Where is your HERMS temp probe?

My HERMS is about to come online. I see some folks using their temp probe at the HEX coil output to monitor the temp of wort as it re-enters the MLT, while others put the probe in the HEX's water bath and monitor/maintain this way.

Where is your HERMS probe? Has it always been there or did you switch from one place to another because of problems?

I dont own one but would imagine that you would want it between the mlt and the pump. This way it would be reading the temps of the most probable cold spot. For example, as you circulate hw through the mlt you will loose temperature through the grain and exit the mlt back to the pump. if you locate your temp sensor between the mlt and the pump, your circ should stop when it sees the desired mash temp return from the mlt, thus leaving you with your desired mash temp in the tun.

Someone please correct me if I am wrong.

KISS water bath. Easy to measure the offset of your system and easy to adjust for different conditions. No overshoot, and easy to control.

DustinHickey said:

I dont own one but would imagine that you would want it between the mlt and the pump. This way it would be reading the temps of the most probable cold spot. For example, as you circulate hw through the mlt you will loose temperature through the grain and exit the mlt back to the pump. if you locate your temp sensor between the mlt and the pump, your circ should stop when it sees the desired mash temp return from the mlt, thus leaving you with your desired mash temp in the tun.

Someone please correct me if I am wrong.

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output of MLT / input of pump is the one place I have seen it almost unanimously recommended to NOT put the probe (on both HERMS as well as RIMS). By the time the bottom part of the MLT hits your set temp, the top part is hotter because the heat has been on the whole time. Overshooting temps seems to be common with the probe there from what I have read.

That makes sense I guess. Like I said, I don't have one. Was thinking in terms of HW heating systems in domestic or commercial uses. Circ pump temp probes are always at the pump suction otherwise there's no way to to measure end of line temps leaving bottom end of system (bottom of tun) cold. Could you solve the overshooting problem by setting hot water bath to desired mash temp?

DustinHickey said:

Could you solve the overshooting problem by setting hot water bath to desired mash temp?

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That's basically when the "monitors HEX water bath" option is. Sounds like there is a slight difference between the temp of the HEX water compared to the temp of the MLT, but you can figure it out and adjust your PID set-temp for it.

I have been planning to locate it at the coil output, but I am having my keg equipped with a coupling in case I find that monitoring at the HEX output doesn't work. I'll have the option of putting the probe in either location and just plugging the other hole.

Part of my reason for putting the probe at the coil output was that the coil later serves as the chiller. I fill the MLT with ice water, put the coil in it, and pump the wort through it, circulating it back to the kettle. With the probe attached to the coil I can watch the chilling progress on the PID display.

Ok, Maybe i'm not understanding what the temp sensor does. I am currently under the impression that the temp senser is used to start the pump when temperatures run low and shut the pump down when temperatures are at set point. Is this not the case? If it is, how would it control the waterbath temperature? I figured the waterbath is set by user and the pump just turns on or off to transfer heat to the mlt when required?

Mine is in the HLT water bath. The HEX is an old immersion chiller, the stirrer is just inside the HEX and the probe (it's a really long one) goes down between, if that makes sense.

I have to set my controller to 3 degrees warmer than my desired mash temperature, but it works great. I assume I "lose" those three degrees going from vessel to vessel. So, for a continued temperature of 153, I set the HLT controller for 156. It's always within .5 degrees of what I want.

DustinHickey said:

Ok, Maybe i'm not understanding what the temp sensor does. I am currently under the impression that the temp senser is used to start the pump when temperatures run low and shut the pump down when temperatures are at set point. Is this not the case? If it is, how would it control the waterbath temperature? I figured the waterbath is set by user and the pump just turns on or off to transfer heat to the mlt when required?

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Most folks leave the pump on all the time (constantly circulating) and use the temp probe + PID to turn the heat off and on as needed.

Ok, yea that makes sense or efficiency i suppose. When you say turn the heat on and off, you mean flame to the hlt?

Right. You monitor and maintain the twmp of the water in the HLT.

DustinHickey said:

Ok, yea that makes sense or efficiency i suppose. When you say turn the heat on and off, you mean flame to the hlt?

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Yes, the controller turns "off" the heat to the HLT and kicks on on when needed. I have a two degree differential on mine. It's not a flame, though. Mine is all electric. It wouldn't work with a flame. You'd have to turn it on and off.

You can do it with flame. You just need solenoid valves and a pilot light.

