Contradictory OG's

JamesB-Hynes

New Member
Trial Member
Joined
Dec 27, 2018
Messages
3
Reaction score
1
Points
3
Have my setting in my recipe editor set to "fermenter" batch size. However I've been thinking about switching to "kettle" batch size. So here is the problem I come across.

If I change batch from fermenter target volume to kettle target volume and adjust the kettle target volume to the essentially the same as the fermenter minus the losses listed in my equipment profile and under water requirements the og drops by 3 points.

Both batch types end up at the same post boil volume so I'm guessing there is a bug one of the calculations.
 

Attachments

  • 20200106_151803.jpg
    20200106_151803.jpg
    215.2 KB · Views: 99
  • 20200106_151826.jpg
    20200106_151826.jpg
    208.6 KB · Views: 99
  • 20200106_151912.jpg
    20200106_151912.jpg
    184.1 KB · Views: 101
Have my setting in my recipe editor set to "fermenter" batch size. However I've been thinking about switching to "kettle" batch size. So here is the problem I come across.

If I change batch from fermenter target volume to kettle target volume and adjust the kettle target volume to the essentially the same as the fermenter minus the losses listed in my equipment profile and under water requirements the og drops by 3 points.

Both batch types end up at the same post boil volume so I'm guessing there is a bug one of the calculations.
Does the "kettle" target require more water? If so, that's your OG drop.
 
Does the "kettle" target require more water? If so, that's your OG drop.
Nope, if you look at the thumbnails when I set it to fermentor the post boil is 24.6L. When I change it to kettle and adjust the volume to 24.6 the OG drops. It is the exact same water requirements up to the post boil. Nothing else changes besides the OG.
 
Are you able to post the fermentables, or a link to the full recipe so we can take a closer look?

Off the top of my head is it possible that there's a sugar or extract late addition? Those are affected separately from the efficiency, so it won't necessarily end up at the same gravity.

Another possibility is that the fermenter target uses brewhouse efficiency, and the kettle target uses mash (kettle) efficiency. Are you using the same numbers for these, if so you should be using different values. If it's 70% at brewhouse/fermenter @ 23L, then it should be ~74.6% at 24.6L with the kettle target.
 
Last edited:
""Another possibility is that the fermenter target uses brewhouse efficiency, and the kettle target uses mash (kettle) efficiency. Are you using the same numbers for these, if so you should be using different values. If it's 70% at brewhouse/fermenter @ 23L, then it should be ~74.6% at 24.6L with the kettle target.""

Mystery solved! How did I not see that, and I fiddled for over an hour before posting this lol. Thanks.
 
Mystery solved! How did I not see that, and I fiddled for over an hour before posting this lol. Thanks.
You're not alone, it took me a few times to put it together too.

Personally I think the batch size and postboil should stay consistent, and the efficiency should be the user input for the drop-down, so it's brewhouse efficiency vs kettle (mash) efficiency instead of target: fermenter vs target: kettle. I think that would be more transparent, but I don't think it's been a big enough issue to worry about.
 
You're not alone, it took me a few times to put it together too.

Personally I think the batch size and postboil should stay consistent, and the efficiency should be the user input for the drop-down, so it's brewhouse efficiency vs kettle (mash) efficiency instead of target: fermenter vs target: kettle. I think that would be more transparent, but I don't think it's been a big enough issue to worry about.

So the issue with equipment losses being included in OG calculations for the fermenter target has been addressed? And the terminology you're using seems clearer to me.
 
So the issue with equipment losses being included in OG calculations for the fermenter target has been addressed? And the terminology you're using seems clearer to me.
I believe so, most of the gravity calculation errors that were found dealt with equipment losses and how pre/post boil gravities were calculated and those have all been corrected in a pending update that will address gravity calculations, and allow for more options for late additions. This update was posted in the beta forum, and is available for reviewing on the beta site still but has been approved after testing and revisions.
 
Just following up, the update regarding boil gravities has gone live today. If there are any questions or issues, please post then in the changelog thread for 1/22 updates.
 
Struggling with gravity calculation ... appears to be error. I brew frequently with Mecca Grade Lamonta pale... it’s 37 PPG, 2.8 L and 150 DP. I entered this as a Custom Fermentable, and for 10 lbs in a 5.5 gallon batch, the recipe builder says OG will be 1.067. Seems high right? When comparing with American Pale 2-row, 37 PPG, 1.8 L, 140 DP, I see it’s showing 1.044 for the same batch size. So something is wonky with the Custom Fermentable feature. In fact, entering the exact values of standard fermentables as a custom will yield VERY different gravities. What am I missing?
 
