[hopfenundmalz]

^^^^
An advantage to the closed loop system is that, as you rack by gravity, when beer flows out of the gas post when the keg is full, it will only rise in the gas return tube until the levels equalize.   You don't have to keep a wary eye out for the moment beer comes through.  At one point I used this method, but currently use CO2 pressure to move the beer so I don't have to lift the fermenter above the keg; but it is a completely closed system and a very elegant solution.

To BrewBama's point about opening the fermenter to dry hop:  there have been some discussions about ways around this on the forum, and I do recall hopfenundmalz (Jeff Rankert) has posted about using a Blichman Hop Rocket in the manner of Sierra Nevada's Torpedo, "rocking" the beer back and forth between two kegs.  A search of the forum should turn up any details he offered.

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Yes, I have done it.

Use whole hops, up to 4 oz. Purge the Hoprocket and lines with CO2. Rack from keg to purged keg through the purged Hoprocket.Transfers take some time, and you may have to go back and forth several passes through the hops. The hop aroma is vibrant. I don't do it all of the time, but I have been thinking about doing it again

[kramerog]

Additionally, when draining beer from the fermenter drain port into the keg ‘out’ post, I like to return a line from the keg ‘in’ post to the fermenter air lock port in an effort to close the CO2 loop. Otherwise, air will displace beer in the fermenter as you drain the beer into the keg increasing odds of oxidation. 

I’ve seen others connect the CO2 tank to the fermenter air lock port and push the beer into the keg using *very* low pressure while opening the keg PRV but that seems slightly risky to me especially if your fermenter is not rated for pressurization. I definitely wouldn’t do it with glass as a matter of principle.

Some will even catch the beer a few points prior to full attenuation, transfer it to a CO2 purged keg and spund to further reduce the possibility of oxygen. Spunding adds the benefit of carbonating the beer as well.

The problem comes from opening the oxygen purged keg to dry hop. I prefer whirlpool additions and hop stands in the kettle vs keg dry hop. ...but then again I’m not really a ‘hop head’. I don’t know how to dry hop without opening the keg — maybe a Randal in-line to transfer from one keg to another or something... but it’s a non issue for me.


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+1 on the return line.  I dry hop in the keg.  I wait until the wort transfer is done.  I open the hatch and throw in a bag of hops and purge the headspace 4 or 5+ times with CO2.  Since only the headspace is has to be purged it is quick and easy to purge a bunch of times.