Batch Sparge Confusion

I'm not sure what you are asking regarding 2nd runnings.

If I was doing this as a 5 gallon batch sparge, (I would not do the multiple temperatures)
1)I would mash with ~6.4 gallons @ 165 (1.5 gal/lb) after conversion, lauter and drain into brew kettle
2)then add ~2.4 gallons @ 190, lauter and drain (this is the 2nd runnings)
that would put ~ 5 gallons into the brew kettle.

I find it is easier to skip the first lauter/drain and just add the 2nd addition at a higher temperature as a mash-out and then lauter and drain into the kettle. Some people refer to this a a "no-sparge".

hope this helps

 

Raising temperature by infusion is problematic for the reason you have identified. You end up filling your mash tun and, yes, you add enough hot liquor that you do not need a second runnings. If you collect all your runnings at once, that is fine. It will probably result in lower efficiency. Or you could do it as a single infusion mash. Why complicate your first all grain batch with a step mash? Leave step mashes for when you have the equipment to raise the heat directly, in a controlled way.

Some will probably argue that a step mash can make the difference between a good and a great beer. Maybe. Sometimes. Possibly for subtly delicious German lagers, but not for an ale with 1.5 lbs of chocolate and 2.5 lbs of caramel malt. Those are pretty large amounts, by the way. If you are uncertain of your recipe design, that is another question. This will be a dark, sweet and roasty, thick heavy beer. I see no reason for a step mash.

 

I don't see much reason for you to go through this much aggravation for an oatmeal stout other than a need to torture yourself. If you want to do this. Go ahead. I'd personally adjust the volume of your first mash and also drop its temperature to 127-138 F so you can really do something with the oats, or maybe do a separate thing for them entirely. I may even soak them and let them set for a day or three before to get them to sour and then add them into the main mash. But...
Honestly, it looks like way too much work for a couple degrees that aren't going to do a whole lot to your beer. Pick one temp, and let it do its thing.

 

Right there is your problem: "1.25 oz per pound". Change this to "1.20 QUARTS per pound".

EDIT: No wait, now I see it. Your preboil volume total will need to be about 8.4 gallons to end up with 5.5 gallons with an assumed 60-minute boil. Or were you planning on only boiling for like 20 minutes? If you only want to do a real short boil, then you need to take your mash ratio down even more to like 1 qt/lb to make this work.

Please tell us how long you intend to boil. At least 60 minutes, right? So then your additions should look like:

5.1 gal at 167 f to get 148 f for 20 minutes
Then .7 gal at boiling to get 155f for 30 minutes
Then 2.6 gal at boiling to get 165f for 5 minutes then drain.

Then 5.1 + 0.7 + 2.6 adds up to the 8.4 gallons that I figure you'll need.

 

I'm no longer able to edit; hence this second post.

The only way your 5.3 + 0.7 +1.5 = 7.5 gallons total water additions will give you a preboil volume of 7 gallons is if you are brewing in a bag (BIAB) and squeezing the living mother out of the grains. Otherwise, with a traditional batch sparge technique (in a big blue or orange cooler), 17 pounds of grain will permanently retain 0.1 gallons per pound or 1.7 gallons of your water additions, which is a HUGE effect that I accounted for in my calculation in my previous post above. Preboil must of course also account for boiloff and trub losses -- need like 1.0-1.4 gallons extra for all that. So, adding all the water you need, you've got to have 5.5 gallons after the boil, plus maybe 1 gallon loss from boiloff, plus the grain permanently soaks up some amount between maybe 0.5-1.7 gallons depending on whether you BIAB or not, and a little extra for trub losses later in fermentation, which is how I got the 8.4 gallons that I assumed above, 5.5 + 1 + 1.7 + 0.2 = 8.4.

 

I know your meant 1.25 qt/lb, but you will not get this 5.3 gallons out of your mash tun. The grain absorbs a lot of this, you'll need to add a lot more water to get your pre-boil volume. I typically use a total of 9+ gallons to get a preboil volume of 6.7 (which yields 5.2 gal after the boil).

I step mash quite often and recommend your first attempt at all-grain should not be a step profile. There are lots of calculators for computing the quantity of water for each infusion step . . . but this is very equipment specific. In my case I double what the calc calls for, that's my equipment . . . you won't know the quirks of your mash tun until you've done a few batches.

Then you want a high FG. You accomplish this by matching your OG with the yeast attenuation which of course if determined by your mash temp. I'm guessing this is someone else's recipe, if they did this correctly you'll be in the range.

A couple of problem areas: You really don't know your mash efficiency yet and this effects everything. No work-around here, you make an estimate and keep good notes for the next brew cycle. You don't know heat loss when you add your strike water. Again, this is unique to your equipment. As a minimum have lots of extra hot (i.e. boiling) water available and a very accurate thermo. It's easy to drop a degree or two, more difficult to raise. Remember, mash temp is the largest variable of fermentability which ultimately drives your "chewiness" result. I typically add boiling water when I stir to keep grain bed at same temp.

As for the caramel, I would go darker (60 - 90) and shoot for something in the 5-7% range. Probably mash around 154 - 155. BTW, fuggles at 45 will not give you anything but a few extra bittering units. Either ditch it or add <10 min.