De-carbonating for bottle conditioning

[iandanielursino]

I haven't seen very much discussion of this.

In a cold crashing system (unitank) where suckback is prevented by adding pressure will it work to reduce the pressure to almost 0 PSI during cold crash (after achieving the minimum temperature of course) so that you can do a standard bottle conditioning afterwards? Can beer go flat at ~.5 PSI or so, and does it take less than two days?

If you racked to a bottling bucket at pressure and gravity bottled you would lose some carbonation vs what you had in the unitank but it would still be way too much for a standard priming calculation, I wonder if there's any offset formula you could use to prime it just enough.

Reason being I haven't got a counter pressure, CO2, or a regulator, I just have a spunding valve and a climate controlled fermentation chamber.
When I make lagers the beer will be completely carbonated by the end of lagering by spunding pressure if I maintain like ~8 PSI it seems so I'm probably going to buy a beer gun, CO2 tank, and double regulator pretty soon, but still in the meantime and for ales (until I get a carb stone) I'm not sure what to do.

Aside: I suppose it would be no problem to ferment under pressure even up to 15 PSI if you were going to use a carb stone to achieve equilibrium after the cold crash since at fermentation temperatures the CO2 in solution would still be low.

 

[mac_1103]

If you fermented and cold crashed under pressure then a standard force carbonation chart will tell you how much CO2 is in your beer and you can adjust your priming sugar calculation accordingly. If you did not ferment under pressure but just cold crashed under low pressure for a couple of days then the beer probably didn't have enough time to absorb very much additional CO2.

 

[McMullan]

Ideally, you’d bottle carbonated beer and get some value from owning a unitank. There must be some DIY beergun-like hacks available? The simplest I’ve seen was literally just a length of 3/8 John Guest beer line pushed into a picnic tap. Similar for the CO2 to purge air (O2) from the bottles before filling. A soda stream canister holds enough for a few batches. In fact, some very basic soda stream machine models (the cheapest) are perfect for purging air from empty beer bottles. Just add a length of tube on the CO2 jet to reach the bottom of a beer bottle. At least enough to get you started.

 

[iandanielursino]

If you fermented and cold crashed under pressure then a standard force carbonation chart will tell you how much CO2 is in your beer and you can adjust your priming sugar calculation accordingly. If you did not ferment under pressure but just cold crashed under low pressure for a couple of days then the beer probably didn't have enough time to absorb very much additional CO2.

That seems complicated. Ale temps are usually off most forced carb charts, but lets say we could calculate the CO2 at the end of fermentation, if we then changed the parameters and got a different amount of equilibrium CO2 volume according to the chart, after just a day or two we wouldn't know where we are exactly.

Maybe the solution is as you lower the temperature you ensure that the chart yields the same value by adjusting the pressure if necessary. (not sure what the relationship is between temp loss and pressure loss, maybe this is already the case by default)

Spike says to put like 5-6 PSI IIRC to prevent suckback, so its not insignificant, and since its spunding I have to collect it the whole time since the amount of CO2 you collect goes down as the fermentation slows.

Ideally, you’d bottle carbonated beer and get some value from owning a unitank. There must be some DIY beergun-like hacks available? The simplest I’ve seen was literally just a length of 3/8 John Guest beer line pushed into a picnic tap. Similar for the CO2 to purge air (O2) from the bottles before filling. A soda stream canister holds enough for a few batches. In fact, some very basic soda stream machine models (the cheapest) are perfect for purging air from empty beer bottles. Just add a length of tube on the CO2 jet to reach the bottom of a beer bottle. At least enough to get you started.

I mean there are many reasons to use a conical tank not just using it as a brite.
1. its easier to clean
2. you can cold crash under pressure which is a simple suckback countermeasure
3. the cone shape and the racking arm help you separate the clear stuff from the murky stuff
4. some people believe pressure fermentation has a significant effect on ester formation

I'm planning to get a beer gun, double regulator, and tank eventually so it doesn't make sense to buy a sodastream.

 

[McMullan]

If you get into pressure fermentation, or just natural carbonation, which I highly recommend, especially if you have a pressure rated conical, you won’t need much CO2 at all. You can even capture some in an empty keg. Sodastream canisters are easier to get hold of, live and travel with, and more than sufficient for transfers and serving. And they’re certified beverage grade CO2, with extra QC checks done to ensure the gas is fit for purpose. Less is more. Price difference isn’t that much where I am, so a no-brainer for me.

