Hi all,
You might remember me from the 'Silvia PID vs. Livietta' thread I started a month ago. It turns out I had the opportunity to buy a great condition 2-year old Oscar from a local seller who posts here at HB and I took the plunge. I've been trying to educate myself about machines, grinders, roasts, etc. for the purchasing phase, now it's time to learn about the ownership/usage/maintenance phase.

There appear to be quite a number of good resources here on temperature operation for HX machines, as well as some recommended cleaning habits I should get into. I'm also looking at the milk foaming tips in the resources part of this site.

The reason I started this thread was to find out any Oscar-specific tips and tricks I ought to know about, as well as anyone's real-life experience/recommendations for maintenance/foaming/cleaning, etc.

My first question, to start things off, is about the steps I ought to follow when pulling multiple consecutive shots. I know about the cooling flush after the machine has warmed up for an hour or so, but what do I need to do after I've just pulled one shot and am ready for another a minute or so later? Is it still necessary to wait for the boiler to heat up for a minute or so, then do another cooling flush?

As I said I'm a total newbie to the home espresso scene, and I'm looking forward to educating both my machine skills as well as my palate as I learn more.

Thanks all for the great resources here at H-B.

I've just pulled one shot and am ready for another a minute or so later? Is it still necessary to wait for the boiler to heat up for a minute or so, then do another cooling flush?

Yes...and yes.

If you did any steaming in between I would give it some more time. What you need to remember is the longer between shots the more volume you will flush (although it will be much smaller than after the machine has been at rest). You kind of want the steam boiler to have equalized its temperature again.

Here is some general times from memory when I was using my Oscar, this is just a starting point to get you in the ballpark, you will find what works best when you become more familiar with the machine.

If I were to pull back to back shots with no steaming...say around 1 1/2 minutes between shots (time to prep, grind, tamp) the flush would be maybe two seconds, watch the water dance from the group and it will end abruptly. I'd then pull the shot in 10-15 seconds time.

If I had steamed 4 to 6 ounces in a pitcher after a shot, I would allow the boiler to stabilze...say 3-4 minutes but then the HX circuit would still have absorbed more heat than during the quick shot sequence without the steaming in between...so you will be flushing more water through the group before the shot, say 5 seconds worth.

Hope this helps, as usual time and experience will give the best results!
Congrats on picking up a great machine!

So, after some time away on a business trip, I've now returned and gotten the chance to experiment with my new machine (and the Rocky doserless that arrived while I was away). So far things are going about as I expected, which is to say inconsistently.

One major question I have though, is that I've observed water leaking onto the counter from underneath the machine, both during a shot, and when backflushing. Is this a sign that the OPV valve is leaking into the bottom of the machine? I've noticed when I remove the drip tray that there is a red rubber tube on the left side and a clear one on the right that tend to get pushed into the interior of the machine when the tray goes back in. I'm trying to figure out a way to reliably remove/replace the tray such that this doesn't happen. I'm assuming this is where the water is coming from?

If indeed this is the case, do I need to turn the machine over and open her up to clean up anything from down there? If I do, is there anything I should check on while I'm in there?

Thanks for the help.

I service about a dozen Oscars and they seem to do well with multiple shots and steamings. The red heat light going out is the best indication on full steam pressure. Water in the bottom is bad. Have had two brains shorted from water. When filling water reservoir, ensure no water is spilled in the bottom. Also, the blow off tube should always be in the spill tray. Usually inserting the tray at an angle helps. Some tend to trip the overheat safety. Six screws in the top for access and push the little red button on the right side of the boiler. If you pull the sceen for clreaning, never tighten the screw beyond barely snug. Hope this helps.

Thanks for the post, Mike. I've been careful now to insert at an angle like you said (discovered that's the most repeatable way) and have had no drips for a couple of days in a row. I think I've got it figured out. Is there anything I need to do to open it up and inspect? I'm not sure I'd be able to do anything at this point besides clean up the few random grounds that might be in there from backflushing.
Also, what does the red tube on the left side do? Is it as important to have that in the drip tray as the clear one?

Thanks

Here's another question: I've been trying to figure out a proper dose/distribute/tamp routine, and noticed something a little odd. It seems that when I grind fine enough to have a shot in the ballpark of 25 seconds, I get water leaking out from the portafilter where it locks in, presumably due to either not a good enough seal (though the gasket was recently replaced), some coffee grounds not being completely cleaned from the rim before locking in place, too-fine a grind causing overpressure, or overdosing such that I can't get a good seal. Are there any indicators I should look for after a shot to see which one is the culprit?

Also, I've noticed that I have pretty watery pucks, and that when I do a cooling flush through an empty portafilter the water takes a couple seconds to stop flowing after the button is pushed. Is this any cause for concern?

TIA.

danetrainer wrote:If I had steamed 4 to 6 ounces in a pitcher after a shot, I would allow the boiler to stabilze...say 3-4 minutes but then the HX circuit would still have absorbed more heat than during the quick shot sequence without the steaming in between...so you will be flushing more water through the group before the shot, say 5 seconds worth.

I'm talking out of school as I've never used an Oscar, but 3-4 minutes seems like an awfully long time for boiler recovery. With a 1200w heater, 30 seconds should do it.

As a comparison the steam boiler on the Vibiemme Double Domo recovers from 1.1 bar to 1.5 bar in 18 seconds after steaming 250mL. The Vibiemme Double Domo has a 1000w heater on the 1.4L steam boiler.

As a test, I opened the steam valve until the pressure dropped from 1.5 to 0.7 bar [ more than 2 minutes ].
Even then, it only took 20 seconds to recover to 1.1 bar and 45 seconds to recover to 1.5 bar.

Leaking from the group seal may be caused by not cleaning the seal thoroughly enough, or possibly the seal itself is starting to fail. However, you said that it was recently replaced, so most likely it's just dirty from old coffee grounds. Have you been cleaning out the seal with a group brush or doing a PF wiggle with a backflush filter after every shot?

As for the wet puck issue, having some water on top of the puck is not necessarily a sign of a problem. Usually, you'll get a slightly wet puck if you use lower doses. Increasing the dose can give you a dry puck, but you may get other problems like channeling if the dose is too high.

I'm talking out of school as I've never used an Oscar, but 3-4 minutes seems like an awfully long time

Ian, the Oscar does have a large boiler (2L) and no boiler pressure gauge, although it had a light to show
the heater element operation (and a loud Sirai Pstat clicking off/on) I normally used that kind of time frame...
I'm not one to rush things when not necessary and like to allow temps to reach a stable state. Looking for consistent temps at the portafilter led me to that general time-line with it.

Beezer wrote:Leaking from the group seal may be caused by not cleaning the seal thoroughly enough, or possibly the seal itself is starting to fail. However, you said that it was recently replaced, so most likely it's just dirty from old coffee grounds. Have you been cleaning out the seal with a group brush or doing a PF wiggle with a backflush filter after every shot?

As for the wet puck issue, having some water on top of the puck is not necessarily a sign of a problem. Usually, you'll get a slightly wet puck if you use lower doses. Increasing the dose can give you a dry puck, but you may get other problems like channeling if the dose is too high.

Thanks!
I've got a group brush on the way, in the meantime just using a kitchen basting brush. I might try the portafilter wiggle as well with the blank filter. If I've got a good seal should I be able to run the backflush procedure with no leaking from around the edges, or is that too much to expect?