Thermostat and CO2 usage

The way I understand the CO2 regulator is that it maintains set keg pressure by adding CO2 if the pressure drops and purging CO2 if pressure increases.
My keezer is set at 3C (37.4F) - 5C (41F), 12PSI - normally.
There must be some expansion and contraction (and therefore changes in pressure) of the beer and CO2 in the keg as the keezer cycles between the two temps.
Am I using CO2 each cold cycle ?
How sensitive is the reg. (kegconn.) to pressure changes ?
How big a change in temp is required to affect pressure to the extent the regulator purges excess pressure ?

purging CO2 if pressure increases.

Click to expand...

No, regulators can't do this.

I think you are way over thinking this. And a regulator doesn't purge if the pressure goes up. If you are worried about it, get a temperature controller that is more sensitive. I think you can do a Love or even PID type controller with a 1 degree differential compared to the 4 degree differential on the analog ones.

Some regs actually DO release extra pressure...but most don't, as others have noted above...(only the fancy ones do!).

I wouldn't worry, you are just fine. The beer has a shyte-ton of thermal mass, so even though your fridge air temps cycle by ±3°F, your beer temp is most likely ±0.5°F or less.

Thanks guys.

Yes some regulators do purge. The 3 I'm using on my kegerator do this. They were very old Cornelius regulators ( actually soda regulators) I bought as a lot off eBay. There is probably a 4-5 psi gap before it will purge. There is a hole on the front of the regulator where it releases co2.