Expobar Office Leva 2 - Brew pressure drop during extraction

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
zablaine
Posts: 8
Joined: 1 year ago

#1: Post by zablaine »

Machine

- Expobar Office Leva 2 (Dual Boiler w/ Heat Exchanger)
- Overview of the model: http://coffeetimex.wdfiles.com/local--f ... ardbcl.pdf

Symptom

- When pulling a shot at 9-10bar, the machine will occasionally lose pressure
- Pressure drop is sudden, accompanied with a change in the sound of the pump, and followed by pressure rebuilding (as if the pump had just started)
- Issue never happens with the blind portafilter basket
- Happens about 1 in ever 3-4 shots, seems to happen more consistently when the machine is thoroughly heated

Investigated So Far

- Initially assumed it was a failing vibe pump, so replaced it with a new one -- same issue continues
- Took apart and cleaned OPV, seems to be functioning normally
- Monitored the reservoir return hose during shot to confirm the OPV isn't the culprit -- when the shot loses pressure (drop happens) the normal flow of water from the OPV also drops to zero -- I believe this rules out a leaking OPV

Other Suspicions

- Autofill Valve / Solenoid -- could this be worn or sticking closed, or somehow losing power in a way that's causing it to close when it should be running?

Any help or troubleshooting ideas are greatly appreciated.

WWWired
Posts: 352
Joined: 5 years ago

#2: Post by WWWired »

Hi zablaine :) Great post and a brilliantly engineered and designed machine!

It appears a loss of resistance ("pressure") in the brew hydraulic pathway is being experienced, although the "loss of pressure" gauge reading is not indicated (it is assumed to drop below 9/10 bar?). One question to reveal more is whether the "change in the sound of the pump" mentioned is quieter/harder working or more-frequent/faster? If this is a drop in resistance ("pressure") in the brew hydraulic pathway a possible sharing of the fixed volume pressure vessel, that is the brew hydraulic pathway, with the atmosphere of the world ("yuuuge" as some ex-president might say) is worth considering. This could be a leaky gasket, fitting, o-ring, or a channel opening up in your coffee powder puck in your portafilter basket during extraction. If this drop in ability to maintain resistance in the hydraulic pathway is the fault cause, then finding the leak to the world's giant atmosphere will be the challenge. However, a bit of an initial test first might assist.

As described below in the Initial Diagnostic method, with the blind-backflush basket in place, lift the hose from the de-aerator-OPV/expansion valve to just out of the water reservoir fill hole so you can watch the water flow. Open your Group Lever and observe the flow from the de-aerator/OPV hose back into the water reservoir. If possible take a video and post here (or describe the result/observations) :)

Initial Diagnostic (process of elimination stage 1)
  1. Have a measuring cup/shot glass on hand that shows volume of ounces or millileters and timer with seconds;
  2. Put blind-backflush basket in portfilter and insert in Group;
  3. Lift OPV/hose out of water reservoir and hold at opening of reservoir fill hole;
  4. Activate Group Lever;
  5. Observe the initial flow from the OPV/Expansion hose. You could see the following:
    1. About 5 to 10 seconds of instant water flow from the de-aerator (connecting the pump and OPV);
    2. A brief 1/2 to 1 second (ish) slowing-stop of flow;
    3. A resumption of flow water flow from the OPV hose as the OPV begins shunting water to the reservoir above 9(ish) Bar. This OPV water shunt may appear as an increasing and drop in flow repetitively as the OPV spring is compressed and gasket-piston are manipulated to shunt the excess water pressure above 9 bar;
    4. At this point take the timer and ounces/milliliter measuring cup and while starting the timer begin letting the OPV water flow into the measuring cup until it reaches about 30 milliliters (ml) or 1 ounce . . . if this takes 11 or 12 seconds or so, reservoir to OPV leg of the hydraulic pathway should be good.
  6. Once this is completed and some information added to light the path and the possible faults narrowed, other components might be worth considering as needed, including a volumetric test from an open group (no portafilter in place) for 30 seconds to 1 minute to measure volume of water through the entire Brew Hydraulic Pathway. Also how old is this machine and when was the last time the E61 Grouphead was opened (*ALWAYS when the machine is cold and after pressure released) and the upper sleeve, filter screen, and jet valve inspected is worth considering placing on the menu.
Is there a water filter cartridge in place? If not, is the end of the hose straight cut or v-cut on the end? Below are two screenshot pictures from original post's linked source, credit to the incredible information from Bella Barista, showing the location of the de-aerator between the pump and OPV and the


Credit/Source: Bella Barista

User avatar
cafeIKE
Posts: 4684
Joined: 18 years ago

#3: Post by cafeIKE »

The block diagram is missing the steam boiler fill valve.