 

[mac_1103]

Ale temps are usually off most forced carb charts, but lets say we could calculate the CO2 at the end of fermentation, if we then changed the parameters and got a different amount of equilibrium CO2 volume according to the chart, after just a day or two we wouldn't know where we are exactly.

The parameters are the actual temperature and pressure at the end of your process. The equilibrium CO2 volume is what it is based on those parameters. The only reason you wouldn't know exactly where you are is if you didn't reach equilibrium. If you only cold crash for a day or two then you not only won't reach equilibrium, but your beer won't even absorb much additional CO2. The suckback is mostly volume change.

 

[hotbeer]

You might be over thinking this and not doing any practical experimentation. Are you able to rack the already carbonated beer into a bottle without agitating it so much that it foams excessively? A little foam is okay, just let that run out the top till you get the bottled filled to the level you desire. But if it is getting too agitated and the foaming activity doesn't die down quickly then that is going to be excessive CO2 lost.

After capping, less headspace means less carbonation lost from the beer as it achieves equilibrium for whatever it's potential is for the vols it's carbonated to. There is no practical reason, IMO, to leave anything more than a smidgeon of headspace. Other than you won't get a satisfying sound of "pffft" after you pop the top unless you have about a inch of space. Which is way too much if you are worried about keeping the beer close to the Vols of carbonation that it is bottled at.

IMO a millimeter or 16th of an inch is more than enough. I have capped on virtually no headspace and there were no issues. Other than the initial reaction when you open those bottles with little to no head space is "oh crap, my beer is flat!" but it isn't.

 

[Broken Crow]

Sorry if this sounds blunt and I mean no disrespect, but a unitank is a very pricey item for a very specific use. Isn't it a bit "Putting the cart before the horse" to buy a unitank without CO2 gear?
If you at least have a keg and some beer lines, you could fill a keg with sugar-water and yeast to get some CO2 under pressure and maybe mount a Tapcooler on your fermentation chamber, or get a beergun or homemade variant.
Just spit-ballin'

 

[iandanielursino]

Thats totally fair, and I wouldnt except I already have a roadmap that includes CO2 gear. That said people buy a spike tank when they could just get a used blichmann on Craigslist for a fifth the price just for those sweet welds and the bottom dump, and it didnt become an issue until I got the ability to cold crash.

Current plan is to get a beergun, cannister, and double regulator in March so it'll be moot then.

In the meantime it sounds like the best options are to either attempt to compute the CO2 in solution at the end of fermentation and prime for the difference, get just a tank and ball valve for now and ferment with a blowoff which is what Spike reccomends, just dont cold crash, or look into alternative methods for bottling with narural fermentation altho I wouldnt do that with an ale if I want it to be quick since id need to wait for equalibrium.

If I make a lager and lager it for 3 weeks im at equalibrium so racking it using a filling straw attached to the unitank seems fine.

I heard some contradictory rumblings about priming after a cold crash but I imagine it will be fine.

Anyways I appreciate the diversity of replies.

BTW if you naturally carb what would take more co2, purging and bottling or pressure transferring and dispensing from a keg?

 

[Broken Crow]

I already have a roadmap

Ah! I have one of those too.... I think it's buried under a pile of bills!

BTW if you naturally carb what would take more co2, purging and bottling or pressure transferring and dispensing from a keg?

That's a little bit "apples and oranges".. You do lose some CO2 if you purge you're bottles, but then you need constant CO2 to dispense from a keg. If you're content to keep bottling, I'd suggest going cheap for now and just getting the CO2 gear and then either a beergun or, more conveniently you can mount a tapcooler on the door of your fermentation chamber and bottle without even opening the door.
https://www.morebeer.com/products/tapcooler-counter-pressure-bottle-filler.html

 

[iandanielursino]

I'm still curious if it's known at just over 0 PSI and cold crash temps how long it takes for beer to de-carbonate. For science.

 

[hotbeer]

I'm still curious if it's known at just over 0 PSI and cold crash temps how long it takes for beer to de-carbonate. For science.

When I learned to scuba dive some 40 years ago, I was told that it takes 12 hours for the nitrogen gas that is pushed into your system to fully desaturate from you system at 1 atmosphere or your 0 psi.

Somehow I think that this is based on the body being mostly water. And that the physics pretty much holds true for any gas.

