-adjust-itself-381919/

What I've found through some testing is that if I heat my HLT about 10* over my target temp for the mash tun, and then dial it back down to the target temp when the mash tun is 8* below target, they'll equal out. Esentially, in the time it takes the MT to heat up 8*, the HLT has cooled 10*, and I hit my target. This also limits the offset I need between what I set the HLT at and what the actual target for the MT is, as the HLT is no longer trying to heat the wort, simply maintain temperatures. In real numbers:

Mash target: 152
Set Value for HLT: 162
Mash starts to heat up. When Mash temp = 144, HLT set to 152 (which basically turns off the element as I'm 10* over).
Mash continues to rise, HLT starts to cool, and everything balances out right around 152*. Element in HLT fires to maintain 152* HLT temp, mash continues to recirc at 152, everyone is happy.

Note - these values were determined by trial-and-error, and the sample size isn't large enough to say that it definitely works, but it's a good target for MY system. Yours will be different.

-Kevin

FWIW I do it the "simple" way: I just set my HLT to the temp I want to the mash to be at and it follows automatically:



In the picture above the mash temp is the middle PID and the HLT temp is the right PID. Both are at 150F (mash temp).

After mash, the HLT temperature is raised from 150F to 168F to perform a mashout. The mash will automatically rise in temperature:



In the picture above the mash temp is at 162F and the HLT temp is at 168F. This picture is 15 minutes into this mash-out, the HLT has already reached and is holding at 168F, and the mash has gone from 150F to 162F. After anothre 5 mins or so it hits 168F as well.

(Pictures taken from my Step by step of my brewday: Doing a massive hop stand thread).

I have more pictures and videos of the entire process in my Brew Day Step by Step article that show how the mash follows the HLT through the various steps if you're curious.

Kal

kal said:

FWIW I do it the "simple" way: I just set my HLT to the temp I want to the mash to be at and it follows automatically:

In the picture above the mash temp is the middle PID and the HLT temp is the right PID. Both are at 150F (mash temp).

After mash, the HLT temperature is raised from 150F to 168F to perform a mashout. The mash will automatically rise in temperature:

In the picture above the mash temp is at 162F and the HLT temp is at 168F. This picture is 15 minutes into this mash-out, the HLT has already reached and is holding at 168F, and the mash has gone from 150F to 162F. After anothre 5 mins or so it hits 168F as well.

(Pictures taken from my Step by step of my brewday: Doing a massive hop stand thread).

I have more pictures and videos of the entire process in my Brew Day Step by Step article that show how the mash follows the HLT through the various steps if you're curious.

Kal

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Another example that like many other things in life, in brewing, patience is a virtue.

kevink said:

OK, delta between HLT and MT, not HLT and HEX out. I don't know why I was thinking delta between HLT and HEX out. That makes sense.

In your example, how much longer will it take to heat the wort if you set the HLT temp to 152 (plus a few degrees for loss from hex out to MT)? Does it add that much more time? I realize that it depends on a lot of variables, but are we talking minutes here or an hour?

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I couldn't give you an exact time frame, as there are so many variables (HEX material, length, thickness, batch size, etc...)

This is something that you can only find out by tuning your system and figuring it out yourself once you've assembled everything. You want to see how big a deltaT you can get while simultaneously avoiding overshoot when you approach SP. trial and error my friend!

We can discuss theory all day, but the fact of the matter is that you'll determine your process based on your brewing style, preferences, time constraints, etc...

i started a thread about this, but i found my MLT was about 15 minutes behind my HLT. i could improve it like what bad news does, but i'm only on brew two of about one thousand.