# HX questions



## Kyle T (Jan 6, 2016)

Recently started looking at HX machines. Taking the MaraX out of the equation do all other HX machines need a cool flush? And is this flush required before the first shot of the day and every shot there after?

also, how does boiler size affect a HX machine? Does it purely affect steam pressure? I've seen machines as low as 1.1L boilers. I'm only make 2 doubles a day max and normally not milk drinks anyway.


----------



## MediumRoastSteam (Jul 7, 2015)

Kyle T said:


> I'm only make 2 doubles a day max and normally not milk drinks anyway.


 Why would you consider an HX machine out of curiosity? Seems that if you are more of a black coffee drinker, the temp fluctuations/surfing of an HX machine will be counter productive of what you want to achieve. I think it would be simpler to just walk up and pull without having to worry about having to cool down the group beforehand.

In a direct answer to your question, as a general rule of thumb, all "dumb" HX machines require a cooling flush before the first shot of a session. subsequent ones don't need it i.e.: you are making 4 coffees in a row. So, after initial warm up and being idle (how long for will depend on how well tuned your machine is) you will need some sort of cooling flush as the temperature of the HX will be the same as the service boiler, i.e.: approx. 120C, which is far too hot for brewing.

Some manufacturers are now adding PID's on HX machines, some say they don't require a cooling flush. I just find it hard to believe, and would believe once someone shows it to me. Until then, I stick to the laws of physics. 😉


----------



## Kyle T (Jan 6, 2016)

I've had a dual boiler for the last few years and fancied something else. Most things in my budget were HX machines and I figured that seeing as I hadn't had a HX machine before I would try one.


----------



## John Yossarian (Feb 2, 2016)

Kyle T said:


> I've had a dual boiler for the last few years and fancied something else. Most things in my budget were HX machines and I figured that seeing as I hadn't had a HX machine before I would try one.


 I have been using HX machines for a more than a decade. For a year now I am with a double boiler one and it is a massive difference in favour of the latter. If just for curiosity you might be disappointed.


----------



## BlackCatCoffee (Apr 11, 2017)

Kyle T said:


> Recently started looking at HX machines. Taking the MaraX out of the equation do all other HX machines need a cool flush? And is this flush required before the first shot of the day and every shot there after?
> 
> also, how does boiler size affect a HX machine? Does it purely affect steam pressure? I've seen machines as low as 1.1L boilers. I'm only make 2 doubles a day max and normally not milk drinks anyway.


 Cooling flushes are need when the machine has been stood idle. As the temperature of the steam boiler is above desired brew temperature in order to generate steam pressure, when the water sits in the exchanger system for a while it becomes too hot. You would not need to do a cooling flush if you were making a series of drinks all in one go.

Some manufacturers say their machines do not need to be flushed. They say the the group acts a little bit like a heat sink to bring the temperature of the water down as it cycles around it and back in to the exchanger. In reality I think this would only work under perfect conditions. I would say if you are looking to purchase an HX machine, work on the basis that they all need some level of flushing. To be clear though, it really is not a big deal at all imo. Since the Mara X landed it has suddenly become a deal breaker for people but the reality is, it is just another little step in your routine, no different to grinding correctly, preparing the coffee puck or purging a steam wand. The Mara X does solve it in certain usage patterns but it is not a silver bullet and in some way it introduces it own new level of temperature instability and little quirks to your routine.

Boiler size is not directly related to steam pressure but it is related to the amount of steam the machine can generate. As a *basic *rule, the larger the boiler the more steam on tap. Other factors affect this though.

All of this said - if you do not drink milk drinks regularly, why don't you consider a quality SBDU? We have the Bezzera Unica landing soon. It has all the looks of traditional machine including the E61 plus PID control for perfect stability and will save you some money over a PID DB machine.


----------



## Kyle T (Jan 6, 2016)

BlackCatCoffee said:


> Cooling flushes are need when the machine has been stood idle. As the temperature of the steam boiler is above desired brew temperature in order to generate steam pressure, when the water sits in the exchanger system for a while it becomes too hot. You would not need to do a cooling flush if you were making a series of drinks all in one go.
> 
> Some manufacturers say their machines do not need to be flushed. They say the the group acts a little bit like a heat sink to bring the temperature of the water down as it cycles around it and back in to the exchanger. In reality I think this would only work under perfect conditions. I would say if you are looking to purchase an HX machine, work on the basis that they all need some level of flushing. To be clear though, it really is not a big deal at all imo. Since the Mara X landed it has suddenly become a deal breaker for people but the reality is, it is just another little step in your routine, no different to grinding correctly, preparing the coffee puck or purging a steam wand. The Mara X does solve it in certain usage patterns but it is not a silver bullet and in some way it introduces it own new level of temperature instability and little quirks to your routine.
> 
> ...


