HERMs brewing, recirculation speed and astringency

[Muz]

For those HERMs brewers out there, how fast do you recirculate your mash and have you ever got astringency from over recirculation?
Over the last few years I've had some low-level astringency with some of my beer. This could come from a number of places in the brew including the grain crush, sparge temp/pH or even the hops. However, I've always suspected it was from recirculating too fast. I've tried to find information on this but there isn't a lot out there. The Electric Brewery states that if you use their setup (which is different from mine) you can run the pumps fully open. I also just purchased a HERMs-it and was told by the store that the limit on how fast I could recirculate was based on how good my false bottom is, indicating faster is better if you can do it. I have an SS Brewtech mash tun with a pretty decent false bottom and central drain so that's not an issue. Am I worrying about nothing when recirculating slower or have others found problems from running the pump too fast?

 

[shmick]

Can't say I noticed anything myself on my old HERMs system using a bag and a march pump running full speed for an hour or so mash. I have fairly soft water so that maybe a factor.
I always monitored/controlled the temperature of the wort coming out of the heat exchanger rather than the mash temp and there was only ever a degree or two difference anyway with the pump running.
My sparge/return outlet onto the grain bed was just under the surface of the wort to reduce hot side aeration (if there ever is such a thing).
Only problem I've noticed on my newer all in one system is a compacted/stuck mash and running the pump dry. First time I had to crack open my 10 year old bag of rice hulls when I 'upgraded'. The stainless is much more shiny though.

 

[TwoCrows]

When you mash in at a required temperature and in a perfect world it remains the same without losing temperature, then you don't have to recirculate the wort.

When I use my 3V setup I sample and control the wort temperature as it leaves the coil. I believe this is the conversion temperature and the turnover / speed of the pump moving the wort, is only to keep the main mash at temp. If you pump too fast, you don't want to remove all the wort from the mash and change the ratio of water to grain that is converting the starches.

When raising the temps for step mashing or the mash out, the bath for the HERMS coil is hotter than the wort, but the wort is not hotter than the target temp.
So, after all that I have not had an issue with husks imparting tannins or astringency due to recirculating rates and water chemistry.

Tony Yates system is what I based mine on, here is his Saison brew day.



I hope this makes sense, liquid lunch today. Semifinal Sesson!!