G'day Guys, I'm trying to sort out a problem with a Bezzera BZ-40 which is being particularly fussy about the dosage. I'm finding channeling to be a major issue and the channels seem to coincide with the holes on the dispersion block (Bezzera call it a shower holder). The machine is fitted with a Procon pump and it's brewing at around 8.5 Bar, 60ml, 30 secs, double basket. I find I have to up-dose considerably and using a Mazzer Mini E the grind is somewhat finer than the "start here" point.

The free flow straight from the shower is 550ml in 30 secs which seems to me that there's no restriction in the line at all, and that's roughly what a Procon pump will flow at 0psi. When I got the machine the gicleur (Bezzera = jet) was missing completely so I machined one up from some available stainless 5mm thread however it wasn't quite concentric in the lathe when I did it and I reckon it's gone over-size (1mm drills and stainless are fun...NOT).

Just wondering on some thoughts from those who may be familiar with this or similar machines if I could be on the right track in suspecting the gicleur. Unfortunately Bezzera put their "jet" on the outlet of the HX and I had all sorts of grief getting that particular fitting to seal properly and since it's under constant line pressure I'm very reluctant to crack it again unless I'm pretty sure it's a likely candidate.

Incidentally, before somebody says it, yes I do know how to dose and tamp; it's the machine.

Cheers
Pete

I agree you're on the right track in suspecting the overenthusiastic water flow. IIRC, gicleurs range from 0.6 to 1.0mm. I don't know if this applies to your Bezzera, but a friend of mine had a Livia 90 and complained about how fussy it was. We thought it might be the 6 hole dispersion block wasn't doing the job, so he had the holes filled and then redrilled the block with 10 smaller ones. It helped quite a bit.

Thanks Dan, I had considered two options to modify the machine. One was to fit a second gicleur just above the "coupling ring" as Bezzera call it. The brass block it attaches to has a fitting which is threaded all the way through so I think I could be able to get one in there and it's often where they're fitted on other makes. The other is to completely machine up a new dispersion block, it's a fairly straight forward lathe job, with more/finer holes as you suggested. However the overwhelming thought in my mind is that it shouldn't be behaving as it is now, and before I begin modifying things I would like to get it working precisely as the manufacturer intended. I generally always try to go back to this base line, with pretty much everything I work on, as generally the manufacturer put quite a lot of R&D into their products and I figure they probably know a thing or two about the product

PeteF wrote:The free flow straight from the shower is 550ml in 30 secs

If you can get the free flow rate (what Al on alt.coffee used to call "water debit") down to 65-90ml in 10 seconds, your extractions will be more forgiving (IMO).

I recently purchased a similar machine. Are you aware of any electronic manual that is available for this machine which is a 1995 model. I cannot find one anywhere (see Need manual for 1995 Bezzera).
Turned machine on and pump runs but there is no filling of the boiler.
Thanks
JM

Thanks Andy, yeah that would seem about right just roughly eyeballing it, it seems to run at about twice the rate I would expect. I will try replacing my DIY gicleur with the Bezzera stock one, and if it's still flowing fast machine up one still smaller.

I'm not sure on any electronic "owners manual" however there are parts diagrams if that's what you may be after?

Pete

I machined up a new gicleur, this time 0.6mm. I use Loctite 567 I think it is, and find it works best if the machine is heated then turned off before the pressure builds as the loctite goes off faster/stronger. In the process I found the OPV was jammed closed which hopefully would explain why I kept blowing a joint seal on the HX inlet as the water expanded when idling!

I have still to pull any shots but did quickly do a flow check and it's now 300ml/30 sec which seems a little more reasonable but I must confess still higher than I was expecting for such a small gicleur. I would imagine most single group HX machines using the Procon would flow at around the same rate.

Look forward to cranking it up in anger come morning.

Pete

PeteF wrote:I have still to pull any shots but did quickly do a flow check and it's now 300ml/30 sec

Sounds better, still a touch on the high side.

The reasons that water debit is generally measured per 10 sec (eg, 75 ml/ 10 sec) are:
1. It puts more emphasis on the initial ramp to pressure, which is a significant factor
2. It saves 20 sec of your time per measurement!

FWIW, your actual brew pressure at the group will be a little less than before, because you'll have a greater pressure drop through the plumbing. Not a big deal, just something to be aware of. It may not show on your gauge, depending on where it senses pressure.

Interested to hear how it affects your espresso making. If you're up for more machining, it would be interesting to compare the results of the new 0.6 and a newer 0.5 mm. My experience is the smaller the gicleur, the finer the required grind. Up to a point, smaller gicleurs may improve the espresso by decreasing the degree of microchanneling. Smaller gicleurs also increase maintenance because they have a tendency to scale up faster.

That last item is NOT a positive.

BTW here's a picture of my gicleur: .

AndyS wrote:If you can get the free flow rate (what Al on alt.coffee used to call "water debit") down to 65-90ml in 10 seconds, your extractions will be more forgiving (IMO).

Given the machine configuration, it might be easier to install a delay-on-make relay and use line-pressure preinfusion. In that case, the larger water debit is what he'd want. This assumes that the line pressure is regulated someplace in the 2-3 bar range, of course.

Hi Pete -

Are you sure you have the "right" Procon pump installed? What does the brew pressure gage go to when you are doing this free-flow test?

BTW, a good friend who has a Quickmill Vetrano (original owner, excellent shape) flows 497 ml/min in a free-flow test.