Pygmalion In a rotary pumped machine, odd things can happen because the water goes into a sealed system through a 1 way valve. The expansion valve in that sealed system is set to 12 to 14 bar.
In your system it’s the expansion valve as you correctly say controlling the pressure, so there is an upper limit….not really sure…am cogitatingt. I even though perhaps air in the capillary tube, but that wouldn’t case the problem you’re getting.
Morning all, I noticed this morning that I have the exact same thing happen! Preheated for about 40 mins, purged for 3-5 seconds out of the hot water tap, waited a minute or 2, puled a shot with a 10 second preinfusion at 2 bar, after the 10 seconds it shot up to 10-10.5 bar before dropping back to 8.5.
Subsequent shots only reached 8.5 bar after PI (I did another 2, one for my wife, the other for ‘science’, aka my second double before 0700 what could go wrong).
The strange thing is, the timings were all exaclty the same, 16g in, 33 out in 33 seconds. I’m wondering if it’s more of an issue with the display then with the valve?
I’ve possibly got some friends coming over tomorrow for a pre/post run brew so if I do more then 3 shots I’ll pay close attention to the needle and report back…
I’ve thought about what might be happening by imagineering how I this could be created if one wanted to do so. and looking at the way the Elizabeths were made (factory photos of first production run…I can’t see how it can happen, or be made to happen, unless i’m missing something. The repositioning of the expansion valve is still within the sealed brew area, and they changed it for a much better and reachable/adjustable valve.
The V2 I had which I modified to a V3 still; has the old valve, as you can see from my review photos, and hydraulically is in essentially the same position (if not physically)
https://coffeeequipmentreviews.wordpress.com/2020/05/08/lelit-elizabeth/
So here is the image, just to orient people
As you can see 1, 2 and 4 , all form part of the sealed brew circuit. The expansion valve is directly connected to the boiler, whatever pressure is experienced by the coffee, the same pressure is seen by 1, 2 and 4. The other numbered components take no part in this. The component under the autofill solenoid (3) is what does the steam preinfusion and incidently takes part in the clever way the machine does hot water. This component can’t have any impact as it still only feeds into the same sealed brew circuit controlled by the expansion valve.
This means any thermal expansion of water would be controlled ultimately by the expansion valve. My only possible conclusion is perhaps a shock wave caused by any slight airspace and water hammer due to closing of valves? Perhaps someone could try switching of bloom phase and steam preinfusion, just have a straight shot…then see if it happens
Do you mean turn off the steam boiler or just not have any preinfusion? If so I got it just now with just a stright shot, no 10 second bloom, just 8.5 bars. It still spiked up to about 10 bars and the second shot rose to 8.5 and stopped.
Del_UK Do you mean turn off the steam boiler or just not have any preinfusion? If so I got it just now with just a stright shot, no 10 second bloom, just 8.5 bars. It still spiked up to about 10 bars and the second shot rose to 8.5 and stopped.
Everything off, probably even steam boiler (even though it shouldn’t matter)…but certainly both preinfusion functions (one is referred to as bloom phase). Effectively turning it into a dumb machine.
If it still does it, more evidence for a water hammer effect due to air…well that’s the theory.
P.S. If you turn off steam boiler…wait until it’s below 100C
Thanks for all the continued feedback and interesting information, everyone. Also glad (sort of) to hear I’m not alone.
DavecUK, this happens even when using no preinfusion of any kind, and also with steam boiler off and cool.
I will keep an eye on mine. I never noticed this. But then again, I only have one coffee in the morning, and one in the afternoon. If there’s any testing I could do, please just let me know. 👍
Pygmalion If that is the case, I can only assume it must be a transient water hammer effect type of thing due to air? I would expect it to have no impact on the shot.
Any chance of video of it doing it?
Hi, all. Here is a video showing the inconsistent pressure with the blind basket. There are three shots total here about a minute apart:
Here is another one that just shows a single shot with coffee, showing the initial spike, subsequent drop, then slow decline. But, the pressures here are generally above what the blind basket shows after a few shots on the first video.
Also, here is a video made by someone else showing very similar behavior to mine (found on a different forum):
DavecUK: if it is due to some air somewhere in the system, do you think it would be possible to bleed it out somehow?
