Cooling flush of a (HX) Heat Exchanger Machine

[Koffee_Kosmo]

Cooling flush of a (HX) Heat Exchanger Machine

In the last month I have been conducting experiments on the best technique to achieve a cooling flush of my Bezzera HX machine

Two things needed to be achieved
Most important this technique had to be easily repeatable
Be able to tell the correct amount to cool with visual references

I normally leave my Bezzera on for 18 hours a day
It could be left unused from 1 hour to 5 hours between shots

The cooling flush method that I have come to rely on was

Method
Place and lock PF with basket fitted but without coffee grinds on group head
Place a container under PF spout to catch the scalding water

Turn on to start cooling flush
At the start you will see a bubbling gusher of water with steam escaping
At the middle of the flush water will slow and settle bubbles will diminish
At the last part of the flush the water trickle will resemble a coffee shot being pulled (this is your visual ref)
Stop cooling flush at this point

Times and water amount discharged will change dependent on how long the machine is idle

I then start the grind and tamp procedure and pull the shot as normal

The experiment was conducted using a Synesso filter basket and the standard Bezzera filter basket. I achieved a repeatable technique with visual references with both.

Testers Required
I would like CS members to test this method on there own HX machines to see if this method works for you as well as it did for me, and report back with your findings

Many Thanks [smiley=dankk2.gif]
Koffee Kosmo

[Thundergod]

Re: Cooling flush of a (HX) Heat Exchanger Machine

I basically do the same except I flush just before locking in the pf because it doesnt take very long and then theres no time variable if my grind/tamp procedure timing varies slightly.

Also I dont lock in the pf to flush or catch the water in a separate container as the drip tray on the Expobar is huge.

[Koffee_Kosmo]

Re: Cooling flush of a (HX) Heat Exchanger Machine

I basically do the same except I flush just before locking in the pf because it doesnt take very long and then theres no time variable if my grind/tamp procedure timing varies slightly.

Also I dont lock in the pf to flush or catch the water in a separate container as the drip tray on the Expobar is huge.

Yea that was how I did my cooling flush

I just wanted to develop an easy method for people that are unsure how to go about it
Well the new method works and works well

TG I value your opinion, please give it a try and tell us what you think?

KK

[Thundergod]

Re: Cooling flush of a (HX) Heat Exchanger Machine

I think there nothing wrong with how you are doing it.
The slight difference to how I do it is negligible and would come down to personal preference.

In fact, sometimes Ill give it a preliminary flush if its been idle for a long time becuase then I know Ill only get steam for a few seconds so it becomes more of a pre-routine thing.

Then Ill start.
Grind
Dose
Flush
Shot

[chartres]

Re: Cooling flush of a (HX) Heat Exchanger Machine

Method
Place and lock PF with basket fitted but without coffee grinds on group head

...

I wonder if you dry the PF basket before putting coffee in it, because otherwise its all moist. I am also pretty sure in this case you probably also need to take the basket out and dry the inside of PF...?
or are you using another PF, not the one you use for coffee?

[Koffee_Kosmo]

Re: Cooling flush of a (HX) Heat Exchanger Machine

Method
Place and lock PF with basket fitted but without coffee grinds on group head

...

I wonder if you dry the PF basket before putting coffee in it, because otherwise its all moist. I am also pretty sure in this case you probably also need to take the basket out and dry the inside of PF...?
or are you using another PF, not the one you use for coffee?

Hi charters

Just wipe dry the filter basket is all thats required
Shake off any water from inside the PF
Then grind,dose & pull shot

No need to dismantle the PF to dry it (think of cafes making 100s of cups a day)

KK

[roknee]

Re: Cooling flush of a (HX) Heat Exchanger Machine

hey KK

im wondering if it would still be pretty easy to water dance without the pf in place. i know what you mean by watching the wtare exit the spouts, but i do this without the pf in place, which works for me.

this would save you from having to shake out all that excess water caught in the pf under the basket. theres usually a fair bit of water that gets stuck in my pf unless i shake it and angle the pf down and to one side to allow all that to escape...

[Thundergod]

Re: Cooling flush of a (HX) Heat Exchanger Machine

Good point roknee; the spluttering is easy to see without a pf in place.

[Koffee_Kosmo]

Re: Cooling flush of a (HX) Heat Exchanger Machine

hey KK

im wondering if it would still be pretty easy to water dance without the pf in place. i know what you mean by watching the wtare exit the spouts, but i do this without the pf in place, which works for me.

this would save you from having to shake out all that excess water caught in the pf under the basket. theres usually a fair bit of water that gets stuck in my pf unless i shake it and angle the pf down and to one side to allow all that to escape...

Yes ronkee what you do is the accepted method
I also did this and can continue to do
However this was an experiment to see what results would come from a different method

Just to see if it is workable as it is very accurate time and time again
Shaking the PF dry is a small inconvenience

KK

[luca]

Re: Cooling flush of a (HX) Heat Exchanger Machine

Hi KK,

I think that this will kinda work with my machine, but the importer had the thermosyphon tricked out so that you dont have to futz around with it. I just do a tiny flush and go.

A few seconds difference doesnt really seem to make much difference. In fact, for some reason, the temp doesnt really drop that much with a free flush. I made a pressurised basket that I use to pull blind shots to decrease the brew temperature.

