High Conversion Efficiency, But Low Brewhouse Effeciency?

[pintoflager]

Hi All!

Came across an interesting issue with my last brew day, and I would welcome some insight from the more experienced brewers here.

Attempted to make an Irish Red (which turned out more brown than red) and using the Brewhouse Efficiency Calculator (linked here : https://www.brewersfriend.com/brewhouse-efficiency/) I determined that I had a conversion efficiency of 94%.

Specific gravity of a blend of both runnings was 1.046 - maximum yield was 1.049 according to the calc.

I then boiled my 8 gallons of wort for 90 mins, and was left with roughly 6 gallons of wort at 1.044, resulting in a "brewhouse efficiency" of 67%.

So I was left wondering:

Is the conversion efficiency a reliable indicator of post-boil OG? My recipe target was 1.060. I was hoping an extended boil would raise more gravity points than 2.

If my target OG was 1.60 as indicated in the recipe builder, with an efficiency set of 75%, is there a reliable way to predict that based on pre-boil readings? I thought it odd that my first runnings read a bit low. My typical brew (golden ales and IPAs) get a much higher reading.

For more information, I brew all grain in a converted cooler as a mash tun. False bottom holds maybe a half gallon of volume, and I left a half gallon in the kettle, minus the trub. I used 8 gallons total water, 5 for mash, 3 for sparge. I boiled 7.5 gallons of wort on my stovetop - so not a "roiling boil" but it boils nonetheless. I typically lose just shy of a gallon per hour due to evaporation.

I would love to hear anyone thoughts on this!

Thank you so much in advance! I've been using this site for a couple years now, and even though I don't brew as much as I'd like to, I truly enjoy the process and I appreciate the great brewing minds on here - I've learned a ton just reading your posts!

 

[GFHomebrew]

Oh gee for sure you should of atleast come out above your pre boil gravity reading especially if your recipie target gravity was 1.060 with a brew house efficiency set at 75%. You must be hitting your efficiency target recently? Leaving a gallon of wort plus trub in kettle seems like a big loss to me and would put a good dent I overall efficiency but still doesn't explain the weird pre boil leading that was so low.

If I'd set my final brew house target at 1.060 I'd expect a preboil around 1.054-6 knowing I usually get 4-6 points out a 60 minute boil.

 

[okoncentrerad]

I'm not sure I understand, your preboil SG was 1.046 and after boil it was 1.044? I may be misunderstanding things, but if I don't... your readings had to be wrong somewhere.

 

[Mase]

+1

You boiled off 2 gallons off of 8 and only dropped 0.002 points. I’d say your initial gravity (preboil) was off.

Can you give us a link to your recipe?

 

[Hawkbox]

Yeah I find sometimes the wort in the kettle isn't mixing uniformly and I will get different readings preboil. I do a good stir to make sure I get an accurate reading.

 

[GFHomebrew]

The low final gravity doesn't make sense neither especially if targeting .060 14 points above FG reading on brew day.

You know it could be a grain measuring fault since the final yield was so low I'd think heck did I put X amount of grain in or what.

 

[Mase]

Great point @Hawkbox , second runnings have much less sugar (3 vessel), if you sample from the top of the BK and haven’t mixed the heavier sugars with the thinner sugars on top, that could definitely through off a preboil gravity.

 

[pintoflager]

Thanks for the responses all!

I definitely didn't stir the wort before measuring - will try that next batch.

As for the low readings, I don't understand it either. Measured the sample with 2 different hydrometers.

I typically hit my targets within a few points over/under and this is the first batch in a while where I've failed to hit OG.

Thanks again for your replies!