Carbonation gone from kegs

[norwegianBrewer]

So, I have a kegerator with 4 perlick taps.
I have 3 kegs in there atm.
One is almost empty, with no co2 line connected.
The two other ones are half-full kegs (all 5 gal. cornelius kegs), with co2 connected at serving pressure (They were all fully carbonated before I turned them down to serving pressure).

The problem came when i returned home after my summer vacation.
Before I went on my summer vacation, I turned the refrigerator off, but i left the co2 on at serving pressure.

When I got home, the beer is totally flat. No carbonation whatsoever.
I imagine this is because of the beer reaching room-temperature and not being able to hold the co2 that well any more.
But why is it still flat after i chill it again? It's a closed system, so unless my kegs are leaking...all of the co2 should still be in there.

I'm force carbonating it now to restore the carbonation...I'm just wondering what happened.
Has anyone experienced something similar?

 

[ong]

I would guess that when the beer warmed up, the co2 came out of solution and went into the headspace in your kegs, all of which had a lot of room above the fluid level. If that's the case, they should have a lot of pressure in them, and eventually recarbonate without additional co2 from the tank, once they're chilled again. If they don't have significant pressure, maybe there's a leak in the system?

 

[grittanomyces]

I'm no expert on carbonation, but that definitely sounds like a leak to me.

 

[mmb]

Sounds like a leaky keg. Beer stays carbed even when warm so long as the vessel is closed. Think cans of beer on a store shelf.

 

[norwegianBrewer]

Could be both suggestions i guess.
But a can of beer stored on a store shelf, won't have half a can worth of headspace.
I'm thinking if the can was half-full, that beer would also be pretty flat.

I'm going to do some soap-water tests on the kegs just to make sure they're not leaking, but I think this might be like ong mentioned. Temperature drops, co2 escapes and is stored in the headspace (which is about 2.5 gallons of headspace).
The pressure that initially carbonated the beer, would keep the beer carbonated at full keg, but when the keg is half full, the pressure from the released co2 won't be enough to recarbonate the beer all on it's own.

This is mostly guessing, but I think that if i recarbonate the beer, drop the pressure to serving pressure and vent, and turn off the kegerator for another two weeks....i'll get the same result.

 

[Kingbogart]

You have mentioned "dropping to serving pressure" twice now. What pressure is that exactly? I carb and serve under 12psi. If I were to reduce to say 4 to serve, and vent, the beer and headspace is going to equalize and eventually the beer will be undercarbed or not carbed at all. Two weeks sounds about right for this situation.

 

[mmb]

Could be both suggestions i guess.
But a can of beer stored on a store shelf, won't have half a can worth of headspace.
I'm thinking if the can was half-full, that beer would also be pretty flat.

I'm going to do some soap-water tests on the kegs just to make sure they're not leaking, but I think this might be like ong mentioned. Temperature drops, co2 escapes and is stored in the headspace (which is about 2.5 gallons of headspace).
The pressure that initially carbonated the beer, would keep the beer carbonated at full keg, but when the keg is half full, the pressure from the released co2 won't be enough to recarbonate the beer all on it's own.

This is mostly guessing, but I think that if i recarbonate the beer, drop the pressure to serving pressure and vent, and turn off the kegerator for another two weeks....i'll get the same result.

So long as you didn't vent the keg, the pressures would have equalized and your beer would still be carbed, not flat. Especially after turning the fridge back on.

Unless your serving pressure is 2psi, serving pressure at temp, 12psi@40F in my case, will carbonate to right around 2 volumes in a week and gives a cold conditioning time to the beer. Serving half the beer will still pressurize the headspace as the keg empties so long as the keg is hooked up to co2.

 

[grittanomyces]

But a can of beer stored on a store shelf, won't have half a can worth of headspace.

That's just a loose example to show that beer does not just go flat because of temperature change. A half-full can also wouldn't have a constant flow of CO2 and headspace occupied by it instead of oxygen.

 

[norwegianBrewer]

You have mentioned "dropping to serving pressure" twice now. What pressure is that exactly? I carb and serve under 12psi. If I were to reduce to say 4 to serve, and vent, the beer and headspace is going to equalize and eventually the beer will be undercarbed or not carbed at all. Two weeks sounds about right for this situation.

I force carbed it at 30 psi, and my serving pressure is 10 psi.