stirring the mash

[ewsaemann]

I use a HERMS. My grain bed compacts enough that the flow cannot keep up with my pump - cavitation. So I stirred the mash, which solved the problem. For about 5 minutes. When I throttle back the flow, so as to minimize pulling the bed down and compacting it, the temp doesn't rise, so I need to keep the liquid flow up there.
Rather than babysitting the mash for an hour and stirring every five minutes, does anyone have any suggestions? I was looking for something I could clip to the side of my SS Brewtech mash tun for auto stirring. I'd have to leave the cover off, which I guess may not be a problem as the HERMS is pretty good at maintaining temp.
Thanks for your help.

 

[Spartan1979]

If you're getting cavitation, you need to restrict the flow with a valve on the outlet of your pump.

 

[tracer bullet]

Agreed. Reduce the flow (at the pump outlet) is the easy thing.

If that's too slow, add rice hulls to the mash to loosen it up a bit. Also consider some insulation so you don't lose as much heat through the pump, tubing, and so on.

 

[ewsaemann]

Thanks for the responses. Yes, I reduced the flow with a valve at the far end, where it comes back into the mash tun, and the mash temp won't rise to the temp in HERMS kettle. Temp drop is not a problem, because the tun is insulated. I do use a couple handfuls of rice hulls in my mash.
Been reading the other mash stirring threads, and there seem to be differing opinions. It seems in my system that I'll have to stir in order to not compact the bed enough to restrict flow to the pump. The mash tun is the SS Brewtech 20 gal. I'm surprised this issue wasn't brought up before.
So I'm thinking about how to rig up a small motor to rake the grains at the bottom of mash tun, just above the false bottom. Isn't this what the big breweries do?
I like the recirculating of mash with the HERMS, but may have to improvise - stirring until temp is reached and then reducing the flow.

 

[tracer bullet]

... the mash temp won't rise to the temp in HERMS kettle. Temp drop is not a problem...

Just want to say this seems conflicting.

I'd say the reason the mash isn't rising to where you want IS because of temp drop. Maybe not outside the mash tun itself, but due to the pump and lines. Look at insulating them to help, or simply raise the temp in the HERMS kettle by a degree or two or whatever it is exactly that you feel you are measuring short in the mash itself.

 

[day_trippr]

I was in the middle of writing the same thing. I think we need some idea of actual flow rates used.

fwiw, I run a 3v2p single tier herms rig with three 20 gallon uninsulated kettles and recirculate the mash at roughly 2 gallons per minute, with my herms/hlt temperature typically 2°F above the target mash temperature. If I try to recirculate at much above 3 gallons per minute it can easily lead to a tight mash that then requires backing down the flow rate which in turn causes mash temperature issues. So I avoid doing that and it all works wonderfully

Cheers!

 

[bkboiler]

Are you mashing at 1.25 qt/lb or thicker/thinner?
What types of grains? Enough wheat and a tight mash is much harder to avoid...

 

[ewsaemann]

Tracer, I hadn't really thought of that, as I thought just a slow flow rate would mean the hotter water in HERMS tank isn't flowing fast enough to raise the temp - though more time in coil should raise temp more. Yes to raising temp on HERMS. I just know that when I opened the valve all the way, viola, the temp rose quickly.

Not sure of the flow rate through the pump. It is a Blichman riptide pump and running fully open.

My last mash was 2 qt/lb and grain was only pilsner, with some rice hulls thrown in.

 

[bkboiler]

this may not be related but thought Id throw it out there :
I recently finished building my system and realized that I thought I had a stuck mash ....
BUT, it was actually just my diptube was way to close to the bottom of the mash tun (I was trying to get every last drop )...causing immense flow resistance.

 

[day_trippr]

[...]
Not sure of the flow rate through the pump. It is a Blichman riptide pump and running fully open.[...]

