Cold Co2 tank readings

Williams 728
Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
S

Stagger5150

Active Member
Joined
Feb 12, 2015
Messages
28
Reaction score
1
Location
Orange Coutny
How exactly does it affect my Co2 readings when I place the tank in my kegerator as opposed to outside of it.

I noticed that I set my room temperature Co2 tank at 12 PSI and place in the fridge with my corny keg and when I go to check on my setup the next day the tank is cold and the readings on the gauges are showing different then when the tank was room temp. If I set it at 12 PSI is it still at that setting after the tank cools despite the readings being different. Not quite sure what is affected and how.

Thank You
 
CO2 in the tank is mostly liquid, so the pressure is determined by the CO2 vapor pressure at the tank temperature. From the chart below the tank pressures at various temps are:
70˚F => 853 psi
40˚F => 567 psi
30˚F => 491 psi​
Only when all of the liquid CO2 is gone from the tank will the pressure drop below these values.

co2pv.gif

Brew on :mug:
 
If you have the option, I'd leave the tank outside. I had mine in the keezer for about two years and hates all the space I lost, especially with a dual body regulator. Then there's the rust ring if you have a steel tank (like me).
 
doug293cz said:
CO2 in the tank is mostly liquid, so the pressure is determined by the CO2 vapor pressure at the tank temperature. From the chart below the tank pressures at various temps are:
70˚F => 853 psi
40˚F => 567 psi
30˚F => 491 psi​
Only when all of the liquid CO2 is gone from the tank will the pressure drop below these values.

View attachment 334821

Brew on :mug:
Click to expand...

Good stuff on the chart, thanks for posting.
 
doug293cz said:
CO2 in the tank is mostly liquid, so the pressure is determined by the CO2 vapor pressure at the tank temperature. From the chart below the tank pressures at various temps are:
70˚F => 853 psi
40˚F => 567 psi
30˚F => 491 psi​
Only when all of the liquid CO2 is gone from the tank will the pressure drop below these values.

View attachment 334821

Brew on :mug:
Click to expand...

FYI this is a chart of the cylinder pressure, not your regulated pressure.

It's normal for the regulated pressure to vary based on ambient temperature. Just set it to whatever is required for the given ambient. If you change the tank pressure you're going to have to reset the regulator. There is no temperature compensation.
 
schematix said:
FYI this is a chart of the cylinder pressure, not your regulated pressure.

It's normal for the regulated pressure to vary based on ambient temperature. Just set it to whatever is required for the given ambient. If you change the tank pressure you're going to have to reset the regulator. There is no temperature compensation.
Click to expand...

A properly functioning regulator should maintain a constant outlet pressure regardless of the tank pressure. Otherwise, regulators for compressed gas cylinders (not liquefied gas cylinders) would have to be constantly reset. Also, a good regulator should not vary much with temperature. They work by differential pressure on a diaphragm along with an adjustable spring to set the outlet pressure. Unless the spring constant varies significantly with temperature, the regulator will be just about independent of temp.

Brew on :mug:
 
Thanks for the helpful info much appreciated.

The past couple kegs I would rack them warm, seal the keg and set at 12 PSI. I would toss them in the kegerator and when I checked it 24 hrs later it had dropped down to 9 PSI on the regulator. I understand the High Pressure gauge for remaining Co2 would be affected but it seemed like my outlet pressure gauge dropped a couple. Could it have been the warm beer I originally put in that cooled ?

Thanks Again
 
The pressure set on the regulator has nothing to do with the temp of your beer. If your regulator is set to 12 it should stay at 12 not drop to 9. That should be totally independent of the temperature. Sounds like an issue with the regulator to me.
 
Thats what I did the past few batches. I put my keg in the kegerator warm at 12 PSI and next day it is cold and at 9 PSI and I just dial it back up to 12 PSI.

This is the only time the gauge changes is when it transitions from warm to cold. The rest of the keg life the gauge stays stable. I was just wondering if this is normal ?
 
doug293cz said:
CO2 in the tank is mostly liquid, so the pressure is determined by the CO2 vapor pressure at the tank temperature. From the chart below the tank pressures at various temps are:
70˚F => 853 psi​
40˚F => 567 psi​
30˚F => 491 psi​
Only when all of the liquid CO2 is gone from the tank will the pressure drop below these values.