 The Bezzera looks quite nice, when will it be in stock? Is it really much more difficult to get a good shot from a HX?


----------



## BlackCatCoffee (Apr 11, 2017)

We are really hoping they will be with us very shortly but have already been subject to covid and brexit related delays....

You just need to learn and understand how Hx machines work in order to get the best from them. They are just not quite as convenient as a DB but then again they are not the same price.


----------



## HowardSmith (Jan 21, 2018)

Kyle T said:


> Recently started looking at HX machines. Taking the MaraX out of the equation do all other HX machines need a cool flush? And is this flush required before the first shot of the day and every shot there after?
> 
> also, how does boiler size affect a HX machine? Does it purely affect steam pressure? I've seen machines as low as 1.1L boilers. I'm only make 2 doubles a day max and normally not milk drinks anyway.


 To get accurate and consistent brew temps on an e61 HX machine you will need some method of monitoring the temperature of the group head. A group head thermometer is easy to buy and install and I wouldn't reccomend a e61 HX machine without one unless your happy to guess shot temps and have large swings.

Do all HX machines need a cooling flush?..... That's going to depend. If you do not plan to use the steam you could certainly tune a HX machine to not require a flush by dropping the boiler pressure to a point that will put the group head where it needs to be. Bear in mind the recovery time between shots would be extended with this method. You could also catch the machine at the correct time on heat up and pull a shot without a flush too.

I have done a lot of testing on my machine using a fan to regulate group temp and I can pretty much hit whatever temp I want almost exactly now on demand. I have a post here names something like "A guide to managing HX brew temps". You will see just how accurate you can be with a little practice.


----------



## Kyle T (Jan 6, 2016)

I saw your in depth thread recently and commented on it with a similar question. I don't have intentions of attaching thermometers to group heads and have it look untidy with wires everywhere.


----------



## HowardSmith (Jan 21, 2018)

Kyle T said:


> I saw your in depth thread recently and commented on it with a similar question. I don't have intentions of attaching thermometers to group heads and have it look untidy with wires everywhere.


 Without a group head thermometer on an e61 HX machine your stabbing in the dark as far as temperature management is concerned.

If you want to be able to get accurate and consistent temperatures out of a machine and dont want to fit a group head thermometer to an e61 HX machine I would avoid an e61 HX machine unless you go for the Mara X which will sort of do this for you.


----------



## Kyle T (Jan 6, 2016)

HowardSmith said:


> Without a group head thermometer on an e61 HX machine your stabbing in the dark as far as temperature management is concerned.
> 
> If you want to be able to get accurate and consistent temperatures out of a machine and dont want to fit a group head thermometer to an e61 HX machine I would avoid an e61 HX machine unless you go for the Mara X which will sort of do this for you.


 Actually I didn't realise you can now buy those thermometers for e61 group heads that screw into the group where the Allen key sits. I'd be happy to fit one of those.


----------



## HowardSmith (Jan 21, 2018)

Kyle T said:


> Actually I didn't realise you can now buy those thermometers for e61 group heads that screw into the group where the Allen key sits. I'd be happy to fit one of those.


 Yeh, that is what I am referring to when talking about a group head thermometer.


----------



## DavecUK (Aug 6, 2013)

Kyle T said:


> Actually I didn't realise you can now buy those thermometers for e61 group heads that screw into the group where the Allen key sits. I'd be happy to fit one of those.


 They look like this..... and the silver part screws into the 6mm threaded hole that the bolt on the front of the E61 sits in.


----------



## Kyle T (Jan 6, 2016)

DavecUK said:


> They look like this..... and the silver part screws into the 6mm threaded hole that the bolt on the front of the E61 sits in.
> 
> 
> View attachment 53167


 And does this help close the gap significantly between HX and DB ?


----------



## Bicky (Oct 24, 2019)

I wish they made better looking thermometers, such ugly things to put on our lovely machines 😞


----------



## ajohn (Sep 23, 2017)

A few people have posted that they prefer the taste that comes out of an HX. Part of the problem - different machines may produce different tastes. That doesn't mean that all will see them as bad. As some one mentioned an HX means finding a routine that gets the results and sticking to them. That may need changing when several are made on the trot. Fit a temperature gauge yes fine but but what matters is taste and frankly I wouldn't be convinced that a gauge on an HX helps with that.

Steam boiler size - what probably matters is what happens pump wise when things are being steamed. If significant cold water goes in it will cool the water. There is also another type of single boiler machine where brew water is taken directly from the steam boiler.

