# A guide to managing HX brew temps



## HowardSmith (Jan 21, 2018)

*A guide to managing e61 Heat Exchnager machine brew temperatures*​
​
A link to a youtube video showing this process is below, I would suggest watching the video (may be best on a computer screen) & also reading.






To begin with I would like to say that managing HX (Heat Exchanger) brew temp is a minefield! Not only because of the technical & design difference between machines but also because there is a mass of information out there, some good, some not so good! Eric Svendson, creator of the "Erics Grouphead Thermometer" did a fantastic job in building the GH thermometer & has also posted a lot of useful info including two methods to manage brew temp named "Flush & Go" & "Flush & Wait". Before we continue with my method & the testing I think it would only be rite to give a quick overview of these two methods to help build the picture, once you understand what is going on here things become easier to take on board.

*Flush & Go (F&G)*

With the Flush & Go method we flush a sufficient amount of water out of the HX to cool the water inside the HX to below target brew temp. The GH (Grouphead) remains above target brew temp.

We then pull the shot immediately (or with a small delay). 'Too Cool' water exits the HX & is heated by the 'Too Hot' group. This results in some heat transfer & we have our brew water.

With the F&G method GH thermometer readouts will appear below actual brew temps during the shot. This is because the thermometer is an inch or so behind the puck & the 'Too Hot' group still has time to warm the water on its way past the thermometer to the puck.

An example of F&G could be as follows.


*Remove PF (portafilter) & prep puck *​
*Flush machine until temp starts dropping *​
*Stop flush at 96°C Lock PF in & GO*​
During the shot the GH thermometer will read below actual brew water temp at the puck (this will vary machine to machine but somewhere around 1-3°C would be a ballpark figure)

The method above may give somewhere are a 93°C temp at the puck

*Flush & Wait (F&W)*

With the Flush & Wait method we flush a sufficient amount of water to cool the mass of the GH below target brew temp. The puck would them be prepped & the shot initiated at after 'waiting' until the GH thermometer hits a pre determined point.

With this method the GH is cooler than target brew temp. The water in the HX has likely recovered to full temp (there or there about, this is really not critical as you will see moving forward). On pulling the shot 'Too Hot' water exits the HX & is cooled by the 'Too cool' group. This results in some heat transfer & we have our brew water.

With the F&W method GH thermometer readouts will appear above actual brew temps during the shot. This is because the thermometer is an inch or so behind the puck & the 'cool' group still has time to cool the water on its way past the thermometer to the puck.

An example of F&W could be as follows.


*Flush machine until GH thermometer drops to 93°C *​
*Group will continue to drop *​
*As soon as group begins to recover & temp starts rising remove PF & prep puck *​
*Lock PF back & 'Wait' *​
*Wait until GH thermometer hits 90.5°C & pull shot.*​
During the shot the GH thermometer will read above actual brew water temp at the puck (this will vary machine to machine but somewhere around 1-3°C would be a ballpark figure)

Both methods will get you where you wan to be. F&W is a little easier as we have nailed down a few of the variables. HX water is going to be about the same temp & GH is at whatever we decide. F&G is a little more tricky. Once the group starts dropping temp as we flush the thermometer is changing rapidly, a slight delay may mean a target flush to 96°C would quite quickly become 96.5 or 95. Not the end of the world but we can do better.

Now that I have given a general overview to the two most commonly used methods out there I want to say that both of these methods work. Both get you where you want to be but my biggest concern is the amount of water that is required to implement them. I know a lot of people have plumbed in machines however I would say a lot of people live in a hard water area & don't want the expense of filtrations systems or simply cannot be bothered with it. Also consider people like me who have a tank only machine. Once fully warmed up my Rocket Appartamento will take between a 150-200ml cooling flush. Follow that with 50ml for the shot & maybe a 30ml screen flush & I get less than 10 shots to a tank & multiple drip tray 'dumps'.

My frustration with misinformation, lack of support from retailers/manufacturers, long cooling flushes, constantly having to dump the drip tray & recycling bins full of empty water bottles forced me to look into how to get around these issues myself.