View attachment 334821

Brew on :mug:
Click to expand...
Can i ask does this happen with a nitrogen bar mix as well. I have a nitro tank in my kegerator and the gauge showed 2000 in the full tank. But when placed in the cold kegerator and on a corny keg of guinness it dropped to 1700 abd holding steady. I checked for leaks and cant find any?
Thanks
Tom
 
tljljc said:
Can i ask does this happen with a nitrogen bar mix as well. I have a nitro tank in my kegerator and the gauge showed 2000 in the full tank. But when placed in the cold kegerator and on a corny keg of guinness it dropped to 1700 abd holding steady. I checked for leaks and cant find any?
Thanks
Tom
Click to expand...
Under normal conditions, there should be no liquid CO2 in the cylinder of a beer gas mix. However, depending on the mix ratio, total cylinder pressure, and cylinder temperature, it might be possible that some of the CO2 would condense to a liquid, thus lowering the CO2 partial pressure, and the total pressure in the cylinder. CO2 will condense when the starting CO2 partial pressure is above the vapor pressure of liquid CO2 at the current temperature.

Cooling the tank will reduce the tank pressure according to the ideal gas law: PV = nRT. V, n, and R are all constants in this case, so P1 / T1 = P2 / T2, or P2 = P1 * T2 / T1, where the 1 subscript means room temp conditions, and 2 means chilled conditions. Temperatures are absolute in °K, where °K = °C + 273.15°, and pressures are absolute, where psia = psig + 14.7 psi. You would also lose some tank pressure because of reduction of "n" from gas filling your plumbing and pressurizing the keg headspace.

What is your gas mix ratio and kegerator temperature?

Brew on :mug:
 
Last edited:
doug293cz said:
Under normal conditions, there should be no liquid CO2 in the cylinder of a beer gas mix. However, depending on the mix ratio, total cylinder pressure, and cylinder temperature, it might be possible that some of the CO2 would condense to a liquid, thus lowering the CO2 partial pressure, and the total pressure in the cylinder. CO2 will condense when the starting CO2 partial pressure is above the vapor pressure of liquid CO2 at the current temperature.

Cooling the tank will reduce the tank pressure according to the ideal gas law: PV = nRT. V, n, and R are all constants in this case, so P1 / T1 = P2 / T2, or P2 = P1 * T2 / T1, where the 1 subscript means room temp conditions, and 2 means chilled conditions. Temperatures are absolute in °K, where °K = °C + 273.15°. You would also lose some tank pressure because of reduction of "n" from gas filling your plumbing and pressurizing the keg headspace.

What is your gas mix ratio and kegerator temperature?

Brew on :mug:
Click to expand...
A drop in temp from 70°F (21.1°C) to 40°F (4.4°C) is not enough, by itself, to reduce tank pressure from 2000 psi to 1700 psi.

Brew on :mug:
 
the output gauge should not change hot or cold. The tank pressure gauge will drop as the liquid contracts from the cold, but the actual volume/quantity in the tank does not change.
 
doug293cz said:
Under normal conditions, there should be no liquid CO2 in the cylinder of a beer gas mix. However, depending on the mix ratio, total cylinder pressure, and cylinder temperature, it might be possible that some of the CO2 would condense to a liquid, thus lowering the CO2 partial pressure, and the total pressure in the cylinder. CO2 will condense when the starting CO2 partial pressure is above the vapor pressure of liquid CO2 at the current temperature.

Cooling the tank will reduce the tank pressure according to the ideal gas law: PV = nRT. V, n, and R are all constants in this case, so P1 / T1 = P2 / T2, or P2 = P1 * T2 / T1, where the 1 subscript means room temp conditions, and 2 means chilled conditions. Temperatures are absolute in °K, where °K = °C + 273.15°, and pressures are absolute, where psia = psig + 14.7 psi. You would also lose some tank pressure because of reduction of "n" from gas filling your plumbing and pressurizing the keg headspace.

What is your gas mix ratio and kegerator temperature?

Brew on :mug:
Click to expand...
Mix is 70 30 i was told
 

Similar threads

F
Need help with regulators/ co2 tank
Replies
9
Views
489
Bobby_M
Bobby_M
kev211
Beer Gas
Replies
1
Views
194
Dr_Jeff
D
R
Refilling a 5 pound CO2 tank
2
Replies
57
Views
2K
whoaru99
W
Draft Master Flash
15 lb Co2 tank overfilled?
Replies
17
Views
517
Draft Master Flash
Draft Master Flash
R
5 pound CO2 tank
Replies
36
Views
2K
Buelos75
Buelos75
InkBird 300

Latest posts

Back
Top