Lelit Bianca grouphead backflushing frequency

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Ecrew888

Postby Ecrew888 » Jan 13, 2019, 8:07 pm

Hi, I am a newbie on this forum! I have a question on the group head flushing, I have about 170 total count on the LCC shot counter since December, I do clean the brew head and use the brush in between every shot. How often do I need to perform back flushing? Another question is does the LCC shot counter triggers and counts every time when I pull the lever that determines PAR or TOT? Sometimes I just pull the lever to run the water, I think it will not count as a shot until it meets a minimum duration on the timer before it count as a shot?

Thanks

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another_jim
Team HB

Postby another_jim » Jan 13, 2019, 10:02 pm

Lelit says the needle valve needs more frequent backflushes than an ordinary E61; maybe every two weeks rather than every month. No idea about the shot counter: it's a feature of some use in commercial environments; but not really for the home.
Jim Schulman

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Jake_G

Postby Jake_G » replying to another_jim » Jan 14, 2019, 12:00 am

I wonder what logic makes Lelit come to that conclusion.

That it needs better water, and perhaps the occasional removal and soak to descale, sure. But what do they expect a chemical backflush to do to a needle valve located upstream of the brew valve? Since the brew valve is closed tight long before the exhaust valve is open, the needle valve never gets a drop of chemical cleaning during any type of backflush activities. I'm confident a backflush would be as effective at cleaning the needle valve as it is cleaning the pump... :?

Cheers!

- Jake

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another_jim
Team HB

Postby another_jim » Jan 14, 2019, 2:26 am

I'm simply relaying what I was told by their engineers. Presumably the brew valve is open while the levetta is up for the backflush. They may be under the fantastic impression osmosis also works for detergent :wink:
Jim Schulman

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Jake_G

Postby Jake_G » Jan 14, 2019, 2:58 am

Touché

:oops:

Ecrew888

Postby Ecrew888 » Yesterday, 1:25 am

Thanks guys, I back flushed with Cafiza tonight and followed with 3grams of detergent and 10sec on/off with 5 cycles. During the back flush cycle, I felt the lever was getting high resistance to pull up? Maybe the pressure built up? After I finished the cleaning process, the lever came back down to normal. Does it supposed to do that?

Thanks

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another_jim
Team HB

Postby another_jim » Yesterday, 1:44 am

On E61s, the lever gets stiff because the detergent removes the coffee oils. Regular 3 way valves also get stiff, but since they are actuated by a magnet, you can't feel it. Think of it as squeaky clean :wink:

In any case, it'll be back to normal after a few shots.
Jim Schulman

Ecrew888

Postby Ecrew888 » Yesterday, 1:56 am

Jim,

Thanks for the info, I already made a shot! This machine is much more fun to play with the shot profiling and taste way better compared to my old Delonghi Perfecta!

Graham J

Postby Graham J » Yesterday, 3:40 pm

Jake_G wrote:I wonder what logic makes Lelit come to that conclusion.

That it needs better water, and perhaps the occasional removal and soak to descale, sure. But what do they expect a chemical backflush to do to a needle valve located upstream of the brew valve? Since the brew valve is closed tight long before the exhaust valve is open, the needle valve never gets a drop of chemical cleaning during any type of backflush activities. I'm confident a backflush would be as effective at cleaning the needle valve as it is cleaning the pump... :?


Backflushing with Cafiza or similar detergents will help remove coffee oils from the all the water flow areas upstream of the filter screen, to the cam and the exhaust valves. As Jim points out, the brew valve is open for the 10 second flush time, so some turbulent flow and mixing may (or may not) occur up inside the mushroom and back to the needle valve. Cycling the brew valve stem up and down 5 times (backflush cycles) in this pressurised fluid will probably result in some detergent solution being injected into the mushroom valve chamber and hence the needle valve.

None of this will descale any part of the E61 group or needle valve though, these detergent solutions don't affect mineral scaling.

I've posted here some photos of my Bianca valve assembly, after 1014 shot cycles. Mine is a medium hardness water area and I've used the Lelit water filters and changed them as the counter on the water tank calls up. They are chunky little water cartridges and I'm not so dismissive of them. I've dried and weighed them before and after their life cycle and they do accumulate a significant load of non solubles. As you can see the valve and surrounding parts are building a fine film of scale, but its not enough to affect valve flow rates yet (I measure them for set valve positions) which are still as original.

Answering (eventually) a question from Jake_G, the valve has 1mm of travel in 180 degrees of paddle movement, so quite a coarse pitch, but the valve is actually a taper in a jet, with a ground taper on the stem, with 0.1mm of reduction in diameter, over this travel (not super accurate measurement, but sufficient for user info).

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Graham J

Postby Graham J » Yesterday, 3:45 pm

Image