Thanks for the offer to experiment, @MediumRoastSteam!
Here is a simple experiment you could try. Turn on your Elizabeth and allow to come up to full temp without running the pump at all. Insert blind basket into the portafilter and then engage the pump with no preinfusion (may or may not matter). Watch the pressure reading. Does it spike and then settle, or does it move to a consistent value? What value? Then disengage the pump and wait a minute or two for the system to read OK and temp to maybe rebound. Then repeat. Does the pressure behave the same way as the first time, or does it settle to a different value?
Pygmalion DavecUK: if it is due to some air somewhere in the system, do you think it would be possible to bleed it out somehow?
Probably not and with coffee in I am surprised the effect was as sustained as it was unless the coffee was quite a tight grind. Also when I say air and water hammer, I would expect the effect to be very transient. Air itself compresses to feck all at 9 or 10 bar….which would cause the hammer and can be fairly quickl;y absorbed at those pressures..
In your first video, what happens if you repeat the experiment, but fill the blank portafilter basked with cold water and carefully lock it into the group, spilling as little as possible.
Otherwise I’m mostly out of ideas.
Nope I’m a little stumped. We can eliminate heat effects, if someone wants to disconnect the brew boiler heating elements, turn the steam boiler off then repeat the blind basket experiments.
Pygmalion Here is a simple experiment you could try.
Done!
The temperature was at 96C because it was on at the end of the heat up cycle towards 93C. For the sake of the experiment, on the subsequent shot, I have set the temp to 96C, let it get here and set it back to 93C.
On the subsequent shot, I emptied the blind basket before starting, so both are from the same starting point. They were taken approx. 7 minutes apart. I also did one with the basket full of water, and the behaviour is the same overall, with the exception that, as expected, it reaches the target pressure faster.
When using coffee rather than the blind basket, the behaviour is the same, but the pressure gradually goes down to approx. 8.75 bar on the dial over the course of 35 seconds, as expected.
From cold:
7 minutes later:
This is an older video where it shows a coffee pour. This was when the Elizabeth’s pressure was set at 10 bar. But you can see the behaviour of the gradual pressure reduction. These days is the same, but at 9 bar or thereabouts.
With coffee (older video):
Hope the above is helpful.
I pulled a shot with no PI, it went to 11 bar then gradually decreased to approximately 9.5 until the end of the shot. I filled the blind basket to the brim with cold water and hit button 1 again (no PI), it went up to 11 bar and stayed there until I stopped the shot. Is it that the opv is tuned to 11 bar (in my case here) and simply reduces as the puck gets extracted? I don’t see an issue really or is this different to the OP’s issue? I had noticed this recently but didn’t worry, as the coffee still tasting great
JahLaza pulled a shot with no PI, it went to 11 bar then gradually decreased to approximately 9.5 until the end of the shot. I filled the blind basket to the brim with cold water and hit button 1 again (no PI), it went up to 11 bar and stayed there until I stopped the shot. Is it that the opv is tuned to 11 bar (in my case here) and simply reduces as the puck gets extracted?
If this is the consistent behaviour, it could indeed be that your expansion valve pressure needs reducing, try reducing it to 9.5 bar against a blind filter and see how you get on.
Yeah, ok, thanks both. I wonder if there’s any need to reduce it at all? I had read somewhere the difference between 9 and 10 bar isn’t worth talking about would you advise to reduce it a bar or so in my case?
JahLaza would you advise to reduce it a bar or so in my case?
Try it, it’s very easy. Only your taste buds will tell. 😊
Thanks for running the experiment, @MediumRoastSteam ! Glad yours is working normally.
I tried the experiment with the blind basket initially full of water, and the behavior was still there with no notable change except for attaining pressure sooner, as expected.
I have opened a ticket both with my reseller and Lelit directly, to see if they can assist. But in the meantime, if anyone else has any theories I’d love to hear them.
Pygmalion out of curiosity, what water do you guys feed your machine with?
Reduced it to 9.5bar with blind filter (yes it was a very easy action!) just pulled a shot, it still went up to 10.5 bar at start of shot but maintained about 9.5 bar from about 13 secs. Tastes great, not sure if there’s a difference, fuller body I think maybe. Apologies if I’ve slightly diverged from the thread topic folks, interesting all the same🤔
