Accounting for grain absorption in my BIAC (Medium)

Apologies if this is covered elsewhere. I did a couple of searches and read the last five pages, but didn't find anything.

I have a Brewha Brew-In-A-Conical (BIAC).  I bought the 15 Gallon (Medium).  I love it overall, but my mash continues to give me a hard time. I am pretty sure that the problem is that I am not adding the grain absorption water to the steps listed in the Beersmith software.  I am continuously pumping the wort out of the bottom to recirculate slowly and ensure uniform temperatures.  After about 10 minutes, it starts to stick/not flow/risk exposing the heating element. I am using the BIAC profiles, so I am wondering if I didn't set up the right brewing profile (I am doing single step Medium for my SNPA clone). 

I can obviously add the two values together, but since it's software, I'm assuming it adds the values together if you have the right profile. 

Any ideas?

Thanks in advance!
Nate

nateglissmeyer said:

I am pretty sure that the problem is that I am not adding the grain absorption water to the steps listed in the Beersmith software. 

Click to expand...

Grain absorption is a constant. You can change BeerSmith's default in Options > Advanced.

However, I suspect that you're trying to recirculate too fast and too long. From the description, it sounds like you're compacting the grain bed. Most standard liquor to grist ratios account for absorption.

Thanks for the tip. I would love some advice.

I do have a valve at the top and I am closing down the valve almost until fluid isn't coming out, so I don't think I am doing it too fast.  Too long does seem possible, though, because I have been recirculating during the entire mash. My thought was that is what the HERMS approach is, that it mixes the wort and grain the most, and that it ensures a consistent temp probe reading and reduces hot spots near the heating element.

Do you think I'm just doing HERMS wrong, or do you think that you get better results when you aren't recirculating all that much?  Would love another perspective if you have the time.

The grain absorption will affect the volume you get out, but the default will be very close; I don't think that's the issue. My HERMS pumps the wort out of the bottom of a 10-gal round water cooler mash tun (with a bazooka filter), through an immersion chiller submerged in a temp-controlled water bath, and back to the top of the mash tun. I control the wort flow with a valve on the output side of the pump - It sounds like your valve is functionally the same and therefore prevents the pump sucking air if the flow through the mash is less than the pump delivers. I recirculate throughout the mash. Restricting the flow should help.

It sounds like your system has an electric heating element near the bottom of the mash tun, so I see your concern with exposing the element. Doesn't sound like what I've been calling HERMS.

To increase the flow through the mash: add some rice hulls, check the roller spacing on your grain mill - usually closer is better for efficiency, but I guess it could be causing clogging of your basket. If all else fails, put your grain in a 5-gallon paint-strainer bag and set that into your grain basket.

On second thought: I'd try the bag first, then consider grinding FINER to improve efficiency. Did I mention the paint strainer bag should not have been used for paint? ;D

nateglissmeyer said:

Do you think I'm just doing HERMS wrong, or do you think that you get better results when you aren't recirculating all that much?  Would love another perspective if you have the time.

Click to expand...

One of the things that happens in long recirculation is the air between the grains gets pulled out of the mash. Plus, glucans and fines (the powdery part of the mash) get put back on top of the grist and can block even water flow through the grain bed. The suggestion of rice hulls is appropriate to help solve this. The glucan reducing enzymes also help by lowering viscosity, if you're into adding them.

I've found that in HERMS systems, I don't get appreciably better extraction by recirculating the whole time, vs just having one rest and recirculating to get mashout temperature. I think, as durrettd suggests, that milling makes a big difference. Certainly coarser grists are going to work better with constant wort flow through them. 

I'd forgotten about the dreaded "layer of crud"; that would definitely stop the flow. For some reason I've not had that problem since I started recirculating. I'd love to know why - and how to be sure it doesn't return.

I've read that cutting through the layer of crud in several places is a fix - temporarily.

I recirculate continuously to clarify the wort and hold my temp. Don't know why my temp falls so much sitting in my mash tun (a 10-gallon Igloo water cooler).

Thanks to everyone for the tips. I also found a really interesting article on how too much water atop the grain causes the bed to compact. It's been helpful to have less water, which was counter-intuitive. I felt like more water = more mixing, but that hasn't been true.

I've also found that in beers with a protein rest, it doesn't matter as much. I think the glucanase comments above make sense; it is better to create a lot of enzymatic activity for beta glucan reduction. I see this in the trüb, as well.

In any case, less pumping has also made a difference, so thanks for that tip, as well.  I'm linking to the Brewha article they added.

https://brewhaequipment.com/blogs/brewinfo/95584257-controlling-vorlauf-and-lauter-rates-to-prevent-a-stuck-mash

That's a great link. It's introducing you to the concept of wort velocity. This is the optimal flow of water or wort through the grain without compacting it. 

Wort velocity is measured in column inches (or cm). The surface area of your false bottom or manifold times 0.29 is the textbook optimum rate of flow in inches per minute. The same ratio works in metric. You can convert that to quarts per minute by dividing by 57.75.

I say "textbook" because it's a determination based on commercial lautering. In home brewing, the weights per square foot don't usually apply. But, this does become very applicable in tall mashtuns (like kegs) when recirculating and sparging. Keeping near that flow rate when recirculating will go a long way towards keeping water flowing throu the mash. As the wort thins during sparging, you can increase the flow 3x to 4x what you started with.