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Air Bubbles in pickup tube on V2B.. is this a wild theory?
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Discussions > Espresso > Machines > Air Bubbles in...  
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DavecUK
Senior Member


Joined: 21 Sep 2005
Posts: 1,466
Location: UK
Expertise: I love coffee

Posted Wed Apr 2, 2014, 4:06pm
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

DeanOK Said:

Do you think hooking it to municipal water would solve the issue?.

Posted April 2, 2014 link

Yes, absolutely.  

Also glad you liked the remote power up solution, which could help in the short to medium term. I think though even if it was plumbed in, for anyone with a varied schedule, it totally makes sense to get one.
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sharky
Senior Member
sharky
Joined: 9 Jan 2013
Posts: 190
Location: Calgary, AB
Expertise: I love coffee

Espresso: QM Vetrano 2B
Grinder: Compak K3 Touch
Posted Thu Apr 3, 2014, 4:09am
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

DavecUK Said:

Leaving any prosumer machine on and not drawing water through it for 24 to 36 hours is not really good....Unless the seals are all perfect. This applies to DB or HX machines. With Vibe pumps, you won't really notice anything much.

in fact if I had your schedule, I would probably be looking for this type of solution.

http://www.belkin.com/uk/p/P-F7C027/

It would allow you to simply switch the machine off or on whenever you want and from wherever you are, or put it on a schedule.

Posted April 2, 2014 link



DaveUK, what a bloody, brilliant device!  I believe this is the answer for DeanOK and his machine!  I am not sure why anyone would ever want to leave their machine on for 24+ hours at a time with no usage, anyways?
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DavecUK
Senior Member


Joined: 21 Sep 2005
Posts: 1,466
Location: UK
Expertise: I love coffee

Posted Thu Apr 3, 2014, 5:29am
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

I only found out about them when I was searching for a relay to convert a machine to have wifi on/off internally. So the whole device could be inside the machine. I never went through to the step of buying one though, because an all steel "faraday cage", probably wouldn't allow it to work. Also the plug in ones are more useful.
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schwaggy
Senior Member


Joined: 5 Apr 2013
Posts: 20
Location: Seattle
Expertise: I live coffee

Espresso: Alex Duetto III
Grinder: Mazzer Mini E Type A w/ SJ...
Posted Thu Apr 3, 2014, 11:34am
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

I've been using a the Belkin WeMo with my Duetto 3 for almost a year.
While it has mixed reviews, especially in regards to it staying connected to WiFi, I have nary an issue with it.
My Duetto has stayed on the same power schedule with the WeMo and it's been amazing.
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DeanOK
Senior Member
DeanOK
Joined: 24 Sep 2012
Posts: 720
Location: OK
Expertise: I like coffee

Espresso: QM Vetrano 2B
Grinder: Vario W
Posted Thu Apr 3, 2014, 3:17pm
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

sharky Said:

DaveUK, what a bloody, brilliant device!  I believe this is the answer for DeanOK and his machine!  I am not sure why anyone would ever want to leave their machine on for 24+ hours at a time with no usage, anyways?

Posted April 3, 2014 link

There is a lot of home coffee makers that are designed to stay on (hot) all of the time ... the Bunn BX series is one that I know of.  Once those insulated tanks are hot, it takes very little energy to keep them warm. My utility company has a online utility to look at your energy use on a 15 minute basis and I can tell you it doesn't cost me but just a few dollars per month to keep mine on all of the time. The water is already hot, your just adding back the heat that escapes when sitting idle. My personal opinion is that this may cause less loading of the heating elements with minerals because the element itself doesn't have to get so hot to keep the water warm as it would if it started with a cold boiler every morning.. I can't prove it, but I suspect it.
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pShoe
Senior Member


Joined: 13 Nov 2012
Posts: 57
Location: Fort Lauderdale
Expertise: I love coffee

Posted Sat Apr 5, 2014, 11:12am
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

I'm happy to report back that the chirping stopped. I just adjusted the OPV back and forth a little before setting it back to normal. For whatever reason, that was the trick. I was kinda hoping by now that the off set for the US version could have been independently verified. I have yet to adjust the offset, but think I will experiment with Dave's recommend off sets soon.