So I'm going to say 12 hours. Assuming there is no fermentation going on and the beers temp is constant.

But I don't know for certain. I can't think of a reason why type of gas would make a difference. My physics class I was required to take didn't go into such. Or if it did, I was daydreaming about other stuff.

It doesn't really de-carbonate. It just releases the amount dissolved CO2 that it can no longer hold due to ambient pressure and temperature. It still will have some CO2 dissolved in it that might come out of solution as the liquid is agitated.

IE, filling your bottles rapidly and letting it splash onto the bottom of the bottle by holding your racking cane too high.

 

[mac_1103]

I'm still curious if it's known at just over 0 PSI and cold crash temps how long it takes for beer to de-carbonate. For science.

If you ferment without pressure and cold crash without allowing air into the headspace, then the beer will absorb CO2 from the headspace as the temperature drops and so the carbonation will increase rather than decrease.

 

[iandanielursino]

Per the original post, the condition would be fermenting under enough pressure to cold crash (~5 PSI), then dropping the pressure after reaching the cold crash temperature to ~0 PSI and waiting 24-48 hours.

 

[mac_1103]

At 5 PSI and 68F or higher, you 're only going to have at most 1 volume of CO2. If you maintain a pure CO2 headspace and cold crash at 40F or lower long enough to reach equilibrium, you will have more than 1.4 volumes of CO2 at 0 PSI. So again, your beer will not de-carbonate when you cold crash.

edit - but of course you will not reach equilibrium in 24-48 hours and the change in carbonation level will be minimal in that time frame

 

[iandanielursino]

Yes that's true. Looking at the table again, it seems the equilibrium volume has indeed increased rather than decreased, so no de-carbonation is possible.

So barring more bizarre and convoluted methods, if the intention is to carb it up from where it is I imagine I can simply estimate the volume at the end of fermentation and compute how much I should add to bring it to that which is desired. It will be low because of losses when racking, and it will be high because of gains during the cold crash, but it would be closer to what it was before the cold crash than to anything else.

 

[doug293cz]

Per the original post, the condition would be fermenting under enough pressure to cold crash (~5 PSI), then dropping the pressure after reaching the cold crash temperature to ~0 PSI and waiting 24-48 hours.

If you do this, the gauge pressure will go negative due to CO2 being absorbed from the headspace during the hold time. I don't think you want to do this.

Better to just vent the excess pressure immediately before bottling, but then you will need make up air, or CO2, in order to keep the beer flowing (if the headspace pressure goes too negative, beer flow will stop.)

If you know the pressure and headspace volume at the end of fermentation, and the pressure at the end of cold crash, you can calculate the amount of CO2 in the headspace before and after cold crash. The difference has been absorbed by the beer, and you can calculate the current carbonation level using this data. You then subtract the current carbonation level from your target carbonation level to determine how much priming sugar to use.

Brew on

 

[iandanielursino]

I'll have to see what the gaseous volume of the Spike CF10 is to get the headspace volume, computing the carbonation level using the pressure change is just what I need though. I imagine this has got something to do with the ideal gas law.

n = pV / (RT)

p is known by the gauge
V is known by subtracting the volume of beer from that of the container
R is a universal constant
T is known from the thermometer

So then you can compute the number of mols of the gas in the headspace before and after the cold crash to find the difference, and then you have to convert to this rather arcane measurement "volumes of CO2" which is also given by the ideal gas law I imagine.

V = nRT / p and then you punch in the parameters of STP along with the number of mols. Something like that?

I forget if I was venting it or not at the time, but I've definitely racked at 0 PSI before using a pump, but I suppose I have no reason to dump the pressure unless I was going to prime in the unitank, which I typically don't do so that I can discard what is below the racking arm and because my filling straw is a different ID of hose than any of the barbs I have for my conical.

After only 2 weeks of fermenting at 68F I wonder if it has reached equilibrium.

We will still lose just a bit of CO2 to the priming process, but maybe that's negligible, just don't shoot for the very bottom of the style I guess.
Also, with the lager example, we could fully carbonate it if we wish, but this seems bad because oxygen will exist in the headspace, I imagine its better to undershoot the final vol of CO2 deliberately just to use up all that oxygen again in bottle conditioning unless this is taken care of by "oxygen absorbing caps". I may simply hold off on doing a lager until after I get a beer gun.