This is a guide that I have built for myself. It compromises of charts, videos & general discussion around what exactly is going on with a e61 HX machine but most importantly it includes an easily repeatable process to hit whatever brew temp you like at whatever boiler pressure you like, shot after shot without flushing. Please consider this is MY routine that works for me & with my machine. In general e61 HX machine will perform in a similar manner as the engineering is similar, however there are many factors that will change between machines so please see this guide as an example rather than the rule.

*What will this guide show me?*

Two sets of six 30 second shots pulled in a b2b (back to back) manner at a 'reasonable' workflow. Both sets took between 30 & 40 mins to record.

One set at 1.1 bar max & one set at 1.5 bar max.

You will see GH temp & 'at Puck' temp during all extractions (in the video) & data will be logged into graphs for reference & review.

You will see a method to produce "hot" "medium" & "cool" shots at both 1.1 & 1.5 bar with no flushing (other than screen flushing post shot) or changes to Pstat/PID during the sequence of extractions.

You will see some attempts to produce a "flat profile" shot where I am trying to eliminate the "HX Hump" at the beginning of the shot that this method produces.

You will also see a comparison of 1.1 & 1.5 bar shots pulled in the same manner producing almost identical brew temp profiles! A chart is included with 1.1 & 1.5 together.

*The method*

Before we talk about the method there are a few basics to understand. Understanding the basics will hep make sense of the process.

An e61 Grouphead is pretty much a solid block of brass & usually weighs around 4kg.

The amount of water required to produce a double shot of espresso would usually be between 30 & 100g. This is taking into account 'puck absorption' & filling any pre-infusion chambers & is somewhat of a 'stab in the dark' but the point I am trying to convey is that it is much less than the weight of the group.

Considering the water during a 'normal' extraction flows slowly there is plenty of contact time between the water & the GH. The GH does an excellent job of tempering the water & bringing it up or down as required.

This suggests that controlling GH temperature plays a large roll in the actual temperature at the puck. It is my belief that controlling GH temp is WAY more important than HX water temp. This will be demonstrated here & the results are shocking.

The method I have been using is to cool the GH with a small battery operated fan. This does not affect HX water temp much although the return will be a little cooler but not massively relevant to the outcome.

​
*Position a small fan so that it rests on the top cap above the mushroom & blows directly down over the group *​
*Cool the group to just above a pre-determined temp (group will continue to drop) *​
*Pull the PF & prep the shot *​
*Lock the PF in & wait for the GH to rebound to a pre-determined temp *​
*Pull the shot at the pre-determined temp*​
​
​
With this method GH thermometer readouts will track above actual water temp at the puck. This is the same as with the Flush & Wait method as the GH is cooler than target brew temp & HX water is hotter than target brew temp.

The best part with this method is that we can fan the group to different temperatures & change actual brew temps shot by shot if we like. Boiler pressure/ temp appears to not drastically affect actual brew temp at the puck with this method.

This method has proven EXTREMELY accurate & repeatable shot to shot. I originally set out to try & produce a "hot", "medium" & "cool" shot but my results show we can target within 1°C fairly easily & even go between temps from shot to shot at any reasonable Pstat/PID setting.

Finally some numbers...


*Hot Shot - Fan to 93°C - Pull Shot on rebound at 92.5°C - At puck temp 95°C *​
*Medium Shot - Fan to 91°C - Pull Shot on rebound at 90.5°C - At puck temp 93°C *​
*Hot Shot - Fan to 89°C - Pull Shot on rebound at 88.5°C - At puck temp 91°C*​
​
I have inserted the data referenced for the six shots at 1.1 bar & 1.5 bar. These shots were pulled over roughly a 40 min period over the course of two nights (one night at 1.1 & the other at 1.5 bar). A screen flush was performed after all shots & the PF was knocked out, dunked in hot water & put back in the group between shots unless otherwise stated.

















Here are a few more graphs to demonstrate some of the findings.

Firstly we have a comparison between shot 1 and 4 at 1.1 bar.









Next up we have a comparison between shot 2 & 6 at 1.1 bar.









As you can see shot 2 (the blue line) had a higher 'hump' at the beginning of the shot. I suspect this is probably to do with the whole machine being just a little hotter.

Finally we have a comparison between 1.1 & 1.5 bar pressure.









