[davidgzach]

I'm having some lower conversion percentages lately.  The only things that have changed are the rollers in my crusher and that I've been recirculating faster.  I don't think the crush is the problem.  So the question for the forum is:

Does faster recirculation decrease the conversion rate?

Dave

[charlie]

What's your flow rate?

When I was cobbling my HERMS rig together I read somewhere that 1 GPM was about right, but my pickup tube is 1/4" ID, so I think my rate is more like 0.25 GPM. Target temp is 152F, and I recirculate roughly 10 minutes on and 10 minutes off, and the wort is clear and starch free in 60 minutes.

Charlie

[davidgzach]

What's your flow rate?

When I was cobbling my HERMS rig together I read somewhere that 1 GPM was about right, but my pickup tube is 1/4" ID, so I think my rate is more like 0.25 GPM. Target temp is 152F, and I recirculate roughly 10 minutes on and 10 minutes off, and the wort is clear and starch free in 60 minutes.

Charlie

When I'm on full tilt it's a chugger pump going through 1/2" hose so I expect it's a lot higher than 1GPM.  It's a 25G pot and there is a significant whirlpool.  I used to go a lot slower but liked how quick the mash equalized with the faster rate.

[narvin]

When I'm on full tilt it's a chugger pump going through 1/2" hose so I expect it's a lot higher than 1GPM.  It's a 25G pot and there is a significant whirlpool.  I used to go a lot slower but liked how quick the mash equalized with the faster rate.

That seems fast, I'm surprised you aren't getting compaction resulting in a stuck sparge.  Perhaps there is channelling or running directly down the sides at this rate, bypassing most of the grain bed?

[oginme]

When I'm on full tilt it's a chugger pump going through 1/2" hose so I expect it's a lot higher than 1GPM.  It's a 25G pot and there is a significant whirlpool.  I used to go a lot slower but liked how quick the mash equalized with the faster rate.

That seems fast, I'm surprised you aren't getting compaction resulting in a stuck sparge.  Perhaps there is channelling or running directly down the sides at this rate, bypassing most of the grain bed?

^^ This ^^.  When recirculating, I cut the recirculation flow down to a pretty thin stream.  You want the mash water to slowly flow through the grain bed while keeping the grains 'floating' or uncompacted.  As soon as you start to push the grains together towards the bottom of the mash tun, the less flow you will get around the individual grains and create more of a tendency to channel.

You also mentioned a change in the rollers of your grain mill.  Did you change the gap?  Tighter or looser?  Your grind quality has one of the biggest impacts on mash efficiency of any other variable.

[davidgzach]

Thanks boys, this sounds right.  I was not thinking that with the faster whirlpool the grain in the middle was getting compacted and not getting equal soaking with the water running down the sides.  This has to be it.  Rollers are the same gap as old ones.  Crush looks perfect.

I'll slow it down for the next brew and report back.

Thanks Forum!

Dave

[goose]

I think my RIMS runs at about 1/2 GPM with 3/8" piping from the MT through the heater, pump,  and back into the mash.  My ball valve is usually about halfway open and I can more easily keep the mash temperature more constant.  I re-circulate during the entire mash rest.  I have gone a bit slower than that when I first started using a RIMS system and but never kept track of any differences in extraction efficiency and it appears that I really don't have any channeling issues.  That said, my extraction efficiency is always lower when I make beers that are in the 20+ degree Plato range and I compensate for that with either more grain or some DME if needed.  Not so with lighter beers, my efficiency is always fine, 80%+ with this re-circulation rate (which pretty much confirms that there are no channeling issues).  We noticed the tendency for lower extraction with bigger beers when I did my pro-brewer gig, especially with Imperial Stouts.  We also noted that different lot numbers of the malts we used could effect the extraction efficiencies.

I will do some evaluating with a slower re-circulation rate when I brew my Wee Heavy this week.  This is one of my bigger beers and I can compare this batch with my historical brewing data for the beer to see how much the efficiency improves, if any and post the results.


 

[charlie]

Thanks boys, this sounds right.  I was not thinking that with the faster whirlpool the grain in the middle was getting compacted and not getting equal soaking with the water running down the sides.

