Grainfather small batch/low-gravity failures?

[rmeskill]

Hey there! I've been brewing for years now and finally made the leap into getting a Grainfather, thinking it'd get me more reproducible and consistent results. My first two batches through (roughly 5%, 23L batches of pale ales) were resounding successes. I didn't have any issue with the equipment, hit my OG within a point, and finished up precisely where I wanted to. However, I also make a lot of low-gravity beers (bitters, berliners) and, because I both wanted to keep those and try smaller 10L batches, I bought the smaller 'micro pipework' (Micro Pipework) and every batch I've made with this has come in drastically under-gravity. Made a 23L berliner with a 3.2kg grain bill which came in at 1.028 instead of 1.037 and just mashed and sparged a 10L batch of a ~6% robust porter that I expected a post-mash gravity of 1.045 but, according to my (sometimes incorrect but never THIS far off) refractometer is showing around 1.020. Again, I haven't had this issue with larger batches, so I'm suspicious it has something to do with the smaller overflow pipe and/or just smaller batch and an improper amount of water somehow.

So all that said, does anyone have any experience with smaller grain bills in the Grainfather and have an idea as to what might be happening here? I think I'm following all the instructions properly and both BeerSmith and Grainfather's recipe calculators are roughly coming up the same. For the 6%, roughly 11L porter I just mashed/sparged it called for 10.8L of water for the mash and another 6.8 for the sparge to get me to 15.3 for the boil. I ended up about 500ml short so added that to the end of the sparge, but, sitting right at about 15.5L, I'm WAY under-gravity. I know the Grainfather has/needs about 3.5L of dead space beneath the mash tun, but is there a chance I need to be adjusting something differently to support these low-gravity/small-batch beers? I'm really getting tired of REALLY small beers or dumping

 

[BrewAgain]

When sparging, did you raise the overflow pipe? Also, did you push the top screen down to slow the flow? It also helps to use the tabs on the top screen as a water depth guide. Are you using the grainfather program to calculate water volumes?

 

[BrewAgain]

Also. The grainfather is finicky on the grain crush. It seems to be worse in low gravity beers. It seems to need to be adjusted or allow an increased grain bill to compensate.

 

[rmeskill]

When sparging, did you raise the overflow pipe? Also, did you push the top screen down to slow the flow? It also helps to use the tabs on the top screen as a water depth guide. Are you using the grainfather program to calculate water volumes?

I do use the overflow pipe, but how high should it be? I thought the bottom of the overflow was meant to push down on the top screen-am I mistaken and that should be far higher? Because if I'm actually not recirculating through the grain that could indeed be an issue... I do notice a fair amount streaming down the overflow pipe...

As for the grain crush-I have also read that, but do you or does anyone have an example of grain crush size? I'd been using a fairly fine crush on my previous mash tun setup because it upped my efficiency and didn't result in any stuck mashes. When I used that crush on the grainfather for the first batch (which, I should note, I hit my efficiency precisely on) it seemed to take FOREVER to sparge-needing to leave 2-3 minutes between 1L water additions so I adjusted my crush down a couple levels so it's bigger chunks. Which now that I think about it, perfectly correlates with my reduced efficiency. Is sparging meant to be that slow on the grainfather?

 

[Pkrd]

I see lower efficiency on my half batches too, not that low though. Usually I'll enter 70% efficiency for the recipe calculator and get close enough, 80% for full batches.

Sparging should be quick with the smaller batches. Some of the GF videos talk about a very long sparge, mine have never been like that (except for that 9kg whiskey mash).

 

[BrewAgain]

The overflow should be set with the height of the overflow adapter. But during the mash, the pump needs to be adjusted by the value to keep the overflow to a minimum. But that being said, it needs to be close to the top.
Sparging for a 5 gallon batch should take 30-45 minutes. For a half batch, I would assume 15-30 minutes.

 

[BrewAgain]

One other point. During the mash, it seems to help to move the location of the hose around the top plate. Not continually, but 10-15 minutes in a location. The flow does create tunnels in the grain bed. Reseating the top screen during sparging does help. I missed that and it caused a 10 point miss.

Grain crush
I changed from a 2 roller to a 3 roller. It took dialing in. It's probably at .025-.028 gap.

 

[rmeskill]

I see lower efficiency on my half batches too, not that low though. Usually I'll enter 70% efficiency for the recipe calculator and get close enough, 80% for full batches.

Sparging should be quick with the smaller batches. Some of the GF videos talk about a very long sparge, mine have never been like that (except for that 9kg whiskey mash).

Ahh, that's useful to know-if it's at least somewhat expected I can work around that. Slightly annoying I won't get to the ~80% of the large batches, but predictable is what I'm aiming for.

The overflow should be set with the height of the overflow adapter. But during the mash, the pump needs to be adjusted by the value to keep the overflow to a minimum. But that being said, it needs to be close to the top.
Sparging for a 5 gallon batch should take 30-45 minutes. For a half batch, I would assume 15-30 minutes.

Aha-I completely forgot the pump adjustment was an option-I just thought that was a shut-off valve, but obviously the point is getting the mash water to strain over the grain bed-I'll adjust my method next time to limit any overflow and make sure the pumped wort only filters through the grainbed. And try to move around the hose a bit, though that's harder with a small batch as it's below the bottom of the hose.

 

[Pkrd]

I'm trying to get my head around whether wort going down the drain reduces the amount going through the grainbed or not.

 

[rmeskill]

I'm trying to get my head around whether wort going down the drain reduces the amount going through the grainbed or not.

It absolutely should, shouldn't it?

 

[BrewAgain]

I look at the process as melting ice with regards to breaking down the starches into sugars. It takes 60 minutes to convert. But it speeds it up pumping the wort over the grains. If you rinse them slowly aka sparging, it should release/ convert more sugars. It's based on crush, heat, and rinsing.

 

[Pkrd]

It absolutely should, shouldn't it?

Well no. You still have wort sitting above it which provides downwards pressure.
If it takes 30 minutes to sparge then how much recirculation is happening during the mash? Is it actually just BIAB?

 

[rmeskill]

Well no. You still have wort sitting above it which provides downwards pressure.
If it takes 30 minutes to sparge then how much recirculation is happening during the mash? Is it actually just BIAB?

 

[BrewAgain]

I would consider it a cousin to biab. The main difference is the pump. With this setup, the wort is forced to flow through the grain bed. That should increase the conversion at a higher rate. It's a continual rinsing of the grains. BIAB does not have that action.

The overflow is set to have a certain height over the grain bed. That height creates a press

 

[BrewAgain]

Pressure forcing the water though the grain bed. Like sparging, the amount of water above the grain bed when the basket is raised will create the force.

These systems are pretty ingenious. They are simulating a 3 V system.