 

[doug293cz]

I'll have to see what the gaseous volume of the Spike CF10 is to get the headspace volume, computing the carbonation level using the pressure change is just what I need though. I imagine this has got something to do with the ideal gas law.

n = pV / (RT)

p is known by the gauge
V is known by subtracting the volume of beer from that of the container
R is a universal constant
T is known from the thermometer

So then you can compute the number of mols of the gas in the headspace before and after the cold crash to find the difference

Correct. Then multiply the # moles by the molecular wt of CO2 (44 g/mol) to get the g of absorbed CO2.

then you have to convert to this rather arcane measurement "volumes of CO2" which is also given by the ideal gas law I imagine.

V = nRT / p and then you punch in the parameters of STP along with the number of mols. Something like that?

The definition of a "volume of carbonation" is pretty clunky, but in simpler units: 1 volume = 1.977 g/L (or 0.264 oz/gal.)

Brew on

 

[iandanielursino]

The definition of a "volume of carbonation" is pretty clunky, but in simpler units: 1 volume = 1.977 g/L (or 0.264 oz/gal.)

Yeah that seems a lot easier. Volume of carbonation is defined as the ratio of the CO2 volume at STP to the liquid volume though right? So I imagine you could also do it by computing the volume and dividing by the volume of fluid. I imagine that would be less accurate than using the mass since CO2 is not an "ideal" gas applying R more times would make it less accurate.

 

[doug293cz]

Yeah that seems a lot easier. Volume of carbonation is defined as the ratio of the CO2 volume at STP to the liquid volume though right? So I imagine you could also do it by computing the volume and dividing by the volume of fluid. I imagine that would be less accurate than using the mass since CO2 is not an "ideal" gas applying R more times would make it less accurate.

Correct.

Brew on

 

[Mr. Vern]

I'll have to see what the gaseous volume of the Spike CF10 is to get the headspace volume, computing the carbonation level using the pressure change is just what I need though. I imagine this has got something to do with the ideal gas law.

Recommend filling it 100% and then measuring what comes out to get an accurate volume, including head volume for the lid.

The ideal gas law will help show you how much has been adsorbed, out-gassed, or lost through leaks. Since we are not talking about big differentials in pressure/temperature I believe this is a non-issue.

Considering the above, I would be confident using volumetric calcs. on the fly.

I imagine that would be less accurate than using the mass since CO2 is not an "ideal" gas applying R more times would make it less accurate.

CO2 behaves like an inert gas and will obey the ideal gas law at these conditions... for our intents and purposes anyways.

 

[doug293cz]

Recommend filling it 100% and then measuring what comes out to get an accurate volume, including head volume for the lid.

The ideal gas law will help show you how much has been adsorbed, out-gassed, or lost through leaks. Since we are not talking about big differentials in pressure/temperature I believe this is a non-issue.

Considering the above, I would be confident using volumetric calcs. on the fly.


CO2 behaves like an inert gas and will obey the ideal gas law at these conditions... for our intents and purposes anyways.

The Ideal Gas law gives 1 volume as 44.01 g/mol / 22.4 L/mol = 1.965 g/L, where the databook value is 1.977 g/L. So, even at relatively low pressures, CO2 deviates noticeably from ideality.

Brew on

 

[Mr. Vern]

where the databook value is 1.977 g/L

Applied math has broken me. I don't exactly brew by instinct but apparently I have a more liberal approach when it comes to defining a split hair. (fun sarcasm, not snark!)

I was attempting to say that the sugar addition will be negligible using ideal gas law or known deviation.

+ 1.6 VOL of CO2 (1.965 -vs- 1.977 g/L)
This scenario seems to be an "ideal" deviation of roughly 1/3 teaspoon of glucose for 20 liters of beer. Scale up to a 300 barrel commercial job and you are looking at 8.5 Lbs or so. This is what I meant by "our intents and purposes" as homebrewers and being confident with loose math. I could be wrong with my calculation, it would not be the first time!

Inversely I think this could vary by 0.1 volumes of CO2. Is that noticable?

My wife is a HS math teacher and we argue/joke over this kind of thing.

 

[iandanielursino]

Incidentally my spund is not going so well.