As you can see although the 1.5 bar profile does take an upward climb towards the end of the shot the profile over a 30 second shot is similar. This shows just how much impact GH temp comes into play here.

As a bonus here is my best attempt at producing a "flat profile".









Please note this shot is at 1.3 bar which is where I have decided to now leave my machine after all of this testing. This is also a 40 second shot.

Machine was warming up from a cold start, PF was pulled at 90°C, puck was prepped, 5 second flush at 90.5°C, PF locking in & go.

This is an easy shot to pull, no 'fanning' required. This is now my go to morning shot every day.

*Conclusions*

I think from looking at the data it is clear to see that we can manage HX brew temperatures fairly easily utilising a small fan. We can also fairly accurately brew at a variety of temperatures without adjusting boiler pressure. The data also shows that boiler pressure/ temp does not directly have a significant impact on brew temp at the puck. Boiler temp will obviously influence the temp of the GH as the thermosyphon will run either hotter or cooler, however GH idle temp with this method has little bearing on the final result as we can regulate the temp with a fan anyway.

*What do I recommend?*

Well first off let me say, I am no coffee expert. I am a Telecoms Engineer. My job is problem solving, dealing with some simple & some complex faults on a daily basis. If I think something can be done better then to me that is the problem & I want to solve it. What I have done here is simply prove that a solution to my problem works in practice. I don't think this method will please everyone & that is fine. I am reluctant to tell anyone what to do, but rather share what I have found & what worked for me. What I will do however is share how I now approach managing HX temps after all of this learning.

My machine comes on at 06:45am every morning on a WiFi timer. I am down by 07:00am & flick the GH thermometer on. I keep an eye on it as I sign on for work, make the wife a cup of tea, make the kids some drinks, watch them beat each other up etc... Once the GH hits 90°C I pull the PF prep my shot, wait for it to hit 90.5°C, quick screen flush, lock it in & go. This produces that nice flat 93°C(ish) shot, easy!

If I want to make another shot any time soon I leave the machine on & fan down as the process above explains & carry on.

At the weekends the machine comes on as normal at 06:45am, same deal, I pull my first drink of the day as the machine is warming up. If we are going out I will turn the machine off, if we are staying in I will leave it on. The machine warms up fully & when I want another shot I will simply fan it down to the desired point & carry on as the process above explains.

For back to back shots I will generally move quickly & keep on top of the group temp (before it rises too high), sometimes hitting it with a bit of air. You get the idea. Keep the GH where it needs to be & you are good to go assuming you are not a super human barista who can knock shots out on the minute every minute I would assume HX water will be 'there or there about' where it needs to be. Please bear in mind all Rocket machines are fitted with a 3mm thermosyphon restrictor in the upper plumbing. This regulates (slows) the flow of the thermosyphon which in turn slows down the rebound of the group. If you have what Dan Ken of Home Barista would describe as a "Dragon" meaning a HX machine probably without a restrictor recovery time may be too fast to stay on top of. Fanning between shots pulled quickly will likely be still be required.

*Considerations*

The first consideration would be to discuss a point I just touched on. HX rebound time. This method relies on maintaining the temp of the GH & always initiating the shot at the same pre-determined GH readout. The other variable at play is HX water temp. I know I have said that HX water temp is almost irrelevant & I still believe this to be the case for the most part. However, large swings in HX water temps will show up in the results. How much? Hard to say but worth considering.

Flow..... Now flow is an interesting variable. Considering we are relying on cooling the "too hot" water by passing it through the group that is below target brew temperature the rate at which the water passes through the group make a difference. Too slow & the temp at the puck will cool below target brew temp. Too fast & the Hot HX water will not be attenuated enough. How much these results vary is another test in the making however I would like to acquire a Flow Control kit for my machine before perusing that avenue.

One thing worth mentioning is that errors in grind that result in a 'too slow' flow may be slightly buffered by the effect of a cooler brew temp at the puck. Meaning if you ground too fine & are likely going to be pushing into 'Over Extracted' tastes, these 'tastes' may be somewhat muted but the fact that the brew water ran a little cooler. Possibly making the e61 group even more forgiving?

