Not hitting OG with BIAB system

Coronajax

So I decided to switch from a fairly primitive propane system to electric to make brewing in the winter months a little more appealing, I bought a 20 gallon brew in a basket system from clawhammer supply. This system works very nice however I feel like I may have made too big of a jump, I was looking at brewing 10 gallon batches but have yet to do so. I have found that I'm not hitting the predicted OG on most of my brews, while the old system was pretty consistent in that regard doing 2 batch sparges into an igloo cooler. I do like this setup but can't help but think I may be overlooking something or may need to adjust my process. I'm wondering if I simply need to adjust up to a 10 gallon batch to allow the system to work more effectively. Also my fermentation capabilities are capped at 1 five gallon vessel ( small freezer with temp controller). Any thoughts or advice would be greatly appreciated.

Minbari

hitting your OG shouldnt change.  as long as you are hitting your PH, and temp there shouldnt be much of a difference.  just make sure your strike temp is correct so you dont end up under conversion temp.
are you recirculating or just static temp?
I am assuming that your recipe and water amounts are the same as well?

Coronajax

Thanks for the response, temperature is very easy to control and holds temp automatically within a degree or two, I haven't seen huge temp swings during a brew session, I am recirculating, recipe amounts are the same as before water volume is very similar as well. I'm going to run a recipe that I have used several times with the old system and see how close I am. The system does do a nice job and allows much more precise temp control throughout the process, I just want to make sure there isn't something that I'm missing.

Minbari

when you say  it is hitting it, is it over or under?  
BIAB tends to be a little more efficient,  you cant also crush your grain a little finer too.
I have done recirc BIAB since I started brewing.  I use a HERMS system to keep temp.
one thing to try, if you dont already, is the iodine test.  make sure you are fully converted before shutting down

Coronajax

seems to be a little low, I don't mill my own grain yet so I'm wondering if the kits I buy could stand another trip through a mill to bump up my efficiency.

Sandy-Feet

I do not know about the basket system, but the regular bag will be low. I set my effeciency lower in the software. If someone else mills, you will not know what the crush is. I have the same problem and adapt by adding more grain or expecting a wider alcohol variation. I shoot for somewhere in the middle and see what happens.

soccerdad

Forgive me for not being here in a long time. I pretty much quit drinking so I brew way way less. I have some catching up to do. Coronajax - when you say not hitting OG, do you mean that your pre boil gravity is low? That you are not getting as much from the mash as you thought? If that is the case, let the mash go another 30 minutes. The folks in OZ who pretty much pioneered BIAB always said to mash for 90 minutes to assure full saturation of the grain. If you ARE hitting the pre boil gravity but coming short at the end of the boil, then it might be that you are boiling off less than your software calculated that you would.

Texas-Ale-Works

Lots of things can be going on here.
Not in any order:
Water Volumes, these need to be pretty close
Crush, you can crush tight with BIAB, but do not over do it
Temps - check you temps, and think about where the system is reading temps
I have always had what I feel is a low brewhouse efficiency, 72%  but I bumped a few points when I dialed in my water, and by gaping my mill tighter.
I try to always use the same brewstore to make sure my crush is consistant, but I think I am going to start running it through my mill prior to brewing
T

Zambezi-Special

Good to see you again @soccerdad

Sandy-Feet

Mine is in the preboil and I only do a 60-minute mash. That might be something for me to think about. Other than missing gravity, the bag is about the coolest thing since sliced bread.

soccerdad

I'M never in a hurry when I brew, so at 60 minutes I check the mash (just with a cheap refractometer). If it looks good, I proceed. If it's low I adjust temp, stir well, and do something else for a while .. maybe cleaning, maybe run an errand.

Sandy-Feet

What you suggest seems to be sound advice with one problem: I have a hydrometer, but I have to take a reading after the bag is drained as everything is in the kettle. If I take readings in the kettle with the bag undrained, it will read extremely high as all the grain will be included in the reading. Are you suggesting draining the bag, taking a reading, and putting the bag in again if it reads low?

Donoroto

If you figure out a way to circulate the liquid those differences could even out. The grain itself does not affect the reading, it is the lack of circulation allowing differences.
No harm in putting the bag back in.
Next brew, maybe try this experiment: Put the 'used' grain in a different pot of hot (150F or so) water, wait some time (half an hour? an hour?) and see what the spent grain left into the fresh water. If the gravity is low (as I guess might happen) then there's not a lot of fermentables left in the grain, and so mashing longer won't improve things. But if the gravity is somewhat higher (like 1.015?) then yes, a longer mash will extract more from the grain and you can add this to your process. By doing this, you find out for certain, right?

Sandy-Feet

It probably won't happen this weekend, but it is something I will keep in mind. I do have a small experiment this weekend that won't take a whole bunch of time. I was thinking about withholding about 1/2 gallon of water, squeezing the crap out of the bag and using the last 1/2 gallon to wash out anything else that might be fermentable.