redistribution of mash after recirculating

[NegFerret]

I did brew number two yesterday (a citra pale ale) in my new HERMS system :party:

I found I had a serious loss of efficiency in the mash, ending up around 7 points below target gravity in the kettle.

When I'd finished sparging I noticed the grain bed was not flat, it was peaked in the middle. I know why this is happening, but my question is do people usually flatten the bed out after recirculation to ensure the sparge washes through the whole thing? I'm thinking my poor efficiency was due to the sparge water finding the easiest way through the mash (down the sides) and therefore missing out the bit in the middle.

I used to have a rotating sparge arm but with the new system everything goes through a pipe that rests on the grain bed.

Cheers

 

[Stone Cold]

i find it hard to believe that low efficiency you have is from lack of good recirculation, in my mash tun the grain is always lower around the sides because of the flow of sparge water. but i get 85% + efficiency. i would be inclined to think strike temp is off , have you got a few different thermometers you can test it is what you think it is?

 

[NegFerret]

So you never redistribute the mash before sparging? Interesting. I have no experience of anything other than fly sparging, and certainly none of recirculation so this feedback is good.

Ok, the next theory then (and the only other theory I had) is as you have said, a temp issue.

When I measured the temp at the start it was 68c. By the end of the 90 minutes it had dropped massively to 60, and 58 in some parts! I don't understand this as I'd been recirculating at 69c (this was the target temp for the mash). I wasn't sure if this would really make a massive difference to efficiency, albeit an annoying feature of a brew in which I wanted to improve on a recipe.

Now, I have used this mash tun once before, and it was great. Hardware is not an issue. What may raise the eyebrows is that my mash volume was 17 liters (by memory) with a tun capable of 50 liters. I was opening the tun up fairly regularly throughout the mash to check on the recirculation rate, as I killed a pump on the last brew due to an over enthusiastic rate.