# Cooling flush HX



## thesmileyone (Sep 27, 2016)

Whats the deal with HX's and having to cool flush them?

I ask because I have been watching youtube videos and...these people don't seem to require to CF their HX machines.

For example:






The only disadvantage I can see is he can't steam and pour his shot at the same time like an R58 could.

Am I missing something here?


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## MediumRoastSteam (Jul 7, 2015)

thesmileyone said:


> The only disadvantage I can see is he can't steam and pour his shot at the same time like an R58 could.
> 
> Am I missing something here?


You can pull a shot and steam at the same time with an HX machine.

Re: cooling flush. It's all relative. Boiler pressure, time it's been idle, etc etc. I had a Rocket HX before and would require a CF about 100-150ml. Some say they don't need one at all.

I believe it when I see it for real, as my experience tells me otherwise.


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## kennyboy993 (Jan 23, 2017)

If we're talking about after the machine has stood idle then unless there's a specific design built in to the machine, by the laws of physics all HX have to CF.

I think the Oscar musica it might be - is the only one that has something built in to avoid it. I can only imagine the HX pipes are empty until shot pull time, who knows. Even then I'd be suspicious.

Even with carefully designed hx tube lengths and widths like on ECM machines - still there's super heated water in there too hot for brewing after 3 mins or so.


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## 4085 (Nov 23, 2012)

Unlsss they have a thermo syphon


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## igm45 (Mar 5, 2017)

dfk41 said:


> Unlsss they have a thermo syphon


My machine has a thermo syphon. I've often wondered, what does this mean?


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## 4085 (Nov 23, 2012)

igm45 said:


> My machine has a thermo syphon. I've often wondered, what does this mean?


In an HX, the water sits in the pipes between the group and boiler, hence the need for a cooling flush. On a TS. the water loops in a continuous cycle between the 2.....so in theory it is always at the correct temp. It is possible for it to stall so even though my L1 has one I still flush a couple of ounces through if it has stood idle for 30 mins just to ensure the syphon kick starts


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## igm45 (Mar 5, 2017)

dfk41 said:


> In an HX, the water sits in the pipes between the group and boiler, hence the need for a cooling flush. On a TS. the water loops in a continuous cycle between the 2.....so in theory it is always at the correct temp. It is possible for it to stall so even though my L1 has one I still flush a couple of ounces through if it has stood idle for 30 mins just to ensure the syphon kick starts


Do most hx have TS? Or is this a special function of the one I bought? If so that was complete fluke!


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## 4085 (Nov 23, 2012)

The odd o e does but not having one defines an HX. Well done!


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## DaveP (Jul 14, 2017)

igm45 said:


> My machine has a thermo syphon. I've often wondered, what does this mean?


Its a part of the internal plumbing that 'can' achieve maximum temperature stability in the group head.....

But .. a few factors can influence the temperature that's stable, (maybe stable to high or to low) like height above sea level and stuff.

I've never measured the temperature (maybe I should,) but always give a flush... old habits die hard


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## u2jewel (Aug 17, 2017)

Thermo siphon is part of all E61 Grouphead design and its variants. By variants, I mean designs from companies like ECM, who have a modified E61 head (the mushroom)

Whether it is single Boiler, HX or dual boiler; if the Grouphead is an E61 variant, then it would have this circuit of pipe going between the boiler and Grouphead to maintain temperature stability.

I'm not totally sure, but I believe all hx machines need cooling flush after some time in idle standby. Even if it is an E61 head, it still needs cf. The Thermo siphon can help keep the temp up, but cannot bring it lower than the boiler water temp. Single Boiler and dual borders don't need flushing.


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## 4085 (Nov 23, 2012)

A TS is a loop running from the boiler to the group and back again. It continually cycles the water in a loop. It is not a standard part of E61 design and it is responsible for in theory, not having to flush. The trouble being that the TS can stall so the water does not loop and unlike a flush on an HX to reduce the water temp a short flush on a TS machine is to make sure it is cycling properly. An Orchestrale Nota is an expensive HX machine that has a TS system built in. I am not an expert but I cannot think of any other HX machines off the top of my head that have this, though there are bound to be some


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## MediumRoastSteam (Jul 7, 2015)

I think @u2jewel is talking about: http://coffeetime.wikidot.com/e61-thermosyphon

Does the Nota have something different @dfk41?


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## 4085 (Nov 23, 2012)

MediumRoastSteam said:


> I think @u2jewel is talking about: http://coffeetime.wikidot.com/e61-thermosyphon
> 
> Does the Nota have something different @dfk41?


Yep, it is a traditional HX with a proper thermosyphon system installed completely doing away with cooling flushes


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## u2jewel (Aug 17, 2017)

My knowledge is limited to Rockets, Bezzera and ECM (and by extension Profitec), but any espresso machine with Grouphead sticking out of the front panel (like a toilet seat ) needs a method of keeping that massive block of metal heated. Some don't go the Thermo siphon route, like the BZ series of Bezzera, where instead of hot water from the boiler, they resorts to using electrical cartridges for heating.