I pressure tested it before, and it was holding 12 PSI just fine. Since the last time I disassembled the PRV I have tested for up to 2 weeks that it doesn't lose any pressure (with air, not CO2). I didn't realize my liquid yeast was the kind you're supposed to pop a bag of LME inside and shake and wait a few hours and perhaps for that reason the fermentation started slow, but there are signs of activity it just took a couple days to take off. No pressure yet though. (granted I checked a couple times, but the gauge read 0 when I checked so how much of a difference could it have made?). Not sure what's up, hopefully I'll start getting some pressure in the next day. I can smell hops though which doesn't' seem like a good sign.

Sprayed down the tank with starsan and no bubbles came out of the PRV or anything. I was kind of worried because I blew a gasket on my sample port, but only one of the two so it holds liquid, and it's underwater so I don't think that matters. Tightened up the band even more, checked for liquid leaks (none). Listened for the sound of a leak from the lid (none). I didn't get a peek today because once I heard gas coming out I closed it right back up, so I'm not sure if its krausening a lot yet or not. Yesterday I looked and saw bubbles, so I knew it was starting real slow. The second night I set the temp to 70 to kick start it a little, today I set it back to 68. The pitch was at about ~68 by the temp probe after in-line chilling and it was set to 68 the first night.

The first time I brewed with this tank I had a really bad leak from the lid which I could hear and it still got above 10 PSI overnight so idk what gives, only thing I can think of is the fermentation is still not going fast yet.

 

[doug293cz]

Sounds like you have a leak somewhere. When you pressure tested, the pressure was enough to seal up the leak, so pressure held. This is a fairly common occurrence with kegs, in that some of them need some pressure to actually seal the lid and prevent leaks. Don't know the details of your fermentation vessel, so can't speculate on where the leak might be.

Brew on

 

[iandanielursino]

It's a Spike CF10 which attaches the lid using a band. I put their new lid gasket on which is thicker with both sides beveled because it was leaking like crazy before, I also had the PRV leaking but I fixed that by adjusting the torque and using more PTFE tape, when I spray now I don't get any pinhole leaking so I imagine it must be the lid once again. I have tightened it more since I realized it wasn't pressurizing too.

The strange thing is, the first time I tried to use this tank it spunded right up to 12 PSI overnight even though it had a slow leak that eventually killed the pressure.

The second time when I determined the issue was the lid it didn't though. After getting the improved gasket I built a pressure gun to test with an air compressor, and then it was winter so I needed to find a freezer to build a fermentation chamber for it because my brewery isn't heated. So this is the third time I've used the tank with a PRV attached (twice with a blowoff).

 

[iandanielursino]

Spike told me to check on some stuff and smack it more and tighten it more, which did get it like another 32nd or two 64ths or so tighter on the band, now the thing is actually raising pressure, 1.5 PSI this morning, 2 PSI currently, so we'll see how it goes. I don't think it's really going to reach equilibrium so the math may be moot but I'll summarize my results in this thread for posterity.

I think if I actually mange to build a significant pressure, I'll assume equilibrium, cold crash, do the math, and then shoot for the very top of the APA style knowing it's going to be less than I calculated + losses when transferring.

If it doesn't build up much I'll just set the PRV low, rack at 2 weeks, and just prime a bit light.

 

[iandanielursino]

The pressure got up to 4 PSI and now it's creeping back down to 3 PSI, so I think it's going to be the latter. Pretty sure that the lid is leaking underneath the band because there's no sign when I spray star san and look for bubbles. I'll give it a few more smacks with a mallet and do some low-pressure tests in a more controlled way and then see if Spike will take it in to have a look.

 

[iandanielursino]

For whatever reason it stuck at 3 PSI, no clue how that works, so I'm going to just start inching the temp down slowly and see how low I can get with positive pressure, I can't find a carb chart that goes all the way up to 68 degrees. My guess is like 0.8, although since its only been under pressure for about a week I'm guessing it has not reached equilibrium. . I'm thinking of priming to add 1.4-2 additional volumes depending on how it seems. Obviously, don't want to blow up the bottles.

I'll try and do the math to guess how much is going into suspension during the cold crash though but the pressure gauge doesn't really read accurately below 1.5 (or perhaps 2, not sure what the half hashes mean close to 0) is my understanding (only 3 full hashes between 0 and 5 instead of 4 like you'd expect) so I probably can't go too low and expect a meaningful datum.

I'm reading 1.01 on the hydrometer so it reached the gravity I wanted anyways.

Ultimately I couldn't really say it was at equilibrium, I ended up winging it and priming the 4 gallons I had afte rracking with 3 oz dextrose, so I'll monitor it and stick it in the fridge if it seems like it's done. Sample at 2 days of bottle conditioning seemed pretty flat so fine so far.

