Posted Sun Dec 26, 2010, 11:56am Subject: Gaggia OWC mods
I recently aquired an Old White Coffee with steam knob on the front and thought I'd post some of the mods I'm thinking about doing.
The very cool thing (I thought) about the OWC is how well it steams - it just steams like crazy, much better than any of the newer Gaggia models. The steam valve is really good too, at least on mine - it doesn't leak and feels like a quality built valve that will probably last forever (it better since I doubt spares are available). Having the OPV and 3-way solenoid valve and better steaming and larger boiler in a metal case like the classic makes it interesting.
I've read that the larger boiler would be less temp stable because of the larger lower brass half of the boiler which isn't heated. But I believe that all that extra brass could actually be more stable than the newer boilers as long as you get it heated up properly - the lower half doesn't get as hot as fast (and doesn't heat up the portafilter as much) as the newer boilers but if you get it up to heat there is a lot more brass and more hot water inside the boiler to keep the temp stable. EXCEPT for one of the glaring mistakes in the design. The OPV bleeds hot water from the boiler instead of cool water from the feed line - big mistake.
The other problem is the lack of dispersion block - it's all one piece with a single hole that squirts a pit into the coffee puck for really fast channeling. This was pretty easy to solve, I cut a thin aluminum disc and put 8 holes around the radius and mounted it under the group and now I get no more of the channeling problem.
So ... back to the OPV. Bleeding off hot water from the boiler is a double whammy. It causes the boiler to cool down really quickly during the shot and it puts hot water back in the reservoir. The pump on this model (at least on mine) is much more powerful or at least has a lot higher flow rate than the newer pumps. So there is a lot more water being bled off by the OPV (more heat being lost from the boiler) and it is also very noisy.
Here's my plan. I've already got the channeling worked out with the aluminum disc I made. The OPV mounts at the same level as the cool water inlet and mounts onto a large casting in the boiler. There seems to be plenty of room on this casting to drill and tap a hole. Then I could move the cool water inlet fitting here and plug the original cool water inlet hole.
I know this seems a bit silly to invest time and energy on such an old machine that doesn't have parts available. But with those flaws corrected and the superior steaming and larger boiler capacity, it should be a pretty capable machine.
Has anyone ever tried relocating the water inlet as I'm proposing? Is anyone even still using the OWC?
randytsuch Senior Member Joined: 11 Jun 2009 Posts: 578 Location: LA, Ca Expertise: I like coffee
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Posted Sun Dec 26, 2010, 12:59pm Subject: Re: Gaggia OWC mods
I think some people at the gaggia users group still use the owc. There may even be one for sale, if you want to pick up a spare for parts.
In the mod directory of the file section there, someone has instructions for adding a quickmill opv to a gaggia. He used quick connect fittings, I have used this type of fitting in my Classic, and they worked fine for me too. You can buy 6mm teflon tubing from mcmaster, if you need some extra.
If you add the quickmill opv as shown, with a T and an adaptor, you could just crank up the existing opv, so it won't open at 9 bar. Then, you don't have to worry about plugging up a hole, you could just leave it there, and it won't have any effect.
Posted Sun Dec 26, 2010, 5:55pm Subject: Re: Gaggia OWC mods
Well ... it's a few hours later after the first post. I've been to the hardware store where I bought a Tap and a brass plug (already had the right size drill bit). I removed the elbow water inlet fitting and put in the brass plug, drilled a new hole in the casting below the OPV, tapped it and turned the original fitting in below the OPV.
I did have a heart stopping moment when I realized that The elbow fitting didn't quite clear the flange where the two halves of the boiler join - in case you need a visual, as I tried to turn the elbow fitting into the threads, the tip of the fitting hit into the flange and couldn't be turned any further - Doh! Fortunately it was only about 1mm too close and I was able to trim the flange easily with a dremel cutoff wheel. But if I were doing it again I would have drilled the hole a little further out on the casting.
How does it work? Terrific! The boiler holds the temp so much better during the shot and the water returning to the reservoir is fresh and cool.
I spent $7 on the tap and the plug - and the whole thing took less than an hour (I spent longer than that walking to the hardware store).
Reporting back the next day. Brought the OWC back to the office after the modification. Been pulling shots for coworkers and the temp stability is awesome now that the OPV no longer bleeds off hot water. The larger boiler works so much better than the newer models - it always was the best steaming of all the Gaggias but now it has better temp stability too.
With the dispersion disk I made, the top of the coffee puck looks beautiful without any signs of channeling like before. I wish I'd taken pictures of the mod - I may open her up again and take a pic of the boiler mod if anyone is interested in seeing how I did it.
Ive been obsessed with the addiction that is caffeine again while Im on break! I've been loving my new BUNN HG and it got me to dust off the old OWC! Mine was bought off ebay years ago and is in pristine condition! The pump is so strong Ireally have to adjust the grind or it blows through the grinds! I've been wondering how to fix the grouphead sparay problem PLEASE show me your mods I would like to duplicate them on mine! I was considering doing the same of plugging the OPV hole then moving the valve and readjusting it. My OPV has the wierd slot with the pin in the center so adjusting it is difficult. I also need to purchase a good portafilter so I can test the pressure. Come to think of it I have a grangaggia that I'm going to take the OPV valve off of and put it on the OWC. It comes off the pump its like this one HERE hmmm
OK ... I'll take some pictures and see if I can figure out how to post them here. Rather than moving the OPV, I left the OPV right where it was and moved the incoming water fitting. It sounds like it would be easier to go the other way - but there isn't a lot of room to add T-fittings and another OPV where the water inlet was on the stock boiler - the brew tstat is right above the original fitting and the boiler heater connection sticks out there too. It was really a lot easier to do it the way I did - but my method requires a drill, drill bit and a tap. I already had the drill and bit so I only had to buy a tap and a brass plug - $7 total cost.
Then, for the dispersion screen, I simply cut a disc out of a beer can with a pair of sissors using the showerscreen as a template. I dimpled the disc on both sides (so it wouldn't act like a reed valve and block the hole when backflushing) and put this between the group and showerhead. It's very low tech but works really well.
Here is a pic of the dispersion disc I made. It's ugly - but I deliberately made it with a very rough, dimpled surface on both sides. The first disc I made was smooth with nice, round holes but it acted like a reed valve and when you finished the shot it didn't allow the pressure to run back and drain into the drip tray - so you had a very wet puck and couldn't backflush properly. Making the disc all dimpled like that keeps it from pressing directly against either the showerscreen or the grouphead and allows a little space.
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