Struggling with gravity calculation ... appears to be error. I brew frequently with Mecca Grade Lamonta pale... it’s 37 PPG, 2.8 L and 150 DP. I entered this as a Custom Fermentable, and for 10 lbs in a 5.5 gallon batch, the recipe builder says OG will be 1.067. Seems high right? When comparing with American Pale 2-row, 37 PPG, 1.8 L, 140 DP, I see it’s showing 1.044 for the same batch size. So something is wonky with the Custom Fermentable feature. In fact, entering the exact values of standard fermentables as a custom will yield VERY different gravities. What am I missing?
I'm not sure, my first thought was maybe Lamonta was entered in the database wrong but it looks correct.

I will troubleshoot and contact the devs asap.
 
I really don't understand why OG would change so drastically by changing the target from kettle to fermentor. If my losses are calculated under my equipment profile, why would there be a .005 difference? Regardless of where I take my reading, kettle or fermentor, the gravity at the end of the boil will be the same won't it?
Fermentor.JPG
Kettle.JPG
 
I really don't understand why OG would change so drastically by changing the target from kettle to fermentor. If my losses are calculated under my equipment profile, why would there be a .005 difference? Regardless of where I take my reading, kettle or fermentor, the gravity at the end of the boil will be the same won't it?View attachment 8812 View attachment 8813
Because the target change from fermenter to changek also changes the efficiency from brewhouse (includes kettle losses) to mash efficiency (exclude kettle losses).

This has repeatedly been a source of confusion, so I'm going to work with @Yooper to see how we can make this more user friendly.
 
I still don't get it. For the longest time, recipes in BF just worked. A while back a check box under the More section of the recipe would also make this same change. That went away and everything was fine. Now this change If I have 6 gallons in the kettle and 5.5 gallons in my fermentor at the end of the boil, the gravity is still the same. I really love BF, but these out of the blue changes have been F'ing up our recipes for the last year or so, and IMHO they are really unnecessary.
 
The update that included the target feature for batch size happened months and months ago, and predates my involvement with brewersfriend so I cannot speak for that communication or testing.

But could you expand on the 6 gallons in the kettle and 5.5 gallons in the fermentor part?

We did recently update, several weeks ago I believe, how the boil gravity calculations work, which more accurately accounts for the process losses. The formula previously used was incorrect and needed to be updated for accuracy but also for how it works in real life.
 
To "expand" on my volume differences: At flame out, I have 6 gallons of wort in my kettle. With trub and counter flow chiller loss I end up with 5.5 gallons in the fermentor. The gravity of the wort is not going to change during the cooling process right? So selecting a fermentor or kettle volume while building the recipe should not change what my OG should be.
 
To "expand" on my volume differences: At flame out, I have 6 gallons of wort in my kettle. With trub and counter flow chiller loss I end up with 5.5 gallons in the fermentor. The gravity of the wort is not going to change during the cooling process right? So selecting a fermentor or kettle volume while building the recipe should not change what my OG should be.
Copy. Completely agree with the expected behavior.

The issue is right now it does, and that's because the when you change target the efficiency type also changes. It shouldn't, but it does.

I'm going to work with yooper and the owners to improve this so that when you're changing the target, it's clearer and maintains consistency.
 
Copy. Completely agree with the expected behavior.

The issue is right now it does, and that's because the when you change target the efficiency type also changes. It shouldn't, but it does.

I'm going to work with yooper and the owners to improve this so that when you're changing the target, it's clearer and maintains consistency.

I was struggling to understand this same issue, although I discovered it in a different manner. I've always had my BF target set to fermentor and used to take my OG reading after transfer from kettle to fermentor, as I was brewing in smaller pot and needed to top off my fermentor. About a year ago I switched to a Mash & Boil unit and no longer need to top off my fermentor. I just started using the volume collected as my final volume and I noticed that OG changed based on fementor volume. I started looking at the options with my most recent brew (yesterday..LOL) and realized I should probably switch to kettle volume, since I now take my OG readiing in the kettle after chilling. When I switched it, I noticed the same isuue as RockyMtnGT.

I understand the difference between kettle efficiency and brewhouse efficiency. One is the volume of wort following the boil, the other is the volume of wort transferred to the fermentor (although, if it's true brewhouse efficiency I would think this would be the final volume of package beer). Like RockyMtnGT, I don't think OG reading should change based on fermentor vs. kettle volume, unless it is assumed that the brewer is topping off the fermentor under the former. The OG of the wort doesn't change unless it is dilluted.

For my purposes, I think I should be using kettle efficiency for the most accurate OG estimate in a recipe. Is this correct, based on what I have described? I'm trying to fine tune an equipment profile for the Mash & Boil that will give me accurate results.

Thanks.
 

Back
Top