120ft Coil Question

[miboyd]

I have a 120ft coil jockey box which I lent to my friend for his birthday last week. I set it all up before I left and it was all working fine. Plenty of ice, water covering the coil, about 25psi of pressure (CO2) and it was pouring beautifully.
It continued nicely for about 2hours and 3/4 of a keg before it started pouring foam. I got a call and went over to check it out. They said that they didn't think anyone touched it or had messed around with it. I checked the gas and all the connections and everything seemed OK. But it still poured foam for me. Then about 20-30mins later after leaving it to settle it started pouring good beer again.

But we continued to have trouble for the rest of the night with foam on and off... without knowing what the problem was it was really frustrating. The keg got finished but that wasn't the point.

What could this have been?

At one stage I noticed some air/gas bubbles near both ends of the beer jumper line between keg and jockey box. They weren't big and they didn't last long but I just thought I'd mention that too.

Thanks in advance for any help!

[Hophead]

Only once have I had some strange things happen like that when using my 120ft coil box. I never did figure it out. In my case, about 1/2 way through the keg, I was getting spitting and sputtering but there was plenty of beer left in the keg. Since it's never happened since, I just figured there was something wrong with the keg.

Air bubbles in the line, though, is never a good thing. I find that I might start out pouring from a relatively cool and full keg at say, 25 PSI, and then about every 1/2 hour or so, I increase the pressure a couple of pounds to compensate for the beer warming up in the keg since I don't ice down the keg.

[Dirtbag]

25 psi is too much applied pressure on the keg for co2, you need to run that thing at about 15psig max.

I suspect that you did not get any foam for the first 3/4 of the keg because the beer was super cold in an ice bath of 120 feet of coil, by the time it got to the glass it was probably 33 or 34 degrees. When beer gets too cold it will suppress foam and give little head.

The keg was overcarbonated from the time it was first tapped by the evidence of the last quarter of the keg being all foam. You ran some through the coil and let it sit for a while, the temp dropped and suppressed the foam enough to pour.

The colder the beer gets the less co2 will absorb into it causing less foam and head (suppressing the foam), and if the temp continues to drop it will turn to solid and freeze.

[TAPMAN]

A jockey box with a 120 ft coil should be running at about 30 to 35 lbs of pressure. I woudn't worry about over carbonation if you are using the keg for a 1 day party. However, I wouldn't plan on using the keg the next day.Then you are talking about over carbonation. Tapman

[Hophead]

Dirtbag, 15 PSI would barely get the beer to flow through all the resistance of a 120 Ft coil. The whole jockey box/coil thing really goes against all the draft rules but it's works very well in "most" cases. There's just no way to avoid overcarbonation with a 120ft coil. But that's not usually a problem because the only reason to use a coil that length is if you plan to pour a lot of beer or want to pour off a room temp keg in less than 24 hours.

Tapman, even though I start at about 25 PSI, by the time I'm near the end of the keg, I've adjusted the pressure up to about 30-33 PSI.

[Dirtbag]

Yes you guys are right, 120ft of coil at 15 psi doesn't make sense. I think if I could use a blended gas I would.

[miboyd]

OK well now I'm confused.

I was running around 25psi and then ran into trouble with the last quarter of the keg. If I run it any faster i.e. 30-35psi then it is too fast and foams anyway. I think it foams at 30-35psi because when you turn the tap on it shoots out built up pressure and then slows back down to the proper pour rate at 30psi. I can see the beer line from the keg to the jockey box "jump" when I turn the tap on and off at this high pressure. Because the first second or so of the pour just shoots out really fast, it foams up as it hits the cup and the cup is full almost instantly.

Does anyone have this trouble at 30-35psi? That's why I was running happily at 25 until the last little bit went wrong... I'd really like to solve this and Dirtbag your first reply seemed to make sense - I just don't know about the amount of resistance. I did try pouring some left over beer (overcarbonated and warm not through ice) at 15psi to see if it would push it out the coil and it seemed to pour perfectly! So is there any reason why it wouldn't do this when it is fresh beer running through an ice-cold box?

All your help is greatly appreciated!

[miboyd]

So at what pressure does the keg become over carbonated?

If I get a fresh keg and experiment from 15psi upwards, at what point is the keg going to be over carbonated?

Is there anything wrong with pouring the beer slower if it still pours OK? Other than it taking longer does the gas affect it at all?

Thanks...

[Hophead]

It depends on the beer itself as well as the temperature of the beer.

The simple answer - anything above 12-14 PSI will begin to overcarbonate a keg.

I'm just guessing here but I suppose that running too little pressure in a 120ft coil system would cause problems as well because 15 PSI at the keg is not going to be 15 PSI at the faucet - much less in fact - and there could be problem with the carbonation coming out of the beer as it leaves the faucet (foam).