Herms setup positioning temperature sensor

[harrie M]

I am building my electric Herms setup and am thinking about the positioning of the temperature sensor. I have a PID temperature regulator and am thinking of not placing the sensor in the HLT, but in the mash tun. This should setup the mashtun faster. Or will it overshoot the temperature because the HLT will aways get to hot? I am curious on your thoughts.

 

[Broken Crow]

There's always a certain amount ot temp stratification in the mash tun, so placement there is highly problematic. The 'best practice' based on my own experience and the majority of those I've read about on here is to put the sensor where it measures the output of the HERMS itself. (That said; I use a RIMS). Given the wide variety of mash tuns, ideally, you'll have to spend some batches with a probe-thermometer checking mash temps at various levels with the system running to fine tune your settings..... so my suggestion; start with it on a tee on the HERMS coils OUT, and see how it goes.

 

[Bobby_M]

If you put your probe in the mash tun, you'll overshoot by rule during any significant ramps.

If you calculate the strike temperature very accurately and the mash settles in at your desired set point, it will hold just fine. If you do any step mashing, it will overshoot because the HLT will continue heating until the probe is satisfied. Now that plays into specific probe placement as well.

If the probe is near the bottom of the mash, it will overshoot more because it will take longer for the affected mash liquor to filter down to the probe. In that regard, the WORST position is on the mash tun output plumbing.

One reasonable compromise would be to mount a long probe into a compression fitting in the lid of the mash tun so you can position the tip about 3" deep in the grain bed. You can also then experiment with the optimum depth so that the static hold temperature is as close to your desired set point as possible. You'll still want to measure the bottom and top of the grain bed to evaluate what the trends are.

All that being said, most people put the probe in the HLT and learn what their system offset is. In other words, in order for the average mash temp to be X, the HLT set point must be X + 5F. The temps between the top and bottom of the mash will be a little variable but once you learn your system and a given set temp's affect on beer character, the exact temps in any one spot is just noise.

 

[Broken Crow]

@Bobby_M .. You're one of the most highly-regarded Authorities on hardware procedures on here, and this is probably the perfect thread to address this:

most people put the probe in the HLT and learn

I'm compelled to put the sensor on the output itself rather than the body of the HLT, as I feel that best determines the temp going in to the mash tun, whereas with it in the body, depending on the HLT, the water out temp may differ... of course I know that an HLT ideally would have a recirculation system running, and a lot of folk don't bother with that, but I've measured up to about 80° stratification below the element in my keggle, which admittedly has the element about 3/4" too high....(hence my desire to keep constant recirculation running in the HLT)

 

[harrie M]

hence my desire to keep constant recirculation running in the HLT

This is exactly the reason why I am currently using two pumps, one for the mashtun and another for the HLT. I have measured and felt statification as well. I am now autotuning on the output of the hermscoil and testing the temperatures with a glasthermometer. For some reason the temperatures are off , but I guess it is because of different responce time index.

 

[day_trippr]

If a HEX is long enough and the HLT bath is circulated to prevent stratification I would expect the output of the coil would be exactly the same temperature as the bath. And indeed I have a 50' 1/2" SS hex in a 3V2P single tier rig and have compared the temperature of the HLT vs the HEX output and they are the same. So I use the HLT's temperature gauge vs the MLT's temperature gauge to determine the differential, and on a typical day and typical batch size I need to run the HLT 1.5°F hotter than the mash temperature to hold the mash dead nuts on target.

This wouldn't work well if at all if everything wasn't in circulation

Cheers!

 

[maddjaxx]

I measure at both the output of the coil and the lower level of the mash tun in my 1 bbl system. Separate pumps for HLT and mash. My PID on the output side restricts the HLT element form
Coming on when temp is reached and the recirc pump is restricted if the lower temp is reached. So basically when I have zen balance system is in hold mode and I get an alarm let me know. I set a timer to mark before moving to a new step. If I am doing a single step then the alarm lets me know I am there and can adjust my recirculating to stay at that temp until finished. Two simple PID and probes accomplish this.