Cheers,

Luca

[Sparky]

Re: Cooling flush of a (HX) Heat Exchanger Machine

I think these techniques depend very much on the machine. For example, the Pav (La Pavoni Bar T2) doesnt bubble or splutter at all. I vary the flush time to suit the bean Im using. Generally darker roasts require longer flushes. For my lighter roasts like the PNG Wahgi, theres only a minor flush to purge the HX lines. In this machine setting the proper boiler pressure is most important, because you really cant flush them down too far.

OTOH, with my previous Bezzera BZ35, after the water dance, each second flush resulted in a 2 degree drop (from memory) in brew temp (as measured with a thermofilter-type device.). This is probably closer to most home machines in operation due to the much smaller HX volume. However, Lucas machine seems to be a good example of how different these machines can behave.

Cheers,

Mark.

[Koffee_Kosmo]

Re: Cooling flush of a (HX) Heat Exchanger Machine

Yea Luca and Sparky
You are both right in saying that it is machine dependent
And what mods a particular machine has to make it operate differently to the norm

So the conclusion so far is
What works for me may not work for others

Well it was worth a try don’t you think

KK

[chartres]

Re: Cooling flush of a (HX) Heat Exchanger Machine

Hi KK,

I think that this will kinda work with my machine, but the importer had the thermosyphon tricked out so that you dont have to futz around with it.  I just do a tiny flush and go.  

even if the machine was idle for few hours? just double checking... I have the same machine (Makin, that is) and its kind of nice to know that its that stable in temperature.
Visually, however, it splatters for few seconds so I do a longer flush, usually... I guess its just "to be sure to be sure"

[luca]

Re: Cooling flush of a (HX) Heat Exchanger Machine

Hi KK,

I think that this will kinda work with my machine, but the importer had the thermosyphon tricked out so that you dont have to futz around with it.  I just do a tiny flush and go.  

even if the machine was idle for few hours? just double checking... I have the same machine (Makin, that is) and its kind of nice to know that its that stable in temperature.
Visually, however, it splatters for few seconds so I do a longer flush, usually... I guess its just "to be sure to be sure"

My machine stays on 24/7, which means that the machine might sit for 15 hours between shots.  Yes, yes; I know - I need to find my timer!  I have never needed to do more than a tiny flush, and I cant really remember it spluttering much ... it might do it a little; Ill have to check next time.  I must confess that I am pretty lazy in my standard flush routine; I treat the machine like a Marzocco and just do a small flush at some random time before brewing.

I borrowed a scace device about six months ago and the results indicated that a longer flush was not required.  Indeed, I wonder if a flush is required at all.  In terms of measurements, I have only done testing on one afternoon and I have only tested my machine, so I cant personally confirm scace results for more than my particular machine.  The temperature was pretty much identical for shots pulled at a reasonable pace - ie. allowing time to grind, dose and tamp in between.  Shots pulled back to back were subsequently a degree or two cooler each time.  Thats how I came up with the pressurised portafilter idea for lowering brew temperature.  Im yet to get on the scace to confirm that it works.

I descale my machine a few times a year and use a brita filter in addition to the standard filter, which I recharge every few months, so I doubt that there is scale slowing down the thermosyphon on my machine.  

I remember that the tweaked thermosyphon was one of the things that Dave really wanted his machine to have and I did note that the machine had it when I was working at Veneziano and introduced the machine to the board.  From memory, at the time the only other domestic machines that I could find out online that had a similar setup were the Expobars.  So I have to confess that its a bit of a surprise to me that this seems to be news to you ... especially seeing as you have one of the machines.  I always thought that the lack of futzing around was a good selling point for it.

I am currently drinking Coffee Supremes Supreme blend, so I have the pstat up a tiny bit higher than usual (1.3 bar).  I cant remember if I get some spluttering or not, but my technique is still just to flush for two seconds or so and not to worry about it too much.  I am currently drinking a very nice long black produced using this technique.  It is nice and rounded, with what might be an unpleasantly strong acidity at a lower temperature (like 1.1 bar) converted to a nice juicy quality.

Could I ask what boiler pressure you are running?

Cheers,

Luca

[chartres]

Re: Cooling flush of a (HX) Heat Exchanger Machine

[quote

I am currently drinking Coffee Supremes Supreme blend, so I have the pstat up a tiny bit higher than usual (1.3 bar).  I cant remember if I get some spluttering or not, but my technique is still just to flush for two seconds or so and not to worry about it too much.  I am currently drinking a very nice long black produced using this technique.  It is nice and rounded, with what might be an unpleasantly strong acidity at a lower temperature (like 1.1 bar) converted to a nice juicy quality.

Could I ask what boiler pressure you are running?

Cheers,

Luca

Luca,
I didnt change pstat setting from what was initially set. The gauge is showing approximately 1.1 (actually it almost like 1.05). I did notice that some blends were not particularly, well, at their full potential when I brew them, comparing to when I had them in cafe (if I did have chance to compare). However, all in all I am happy with how, for example, BBB espresso blend or Veneziano Concordia work for me...

What I didnt do, I didnt compare shots with tiny and longer flushes... maybe I should do that. Is not that I have a lot of splattering, but the water flow from the group without p/f is definitely steadier after 10sec comparing to, say, 3sec flush

How I bought the machine - its a different story, the one I bought initially wasnt this one, I had to return it and negotiate upgrade with the seller to the best available at the store. Which by several accounts was Maver Makin espresso. I never regretted that decision, though ;-) By the way, review at your blog was one of the opinions I took into account. Somehow you earned my trust with your posts here ;-)