Keeping it piping hot might help making tasty coffee, but jeez, number of times I've burnt myself on that damn piping hot Bell-end!  (mainly because of squirters from crotchless pf, and being an ocd clean-freak, I've got to get those brown spots off the shiny surface immediately)


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## u2jewel (Aug 17, 2017)

Talking of Nota..

On the ground floor of the building I live in, there's a brand new Cafe with a brand new 2-group Orchestrale (not sure model name.. Just recognized the distinctively Orchestrale design)

It will, by my reckoning, go on sale very soon, judging by the number of espressos they serve daily  (hint, single digit)


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## thesmileyone (Sep 27, 2016)

So really it is irrelevant because most people do a flush anyway to get the grouphead and shower curtain etc up to temperature before a shot don't they? I know I do on my Gaggia.

I thought CF's were something to do with the steam temp being a different temp to shot temps.


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## u2jewel (Aug 17, 2017)

thesmileyone said:


> So really it is irrelevant because most people do a flush anyway to get the grouphead and shower curtain etc up to temperature before a shot don't they? I know I do on my Gaggia.
> 
> I thought CF's were something to do with the steam temp being a different temp to shot temps.


Operation routine probably varies from model to model. Tbh I don't know the Gaggia routine.

As @DFK pointed out, well designed HX machines might not require CF before every use.

Re-reading your original post at the start, you questioned why some YouTubers don't CF on HX machines. The clips of videos you've seen are exactly that. Clips of real events, not the whole event from the moment of last use. The likelihood that the machine had been in recent use before shooting the clip probably answers why.

It goes without saying, but you can see people using HX without CF, but you can't taste what they just made to verify. If the HX machine is well designed (thus not needing regular CF), or, ought to CF but choose not to because a) they cannot be bothered, b) cannot taste difference; then it won't be a permanent or mandatory step in espresso making routine.

Again, I cannot say for sure because it isn't as if I have tested all hx machines in the world, but the very nature of its concept and design makes the first shot (after considerable idling) badly needing a CF. Thermosiphon or not.

You mention yourself as a Gaggia user, so making a huge assumption that yours is a Classic, thus not an HX; is that what many users do? Not a cooling flush, but a heating flush? I guess heating or cooling, flush is a flush

Circling back a bit, since quite a few of popular espresso machines' designs/layout are E61 variants, as long as the E61 variant isn't an HX (in another words single or dual boiler machines) then flushing to manipulate brew water temperature isn't part of any standard routine.

Popular Gaggias and Breville/Sage (just to name some of the big players) don't use E61 design; these need heating flush? If so, I didn't know (you learn something everyday!)


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## DaveP (Jul 14, 2017)

thesmileyone said:


> So really it is irrelevant because most people do a flush anyway to get the grouphead and shower curtain etc up to temperature before a shot don't they? I know I do on my Gaggia.
> 
> I thought CF's were something to do with the steam temp being a different temp to shot temps.


The reverse is also true.... getting the grouphead down to temperature, as different machines have different plumbing and temperature can rise when idling, the steam being a different boiler / plumbing (kinda)


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## espressotechno (Apr 11, 2011)

Google "Espresso heat exchanger diagrams" or similar for lots of schematics. Be careful though, some of them are weird & wonderful (!)


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## kennyboy993 (Jan 23, 2017)

Yep jewel is right - the only way that rocket on the vid didn't flash boil is because it was CF off camera or it was still warming up from cold


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## Dylan (Dec 5, 2011)

@dfk41 - how does a loop of water coming from a boiler sitting at well above boiling temp keep the group stable?

Something that has always confused me... unless you are looping in cold water then surely any circulation of water should be too hot? At what point does the water cool to the appropriate temp?


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## 4085 (Nov 23, 2012)

Who do me! It the point I was making is that an HX just sits there and a TS runs a loop. After that, it takes N expert!


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## DaveP (Jul 14, 2017)

Dylan said:


> @dfk41 - how does a loop of water coming from a boiler sitting at well above boiling temp keep the group stable?
> 
> Something that has always confused me... unless you are looping in cold water then surely any circulation of water should be too hot? At what point does the water cool to the appropriate temp?


In a hot water boiler loop.... it starts as 'hot and cold' but the thermodynamic flow quickly progresses to 'hot and not as hot' .. if there is any tempature difference then the flow will continue until there isn't.

Mr Boyle and lots of others did some teckie work on the subject https://en.wikipedia.org/wiki/Thermodynamics

But a question arises... is it that hotter rises, or is it that cooler falls, lol

Here's a diagram of a grouphead that has two connections and allows a 'flow'











> At what point does the water cool to the appropriate temp?