If our offset is incorrect, a brew temp set at 203 would be closer to 209. I think there would be more steam and other signs that it was at 209 instead of 203. I think there might be just enough differences between the V2B and the Verona that both offsets are difference but correct.
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Dave_E
Senior Member


Joined: 25 Mar 2014
Posts: 50
Location: Edmonton, Canada
Expertise: I love coffee

Espresso: NS Appia, Rocket Cellini
Grinder: Mazzer Major, Compak k3
Posted Sat Apr 5, 2014, 2:34pm
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

Glad you got it fixed - just a quick note on bubble formation:

The formation of bubbles depends on how much and how long you have suction (negative water pressure) in your line.  Cavitation is a weird thing in that the actual cavitation pressure of water is not really known.  Before you trolls jump up and start screaming - the tensile strength of water on a molecular level is still a mystery to scientists.  I am a soil scientist/engineer (PhD in soil mechanics) who specializes in soil suction.  What you are witnessing (if it is indeed due to suction) is what we refer to as cavitation nuclei.  This means that during periods of extended sub-zero pressure within the draw tube; say a siphon, occluded air bubbles that fill the tiny voids in the seemingly smooth plastic tube, come out of their imperfections and coalesce together to form a bigger bubble.

I have done experiments where a small suction was applied to a plastic tube - say -20 kPa; no where near the atmospheric pressure that would cause "cavitation" (-100 kPa) and given a period of 24 hours or more, bubbles of appreciable size would form in the tube being tested.  This is a very real phenomenon and will eventually result in a loss in suction as the bubble breaks the tension in the water line.

Now if those bubbles were to be drawn into the pump, then yes the intermittent flow rates can damage the pump in the long term as most pumps are designed to be run "wet" at all times.  That said, I am not familiar with what kind of pump is in the machine and whether it is vibratory (where occasional bubbles may not affect it very much) or a rotary vane pump (which does).  If you have a rotary pump, you will want to make sure that you minimize the cavitation nuclei (read bubbles) to ensure you do not damage your pump long term.  

See this article on the pump types.  http://www.1st-line.com/cofffact/vibration-vs-rotary.htm
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DavecUK
Senior Member


Joined: 21 Sep 2005
Posts: 1,466
Location: UK
Expertise: I love coffee

Posted Mon Apr 7, 2014, 1:07am
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

pShoe Said:

I'm happy to report back that the chirping stopped. I just adjusted the OPV back and forth a little before setting it back to normal. For whatever reason, that was the trick. I was kinda hoping by now that the off set for the US version could have been independently verified. I have yet to adjust the offset, but think I will experiment with Dave's recommend off sets soon.

If our offset is incorrect, a brew temp set at 203 would be closer to 209. I think there would be more steam and other signs that it was at 209 instead of 203. I think there might be just enough differences between the V2B and the Verona that both offsets are difference but correct.

Posted April 5, 2014 link

I use about 11.5 on my specific machine, but if you want to be sure simply set your machine (with it's US offset) to a brew temperature of 210F, wait 60m and pull some water through the group......what happens
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DeanOK
Senior Member
DeanOK
Joined: 24 Sep 2012
Posts: 720
Location: OK
Expertise: I like coffee

Espresso: QM Vetrano 2B
Grinder: Vario W
Posted Mon Apr 7, 2014, 5:03pm
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

This thread seems to have a pretty broad spectrum of conversations going on, but I wanted to get back to brew temperature.

I don't really know why there is a difference in offset between the European version of the Vetrano and what CCS decided to use in the US, but I have found myself back at CCS's settings.

My homemade temperature device is almost identical in function to this one:
http://www.espressoparts.com/EP_THERMOFILTER1

... and I am getting temperatures a couple of degrees lower than the brew temperature display when using the CCS's offset when I do a warming flush. Without the warming flush, it starts out a little lower than I think it should. Maybe it is the mass of the blind basket I have the K thermocouple installed in causing that, but I do have a layer of silicone in the bottom of the basket it insulate the probe from the mass of the basket. A short warming shot does take care of it and makes the shot pretty stable throughout if I have a flow rate of about 2 oz in 25 seconds.  I have checked the calibration of my K thermocouple in boiling water and adjusted it for my 1000 ft elevation and I feel that I am very close with my measurements.  

At the end of the day, I am not telling anyone where they should run their offset. Maybe I have strange tastes.... who knows.  Since I don't drink straight espresso, I may not even be the one to ask... I know I have had some great tasting milk drinks. The good news is that high or low brew temperature won't kill anyone, so experiment away. I would love to hear the different opinions about where everyone ends up!
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pShoe
Senior Member


Joined: 13 Nov 2012
Posts: 57
Location: Fort Lauderdale
Expertise: I love coffee

Posted Mon Apr 7, 2014, 6:21pm
Subject: Re: Air Bubbles in pickup tube on V2B.. is this a wild theory?
 

Here is a video of the US CCS off set with the brew temp set to 210. Machine was allowed to warm up 60 mins and the brew temp displayed 210 while water was ran through the group (twice).

Thoughts?
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