Another consideration worth touching on is the commonly talked about 'advantage' of a HX machine vs a Dual Boiler (DB) & that is brew water 'freshness'. It goes without saying that generally HX machine have a quicker turn around of water being used for brewing when comparing to a DB machine. This is because the HX is significantly smaller than that of a conversional brew boiler on a DB machine. Not flushing a HX machine would obviously slow down the turn over of water (which is kind of why this whole project started for me) which may in turn show up in the taste. I couldn't tell, maybe you could, if you would like to 'freshen' things up a bit a 5 second screen flush prior to each shot will not negatively impact temp stability, it may in fact help produce a flatter shot if that is what your after, which conveniently leads me onto my next point.

'Flat' profiles vs 'Humped' profiles. Throughout this whole process here I have been mentioning the 'HX hump' & have also mentioned ways to avoid it. Please consider this is only for experimental purposes. There has been a lot of discussion around 'flat vs humped', 'inclining vs declining' temperature profiles & to be honest I think the 'jury is out' as to which is better. I'd say don't worry about it, play with both if you like, have some fun.

*Further experimentation*

Although I feel I have reached a conclusion & am now happy with how to manage my Rocket machine I simply cannot leave it there. This process needs automating. Unfortunately machine manufacturers generally want to focus on their higher end machines & simply slapping a PID on a HX & claiming it somehow magically produces normal brew temps is simply not the way forward.

Lelit are the only manufacturer I am aware of who have done anything that resembles a solution, the Mara X. They have however gone about it completely 'arse about face' if you ask me. I am not knocking them as I think innovation is important & it is great that they are trying, but with all the resources at their disposal to simply regulate brew temp by effectively ramping boiler pressure up & down (based on return thermosyphon water temp) is urrggghhhh, well it works, sort of but I just don't like it. Hard to really explain but I think they could have come up with a much simpler solution. I have one in the making that would actually work better, no boiler swings, no flushing (it is not a fan but I will not share until I have proven the concept).

I have automated the fan process myself with a small brushless DC fan linked up to a PID with a thermocouple mounted to the underside of the group. The PID can be programmed to turn the fan on/off at whatever temp you like. Maintaining GH temps this way results in a fluctuation of around 1°C at the group. Brew water at the puck would likely fall within the same range & brew profiles will possibly run 'flatter' due to the constant cooler idle that this process results in (return leg on thermosyphon will be cooler for extended periods may drop the HX temp a little, certainly stopping it 'superheating'). The set up for this is a little ugly, I am still at the proof of concept stage, playing around with a few options but I have a much better idea that has popped into my head that I will share if I ever get around to it.


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## kennyboy993 (Jan 23, 2017)

Thanks for taking the time Howard, the most comprehensive e61 hx analysis I've seen on here. I will read at my leisure later.

Re the video - could you upload a bigger version? It plays in very small dimensions

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## HowardSmith (Jan 21, 2018)

kennyboy993 said:


> Thanks for taking the time Howard, the most comprehensive e61 hx analysis I've seen on here. I will read at my leisure later.
> 
> Re the video - could you upload a bigger version? It plays in very small dimensions
> 
> Sent from my iPhone using Tapatalk


It has to be that way to include the larger graphs, watch on a computer rather than phone and you will be ok.

I have done a voice over on the video so it is fairly easy to follow even on a small screen

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## kennyboy993 (Jan 23, 2017)

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## Rob1 (Apr 9, 2015)

Is this an aticle? If not you might want to look into it, though I'm not sure you can really translate this to other HX machines due design differences, but if not you'll be able to replicate the process and find temperatures for different machines.

I have a couple of questions:

How long do you stand there waiting for the temperature to change with the portafilter locked in loaded with the coffee? I typically attempt to start the shot asap from when I lock the portafilter in and was wondering if you see any negative effects to leaving it and letting it heat up. Part two: I see at one point the thermometer reads about 60c at the puck before pulling the shot, is this accurate or is the thermometer placed above the bed? Maybe a scace will provide more accurate results regardless of placement?

Regarding target temperature: The charts show you hit a stable temperature approx 20 seconds in most of the time, by which point extraction rate will be slowing down with a standard 30 second shot, so is't it more appropriate to target the average temp, especially when different boiler pressures produce different profiles?


