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HERMS - Mash Temperature

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Brian Parfitt

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I've recently upgraded to a DIY HERMS setup and had some questions about Mash temps.

I currently monitor temperature in my HLT where the HERMS coil is parked as well as at the discharge of the HERMS coil. I take measurements of the grain bed temperature throughout the brew cycle with a handheld thermometer. In general, I find the grain bed to be 7-8 degrees cooler than the water temp in the HLT and the discharge out of the coil.

So what is more important to control? The temperature of the wort/grain bed? Or the temperature of the wort as it passes through the coil in the HLT?

On one hand. you don't want the grain bed to drift too low, but on the other hand, if the HLT temp is 8-9 degrees warmer, does that adversely effect the wort as it passes through? i.e. You have conversion taking place for that brief window within the coil at a higher temperature.

My intuition tells me that the wort spends so little time passing through the coil that it all just averages out to the actual grain bed temperature anyway. Just curious to see what others thought.

Brian
 
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i say its called a grain "bed" because thats where the magic happens. so thats the important one to monitor. my herms runs about the same differential in temp. i set my hlt about 8 degrees higher then desired mash temp.
 

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i measure my MLT and HLT temps at the output valve. I get anywhere from 0-3 degrees F difference depending on my basement temperature and how long the system has been recirculating. To reduce the difference, you can get thicker walled tubing or shorten the tubing lengths to minimum amounts. I would think that the short time the wort gets hotter would reduce your beta amylase concentrations by a small amount compared with a setup with a smaller difference but not a ton. Time and temp. are important for enzyme stability and the resulting attenuation of the beer. You can just keep track of all temperatures for each brew and note attenuation of each brew and then compensate for your system.
 

day_trippr

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fwiw, I set my hlt temperature 2.5°F above the target mash temperature once the middle of the mash has reached said target. I can then walk away/do other brew day stuff for long periods without concern, it just sits at that state.

An 8 degree differential suggests the recirculation rate isn't keeping up with the rate of mlt thermal loss. Must be tricky to manage. Eg: the output of the hex would be 160°F when trying to hold a 152°F mash temp. And that ain't good...

Cheers!
 

Bobby_M

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Agree. 8F is too high of an offset. I would look at insulation on the mash tun or trying to squeak your recirculation rate up just a touch by adding some rice hulls or milling a little courser. Average offset is about 3-5F.
 
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interesting, do volume and ambient temp play a role? i brew 15gal batches and in my basement ambient temps are typically 55f to 60f, i do typically use rice hulls, maybe on my next batch ill use a different temp probe in my mash. suppose it could be off also.
 

crane

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Hopefully you have a bad thermometer for measuring the grain bed. If that is not the case and you are still seeing such a large difference then it might be good to measure the temp of the water entering the mash tun before getting into the grain bed. This will tell you if all 8 degrees are being lost in the transfer hose from HLT to MT.
 
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yeah i was thinking the same thing. my hose from outlet of coil to MT is about as short as possible but i have never measured the temp there. i am typically very close to my estimated OG and efficiency is in the mid 70s depending on the grain bill, sometimes higher. I will definitely check that next time and swap out my temp probe.
 
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Brian Parfitt

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I suspect that my flow rate through the hex may be the culprit here. When I say diy HERMS... I have a 3/8" x 50 stainless coil (former immersion chiller) that I have been using with a Riptide pump. That then flows through a sparge ring which is suspended on top of or just above the grain bed. With no throttling on the pump discharge I get a very gentle trickle out of the sparge ring outlets. I'm thinking that the amount of fluid flow carrying heat into the mash tun is too low to properly control temperature. Most of the coils I have seen in commercially available products are much shorter and 1/2" diameter.

With respect to hose length out of the hex... I have about 10" of stainless tubing exposed to ambient and maybe 3' of 1/2" silicone tubing between coil and sparge ring. It's about as short as it can be.

I've only had about 4 batches through this system and have been concerned about the ~10 deg differential between bed temp and HLT.
I'm planning a brew day tomorrow and will collect some more data.

Thanks for the responses here. Very much appreciated.
 

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I think you are on the right track.

It's a balancing act between your flow rate, where you make your measurement, and so on. Generally speaking try to tighten up the system meaning shorter runs, insulated hoses and vessels, and so on if possible. Try to maintain pretty tight temps all around and not have hot and cold zones. As a goal anyhow.

You may not want to measure the grains directly, but perhaps just barely above them. Measuring the grains might allow "too hot" water hitting them and taking a bit to be realized. Measure too far away of course and you'll lose a lot of heat along the way and they'll end up cooler than desired. I'd consider measuring just above them if possible, in the liquid pool, if there is one. Or possibly just before the returned wort exits whatever contraption you have for showering them, if things are covered and that temp can be maintained (you'll be off a few degrees if they rain into an open tun).
 

day_trippr

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Maybe put up a pic of your brew rig so we can gather some context? Almost 4 feet of mixed plumbing between hex output and mlt input might be an issue worth insulating. fwiw, my corresponding path is less than 24" of thick wall silicone hose...

Cheers!
 

Gozie Boy

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+1 on the flow rate, although the other factors mentioned could also be material contributors. But I'd be looking at your rate first.
 

jcav

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I brew outside on my back lanai so there is ambient temperature/weather that is a factor effecting the hoses, and there will be a temperature loss. Even with this though, I am in the middle of a mash right now and I have the HLT set 3 degrees higher to keep the grain bed at my target temperature. I do run the valves wide open though to get maximum flow and turnover throughout the grain bed, and this is important on my rig and brewing outside.

