Stirring the mash

[PaulC]

Hi All,
I've been brewing for a few years now, but I upgraded my rig a while back to a 3-tier HERMS setup, and so far I've only put a few brews through it. I'm still learning the AG process, and I have a question about how you guys control your mash temps in your HERMS system.

My system is a 3 tier direct fire system, with a pump controlled by a digital temp controller. The thermowell for the controller is towards the bottom of the MT.

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My process for temp steps is to ignite the MT burner, turn on the temp-controlled pump, and wait for the pump to shut off to kill the burner. What I've noticed is that due to where the thermowell sits in the MT, the hot mash water being recirculated and added to the top of the MT takes quite a while to get all the way down to the thermowell. By the time it does, the volume of hot water above the thermowell is sufficient to raise the overall temp of the mash another 4-5 degrees. What this means is that I've overshot my steps on pretty much all occasions.

Do others have similar setups? If so, how do you address this issue? Last batch, I stirred the mash during my steps, which helped considerably, but I've read that mash should be left alone for the most part, and I had to stir quite a bit to get my temps right last time. I also thought about lowering the temperature on the controller by a few degrees to account for this, which is what I'm going to try Saturday.

I also noticed about 10-15 minutes to go from one step to the next, usually around 15 F. That seems ok to me, but wondering what the norm is and what I should shoot for - as quickly as possible, or a slower rise?

Thanks for your time and cheers!

 

[Sippin37]

I'm not very familiar with your type of setup but I do a recirculating mash using an electric heating element and Brew in a Bag. My temp probe is near the bottom of the MT as well but I have plenty of liquid around the bag of grain that keeps the temps pretty uniform. Is it possible for you to move the temp probe a different location? Perhaps put it right where the heated wort is entering the MT and therefore you know the exact temp of the freshly heated wort? This should keep you from being 4-5 degrees high on the temp.

As for stirring during the mash, it seems fine to do it during the beginning of the mash and I personally haven't seen any ill effects doing it once or twice throughout a 60 min mash. But lately I have just been doing it only at the beginning to break up any clumps and then leaving it alone after that. This has given me a much better grain bed and clearer wort. Hope this helps!

 

[rklinck]

I do not have a HERMS systems, so take my comments with a grain of salt, but I am a bit confused by your description.

Do you have a controller that monitors the temp of the HLT where the HERMS coil is? My understanding of HERMS is that you should maintain that liquid in the HLT at a constant temp (I am not sure what the temp is, but I am guessing that it is only a couple of degrees above the desired mash temp). The pump kicks on when the MT is too cold and circulates the wort through the HERMS coil in the constant temp HLT to warm it back up. Is that how the system work during each step?

I am also a bit confused about what burner you are turning on to get between steps. If you are turning the MT burner on, wouldn't the wort at the bottom of the kettle (where the temp probe is) get hot quickest? Seems like that should cause you to undershoot your temps. Based on this, I am guessing that what you are doing is turning the HLT burner on when the pump kicks on and then keeping it on the whole time. Is that right? I'm not sure that is how it should be done. Seems to me that you should have the HLT temp controlled separately and get it to a temp that is slightly above your desired step temp and then just let the pump do all the work. If the HLT water is 30 degrees hotter than your desired mash temp, it seems like you are going to overshoot every time. If it is only a couple of degrees above your desired temp, you are less likely to overshoot.

 

[gpack]

You may want to think about putting the temp probe in the recric wort (post) herms coil prior to entry into MT and keep your HLT nice and warm all the time.

 

[gpack]

For clarification. On RIMS it is most common to find the temp probe between the MLT and the heating element to keep from overshooting mash temps/steps. it would seem logical to likewise do the same with a HERMS.

 

[rklinck]

You may want to think about putting the temp probe in the recric wort (post) herms coil prior to entry into MT and keep your HLT nice and warm all the time.

I thought about suggesting that, but that would not work for a HERMS system. If the HLT temp is really high, the wort coming out of the HERMS tube is going to be above the desired mash temp almost immediately. So the system would immediately turn off. But then the probe would immediately cool down becuase no wort would be flowing by, and it would turn back on almost immediately. I think the probe needs to be in the wort in the MT somewhere.

 

[rklinck]

For clarification. On RIMS it is most common to find the temp probe between the MLT and the heating element to keep from overshooting mash temps/steps. it would seem logical to likewise do the same with a HERMS.

I think this is wrong. In a RIMS system, the pump is always running and the temp controller simply kicks the heating element on and off. My understanding is that a HERMS system is different because the pump only runs when the wort needs to be heated. So the placement of the temp probe from a RIMS system will not work for a HERMS system (for the reasons set out in my last response).

 

[rklinck]

This article seems to suggest that you should be precisely controlling the HLT temp and constantly pumping the wort through in a HERMS system. That means that you are controlling the wrong component with the temp controller. You need the temp probe to be in the HLT and then the controller will need to control the burner to kick it on to maintain the temp.

http://www.brewersfriend.com/2009/02/22/introduction-to-rims-and-herms/

Here is another article suggesting that the HLT water should be at about 180 degrees. I am not sure where you would put the temp controller probe. But where ever the probe is, it would kick on heating of the HLT.

 

[PaulC]

...Do you have a controller that monitors the temp of the HLT where the HERMS coil is? My understanding of HERMS is that you should maintain that liquid in the HLT at a constant temp (I am not sure what the temp is, but I am guessing that it is only a couple of degrees above the desired mash temp). The pump kicks on when the MT is too cold and circulates the wort through the HERMS coil in the constant temp HLT to warm it back up. Is that how the system work during each step?