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## HowardSmith (Jan 21, 2018)

Rob1 said:


> Is this an aticle? If not you might want to look into it, though I'm not sure you can really translate this to other HX machines due design differences, but if not you'll be able to replicate the process and find temperatures for different machines.
> 
> I have a couple of questions:
> 
> ...


 I think you have raised a few things worth talking about. I will give my opinion.

Is this an aticle? If not you might want to look into it, though I'm not sure you can really translate this to other HX machines due design differences, but if not you'll be able to replicate the process and find temperatures for different machines.

*Nope, this is just done data that I logged for myself but figure I should share in an easily digestible format. Machines will show variation. I'd guess the process would work but would require re-testing. I'd encourage people to test themselves. Recored the GH thermometer during a normal extraction, **log the data into a graph as see how it compares to my results. The 'peak' & the 'low' could also be a really quick & easy reference point. Please post any findings below.*

How long do you stand there waiting for the temperature to change with the portafilter locked in loaded with the coffee?

*I will give an example or my normal workflow.*

*I fan the group to 91°C (it will now continue to drop to below 90.5°C)- Pull the PF & prep the shot (this may take 30 seconds) - The group begins to rise while all this is going on - Depending on the rebound time the PF will be back in the group with 10-30 seconds to go (something like that).*

I typically attempt to start the shot asap from when I lock the portafilter in and was wondering if you see any negative effects to leaving it and letting it heat up.

*I don't have the palette do **decipher. Try yourself & let me know... If you are a 'super taster' you may be surprised. I can only see an advantage in allowing the PF to warm the puck as it allows for a more even extraction. Scott Rao touches on this with his "Blooming Espresso" but more in the context of allowing a dwell time after pre-infusion to help equalise the temp across the puck.*

*Put it like this, you are certainly not going to 'burn' the coffee. Search Youtube for James Hoffmans video on microwaving coffee. I can't exactly remember the outcome but it was interesting.*

I see at one point the thermometer reads about 60c at the puck before pulling the shot, is this accurate or is the thermometer placed above the bed? Maybe a scace will provide more accurate results regardless of placement?

*The 60°C is accurate because it is showing the temp before the shot is pulled. My set up here is a thermocouple **encapsulated is foil tape that sits on top of the puck. It has very little thermal mass so is very responsive to the temperature of its surroundings. Once the PF is removed it begins to measure the temp of the air around it.*

*A SCACE is a good tool for measuring repeatability and consistency from machine to machine, this is why it was created, for barista competition where the organisers are looking to dial a machine in to a set temp.*

*The issue with a SCACE is that it does not give an accurate representation of what is actually happening during a shot. It give an accurate representation of a simulated shot. SCACE devices do not vary the flow. Flow plays a MASSIVE role here in actual water temp. If i had a SCACE I would have used it but now that I have this 'on puck' thermometer I would probably rather use this a simulate real shots. *

Regarding target temperature: The charts show you hit a stable temperature approx 20 seconds in most of the time, by which point extraction rate will be slowing down with a standard 30 second shot, so is't it more appropriate to target the average temp, especially when different boiler pressures produce different profiles?

*That may be the case. Considering we have 'lows' as the puck comes up to temp & a 'high' as the puck peaks you will actually find that average brew temps come out to be pretty much where the temp settles off after 20 seconds or so. Either way I think we are sweating the small stuff here, most e61 HX owners are probably pulling with massive variations. Like i said in the post, use this as a method for controlling the temp, rarely do we need to know exactly what the number is. If I have a really dark roast my intuition would be to shoot for a "cool" shot. With this process we can hit cooler or hotter, it is up to you to decide what that means.*


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## ronan08 (Dec 21, 2019)

Wow thanks for sharing this I'm definitely more onboard with flush and go method on my HX as it is an absolute hog if left for too long and will require a 40 second flush to adequately cool


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## HowardSmith (Jan 21, 2018)

ronan08 said:


> Wow thanks for sharing this I'm definitely more onboard with flush and go method on my HX as it is an absolute hog if left for too long and will require a 40 second flush to adequately cool


40 seconds seems a lot. How many grams of water? What is your GH at idle? What pressure is the boiler at?