I have two goals when recirculating: 1. Deposit the fines on top of the grain bed to filter them out and clear the wort, and 2. Add enough heat from the HERMS to maintain mash temperature. With the HERMS set at 153F (summer) or 154F (winter) and the 0.25 GPM flow rate I can maintain my target temp of 151F with the 10 on/10 off regime, and make crystal clear wort in 60 minutes. I know enough to know that I don't know it all, so I'm always open to new ideas, but 10 years into this game I have found that this scenario works for me.

Charlie

[BrewBama]

... I know enough to know that I don't know it all, so I'm always open to new ideas, but 10 years into this game I have found that this scenario works for me.

Charlie

Words to live by.

I spent a lot of time dialing in my system to the point that results are very predictable crystal clear wort into the kettle.

To create good permeability I use a fairly thin mash (1.75:1), a fairly course grind (70% on a No14 screen), and a fairly slow flow (.155 gap on a Blickman linear flow valve) to recirculate for the entire mash. 

With this setup I found OG was still climbing at 60 minutes so I increased mash time. Above 90 I found only negligible increase so I landed at my standard 90 minutes.

I image each system has their similar sweet spot.

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[davidgzach]

I know enough to know that I don't know it all, so I'm always open to new ideas, but 10 years into this game I have found that this scenario works for me.

Charlie
[/quote]

Exactly why we have this Forum and why I come here for advice.  We can all always learn something from our brewing family!

Thanks again all, I'll report back Friday when I brew my Dopplebock with a Hochkurz....always at 85% in the past.

ave

[goose]

I brewed my Wee Heavy yesterday and evaluated the mash efficiency of a slower re-circulation rate.  Because of mash tun space (32 lbs of grain for a 11 gallon batch) my liquor to grist ratio was 1.25.  Here are the results compared to the last brew.

12/5/2018 brew.  Re-circulated with ball valve about halfway open
Full kettle gravity (13.8 gallons) 17.95 degrees Plato
OG 21.0 degrees Plato

11/2/2020 Brew.  Re-circulated with ball valve about 1/3 open
Full kettle gravity (13.8 gallons)  17.26 degrees Plato
OG 21.65 degrees Plato

The differences are negligible, 4% different on full kettle comparison and around 3% on OG.  Note:  I boiled down a bit farther on yesterday's batch to make sure I was close to my desired OG and slightly overshot by about 2%.  From my refractometer readings during the boil, it looked like I was going to be about 1 degree Plato low, which turned out not to be the case.   I always strive to be less than 4% from predicted OG and if it down around 2% either side of desired OG, I have done well given differences between different extractions for different lot numbers for the grains, etc.  This could also be due to the fact that in the 2018 brew I used Crisp Maris Otter and yesterday, I used Muntons Maris Otter as the base malts.  But again, the results are pretty close.

It was a bit harder to maintain mash temperature using the slower rate but other than that I see no no advantage on my system by re-circulating at and the slower rate.  This also confirms that my standard procedure produces no unwanted channeling in the grain bed.  Another thing that I do is knife the top few inches of the grain bed with the handle of my SS spoon about every 1.5 gallons or so during the runoff, since this tends to increase my mash efficiency.  Obviously, YMMV here depending on your brew system, and obviously you don't want to run the re-circ full bore to prevent a stuck mash.

[Dustin_J]

Words to live by.

I spent a lot of time dialing in my system to the point that results are very predictable crystal clear wort into the kettle.

To create good permeability I use a fairly thin mash (1.75:1), a fairly course grind (70% on a No14 screen), and a fairly slow flow (.155 gap on a Blickman linear flow valve) to recirculate for the entire mash. 

With this setup I found OG was still climbing at 60 minutes so I increased mash time. Above 90 I found only negligible increase so I landed at my standard 90 minutes.

I image each system has their similar sweet spot.

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Were you getting demonstrably  less clear wort and/or different conversion times when recirculating  faster? I run a HERMS as well and am trying to improve wort clarity into the kettle. Am current recirculating nearly full bore  and its still a bit less than crystal clear.

[BrewBama]

No. I was getting a stuck mash.


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