Well there's your problem: that pump is capable of 6-7 gallons per minute, and I can't imagine a mash in a 20 gallon kettle could pass anywhere near that much fluid...

Cheers!

 

[ewsaemann]

Ah, so I'll turn down the knob on the pump and will put on a smaller restricter and hoses to avoid air bubbles; cut it down to 2 gal/min. Sound like a possibility?

Saved me from hunting for or making an auto stirrer. Thanks.

 

[tracer bullet]

Ah, so I'll turn down the knob on the pump and will put on a smaller restricter and hoses to avoid air bubbles; cut it down to 2 gal/min. Sound like a possibility?

For certain. Next step is to slowly raise the HERMS temp a degree or two, and keep measuring the mash temp until it's where you want. Then note the difference and keep using that same difference each batch assuming you keep the flow rate the same. Technically the difference will vary batch to batch, day to day but it'll probably be close enough to call it universal.

Basically you are losing a few degrees from the water on its way to the mash tun, as it heats up the pump, tubes, valves, etc. and all those in turn lose that heat to the ambient air. You're seeing the physics of that in action. The temp difference in the mashtun is an indicator of what you've lost. Simply raise by the same amount at the source, allow that loss to occur, and end up with the perfect mash temp.

Insulating those things will help, but may not be worth the work.

Upping the flow rate does it too, since less heat is lost per gallon that is flowing. but of course that has adverse reactions.

Find a good flow rate, determine your temp loss, and then compensate for it by upping the source by that amount.

 

[Brewbuzzard]

Tracer, I hadn't really thought of that, as I thought just a slow flow rate would mean the hotter water in HERMS tank isn't flowing fast enough to raise the temp - though more time in coil should raise temp more. Yes to raising temp on HERMS. I just know that when I opened the valve all the way, viola, the temp rose quickly.

Not sure of the flow rate through the pump. It is a Blichman riptide pump and running fully open.

My last mash was 2 qt/lb and grain was only pilsner, with some rice hulls thrown in.

You say the pump is running fully open, I thought you were restricting the output with a valve. If not that's your problem like day-tripper said.

 

[ewsaemann]

I tried it both wide open and slowed down. Wide open is when the pump ran into problems, cavitating. Slowed down is when the mash wasn't heating up.

 

[Brewbuzzard]

How do you mill your grain, do you mill it yourself or have the Homebrew shop mill it?

 

[ewsaemann]

Do it myself. I use the grain mill from SS Brewtech. I'd have to check on the setting. I think its pretty coarse.

 

[bailey mountain brewer]

How long is your hose from the coil output to your mash tun and how does it enter the mash tun? When I first set up my system my hose was longer then it needed to be which allowed for more of a temp drop. I have also added the SS brewtech recirculation manifold and that helps maintain an even temp in my mash tun. I usually have my hlt set to about 2 degrees above where my mash target is.

 

[ewsaemann]

high temp (thick) hose is 3 ft from HLT to MT. It's the minimum it can be for my setup. It enters MT at the top (cover is on MT), hose inside MT sitting on top of the liquid on top of grain bed. I have a distributor that can sit on top of the bed which I could use, but there is at least an inch of liquid on top of the grain bed anyway.
Not familiar with the recirc manifold, and don't see it on their website.

 

[ewsaemann]

Oh actually, it may be the manifold you are talking about that I have.

 

[bailey mountain brewer]

Well it sounds like that shouldnt be an issue either based on how you are set up. But if your interested here is the link for the manifold.

 

[bailey mountain brewer]

Where are you taking your temp reading at?

 

[ewsaemann]

yeah, that's what I have. temp probe is a little below mid point of MT. I also have a floating thermometer in the MT. They are about 6 degrees apart, so I figure midpoint.

 

[bailey mountain brewer]

Interesting, that seems like more of a temp difference then I would expect. I have a 30gal system and from top to bottom I only get a degree or 2 difference. Maybe flow rate is still your issue, finding that sweet spot can be difficult, I use a chugger pump that is throttled back to a little below half. Also are you taking into account the water volume in your herms coil when you calculate your mash water? Do you use software to determine volume and strike water temps?