 

[Bobby_M]

With all this being said, it's also the reason why I don't use a HERMS system. Stratified temperature zones, system offset, and temperature oscillation is the bane of any 3 vessel system.

 

[harrie M]

With all this being said, it's also the reason why I don't use a HERMS system. Stratified temperature zones, system offset, and temperature oscillation is the bane of any 3 vessel system.

I think other systems have the same kind of problems, that needs to be mitigated as well.

 

[day_trippr]

One can prefer single vessel brewing without casting aspersions at the alternatives.

• With proper recirculation there should be no stratification, true of single as well as multi-vessel systems.
• Even all-in-one systems have to account for thermal losses.
• "Offsets" are indeed unique to multi-vessel systems, but can be easily accounted for with no negative impacts.
• Temperature oscillation simply is not a problem unless one makes it so with crap controls. Once the mash temperature stabilizes after strike my herms recirculates for the entire mash hands-free and the temperature stays put...

Cheers!

 

[doug293cz]

• "Offsets" are indeed unique to multi-vessel systems, but can be easily accounted for with no negative impacts.
• Temperature oscillation simply is not a problem unless one makes it so with crap controls. Once the mash temperature stabilizes after strike my herms recirculates for the entire mash hands-free and the temperature stays put...

Probably one of the most frequent causes of temperature oscillation is brewers who think: "if I control the HLT power based on a temp sensor in the MLT, I can eliminate the offset." What this does is introduce a significant time delay between adding heat to the HLT and detecting a temp change in the MLT, thus the HLT overheats before the temp sensor detects the condition. The HLT overheating is followed by the MLT overheating. Then you get a similar but opposite temperature excursion as power is withheld from the HLT so it can cool down from overheating, but cools too much before detected by the controller.

Time lags between power adjustments and detection of temperature changes lead to system oscillations.

So, embrace the offset, and control heat input with a temp sensor close to the heating element (in the HLT for a HERMS) to minimize sensing and response delays.

Oscillation problems caused by sensing delays are worse in systems with enough power to change the temperature rapidly (i.e. systems that can heat up rapidly, or do rapid temp steps.)

Another cause of temp oscillations is PIDs that haven't had their parameters tuned for the system they are controlling.

Brew on

 

[cdug619]

In my 3 vessel system, I have one probe in the HLT, one coming off the HERMS coil on its way to the mash tun and one at the out of the mash tun going to the HERMS. Using one pump for mash circulation, obviously , and one for the HLT to keep the temp consistent within the vessel.

This past Monday I had the following for my target of 156.

HLT at 157
HERMS out was 156.9
Mash tun out was 155.4

Splitting the difference lands me on target and over many brews I've determined that 1 degree above for the HLT gets me my target mash temp. Usually takes 5-8 minutes for the HERMS and mash tun to sync up so to speak after a temp change.

So I'd say keep a probe in the HLT and use a instant read and check the mash and over time you'll determine what temp your HLT needs to be for your target mash temp...if you are only going with the one probe.

 

[day_trippr]

HLT at 157
HERMS out was 156.9

This goes to a point I made earlier: if a hex is long enough the wort out will be the same as the HLT bath...

Cheers!

 

[superiorsat]

I use a 4 vessel system. My HLT is always heating water for initial strike temp and sparge or a quick cleaning/flush run (205 degrees) right before I top it off for the next batch which gets me close to strike temp( I always double batch). I use a small 5 gallon pot for my herms coil. With such a small volume of water ramping up temp is much quicker. I don't monitor the temp of the 5 gallon herms pot once it is up to temp which is 10 degrees hotter than my recirculation temp. I switch over to a temp probe in a T at the top of the mash tun so I know exactly what the temp is going in on the top of the mash. I have an analog thermometer towards the bottom of the mash much like @cdug619 said above it takes 10-15 minutes before a temp change like mash out to make its way through the entire mash on a 10 gallon batch of grain. Not for everyone but just how I run my rig.

