Batch vs Fly Sparge and the Amount of Grain

Curious what some of the opinion/facts some of you more seasoned brewers think about fly vs batch sparge and the amount of grain. I have keggles for everything and fly sparge. I am noticing that I am having higher eff with larger grain bills over 15 lbs. 10 and under are significatly lower. Can anyone speak to this. Thanks

Generally, for a given batch size your efficiency will be somewhat lower with a larger grain bill (ie higher gravity or OG). Apparently you are experiencing the reverse of this for some reason. Much also depends on how you define efficiency and the accuracy of your volume measurements. Fly sparging by nature is supposed to be more efficient as it is essentially displacement vs. dilution. How large is the efficiency difference you speak of? There are a number of possible variables involved, so it's hard to say that the difference is due to the size of the grain bill alone. Much the same for fly vs sparge. With either you can do it poorly, so the method alone is no guarantee of anything.

If I had to guess, in your case it probably has to do with lautertun shape. Large grainbills set up a deep bed and small bills are shallow. Deeper beds in fly sparging are usually more efficient.

Dead space??

I experience something similar...even when I do a max capacity brew (which for my Zapap is only about 14.5 maybe 15 pounds) my efficiency doesn't change (and intuitively you'd expect it to drop at least a little). I think it's mostly due to what Bobby mentioned but the deadspace contributes as well. Any gravity points left in the deadspace represent a larger percentage of a lower gravity brew than a higher gravity brew.

To answer the question on the Eff differece I can hit high 80s with a larger grain bill and with 10# and under I am at 70 and under. I would say a good 15 points. When you say dead space do you mean the space between your screen and the valve. I know on most the pipe comes up and out the side leaving you with a good inch of fluid below that you would dilute with extra fluid to remove the sugars.

For my Mash tun I acutally put the pipe directly out the very bottom so any sugar coming out should go directly into the kettle. I can post a pic if you would like to see.

I cant figure it out.

Just an Idea, but how are your temps? and how well are you maintaining them?

With a larger grain bill you will have more thermal mass, and thus hold your mashing temp better than a small grain bill. I can't imagine that a drop of a couple degrees would knock you down 15 points, but if you are dropping 10º over the mash, and you come in with your sparge water at 175-180, you might not get a good dilution of your sugar in to the wort and leave a lot behind.

One more thing? How fast are you sparging?

You might be pulling out the wort before the sugars get a good chance to dilute with the small batch, and with the larger batch just because its a larger volume it takes longer and you get more sugars out of the grain bed.

As far as temp I am holding pretty well. maybe 2-3 deg at most. and I make sure I sparge pretty slow. About a gallon every 2-4 minutes.

1602JJ said:

As far as temp I am holding pretty well. maybe 2-3 deg at most. and I make sure I sparge pretty slow. About a gallon every 2-4 minutes.

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So for a 5 gallon batch you are sparging in 10-20min? I think for fly sparging that is on the fast side. If you are doing 20-40 for a 10 gallon batch thats about right. (in general I fly sparge for 35-60min)

also If you are disturbing your grain bed while sparging, you will mix the layers and dilute your wort.

Just trying to narrow it down but it sounds like a combination of lautertun shape and sparging too fast. It may the case that the shallower the grain bed, the more the sparge rate affects efficiency.

With your rig it doesn't sound like deadspace is an issue.

How deep is the grain bed in a keggle with just 10# grain?

EDIT: BTW/FWIW, last weekend I did a big 1.100 OG Belgian and this weekend I'm doing a low-ish gravity (for me) lager that should have an OG around 1.047. Most of my beers are bigger than 1.047 and nowhere near 1.100. I got right at 79% Brewhouse on the Belgian so I'll be interested to see what I get this weekend. I'll post it, Sunday prob.

1602JJ said:

As far as temp I am holding pretty well. maybe 2-3 deg at most. and I make sure I sparge pretty slow. About a gallon every 2-4 minutes.

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Seems fast for me, I will sparge 7.75 gallons and I set my time to a minimum of 45 minutes.

I will try sparging slower. That could be the trick. As far as the depth of grain if i look in the keggle it is about an inch below the lower rung if that makes any sense. If I had to guess maybe 3-5 inches thick.

Shallow beds are more likely to form channels, so the sparge water bypasses some of the grain. You could try raking the top inch or so of the bed during the sparge. This seals the channels.

david_42 said:

Shallow beds are more likely to form channels, so the sparge water bypasses some of the grain. You could try raking the top inch or so of the bed during the sparge. This seals the channels.

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I can see how that would change things. Do you have a reccomended technique or type of sparge arm?

I currently use a copper tubing that sits on top of the grain bed that has 1 in from the HLT 4 outlets facing the top of the kettle. Kind of looks like a big H from the top outlet on each tip.

EDIT: BTW/FWIW, last weekend I did a big 1.100 OG Belgian and this weekend I'm doing a low-ish gravity (for me) lager that should have an OG around 1.047. Most of my beers are bigger than 1.047 and nowhere near 1.100. I got right at 79% Brewhouse on the Belgian so I'll be interested to see what I get this weekend. I'll post it, Sunday prob.

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Nevermind. I used a 'new' grain (for me) and don't really know the extract potential of it...and my spigot got a tiny clog so it stopped flowing mid-sparge. It stopped pretty much just after the first runnings/vorlauf but before most of the sparge water had flowed through it...so the mash 'sat' in sparge water for a little while. All I had to do was open the valve a little more and it immediately cleared but my efficiency went way up (90% Brewhouse...ooops ). I think the clog simulated a really slow sparge (I was sparging even slower than normal which is why the spigot clogged so easily).

If nothing else it does seem to reinforce the notion that when doing these smaller grain bills that sparging slowly (especially at the beginning imo) is key.