Temperature measurement Bezzera BZ07 PID - Page 2

by **bas** on Wed Jan 05, 2011 9:55 am

I'll let you know...and about temperature fetish...is more "nice to know"' than "need to know"...I never get sink shots with this machine...and I've discovered that at least as far as my taste buds are concerned I get the most variation in taste by changing dose and flow!

by **another_jim** on Wed Jan 05, 2011 2:08 pm

I wasn't accusing you of being a temperature geek -- on this board, we all are -- more a reminder for the people reading along on what to expect from this style machine, i.e. simple flush routines, but only limited control.

A long flush, 5 to 7 seconds past the boil, should drop the temperature down to around 90C. The volume of the HX is so small that the water in it heats almost instantly. This means I prefer no delay after the flush, and have the basket ready to go as soon as the flush is done.

by **saepl** on Wed Jan 05, 2011 2:19 pm

Jim, thanks for the detailed info on the differences between the Bezzera grouphead and the E61 grouphead. I am trying to learn as much as I can about the differences in these two groupheads so that I can make an informed purchase in about a year or so (as of right now I am really drawn to the BZ-10)

Sorry, don't want to go off topic but wanted to quickly say I appreciate the detailed info. Any more info like this would be greatly appreciated. Much is written about the E61 grouphead and not so much about the Bezzeras.

by **brokemusician77** on Wed Jan 05, 2011 2:40 pm

Been forever since I've posted on here, but I've been following this thread with a keen interest. I'm in the same boat. Really feeling the limitations of my Gaggia in terms of entertaining, but especially in terms of temperature stability.

I hope to upgrade within the year and I'm stalled between choosing the BZ02, BZ07 and the BZ07 with PID. Not knowing enough about HX's and PID's, I'm not sure how to interpret these findings. I guess I'm wondering what the verdict is after doing this kind of analysis.

Namely:
a.) Are these results what you'd expect to see from this machine?
b.) Do they indicate that the Bezzera stands out from other machines in this class/ price range?
c.) Does the data give any indication as to whether the PID is worth the extra expense?

by **another_jim** on Wed Jan 05, 2011 4:50 pm

The Bezzera and Elektra groups derive from an early 1980s Brasilia design that separated the group bell, consisting of a 10 hole dispersion block, shower screen, and PF slot, from the valving block that connects the group to the HX and three way valve. The bell mates to a second, 4 hole dispersion block in the valving block via three screws. This design has the advantage that you can create different kinds of valving block for different machines. The commercial Elektras and Bezzeras have thermosyphon blocks, the home Elektra and BZ02 have bolt to the boiler blocks, and the BZ07 has an electrically heated block that mounts on the exterior of the machine.

This design is light weight and holds very little water. The E61 designs are much more heavy, hold more water, and do preinfusion. This means the Brasila designs are easier to get to the right temperature, but are less thermally stable. One problem with almost all the home E61 machines (as opposed to the commercial ones) is that the thermosyphons do not have the required jets and valves to be properly tuned. This means the heads overheat and need long cooling flushes. If they were produced with the proper jetting, there would be much less of a niche for the alternatives.

In addition to these operating differences come taste differences. This is a lot more controversial, but I and most others who have done the comparision think the Brasilia style group does better with lower doses and clean SO style coffees, while the E61 groups do better with the high dose, heavy tasting Seattle style of espresso. To me, these differences are slight, both types of group can make excellent shots with any style of espresso; it's just a matter of which has the edge at what.

by **saepl** on Wed Jan 05, 2011 5:00 pm

The E61 designs are much more heavy, hold more water, and do preinfusion. This means the Brasila designs are easier to get to the right temperature, but are less thermally stable.

What does this mean in the "real world"? Faster warmup times for the Brasila design? Is the E61 more stable if pulling lots of shots in a row? Is it possible to notice a difference on either grouphead if you pull a shot every 5 to 15 minutes (as you might while hosting a dinner party)?