 

[ewsaemann]

It could be stratification within the grain bed, but another variable could be the thermo's aren't reading the same. I may put them both in a small glass of water to eliminate that variable.
Though I was an engineer, I don't do the calcs. Last batch I heated MT water to mash temp and threw in grains, stir vigorously with paint stirrer and power drill, and let HERMS heat to mash temp again. I used to go a little over mash temp before adding grain, and will have to go back to that. Will have to increase HERMS temp more when raising temp if doing step mash or mash out. It'll get figured out.

 

[bailey mountain brewer]

I do 15gal batches and see an average drop of 15f to 17f when I mash in. My grain temp is around 60f and normally about 35lb to 40lb of grain. I use beersmith to calculate my strike temp and once you get your equipment dialed in it it pretty spot on. Maybe a shoot for 10 degrees over your mash temp, or if you kept notes on how much your temp dropped at mash in you could base it on that. Definitely check on those thermometers, maybe one is off.

Cheers!

 

[Brewbuzzard]

high temp (thick) hose is 3 ft from HLT to MT. It's the minimum it can be for my setup. It enters MT at the top (cover is on MT), hose inside MT sitting on top of the liquid on top of grain bed. I have a distributor that can sit on top of the bed which I could use, but there is at least an inch of liquid on top of the grain bed anyway.
Not familiar with the recirc manifold, and don't see it on their website.

https://www.ssbrewtech.com/products/re-circulation-manifold-for-infussion-mash-tuns
Here you go. There is also an eight leg one.

 

[Mad Mann]

I have the same mash tun and experienced the same issues. Went through the progressions mentioned above, temperature, flow rates, etc. I ended up using a BIAB on top of the false bottom with a continuous sparse and have had no problems since. I now crush the grains very small which provides a little higher efficiency and no issues with a stuck mash. Didn't spend too much time on it after the using the BIAB but it appeared to me that the drain slots were being plugged by the grains regardless of temp.

 

[BarryBrews]

Stuck mashes became a thing of the past since installing a false bottom in the mash tun and using a nylon brew bag. Have even stopped using rice hulls, which by the way make the most awful tea. Seriously, steep some rice hulls. Yep, you'll stop using them or wash some which is just too much effort.

Also, knowing your flow rate will help avoid compaction (hehe) problems. The Dakota Instruments polysulfone flowmeter measures 0.5 to 5.0 gallons/minute. I recirculate at 3 gallons/minute and can step the mash 0.4 degrees/minute with 20 gallons and 25 lbs grist. I believe the best place to measure wort temperature is immediately before and immediately after the heat source. In my case, the inlet and outlet of the RIMS tube. And having the flowmeter directly above the Riptide outlet valve makes setting the flow rate quick and easy.

 

[Brewbuzzard]

Stuck mashes became a thing of the past since installing a false bottom in the mash tun and using a nylon brew bag. Have even stopped using rice hulls, which by the way make the most awful tea. Seriously, steep some rice hulls. Yep, you'll stop using them or wash some which is just too much effort.

Also, knowing your flow rate will help avoid compaction (hehe) problems. The Dakota Instruments polysulfone flowmeter measures 0.5 to 5.0 gallons/minute. I recirculate at 3 gallons/minute and can step the mash 0.4 degrees/minute with 20 gallons and 25 lbs grist. I believe the best place to measure wort temperature is immediately before and immediately after the heat source. In my case, the inlet and outlet of the RIMS tube. And having the flowmeter directly above the Riptide outlet valve makes setting the flow rate quick and easy.

View attachment 727686

What did you pay for the meter if you don't mind me asking?

 

[BarryBrews]

www.dakotainstruments.com/ $67 back in the day. Just checked, $112, part # 6B0100-04D.