 

[iandanielursino]

It seems like priming calculators take the temperature so that it can compensate for 0 PSI carbonation, is anyone familiar with the formulae used for this? Do priming calculators assume equilibrium (hence would cold crashing ruin it?)

 

[mac_1103]

Do priming calculators assume equilibrium (hence would cold crashing ruin it?)

Yes, the calculators assume equilibrium. Whether cold crashing "ruins it" depends on how long you keep the beer at crash temps. A couple of days is generally thought not to matter much, so most people just use the temp the beer was at prior to crashing. I guess one way to think of it is that it's analogous to set and forget force carbonating - it takes about two weeks to reach equilibrium. So if you cold crash for two weeks you should use the crash temp in the carbonation calculator.

 

[iandanielursino]

That being the case I think if you're computing an adjustment for pressure you probably need to use a different formula than what the standard priming calculators use. If volumes are commutable in the necessary way than I suppose you simply determine the zero that the calculator is using (ie the desired volumes at which it tells you to add 0 sugar), and then add that number to your actual desired delta.

I'm thinking for my next batch (still no beer gun or carb stone) I'll just cold crash and spund carbonate everything for at least 2 weeks (3 for lager) and try priming a negligible amount simply for sanitary reasons.

I wonder if the priming models become inaccurate with small numbers though.

 

[mac_1103]

That being the case I think if you're computing an adjustment for pressure you probably need to use a different formula than what the standard priming calculators use.

Because?

I could be wrong, but I think you're overthinking this. If you ferment under pressure, use a force carb calculator to determine how many volumes of CO2 you're starting with. Then trick a priming calculator by adjusting the temperature until it gives you that starting level. I'm pretty sure that will work, because yeast fed any given amount of sugar will generate a knowable amount of CO2.

 

[iandanielursino]

Sure that works, what wouldn't work would be to determine the volumes you already have and simply subtracting that from the amount desired because that would be compensating for the wrong pressure.

 

[doug293cz]

It seems like priming calculators take the temperature so that it can compensate for 0 PSI carbonation, is anyone familiar with the formulae used for this? Do priming calculators assume equilibrium (hence would cold crashing ruin it?)

A good formula to use is equation 2.1 in the attached .pdf file. This is easy to solve for volumes if you know CO2 pressure and temperature. The equation only applies at equilibrium.

I did an analysis of cold crashing, that includes air suck back if using a simple airlock. The net is use the fermentation temperature to calculate priming, not cold crash temp.

I guess one way to think of it is that it's analogous to set and forget force carbonating - it takes about two weeks to reach equilibrium. So if you cold crash for two weeks you should use the crash temp in the carbonation calculator.

Only if you backfill the headspace with CO2 instead of allowing air suck back. See the link above.

Brew on

 

[iandanielursino]

A good formula to use is equation 2.1 in the attached .pdf file. This is easy to solve for volumes if you know CO2 pressure and temperature. The equation only applies at equilibrium.

I did an analysis of cold crashing, that includes air suck back if using a simple airlock. The net is use the fermentation temperature to calculate priming, not cold crash temp.

Only if you backfill the headspace with CO2 instead of allowing air suck back. See the link above.

Brew on

Actually I meant the formula to decide how much sugar to use. It seems the one in a priming calculator is computing the volume of CO2 so it wouldn't be useful if you've already done so at greater than standard pressure.

I think the method I suggested (determine the "zero" volumes computed by the calculator at any temperature and add this to the desired change in carbonation) or the one suggested by mac (find the temperature at which the priming calculator's "zero" is your actual computed volumes) both should work but are lacking in parsimony.

 

[mac_1103]

Only if you backfill the headspace with CO2 instead of allowing air suck back.

Yes, that's what I meant. Should have been more specific.

 

[iandanielursino]

I like mac's method.

In https://www.northernbrewer.com/pages/priming-sugar-calculator if you input 162.5 as the temperature it zeroes the starting CO2 and so if you ask for 0 vols it suggests 0 sugar.

 

[mac_1103]

That's not exactly how I would have done it but I guess it doesn't really matter if you zero the starting CO2 or adjust the calculator to your actual starting CO2. Either way you're priming for the desired delta.

Also not my favorite calculator; I think it tends to undercarb; but YMMV of course.