Sounds like the steam boiler is cooling enough to engage the steam element and/or boiler fill. This would drop the pump voltage and change sound.

How much is 'lose pressure' and for how long?

How long has the machine been on?

Do you steam whilst brewing?

Ever descaled? Could be scale on the steam boiler water level probe.

Make sure the air bleed hose is UP - not related to current problem, but less troublesome if it points up.

zablaine (original poster)
Posts: 8
Joined: 1 year ago

#4: Post by zablaine (original poster) »

Thanks so much for the detailed responses, and apologies for the delay in following up--I hadn't realized my notifications were turned off.

I took two videos with sound here: https://imgur.com/a/Uy0wWze:
- 1 of the pressure drop during extraction (there are actually two drops, one as pressure just starts to build, then another around the 23 second mark).
- 1 of the diagnostic test with the OPV hose into a shot glass

From the diagnostic test, the "slowing-stop" didn't seem to occur, but the volume reaches 30ml in around the right amount of time.
Sounds like the steam boiler is cooling enough to engage the steam element and/or boiler fill. This would drop the pump voltage and change sound.
^ This definitely seems worth investigating further, as I notice the issue most when steaming/pulling a shot simultaneously. That said, I've done so for the 8 years I have owned the machine and it's a new problem.

Additional questions that were asked:
- Filter cartridge -- none in place
- Machine is almost always on 6am-2pm
- "Lose pressure" means dropping from 10 bar to zero
- Descale about 1x per year

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cafeIKE
Posts: 4684
Joined: 18 years ago

#5: Post by cafeIKE »

8 years could be EoL for the pump.

Have you checked the electrical connections in the machine?

Any water leaks that could corrode terminals?

Any severely discolored wire or terminals?

zablaine (original poster)
Posts: 8
Joined: 1 year ago

#6: Post by zablaine (original poster) »

Pump is brand new, replaced it when this issue started assuming that was the culprit. Also recently replaced both heating coils and vacuum relief valve. No other signs of leakage etc.

User avatar
cafeIKE
Posts: 4684
Joined: 18 years ago

#7: Post by cafeIKE »

Does your pump have a thermistor?
Sometimes they do go bad.

You can run the pump without it to test and replace if faulty.


WWWired
Posts: 352
Joined: 5 years ago

#8: Post by WWWired »

Brilliant next step in the fault diagnosis by CafeIKE :) CafeIKE's insights and experience are epic!

Additional Observation:
Just reviewing the two amazing additional imgur videos provided by zablaine and perhaps others can offer insights on something notable that at about 20 seconds of the first video, as the steam tap is being closed, the red boiler light (on the right side of the machine below the hot water tap) suddenly shuts off. This coincides with the sudden pump shut-down as well and instantaneous drop in resistance measured on the Brew/HX hydraulic pathway gauge. The pump has two electrical possible fault locations with the Thermal Fuse (mentioned by CafeIKE) being the best consideration and the second being the Diode inside the pump molding developing a possible fault. Given the pump de-energization appears to coincide with the sudden de-energizing of the Steam Boiler's heating element (as indicated by the sudden turning off of the red light (on the right side of the machine) briefly, this may offer some further insights for experts like CafeIKE and other experienced folks here too :) There doesn't appear to be an interruption to other circuits as the main Power Switch (red large toggle on the upper left) and PID seem to stay fully powered. The question jiggling around possibly is what is causing this brief circuit failure in both the Steam Boiler Heating Element and Pump at the same moment, and then they both kick on at the same time a moment later, and yep, CafeIKE's Pump Thermal Fuse short is for sure one of the possible faults at the front of the que lol . . .
zablaine wrote: . . . I took two videos with sound . . .
From the diagnostic test, the "slowing-stop" didn't seem to occur, but the volume reaches 30ml in around the right amount of time.

^ This definitely seems worth investigating further, as I notice the issue most when steaming/pulling a shot simultaneously. That said, I've done so for the 8 years I have owned the machine and it's a new problem.