Personally when I buy a machine I spend a lot of time with google. Problems with them get mentioned and etc. Youtube reviews can be interesting at times I recollect one where the camera zoomed in onto a gauge while a shot was being pulled. I lost interest in it immediately.

My answer to curiosity is to buy used. Only problem is the need to check them over before use and I have 2 but my garage is currently out of order. One's HX and the other E61. The HX could do with a new water tank. It's discoloured. The E61 had previous problems owned by some one on here. Best check for scale and a couple of other things.

 I'll probably remain with a Sage DB whatever.


----------



## BlackCatCoffee (Apr 11, 2017)

Kyle T said:


> And does this help close the gap significantly between HX and DB ?


 Yes and no. It means you will be able to learn to use you machine consistently to get the same temperature at group which imo is not particularly difficult providing you are methodical.

What it wont really allow you to do very accurately is get different temperatures easily like you can with a DB. If you did want this functionality you would need to look at an Hx with PID control.

See below video -


----------



## cuprajake (Mar 30, 2020)

now having a dual boiler, theres no way id jump back down to an hx, while the hx is good, you can see the temp change going through the shot, id see over 1 degree in a shot sometime, this was with a coffee sensor


----------



## HowardSmith (Jan 21, 2018)

> 37 minutes ago, BlackCatCoffee said:
> 
> Yes and no. It means you will be able to learn to use you machine consistently to get the same temperature at group which imo is not particularly difficult providing you are methodical.
> 
> ...


 Based on the testing that I have done I would disagree that a PID will enable you to "get different temperatures easily".

A PID will allow you to conveniently adjust boiler temp, which is more convenient than using a PSTAT but both are achieving the same thing, changing the boiler temp/pressure.

Any claims from manufacturers that a PID somehow makes an e61 HX able to produce more accurate brew temps or somehow eliminated the need for some kind of cooling flush or group head calling is just not true.

If a manufacturer adds a PID and changes the plumbing to a machine at the same time yeh, sure maybe you dont need to flush that machine... But it certainly isnt because of a PID, it is most likely to do with the way they have 'tuned' the thermosyphon/ e61 loop...


----------



## cuprajake (Mar 30, 2020)

@HowardSmith can you explain,

if you have a dual boiler and brew e61 is set at 92 - it cant get hotter can it, it shouldnt heat soak? if it were an hx though then it would run hotter due to the nature of a hx boiler?


----------



## BlackCatCoffee (Apr 11, 2017)

HowardSmith said:


> Based on the testing that I have done I would disagree that a PID will enable you to "get different temperatures easily".
> 
> A PID will allow you to conveniently adjust boiler temp, which is more convenient than using a PSTAT but both are achieving the same thing, changing the boiler temp/pressure.
> 
> ...


 I obviously cannot comment on the machine you are using and your test results but we have a scace we use to test brew temperatures which is the industry standard and my own testing reflects the results from the video above.

Whilst it is not a perfect system of direct control like a DB, on a well designed, modern PID hx machine you can absolutely have control over brew temperatures.

Yes you still need to perform flushes.

David

(when I said get different temperatures easily I was referring to DB machines. I realise the relationship between steam boiler temp and brew water temp on an HX machine is not 100% direct)


----------



## HowardSmith (Jan 21, 2018)

Cuprajake said:


> @HowardSmith can you explain,
> 
> if you have a dual boiler and brew e61 is set at 92 - it cant get hotter can it, it shouldnt heat soak? if it were an hx though then it would run hotter due to the nature of a hx boiler?


 Can you just clarify what you are asking exactly. I will do my best to share my experience in my machine.


----------



## HowardSmith (Jan 21, 2018)

BlackCatCoffee said:


> I obviously cannot comment on the machine you are using and your test results but we have a scace we use to test brew temperatures which is the industry standard and my own testing reflects the results from the video above.
> 
> Whilst it is not a perfect system of direct control like a DB, on a well designed, modern PID hx machine you can absolutely have control over brew temperatures.
> 
> ...


 Just to be clear. I am not saying you cannot have control over brew temps on any e61. PID or PSTA you can have great control...

The PIDis just a means to controll the boiler temp. You could do the same with a PSTAT.

If you matched boiler temp on identically plumbed PID and PSTAT machines I'd bet your testing would produce almost identical results. This is where a PID makes things more convenient.


