Author Topic: how to properly measure mash temp with herms or rims system  (Read 632 times)

Offline dlauridsen

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how to properly measure mash temp with herms or rims system
« on: March 26, 2019, 02:25:34 PM »
I'm brewing on a herms system to help regulate mash temp stability and occasionally do a step mash and have been feeling that my beers aren't quite as light bodied as I'd like them to be for the mash temps I'm targeting (generally 147-149). I'm starting to wonder if I might be measuring the mash temp incorrectly and was hoping for some input. I've got three thermometers to watch my mash temps... one on the mash tun, one on the HLT, and one on the mash recirculation line just before the wort re-enters the mash tun. The HERMS coil seems to be quite efficient as the HLT temp and wort recirculation temps are always exactly the same. To keep my mash where I want it, I generally have to keep my HLT about 8-10 degrees hotter (I believe the proper term for this is delta T) than the temp reading I'm getting on the mash tun. What I'm starting to wonder is if I am correctly controlling my mash temp by monitoring the mash tun, or if I should be going off the wort recirculation temp? The fact that the delta T is 8-10 degrees would make quite a big difference in the body of the beer if I'm measuring at the wrong place. I get great efficiencies; my saisons and farmhouse beers are generally finishing around 1.001 to 1.003, so it doesn't seem like I'm doing it wrong, the dryness and body just aren't quite what I'm aiming for. Could be a water issue too, but thought I would see what opinions are out there from any experienced HERMS brewers. Thanks in advance for any feedback.

Offline billski48

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Re: how to properly measure mash temp with herms or rims system
« Reply #1 on: March 26, 2019, 02:56:58 PM »
I’m sure others will reply with more detail than I can provide at the moment, but you will want to maintain the temp that’s coming out of the herms coil, going into the mash tun. Not the actual temperature in the mash tun itself. The issues you are having definitely reflects on that theory.

Offline BrewBama

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Re: how to properly measure mash temp with herms or rims system
« Reply #2 on: March 26, 2019, 03:10:26 PM »
I measure temp about 2” downstream of the RIMS element which is controlled by PID.


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Offline goose

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Re: how to properly measure mash temp with herms or rims system
« Reply #3 on: March 26, 2019, 04:11:12 PM »
I may be the oddball here but I measure my temps at the outlet of the mash tun and before the RIMS heating element.  My thermocouple sits about 8 inches from the MT dip tube (right next to a calibrated thermometer to check accuracy) and controls the PID.  I may be totally out of line here but I worry a bit about measuring downstream from the HERMS or RIMS elements since you are measuring heated wort and not the actual temp. in the grain bed.

When doing a step mash,  I use the RIMS element and an external burner with a low flame to raise the mash temp to the next step.  I will externally heat until the RIMS contactor shuts off, turn off the flame, and wait for the mash temp to stabilize before repeating the process if necessary (about a minute or so).   It takes maybe 10 minutes at most to get to the next step temp and/or mashout temp with a large grain bill.  I feel by doing it this way I have pretty good handle that the mash temp is inline my target temperature and the thermal mass of the mash helps keep me from overshooting.  FYI, my brew system was patterned after what SABCO does on its BrewMagic system.

I make a pretty dry saison, have not noticed any extra sweetness in the beer using this method, and have medalled several times with this beer in competition.  I always get the FG down below 1 degree Plato (4 SG).  That said, all brew systems are not the same and you may have to play around with where you measure to get the accuracy and results you desire.
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Offline kramerog

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Re: how to properly measure mash temp with herms or rims system
« Reply #4 on: March 26, 2019, 05:43:10 PM »
From a process engineering perspective, moving the control point does not really solve the problem when the system consistently has hot spots and cold spots that all the wort goes through.  I would set you control temperature 5 F (1/2 delta t) cooler so the average temperature in your system hits the target temperature.

You should also see less of a delta T and better results, if you insulate your tun or lines better.

Offline mabrungard

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Re: how to properly measure mash temp with herms or rims system
« Reply #5 on: March 26, 2019, 07:06:21 PM »
The temperature of the mash bed is completely irrelevant with respect to enzyme denaturing. The only thing that does matter in that respect is the maximum temperature that the wort reaches at each step. So the 8 to 10 degree overshoot is the reason that the resulting beers tend to be less attenuated.