Additional questions that were asked:
- Filter cartridge -- none in place
- Machine is almost always on 6am-2pm
- "Lose pressure" means dropping from 10 bar to zero
- Descale about 1x per year
Awesome imgur videos and great summary by zablaine :) Appears when the E61 Lever is lifted, you get about 6 or so seconds of the de-aerator running followed by a short flow-cut-over of a second or so and then the OPV kicks in right on schedule and starts shunting the pumped water back through the reservoir return hose . . . and as you indicated, you got the 30ml in a near perfect amount of time.

Further Considerations (adding when time allows haha) :
  1. As the steam tap is turned down (apparently not completely closed as the frothing continues with reduced turbulence), it takes about a second or two and then what sounds like a Relay flip (*EDIT, see DefaultIT's post below re: solenoid dropout) can be heard and the Steam Boiler's Heating Element red light goes off and the pump de-energizes causing a sudden drop in resistance in the Brew/HX hydraulic pathway. I agree with zablaine's observation there was a sudden pressure drop when the steam tap was being closed. This operation of the steam-tap is a purely mechanical action. As the steam tap valve is closed, the sudden sealing of the Steam Boiler's fixed volume pressure vessel/hydraulic pathways occurs. The Steam Boiler is not regulated by the PID, but has a Pressurestat.
  2. Noting the hydraulic resistance on the Steam Boiler gauge is indicating just over 1.0 Bar approximately That should be enough to maintain the continuity necessary to continue energizing the Steam Boiler Heating Element . . . and yet the Steam Boiler's Heating Element (and the Pump) still got temporarily de-energized below 1.1 Bar (where the Healting Element should be switched to energized unless the water level is not touching the Steam Boiler's Water Level Probe, again in which case the pump should remain energized). The Steam Boiler pressure gauge does seem to eventually show recovery to over 1.2 Bar and shows a good 1.3 Bar in the second video. For a dual boiler, I seem to recall reading somewhere, possibly in a post by CafeIKE or one of the other geniuses here on HB haha, that perhaps 1.3 Bar might be a setting to consider for the Steam Boiler of a dual boiler machine. Thinking now you might have discovered an unusual design functional issue haha! The Steam Tap is reduced, but not closed, and it is at that time, it sounds like a Relay flips (Edit: See DefaultIT's post below re: Solenoid) and the Boiler Heating Element and Pump circuit are de-energized! Fascinating! What is causing this brief circuit energization issue with the Pump during the Steam Tap reduction/closure . . . Some of this may raise questions about the Steam Boiler's Pressurestat diaphragm function. Experience helps here and there are several true experts with vast experience here on HB who can narrow this much further;
  3. Yerp! Some great insights in another >>HB thread here<< (notice wiring schematic suggests 1.2 Bar cut-off for the shown dual boiler system and also I believe these pressurestat's cycle on about 0.1 bar set pressure variance) . . .
Does this only occur when the Steam Tap is reduced perhaps? Awesome transfer condition! Of course the entire reason for a dual boiler machine is to allow for uninterrupted steaming and brew extractions . . . would be fascinating if the electrical logic in the machine could result in a short interruption in the power to the pump circuit. Just having a closer look at the electrical schematics and photos of the Expobar Office Leva 2 relating to wiring and confident one of the brilliant experienced experts here will add more clarity as well soon!

*EDIT Yep, DefaultIT's post below indicating a possible Solenoid coil sound makes great sense (compared to a Relay flipping as mentioned above). Haha! Very interesting!

DefaultIT
Posts: 45
Joined: 2 years ago

#9: Post by DefaultIT »

In your video i can hear a solenoid valve firing... that is probably a boiler refill call, which is opening a solenoid valve, which is in turn releasing the pressure from the group head since there is just the one pump for both refill and brew purposes.

I would think that much less likely to happen if not steaming during extraction... my machine has an indicator light for boiler fills (inline with the fill valve), presumably so that you can avoid initiating a shot while that valve is open.... makes it easy to monitor what the control board is up to

zablaine (original poster)
Posts: 8
Joined: 1 year ago

#10: Post by zablaine (original poster) »

Great insight, thank you. Would raising the p-stat limit to increase the steam boiler pressure help avoid the pressure drop issue here? Anu risk to running the steam boiler a bit higher, say 1.4b?