Author Topic: Constantly Missing OG in Kegs  (Read 1083 times)

Offline babbguy

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Constantly Missing OG in Kegs
« on: June 09, 2020, 07:36:43 AM »
Hi Brewers!

A couple of months ago I took the leap into homebrewing. I absolutely love the process but I have ran into an incredibly frustrating problem when trying to hit my target OG's.

I am using the Adventures in Homebrewing 15.5 gallon all grain keg system (https://www.homebrewing.org/155-Gallon-All-Grain-Brewing-System_p_1809.html) and BeerSmith3 to develop my recipes. The keg system has a massive 2.25 gallon "dead space" in the mash tun (I have measured it several times) due to the mash screen. This space is recoverable because there is a dip tube and I clicked the account for recoverable dead space inside of BeerSmith but I am still way off on my OG numbers. And I mean way off! The last DIPA recipe I ran (see recipe here - https://drive.google.com/file/d/1AlF8rD56EVBLcc5HQXFFxRZ9MLC9mEts/view?usp=sharing) called for a OG of 1.073, mine came in at 1.053.

I have done so much research on this issue and tried the suggested changing the grain milling and sparging slower. I have even changed from fly sparging to batch sparging to see if this would fix the issue but no luck.

Is anyone brewing in kegs and can offer some advice??

Thank you in advance for taking the time to help!


Offline brewfun

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Re: Constantly Missing OG in Kegs
« Reply #1 on: June 09, 2020, 08:08:11 AM »
I like your scientific method to eliminate most of the usual suspects.

The first thing I notice is that both your mash and brewhouse efficiency are the same. Meaning that your telling BeerSmith that all wort is going to the fermenter. Is that the case, or are you leaving the trub in the kettle?

Even with the trub, It appears that your mash efficiency is close to 50%. What does your water profile look like? Are you adjusting the pH of your mash? Are you recirculating your mash to make sure it's all at the same gravity before you run off to the kettle? Aside from an iodine test for basic conversion, the mash wort gravity will rise until conversion is finished. Use a refractometer to check that it's not still rising when your recirculating.

The braukaiser.com site has lots of great information on pH and mash conditions. I've attached a first wort gravity chart from his site that shows what to expect from various mash ratios. I use this for work, but often don't get quite as much first wort gravity as the chart says. However, I do get over 90% mash efficiency, so I'm making it up in the sparge.
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