I recommend that you use the HERMS discharge temp as your mashing criterion in the future.
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Offline BrewBama

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how to properly measure mash temp with herms or rims system
« Reply #6 on: March 26, 2019, 07:15:32 PM »
I may be the oddball here but I measure my temps at the outlet of the mash tun and before the RIMS heating element.  My thermocouple sits about 8 inches from the MT dip tube (right next to a calibrated thermometer to check accuracy) and controls the PID.  I may be totally out of line here but I worry a bit about measuring downstream from the HERMS or RIMS elements since you are measuring heated wort and not the actual temp. in the grain bed.

When doing a step mash,  I use the RIMS element and an external burner with a low flame to raise the mash temp to the next step.  I will externally heat until the RIMS contactor shuts off, turn off the flame, and wait for the mash temp to stabilize before repeating the process if necessary (about a minute or so).   It takes maybe 10 minutes at most to get to the next step temp and/or mashout temp with a large grain bill.  I feel by doing it this way I have pretty good handle that the mash temp is inline my target temperature and the thermal mass of the mash helps keep me from overshooting.  FYI, my brew system was patterned after what SABCO does on its BrewMagic system.

I make a pretty dry saison, have not noticed any extra sweetness in the beer using this method, and have medalled several times with this beer in competition.  I always get the FG down below 1 degree Plato (4 SG).  That said, all brew systems are not the same and you may have to play around with where you measure to get the accuracy and results you desire.

That’s interesting. I can see where externally heating the MLT would allow placement of the temp bulb in the MLT itself.

I heat the wort by the 1650 ULWD element inside the RIMS tube.  By placing the temp bulb immediately downstream of the element I control the max temp the liquid in the tube ever sees.  The MLT drain is at the low point of one end, the wort is pumped thru the RIMS, and the return is at the high point at the opposite end of the MLT (discharging just under the liquid level). Cooler wort enters the tube, is heated until the error between SV and PV are within tolerance, the element shuts off, and the cycle continues until the wort entering the tube is at (or really close to) the SV.  Once the temps quit cycling I know the mash is at the step temp. It takes a little more than 10 min to step up the entire mash 10*F.  I know the wort never exceeds the SV (within tolerance) because the display tells me the PV. It also tells me the % power applied to the element and whether the element is firing or not.


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« Last Edit: March 26, 2019, 07:18:12 PM by BrewBama »
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Offline charlie

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Re: how to properly measure mash temp with herms or rims system
« Reply #7 on: March 27, 2019, 12:02:36 AM »
I measure my mash temps in the same places that you do, and I run my HERMS vessel (which isn't my HLT) two degrees higher than the desired mash temp. This usually requires that I run its pump 10 minutes on, and 10 minutes off (keggle system, 10 gal batch, MT is lightly insulated).

I agree with others above. I think you're going over temp.

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Offline ynotbrusum

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Re: how to properly measure mash temp with herms or rims system
« Reply #8 on: March 27, 2019, 10:46:38 AM »
My controller temp probe is always downstream of my HERMS coil, just as the wort re-enters the Mash tun from the top.  If I have it measuring in the middle of the Mash tun, it calls for too much heat in the HERMS vessel, typically, which may be a function of the strentgh of my element (4500 watts) with respect to the size of the HERMS vessel (9 gallons).  Using it at the return to the mash tun puts the Mash tun spot on after a few short minutes.
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Offline dlauridsen

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Re: how to properly measure mash temp with herms or rims system
« Reply #9 on: March 27, 2019, 01:16:06 PM »
Thanks for the input everyone. I will be monitoring mash temps out the HERMS outlet for my next batch to see if that helps me get closer to my goal of lighter and drier beers.

Offline yugamrap

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Re: how to properly measure mash temp with herms or rims system
« Reply #10 on: April 01, 2019, 08:07:11 PM »
FWIW, the Spike System I use is configured to monitor mash temperature at the outlet of the MLT (there's a tee fitting with a valve and a temperature probe).  I find that I get very stable temperatures running the HLT (where the HERMS coil is) just a degree or two higher than the target mash temperature.  That may vary with the length and type of hoses used, but can be figured-out through trial & error.

I've added a sparge manifold I built to the Spike System's return from the HERMS/HLT.  It sits on top of the grain bed, submerged about an inch below the wort surface and directs wort upward/sideways through holes drilled at a 45-degree angle.  This helps avoid channeling in the MLT while recirculating during the mash and when sparging afterward.  It also reduces splashing, oxygen exposure, and post-HERMS temperature loss compared to the simple return elbow of the Spike System that runs wort down the inside wall of the MLT.   
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