For quite some time now (2 months or so) I cannot help but feel that steam power on my Oscar has diminished continuously. It is one of these phenomena where you cannot quite put your finger on exactly when or how it started. But one day you realize something's afoot and has been for some time. Actually it was not the change in steam power I noticed, but that I had inadvertently been turning open the knob some more than I used to. The Oscar steam knob has a ridge which always used to be horizontal when I was steaming along, about a quarter turn from full throttle. Over these past weeks I have been nearing vertical, and thus full throttle. If things go on like this there is no more turning to do and I'll end up with a serious no-foam problem

At first I thought it might be a consequence of an exchanged pressurestat in October. My Ceme broke on holiday (in Italy )and was replaced by a Mater (at absurd cost, but unfortunately I had no tools with me). I thought maybe the Mater has a different deadband and somehow this would contribute to a change in steam level. That would explain a one off change in steam power if any, but it continued to go down.

Next thought was scale in the steam path. My strictly non-scientific, non-techie mind tells me that "impeded" steam is not necessarily diminished (the contrary even), but then who am I to know. So, off came the steam tubing, valve etc. starting from the boiler. It looked absolutely clean to me, but went into a citric acid bath nonetheless. Alas, to no avail.

Fill probe maybe? Maybe those Italian mechanics tampered with it? Off goes the cover. The probe is all the way in, that in my book should provide max steam. But - trial 'n' error - I drew it out a centimetre or so. No change.

Mmm ... I haven't got any more ideas to be honest. Maybe you guys have something up your sleeve. The whole thing doesn't make any sense to me. The Oscar as you may be aware has no boiler pressure manometer, so I have to rely on the styrofoam cup temp measurement. Temp is quite the same as ever, which, given identical fill probe seating and descaled steam path, should mean same steam power. It doesn't though.

Your input is very much appreciated by
Sheygetz

my vote is scale on boiler ( less boiler volume ) or pressurestat ( its either set lower now than before, or the adjuster is loose and is slipping )

Thanks for your opinion, 2xlp.
Actually the fact that the steam path was virtually scale-free made me postpone plans for an in situ descaling of boiler and HX.
If this ps was set lower than its predecessor, it would not produce the same temp as the other one did, or would it? The adjusting screw does not slip, X marks the spot I set it to.

Sheygetz

hmmm.. have ya poked the holes in the steam tip lately? they could be filling up.. easy enough to do with a paper clip.

also i read in a thread that i cant find at the moment about the probe length being counter intuitive for some reason there is more steaming power/stamina with the probe pull out (less head space) than pushed in (more head space)

also possibly in a related sense is that boiling water takes up more volume than cold water. during normal operation your hot water is touching the probe.

you turn off machine.. the water shrinks and now the probe isnt touching the water.

you turn your machine on and it fills back up to the probe with COLD water which becomes hot and expands PAST the probe, this also creates a situation with less head space you have more steaming power.

but this changes because the water gets used and gradually you get more headspace for the steam and then at some point the boiler refills with hot water already in the boiler and already expanded. now the water is not past the probe . it is touching the bottom of the probe (less head space) less or variable steaming pressure that you notice.

the solution i read about called for.

heating your machine.

then before you steam, make it "ask" for water by letting out water from the hot water tap, just enough to make it refill. this will create a situation where you will always have the same amount of headspace of steam.

i hope that makes sense.

jon

I make a point of cleaning the steam tip every time it's used and cannot recall any of the holes ever getting stuck with residue, maybe the Oscar steam tip isn't prone to clog.

I could not quite follow the bit about the probe and the hot and cold water, but suffice it to say, I've tried the probe at three different settings, all in, almost out and "somewhere inbetween" (not exactly scientific, I know). It did not change steam power. In theory it changes steam duration, but as I only ever steam for 1 cappu, I couldn't say and it hardly matters to me.

One other finding though: With the probe all the way in, the need to bleed false pressure off the Oscar is all but gone. If allowed to heat for, say, an hour, you get "real" steam right away, the group and pf are hot alright. So, if you just take off a little steam to get the heater running once more, you'll notice it goes off again by the time you've ground your coffee - and you're ready to shoot. On the other hand, if the probe is far out and you open the steam valve after an hours heating, all you get is a whiff of air, but hardly any steam at all. After bleeding it will take like 10 min to build up proper steam and - worse - another 10 to properly heat.

Sheygetz

sheygetz wrote:I make a point of cleaning the steam tip every time it's used and cannot recall any of the holes ever getting stuck with residue, maybe the Oscar steam tip isn't prone to clog.

wiping the outside and spraying steam out is no substitue for a good hole poking..

trust me.. its easy to bend a paper clip and poke the holes.. then spray steam stream onto some white paper.. any chunkies come out?? what do you have to lose 20 seconds of time?

on the other part. look around on here it is well known that the probe length can control steam power, and steam duration. i think i saw it said that its position can impact brew temps also.

DaveC wrote:P.S. To be honest and not to overthink the whole issue, you might just want to measure half way down your boiler and stick the probe in that far, or possibly 40% in (e.g. boiler 25cm high, stick the probe in 10 cm). In all likelihood this will actually be fine. Just remember the HX rule for boilers of this configuration.

The lower the water level = hotter the brew temp & weaker steaming (in terms of stamina)
The higher the water level = cooler brew temps and stronger steaming (in terms of stamina)

perhaps the opposite of what you would expect...but true.

from http://www.home-barista.com/espresso-machines/need-help-with-expobar-probe-length-t2668.html#p31291

hope that helps.

jon