 

[D-Max]

Probably one of the most frequent causes of temperature oscillation is brewers who think: "if I control the HLT power based on a temp sensor in the MLT, I can eliminate the offset." What this does is introduce a significant time delay between adding heat to the HLT and detecting a temp change in the MLT, thus the HLT overheats before the temp sensor detects the condition. The HLT overheating is followed by the MLT overheating. Then you get a similar but opposite temperature excursion as power is withheld from the HLT so it can cool down from overheating, but cools too much before detected by the controller.

Time lags between power adjustments and detection of temperature changes lead to system oscillations.

So, embrace the offset, and control heat input with a temp sensor close to the heating element (in the HLT for a HERMS) to minimize sensing and response delays.

Oscillation problems caused by sensing delays are worse in systems with enough power to change the temperature rapidly (i.e. systems that can heat up rapidly, or do rapid temp steps.)

Another cause of temp oscillations is PIDs that haven't had their parameters tuned for the system they are controlling.

Brew on

I'm confused that the recommended PID settings have the Derivative set on zero and don't want to use this control function. Derivative control takes into consideration "rate of change of temperature".
Kegland have designed a great compact system mechanically and its up the the brewer to determine best practise re temp control of mash. The blue tooth external temp probe should help the process but I'm uncertain about the new restrictive flow plate that is to direct more Wort flow over the temp probe. I guess when it's available here in NZ it will be an experiment.
I get back to, its the brewers ability to see what works for them.
I'm impressed with my BZ Gen4 with the added efficiency at 84% last brew.

 

[Bobby_M]

I think other systems have the same kind of problems, that needs to be mitigated as well.

My single vessel system generally has none of those problems.

 

[Bobby_M]

In my 3 vessel system, I have one probe in the HLT, one coming off the HERMS coil on its way to the mash tun and one at the out of the mash tun going to the HERMS. Using one pump for mash circulation, obviously , and one for the HLT to keep the temp consistent within the vessel.

This past Monday I had the following for my target of 156.

HLT at 157
HERMS out was 156.9
Mash tun out was 155.4

Splitting the difference lands me on target and over many brews I've determined that 1 degree above for the HLT gets me my target mash temp. Usually takes 5-8 minutes for the HERMS and mash tun to sync up so to speak after a temp change.

So I'd say keep a probe in the HLT and use a instant read and check the mash and over time you'll determine what temp your HLT needs to be for your target mash temp...if you are only going with the one probe.

This is pretty typical give or take a few degrees but where these systems become frustrating is when you want to make a large step ramp in a step mash. If the HLT is the measured and regulated zone for the mash to react to based on your established offset, ramps take FOREVER.

Controllers with schedules can help because you can run your HLT at a intentionally higher offset for a set time period during the ramp up so that you don't have to wait for 10 mash tun turnovers to even get close.

 

[Deadalus]

This is pretty typical give or take a few degrees but where these systems become frustrating is when you want to make a large step ramp in a step mash. If the HLT is the measured and regulated zone for the mash to react to based on your established offset, ramps take FOREVER.

Controllers with schedules can help because you can run your HLT at a intentionally higher offset for a set time period during the ramp up so that you don't have to wait for 10 mash tun turnovers to even get close.

I sometimes manually do what you are saying and I think I may know what you are referring to but what does "10 mash tun turnovers" mean? I will set the HLT PID higher than I want the offset to be (usually ~3 degrees) so that the element is fired longer and the HLT is hotter. I can always overshoot a little and then when the MT hits the desired temp I can kill the MT pump, maybe take a lid off or if I wasn't paying attention, throw a half gallon-gallon of water in the HLT to bring it back down. I can be mostly patient waiting for the temp to stabilize at mash out but I just did a step mash last weekend and boosting the temperature took a while.

 

[harrie M]

Thank you all for the replies. It gave me a lot of new insights.