sugar carbonization in a 5g corny with 3g beer

[csh]

So, I'm doing 5 gallon batches and putting 1.5 to 2 gallons into bottles with the remainder going into the keg. I can do the math: if I'm using 5oz of sugar for 5 gals of beer, use 3oz of sugar for 3 gals of beer.

Ok, that's fine for a 3 gal corney... The question is more about the extra headspace in the 5 gal corney... ??? ...

There are a few other postings I found in a search but several of them don't make sense to me, like this one:
https://www.homebrewtalk.com/f35/carbonating-3-gal-5-gal-keg-255915/

Basically, the guy is saying don't change anything. I guess I'm trying to understand how this works for him... Unless he's force carbing later.

One option seems to be to pressurize the keg. Ok, I can do that... but the whole reason I'm not force carbonating is because I don't have an extra (I mean another extra) fridge that I can set at 35-40F to do force carbonation. The thought was to keg condition the beer at 76-80F for three weeks or so and carbonate at that time using sugar rather than waiting another two to three weeks to correctly force carb.

I'd love it if someone can explain either what to change to account for the extra headspace in the 5 gal keg or how I'm over complicating this issue.

 

[2stupid]

at first i had no answer. then i switched my thinking to bottling instead of kegging and the last bottle. sometimes it's 2/3 full. It still turns out like the rest of the batch even though it has alot of headspace. I would say just pretend you dont have all that extra space in there..

 

[audger]

I would say just pretend you dont have all that extra space in there..

all that headspace is not inconsequential. you need to produce enough CO2 to both carbonate 3 gallons AND fill 2 gallons of space with enough pressure to do it. im not sure exactly what the rule is for how much extra sugar you need, but you will need extra. unfortunately that much extra sugar can change the taste of the beer. anyone who says they do it without adding more sugar just doesnt recognize the difference in carbonation level that the extra headspace is causing. if you were to bottle half the beer with the correct amount of sugar, and keg the rest the way you describe (with that much extra headspace), the bottles would be more carbonated than the keg.

but the whole reason I'm not force carbonating is because I don't have an extra (I mean another extra) fridge that I can set at 35-40F to do force carbonation. The thought was to keg condition the beer at 76-80F for three weeks or so and carbonate at that time using sugar rather than waiting another two to three weeks to correctly force carb.

you can force carb just fine at room temperature as long as you follow a carbonation chart (google image search it). what you could do if you want to save some gas, is put 3-5 oz of sugar in the 3 gallons of beer, wait for it to ferment, then hit it with the correct gas pressure to finish it off. if you have the gas and dont specifically need to use sugar, you can just set the gas to the right pressure (30psi or so) and leave it for a few weeks. when you go to chill it turn the pressure down to the correct level (maybe 12psi).

 

[csh]

you can force carb just fine at room temperature as long as you follow a carbonation chart (google image search it). what you could do if you want to save some gas, is put 3-5 oz of sugar in the 3 gallons of beer, wait for it to ferment, then hit it with the correct gas pressure to finish it off. if you have the gas and dont specifically need to use sugar, you can just set the gas to the right pressure (30psi or so) and leave it for a few weeks. when you go to chill it turn the pressure down to the correct level (maybe 12psi).

I like that idea: keg condition and carbonate with bottling sugar then connect to co2 at room temp to finish the carb. My plan is to keg condition and carbonate for four weeks.

Can I do both at the same time or will that lead to issues? I'm thinking 3-4 weeks between primary and secondary plus another four weeks for conditioning and carbonation. I guess I would wait until the last (8th) week to hook up the co2 at 30lbs.

 

[JeepDiver]

Well 5 gallons in a Keg, takes 2.5 oz of sugar instead of 5, so you are over carbing your beer. Guess the difference is enough to take care of the extra headspace.