Mine is at the return to the top of the MT. I have always done it that way. I monitor the temp of the wort leaving the bottom of the MT but it does not control anything. I think using the temp of the wort returning to the MT to control the HLT heating output is the simplest way to do it. Once you figure out the desired temp differential between mash temp and the temp of the wort returning to the MT, your system is dialed in. When I did 15 gallon batches, it was 2F but now with 30 gallon batches it is 4F. All dependent on wort flow relative to the thermal mass of the mash. That said, there is more than one way to skin a cat...

Walker said:

You can do it with flame. You just need solenoid valves and a pilot light.

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Duh! Of course, you're right. I was thinking of my old burner, and not a burner with a pilot light. I'll go crawl back to my (electrical) brewery now...........

Hi Walker, I missed this thread when it first went through. It's a great idea for a poll, and I'm bumping it back to the top so, hopefully, you get some more responses.

I put mine in the water bath after alot of thought the overshoot is what really made me leary of putting it almost anywhere else. Once I auto-tuned the PID I get maybe 1 degree of overshoot and with the temp losses to ambient and less than 100% heat transfer in the HEX I saw almost constant temps over the entire mash maybe .5 degree +/-.

Mine is currently in the output of the HEX coil, but if I ever upgrade from my K thermocouple to an RTD, I'll probably move it to the return to my MLT.

My new HERMS is going to have BCS temp inputs from the MLT output, HLT output and the HERMS output...

That being said, with the BCS I can choose which temp. output controls my HLT heating elements with a mouse click... I am going to use the HLT water bath temp. Period. Though the other options are there.

Thanks for bumping the thread/poll. I have not brewed with my HERMS yet, but I spent a few days doing water tests with it.

My probe is at the HEX output and seemed to work just fine for the wet tests. When ramping up temps, the temp at the probe would overshoot a few degrees before settling back down to my set-temp, but the temp of the water in the MLT did not overshoot by more than 0.5*F.

I think I'm going to give it a shot with the probe mounted to the output of the coil, but I did go ahead and have my welder friend install a 1/2" coupling in the side of the HLT. I plugged it for now, but can move the probe there and plug the hole in the coil output if I decide I want to try it the other way.

Walker, howd this work out for you? I've got a coupler welded into the side of my future eHLT to mount a temp probe, but I'm going to try to put a T on the HERMS coil out.

Maltose said:

Walker, howd this work out for you? I've got a coupler welded into the side of my future eHLT to mount a temp probe, but I'm going to try to put a T on the HERMS coil out.

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With the probe on the coil output, it is working perfectly.

For my first 4 or so batches with the HERMS, I used a bunch of thermometers. One was the PID probe at coil output, one was a digital probe inserted in a DIY thermowell through the side of my TUN, and the other was my floating thermometer pushed down as deep into the grainbed as I could get it.

These three thermometers are within 1*F of each other and are right at my set temp. I don't think I could get things working better no matter how hard I tried.

I originally built my HERMS with the probe in the HLT (measuring the water bath around the HEX). I had overshoot problems right away because the probe was measuring at the bottom of the HLT, and things were much warmer higher up. I thought maybe the temps would average out because the HEX is exposed to cooler and warmer temps as it goes up through the water column, but no dice. To me, it's clear that measuring the temp of the water in the HLT only works if you stir the water to even out the temps.

For me, it was easier to try moving the probe to the HEX output before investing in stirring hardware. Just brewed my first batch with this setup, and everything seems to work much better. I think this may be the best solution.

Walker said:

With the probe on the coil output, it is working perfectly.

For my first 4 or so batches with the HERMS, I used a bunch of thermometers. One was the PID probe at coil output, one was a digital probe inserted in a DIY thermowell through the side of my TUN, and the other was my floating thermometer pushed down as deep into the grainbed as I could get it.

These three thermometers are within 1*F of each other and are right at my set temp. I don't think I could get things working better no matter how hard I tried.

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Hey Walker, what kinda temp diffrerential are you seeing from MLT to HLT? I'm getting about 13deg, and I really want to minimize it. When I do a mashout, my htl water is like 183ish. I am wondering if moving the probe to the output of the hex would help at all...

McCuckerson said:

Hey Walker, what kinda temp diffrerential are you seeing from MLT to HLT?

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I have no idea, because I don't ever check the temp of the water in the HLT. If I remember, I will check it on the next brew for curiosity's sake.

Great thread topic walker. I have been debating this myself as I am in the planning stages for my futures HERMS set-up.

Yooper said:

Mine is in the HLT water bath. The HEX is an old immersion chiller, the stirrer is just inside the HEX and the probe (it's a really long one) goes down between, if that makes sense.