Thanks for your responses. There is no controller monitoring the HLT. There is a thermometer which I use to monitor temperatures and adjust the flame intensity accordingly. The instructions which came with my brew rig suggest stabilizing HLT temp at 170 throughout the entire process. The temp differential at 170 isn't really enough to quickly raise temperatures 15+ degrees F, so the burner under the MT is used in conjunction with the recirculation through the HERMS coil to raise temps during the steps.

I am also a bit confused about what burner you are turning on to get between steps. If you are turning the MT burner on, wouldn't the wort at the bottom of the kettle (where the temp probe is) get hot quickest?

The MT burner does get turned on, and heats the wort at the bottom of the MT. The drain valve, located right next to the controller thermowell, is plumbed to the pump, which then re-circulates this wort through the HERMS coil and back into the top of the MT. It could be that I am using too much flame which is causing this wort to heat too much.

Seems like that should cause you to undershoot your temps. Based on this, I am guessing that what you are doing is turning the HLT burner on when the pump kicks on and then keeping it on the whole time. Is that right?

HLT burner is on to varying degrees of intensity at all times until the boil.

I'm not sure that is how it should be done. Seems to me that you should have the HLT temp controlled separately and get it to a temp that is slightly above your desired step temp and then just let the pump do all the work. If the HLT water is 30 degrees hotter than your desired mash temp, it seems like you are going to overshoot every time. If it is only a couple of degrees above your desired temp, you are less likely to overshoot.

It seems to me like this would result in very long transition times through steps due to the lack of a significant temperature differential and resulting heat exchange. Additionally, heating the ~15 gallons in the HLT takes a while as it is, so raising that in temperature once and keeping it at 170 I think does a few things - 1) Gives a wide enough temp differential to cause a significant heat exchange. 2) Gives me sparge water at the right temperature ready to sparge immediately at the end of the mash 3) Is one less thing to worry about during the mash.

Is it possible for you to move the temp probe a different location? Perhaps put it right where the heated wort is entering the MT and therefore you know the exact temp of the freshly heated wort? This should keep you from being 4-5 degrees high on the temp.

Thanks for your response. Moving the probe could be an option, but probably easier said than done. If possible, I'd prefer to go down the route of process change prior to equipment modifications.

As for stirring during the mash, it seems fine to do it during the beginning of the mash and I personally haven't seen any ill effects doing it once or twice throughout a 60 min mash.

Stirring during the step seemed to work last time. My only worry is that I seem to be defeating part of the purpose of the HERMS system, which is to result in very clear wort. Stirring the mash disrupts the grain bed and I lose some of that benefit. That said, my wort was still pretty clear last time without any vorlauf.

I think this is wrong. In a RIMS system, the pump is always running and the temp controller simply kicks the heating element on and off. My understanding is that a HERMS system is different because the pump only runs when the wort needs to be heated. So the placement of the temp probe from a RIMS system will not work for a HERMS system (for the reasons set out in my last response).

I agree with this. The pump needs to run only when the wort needs to increase in termperature. What ends up happening is that the controller registers a 1 degree drop in temperature, turns on the pump, recirculates hot wort and shuts down relatively quickly. Holding a mash at temp hasn't really been a problem, its just the steps which are causing some issues currently.


All good ideas, thanks for your time guys.

 

[PaulC]

This article seems to suggest that you should be precisely controlling the HLT temp and constantly pumping the wort through in a HERMS system. That means that you are controlling the wrong component with the temp controller. You need the temp probe to be in the HLT and then the controller will need to control the burner to kick it on to maintain the temp.

http://www.brewersfriend.com/2009/02/22/introduction-to-rims-and-herms/

Here is another article suggesting that the HLT water should be at about 180 degrees. I am not sure where you would put the temp controller probe. But where ever the probe is, it would kick on heating of the HLT.

The article you linked is very interesting. It has me considering how I have this system setup and how I could adapt

If you have the link to second article you mention I'd love to read it.

Thanks!

 

[rklinck]

If the only problem is with steps, I would turn the MT burner on to start the steps but cut it off when you are within 5 degrees of the next step. That should prevent you from overshooting.

 

[rklinck]

The article you linked is very interesting. It has me considering how I have this system setup and how I could adapt

If you have the link to second article you mention I'd love to read it.

Thanks!

Sorry about that. Multitask fail! Here it is:

http://byo.com/stories/issue/item/1325-rims-and-herms-brewing-advanced-homebrewing

 

[PaulC]

So, to follow up on this thread, I am mashing right now, and I took some advice from this thread. I am keeping my HLT within 10 degrees of my target mash temp, and stepping the HLT temp up at the same time as the mash steps. Its working quite well, I haven't had to stir the mash at all outside of dough-in and I'm hitting my target temps on the nose. Currently in mashout, about to sparge with perfectly heated water


This really makes me want to look into some automation for controlling the HLT temp. It looks like I need a pilot light assembly and another temperature sensor assembly. Can anyone point me to a good DIY thread on installing a gas pilot light assembly with a digital controller? When i search for Digital HLT I find mostly electric heater setups.

Thanks again!

 

[rklinck]

Good to hear it's working. Maybe search "solenoid". You will need a solenoid to turn the gas on and off. That might get you what you want.

 

[rklinck]

Also, you are probably going to want a PID controller. Not sure what temp controller you are using, but PID controllers use advanced logic to prevent overshoots. I'm going with one for my RIMS build.