I do not run the pump valve of the mash tun wide open at first and just open it about halfway, so I don't compact the grain bed and get a stuck mash. After a few minutes into the mash, when the grain bed settles, I can then slowly open the valve wide open and let it rip for the mash rest and the temps are held perfectly and with only a 3 degree offset between the HLT and the grain bed. On hot summer days I sometimes only have a 1-2 degree difference as there is less temperature loss in the hoses, due to the hot ambient temperature on my lanai.

I also use rice hulls in every batch regardless of what grains I am mashing (not just for wheat, oats, flaked, etc.) as this keeps the grain bed porous, and it helps to regulate a more even temperature throughout the mash tun. The late Mike (Tasty) McDole, talked about the rice hulls and what they do in a pod cast several years back. I tried it and found it works very well for my set up. I have an electric 3 vessel herms system. So this is something maybe to try on your rig and see if it helps.

John
 

Bobby_M

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Add yourself the to list of about 100 brewers who have reported problems with a 3/8" HERMS coil. That's too small for a 5 gallon batch, nevermind 15. I get calls all the time from people looking for compression bulkheads for 3/8" coils. I warn them. They thank me and buy the 3/8" fittings anyway. I get calls back asking if I'd take the fittings back in exchange for a 1/2" OD HERMS coil and fittings.
 

jcav

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Also I do have a stainless steel 1/2 inch 50 foot herms coil. I got my fittings from Bobby. Those compression fittings are top notch by the way!

John
 

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I do 12-20 gallon batches. I also have 1/2 x 50' coil, and MT is 120qt cooler w manifold. I also brew outside and I use pipe insulation on all my lines and fittings. It made a huge difference in holding the temps I want. I had little knowledge when I built my 3 tier setup. I've never used any rice hulls. Mill is set at .030 I think and run full out. I don't insulate the HLT. I agree with Bobby, you have to have 1/2" no doubt. I have dials all over my system, but only really look at the one that is right before it enters my return. My setup just isn't efficient enough to handle stepping that size of grain bill. Once the bed reaches its temp, I only look at the wort temp. I've done enough batches and checked the mash. The mash will follow once it reaches the first step temp, if that makes sense.
 
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The enzymes are in the grain, and will become less active below optimal mash temp, so that’s the one you want to watch. All the conversion is happening in the grain itself. Once starches in grain are converted to sugars, they become soluble and dissolve in the water making wort. The higher temps don’t hurt the circulating wort at all (it’s going to boil eventually). But to my understanding, the unconverted starches and enzymes are not soluble, and remain in the grain.
 

VikeMan

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The enzymes are in the grain, and will become less active below optimal mash temp, so that’s the one you want to watch. All the conversion is happening in the grain itself.
The enzymes do come from the grain, but they definitely end up in the wort. Conversion is happening in the wort in the grain bed and in any wort that's being recirculated.

Once starches in grain are converted to sugars, they become soluble and dissolve in the water making wort.
Starches in the mash do dissolve. It's these starches in solution that are converted by the enzymes to sugars and dextrins.

The higher temps don’t hurt the circulating wort at all (it’s going to boil eventually).
Enzymes in the recirculating wort can most certainly be denatured by high temperatures.
 
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Brian Parfitt

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All,

Great responses to this. I did get out for a brew session this past weekend and here is what I observed.

I initially set my HLT controller to 160F. I wanted to Mash at 150-151. Wort temp right out of the HERMS coil was ~154-155 (I was not able to verify this with multiple thermometers.. seems a bit much -next time). Mash temp in the tun was very steady between 151 and 152. I then dialed my HLT temp down to 157 and watched the MT temp drop to 148-150. I finally settled on a HLT temp of 158 which stabilized me right at 149-150. I have about 3 feet of silicone tubing connected to the output of the HERMS coil. I tucked as much of that inside the MT as possible and placed the lid on in an attempt to conserve heat losses.

For my setup, I've just repurposed my stainless steel immersion coil to use as a HERMS setup. It's not ideal as there is a tall vertical section of the exchanger where the coil inlet runs parallel and in contact with the coil discharge. I imagine this contributes to a bit of the cooling taking place. Similar to what is shown below, but not my exact setup.

40474-silver-serpent-stainless-immersion-wort-chiller_913d8e60-d3ee-4634-ae28-e2762ac36c6a_x700.jpg


Bobby_M - I was one of the guys you talked to about the 3/8" compression fittings.. And I agree with what you said 100%. For me it was just a matter of not being able to afford the larger HERMS coil, fittings, and kettle modification at this time. A couple of cheap 3/8" fittings opened up a whole new part of this process to me... That being said, I am saving for my next upgrade. And I would wholeheartedly recommend to others the 1/2" coil over 3/8" at this point if you were on the fence.

I'll get some pictures of my setup posted later today. I did not think to snap any while brewing this weekend.

Thanks again for all the tips here.

Brian
 
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not trying to hijack, just sharing my issue (that i have learned via this thread) love hbt for this exact reason. so my coil is 1/2" and seems as though i need to change where my my mash temp probe is, i have been measuring from the bottom and one in the middle, not the top, and therefore likely have been mashing to hot. i wont be brewing for a few weeks so ill have some time to look at things and adjust accordingly. I am always happy to find ways to improve and they usually come from here. thanks everyone.
 
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