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Yooper, do you have a picture of your stirrer or know of a thread showing good pictures? I hadn't considered stirring the HLT but I can see how that would be great for maintaining constant temperatures.

McCuckerson said:

Hey Walker, what kinda temp diffrerential are you seeing from MLT to HLT? I'm getting about 13deg, and I really want to minimize it. When I do a mashout, my htl water is like 183ish. I am wondering if moving the probe to the output of the hex would help at all...

Click to expand...

I don't have a HERMS, so maybe I don't know what I'm talking about, but I don't see how moving the probe would decrease the temp. differential. The heat going into the HEX from the HLT water has to be equal to the heat losses from the MLT, pump, tubing. I would think the only way to reduce the temp. differential is to either cut the heat losses (better insulation on MLT and tubing) or increase the heat transfer efficiency from the water in the HLT to the wort inside the HEX (longer HEX tubing, bigger diameter HEX tubing, or constantly stirring the water in the HLT).

DeafSmith is right. Moving the probe won't change the differential. that differential is just a property of your system. You have to change the heat transfer of your system to change that differential.

Complete buzzkill guys! Ok, I have 20' of 3/8OD soft copper in my HLT. Should I increase that? Maybe solder another 20' section on to it? Or would insulating my keggle HLT and MLT be more beneficial... or both?!?!?!?! help! Double decoction lager is good

McCuckerson said:

Complete buzzkill guys! Ok, I have 20' of 3/8OD soft copper in my HLT. Should I increase that? Maybe solder another 20' section on to it? Or would insulating my keggle HLT and MLT be more beneficial... or both?!?!?!?! help! Double decoction lager is good

Click to expand...

Have you just tried slowing down the flow from your pump?

Walker said:

Have you just tried slowing down the flow from your pump?

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Or speeding it up? Changing the flow rate has two opposing effects - for example if you slow the rate, you allow more time for heat to flow into the wort in the HEX, heating it to a higher temperature, but on the other hand you are heating less wort per unit time - I'm not sure which will be the dominant effect.

Maybe adding a motor driven stir paddle would help, given how much difference whirlpooling an immersion chiller makes - a lot more heat transfer when the wort is moving over the coils.

Probably best to get some details on other peoples systems who don't have the big temp differential - see what's working for them.

I do stir with a 60rpm paddle. I have done fast to medium recirc. I can try slow next

DeafSmith said:

Or speeding it up? Changing the flow rate has two opposing effects - for example if you slow the rate, you allow more time for heat to flow into the wort in the HEX, heating it to a higher temperature, but on the other hand you are heating less wort per unit time - I'm not sure which will be the dominant effect.

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Yeah, I was just commenting on how to keep the temp difference between the HLT and mash to a minimum, but you are right.

There is no reason he has to crank the temp up 18*F higher than his mash-out temp. Just set it to the mash out temp and let the stuff circulate long enough and it will eventually get there.

He's got it cranked up to get it does as fast as possible I guess?

Walker said:

Yeah, I was just commenting on how to keep the temp difference between the HLT and mash to a minimum, but you are right.

There is no reason he has to crank the temp up 18*F higher than his mash-out temp. Just set it to the mash out temp and let the stuff circulate long enough and it will eventually get there.

He's got it cranked up to get it does as fast as possible I guess?

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I'm confused. I am not concerned with ramp time. At rest it has a 13deg difference. I think if I lengthen the coil and insulate the kettles it will improve. Thoughts?

sure retaining heat within your system will help, and a longer coil will transfer heat to the wort faster. I believe the others were trying to say you could cut the flow through the coil to give the wort more time to absorb heat.

sonex said:

sure retaining heat within your system will help, and a longer coil will transfer heat to the wort faster. I believe the others were trying to say you could cut the flow through the coil to give the wort more time to absorb heat.

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Yeah but then I'm not turning the water in the mlt over enough. It's a tradeoff

I'm running a temp/cleaning cycle right now. I moved the TC to the output of the coil in the MLT. I ran autotune and the thing is dead nuts. The mlt is 154f and the hlt is at 154. The only thing I noticed is that the autotune ran A LOT longer than it usually does.

Am I witnessing the magic of the PID? I am so happy right now, but I would love for someone to explain what I am seeing.

Thanks,
McC

I'm glad you got auto tune to work for ya. Auto tune seems to over shoot before it wants to settle down for me. Good for you, wish I could explain it to ya but I have never been able to get it to work perfect for me.