When one does the Cooling Flush


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## Dylan (Dec 5, 2011)

In so far as I can tell, that is a bog standard HX design - so if there is some type of thermosyphon that aids cooling beyond the standard e61 design then I would be interested to know how it works.

I know a few machines have an extra gicleur in the thermosyphon to restrict the circulation to try and limit overheating (although I saw little to no difference after fitting one of these.) but many machines claim their HX designs simply have the group always at the correct temperature and require no flush, I struggle to understand how these work if they do not bring in cold water as the only source of heat in a HX machine is way too hot.


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## u2jewel (Aug 17, 2017)

@Dylan

From what I've read and researched (mid to higher end prosumer level; what I was in the market for), as you say, unless there is an ingenious design that totally evaded my research, I'm not aware of such system that cools Grouphead and brings down brewing temp water without cf.

Also, since the source of flash boiling is combo effect of super hot head and super hot water inside the hx tube coming together (nearly identical to steam boiler water just outside of that hx tube wall) I'm not surprised any clever gicleur didn't make much difference. It sure might help reduce the effect, but not rid of the problem.

Now, what the super high end machines do and have.. No idea. I've yet to go down that upgrade route!

Out of curiosity, which company(ies) claim no cf is required? Claiming something is one thing. Grinder company not saying anything about purging (because strictly speaking, I guess it isn't mandatory) is another. Well, actually, I guess cf isn't mandatory...you'll still get espresso brewed at scorching temperatures.


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## MediumRoastSteam (Jul 7, 2015)

u2jewel said:


> @Dylan
> 
> From what I've read and researched (mid to higher end prosumer level; what I was in the market for), as you say, unless there is an ingenious design that totally evaded my research, I'm not aware of such system that cools Grouphead and brings down brewing temp water without cf.
> 
> ...


There are people here who own Fracino machines and they say it does not require s cooling flush. I remember someone even saying that Fracino engineers treat CF as a design flaw and their machines don't require one. Have a search on the forum.


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## u2jewel (Aug 17, 2017)

MediumRoastSteam said:


> There are people here who own Fracino machines and they say it does not require s cooling flush. I remember someone even saying that Fracino engineers treat CF as a design flaw and their machines don't require one. Have a search on the forum.


Will do. Thanks 

From mid point of my shopping research my attention turned to dual boilers and machines available from Bella Barista. Good opportunity to do some reading on them, out of curiosity


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## Dylan (Dec 5, 2011)

Yea I think I was thinking of Fracino when I wrote the above - although I think it is something other machines claim as well.

@dfk41's feedback on the Orchestrale Nota was that it was exceptionally stable and basically required no flush, but I think it too achieves this via a simple flow restrictor within the thermosyphon. Perhaps it is simply the size of the thermosyphon loop in tandem with restricted flow that allows the temperature to be managed.

I think the confusion lies with the thermosyphon itself being used as a reason for a lack of cooling flush, when as far as I understand it the thermosyphon is a part of the design of just about every HX machine.

I would guess Fracino probably also use a flow restrictor to achieve the same thing as their designs are nothing out of the ordinary.


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## kennyboy993 (Jan 23, 2017)

A modern, high end prosumer HX like my ecm mechanika achieves desired temp by heating new water as it passes through the HX pipes and then on in to the group head where it gets heated more.

And then as it comes out of the head it's a good temp for brewing. This is by design and the HX tube lengths are tuned to balance it just right along with the extra heating the group head does.

So this means it's critical that a CF is done first as the whole thing is designed to heat new (cool) water just in time.

So boiler temp influences brew temp but as long as it's within a certain range brew temp is fine.

On my machine the group head is heated by water circulating through it from the main boiler - I'm not sure if this means it has a thermosyphon


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## Dylan (Dec 5, 2011)

kennyboy993 said:


> On my machine the group head is heated by water circulating through it from the main boiler - I'm not sure if this means it has a thermosyphon


Yea, thats the thermosyphon which I think exists in nearly every HX design and is being mistakenly labelled as something extra that solves the cooling flush. If anything it seems that having a flow restrictor within the thermosyphon is what aids in reducing the need for a flush.

I have an Eric's on my HX and I have found it incredibly useful to tune the flush needed on my machine, as you say it is a balance between the heat of the water in the loop and the temperature of the group itself.


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## u2jewel (Aug 17, 2017)

kennyboy993 said:


> A modern, high end prosumer HX like my ecm mechanika achieves desired temp by heating new water as it passes through the HX pipes and then on in to the group head where it gets heated more.
> 
> And then as it comes out of the head it's a good temp for brewing. This is by design and the HX tube lengths are tuned to balance it just right along with the extra heating the group head does.
> 
> ...


Yup, that's TS. All ECM single groups are E61 (thus Thermo siphon being integral part of it, except the Casa)


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## dwalsh1 (Mar 3, 2010)

My Faema Legend has an adjustable thermosyphon loop and I don't need to do a cooling flush but do just to clean the shower screen. Don't ask me how it works though.


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