Very interesting stuff...

by **bas** on Wed Jan 05, 2011 6:19 pm

another_jim wrote:...This means I prefer no delay after the flush, and have the basket ready to go as soon as the flush is done.

@Jim: do you means you flush with a basket-less PF in place and watch the water dance at the spout?

Perhaps that's why there is a difference in flush length: I watch and listen to the flash boil at the screen without a PF (PF is already prepared with coffee and ready to go

),,,I can imagine that the PF mass cools down the water to a certain extent, so at the spout it'll settle down quicker...

Anyway, I'll shoot a video of a flash boil on my machine...

by **bas** on Thu Jan 06, 2011 8:43 am

another_jim wrote:A long flush, 5 to 7 seconds past the boil, should drop the temperature down to around 90C.

Today I flushed 5 seconds past flash boil (almost a 15 second flush; longer than any flush on my previous E61 HX machine :mrgreen:

)...immediately locked my PF and hit the brew button...just by taste: shot was a little cooler, moren balanced and more tasty...but interesting enough the flow was much more even in the 2nd half of my shot...

That makes me wonder if I'm not getting a flash boil in the 2nd half of my shot when I do only a quick 2-3 seconds screen flush...

I'll contact Bezzera: I spoke to some people and they all tell me the same story, e.g. no flash boil or just a few seconds with a comparable boiler pressure and GHT...

For the time being I'm going to use it as a "dragon HX"...like the Olympia Maximatic...

And yes: after about 10 seconds temperature drops during an unloaded flush:
t=0 --> T=90
t=5 --> T=96
t=10 --> T=98
t=15 --> T=96
t=20 --> T=92

by **cpreston** on Fri Jan 07, 2011 3:41 pm

I have a BZ07 PID and have run some temperature tests. (I had to modify my Scace puck slightly by machining it down a bit to clear the low headspace Bezzera group.) The OPV is set for 9 bar into a blind filter. Under test, the Scace flowed a little over the Scace standard 75 ml/30 sec.

My tests used 5 minutes total time between pulls. Kind of long, but I think I was getting less consistency when the period was much shorter than that. The time included about 45 sec with portafilter removed for loading. The BZ07 seemed to keep the same temperature behavior even if the time between shots was increased up to15 minutes or so.

My machine flash boils at for about 7 sec. at 1.1 bar with the group open.

The times below were measured at 1.5 bar, which I like for steaming performance. I've also tested with 1.1 bar, without finding a dramatic difference in behavior. For lower boiler pressure, shorten the flush times by a second or two.

Here are a few results per Scace device, 15 sec into shot:

- flushed until boiling stops: typically 203.5F.
- flushed until boiling stops +7 sec: typically 197F.
- flushed until boiling stop + 14 sec: typically 192.5F.

[edit- It later turned out my pump was not working quite right... after replacement, the flush times are now two or three seconds shorter for the same temps...]

Temps were generally repeatable within plus or minus about 1.5 degrees. All showed a rising temp through the shot, except for the highest temp shots which were flat. BTW I would not be confident that these measurements could be compared to any other kind of machine, particularly given the tight fit of the Scace device. But within the limits of my tasting ability, I would say they seem believable with real coffee.

Overall, the BZ07 seems to me to have a character pretty much as Jim S. described it.

Hope this is of some use.

by **bas** on Fri Jan 07, 2011 5:55 pm

thanks for your results!
seems to be the same behaviour as my machine!
and what I've been doing for the last couple of days: 5 sec. past flash boil...

interesting though that my machine had no or only a tiny flash boil before (as many people describe)...and these days 8 seconds with 1,3 bar boiler pressure and 7 seconds with 1,1 bar...

did you run some test shots WITHOUT any flush?

Bas

PS. just got a mail from someone who says he gets zero flash boil at 1,1 bar...maybe it has something to do with room temperature of scale build up...or too soft water...or altered boiler water volume...


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