----------



## cuprajake (Mar 30, 2020)

@HowardSmith

so atm i have a minima which is an e61 group but dual boiler with pid, so in theory this should be stable

if you have a hx machine with a boiler with higher temps and a pid would you struggle to maintain temps


----------



## ajohn (Sep 23, 2017)

There is another way an HX machine with PID can be used. I noticed a review on one that had 2 pid settings. One for steam and one for brewing. More like single boiler dual use. The quickest way to get from steam temperature back to brew was to let off steam and the delay from brew to steam wasn't long. Couple with some sort of group head that offers some thermal stability this should give good results for brew. The review of the machine mentioned the intended temperature of the shot in the mug/cup.

 Our resident expert would suggest say 600 to 700ml or so boiler for PID brewing with an thermosyphon type group head. Steam pass. My Sage DB uses 600ml but doesn't pump cold water in while steaming. @DavecUK May comment on that and may know which machines work like that.


----------



## HowardSmith (Jan 21, 2018)

Cuprajake said:


> @HowardSmith
> 
> so atm i have a minima which is an e61 group but dual boiler with pid, so in theory this should be stable
> 
> if you have a hx machine with a boiler with higher temps and a pid would you struggle to maintain temps


 So your DB e61 machine would likely be easier to create a consistent routine with as there are less variables. I good warming flush prior to your first shot may help to make the machine as consistent as it can be.

An e61 HX requires the opposite, it would need to be cooled down.

If by 'maintain temps' you mean from shot to shot that will depend on target brew temp, boiler pressure, ambient temp and time between shots. All of these this influence a DB e61 but these factors will be less influential as the DB creates a more stable starting point to being with.


----------



## HowardSmith (Jan 21, 2018)

ajohn said:


> There is another way an HX machine with PID can be used. I noticed a review on one that had 2 pid settings. One for steam and one for brewing. More like single boiler dual use. The quickest way to get from steam temperature back to brew was to let off steam and the delay from brew to steam wasn't long. Couple with some sort of group head that offers some thermal stability this should give good results for brew. The review of the machine mentioned the intended temperature of the shot in the mug/cup.
> 
> Our resident expert would suggest say 600 to 700ml or so boiler for PID brewing with an thermosyphon type group head. Steam pass. My Sage DB uses 600ml but doesn't pump cold water in while steaming. @DavecUK May comment on that and may know which machines work like that.


 This is a good point and this is basically what the mara x is doing but just in an automated process.


----------



## ajohn (Sep 23, 2017)

HowardSmith said:


> This is a good point and this is basically what the mara x is doing but just in an automated process.


 I wondered if the one I noticed just simply took water directly from the boiler. If so it should offer a more economic price for people that want to get similar results to a dual boiler and don't use steam much or don't mind the wait. There are some machines that have single boilers and work that way anyway. I think Profitec make one. Some one might think it's an HX machine but it isn't. Some one referred to it as a dipper. I hear hot water comes out of a steam boiler at high 90's degrees so suppose more could be lost some how or the other on the way out but it sounds NVG to me.


----------



## Kyle T (Jan 6, 2016)

What I'll never understand is how HX machines are being sold so often if they are such a shot in the dark without extra equipment. Seems baffling to me. I think I'll just increase my budget and either buy a new Domobar Dual Boiler or the Crem One dual boiler.


----------



## HowardSmith (Jan 21, 2018)

Kyle T said:


> What I'll never understand is how HX machines are being sold so often if they are such a shot in the dark without extra equipment. Seems baffling to me. I think I'll just increase my budget and either buy a new Domobar Dual Boiler or the Crem One dual boiler.


 The e61 HX machine is fairly old technology and considering its age it does a really good job of getting you into the ballpark for espresso.

Remember when the e61 was first made and for a long time it was probably being used in commercial machines where shots were being pulled back to back. This creates a routine and the machines settle into a consistent temperature when used like this. Being left for 30-60 mins and only putting one shot or maybe pulling one and then another just after doesn't create this consistency hence the need for a group head thermometer.

My routine is now simple. I fan the group down to 2.5°c below my target brew temp and then pull my shot on the rebound at 2.5°c below target brew temp. Simple, takes about 30 seconds, doesn't require any flushing and is easily repeatable.


----------



## Kyle T (Jan 6, 2016)

I get that you've created a system for repeatable shots but having to attach a fan above your group is ludicrous.


----------



## HowardSmith (Jan 21, 2018)

Kyle T said:


> I get that you've created a system for repeatable shots but having to attach a fan above your group is ludicrous.


 You can do the same thing with flushing. The flush and wait method will be the most accurate but it will use a lot if water (on my machine that could be over 200ml of water). To me this is more ludicrous.

Fyi I just have a small rechargeable fan, sit it on top of the machine and it blows over the group. I then remove it. Nothing is attached.

Another way to cool the group could be to insert a cold portafilter with a bit of cold water in a blind basket and perform a couple of back flushes.


----------