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## ronan08 (Dec 21, 2019)

It's not an e61 system or insulated so keep that in mind its temperature based whitch I believe to be at 135° is that normal


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## HowardSmith (Jan 21, 2018)

For anyone wondering I will outline the 'at puck' thermometer set up.

I purchased a cheap meat thermometer from eBay, dismantled it and encapsulated the thermocouple and wiring in a few layers of foil tape. This contraption is then centred in a blind basket within a PF and formed to the shape of the basket/PF rim... It is then worked into final position slowly by pushing up the PF into the group a few times before finally being fully locked in with slightly firmer than normal force.

Removal of the PF now will normally result in the set up remaining in place but sometimes it needs to be repositioned. Removal is also easy.

The advantage of this set up vs a SCACE is that we are able to measure a 'realtime' extraction of a coffee puck where flow will vary unlike a SCACE where flow is a constant.

I have included a few photos photos to demonstrate the set up.



















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## tommyp215 (Apr 2, 2016)

Glad the technique you settled on was the simplest and quite similar to mine. I pull two double shots twice a day normally. I tend to try to 'catch the rise'. My simple logic is if the machine is too cold when first switched on and too hot if left on for an hour there must be time in between that is 'just right'. (I Know this is a oversimplification). My machine kicks on at 6.30 and normally pull my first shot around 20 mins later. I normally pull around 91 to 92 with a very short coiling flush 5s . Also if I've missed this window and the group is too hot I sometimes put on a cold double portfilter for 5-10 mins and this cools the group. (do you know how much of an effect this has?) I kind of feel with a HX it will always be a bit hit or miss and I'm happy to be in the ballpark. Do you have any advise on the second shot after first shot? Thanks for the work.


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## HowardSmith (Jan 21, 2018)

tommyp215 said:


> Glad the technique you settled on was the simplest and quite similar to mine. I pull two double shots twice a day normally. I tend to try to 'catch the rise'. My simple logic is if the machine is too cold when first switched on and too hot if left on for an hour there must be time in between that is 'just right'. (I Know this is a oversimplification). My machine kicks on at 6.30 and normally pull my first shot around 20 mins later. I normally pull around 91 to 92 with a very short coiling flush 5s . Also if I've missed this window and the group is too hot I sometimes put on a cold double portfilter for 5-10 mins and this cools the group. (do you know how much of an effect this has?) I kind of feel with a HX it will always be a bit hit or miss and I'm happy to be in the ballpark. Do you have any advise on the second shot after first shot? Thanks for the work.


 Glad the technique you settled on was the simplest and quite similar to mine.

*Not settled yet! We have more to come. I will be sharing the automated set up within a few days. I have a PID/Thermocouple/Micro DC fan set up on the machine currently, testing is underway!*

I pull two double shots twice a day normally. I tend to try to 'catch the rise'. My simple logic is if the machine is too cold when first switched on and too hot if left on for an hour there must be time in between that is 'just right'. (I Know this is a oversimplification).

*Not a simplification, this is spot on. Somewhere around 90°C on the rise is going to give you around a 93°C shot after the 'HX Hump'. GH readouts will likely be around 1°C above 'at puck' temps from around 20 seconds on a vibe machine, maybe a little sooner on a rotary pump.*

My machine kicks on at 6.30 and normally pull my first shot around 20 mins later. I normally pull around 91 to 92 with a very short coiling flush 5s . Also if I've missed this window and the group is too hot I sometimes put on a cold double portfilter for 5-10 mins and this cools the group. (do you know how much of an effect this has?)

*The cool PF will cool the group, test it **yourself, if the GH doesn't come down to your normal 'catch it on the rise' pulling temp then shots will likely be hotter. It will all depend on time, how hot you let the GH get etc...*

*If I had to guess I would say that the temp at the puck will read about 2.5°C above the GH reading prior to pulling the shot assuming GH readout is rising & not dropping. Meaning that if your GH is at 95°C & you lock a cold PF in & it drops to 93°C, you then pull & prep the PF, during which time the GH begins to rise, you then screen flushing go at 93.5°C... I would expect 'puck temp to be around 96°C (2.5°C above GH readout prior to shot).*

I kind of feel with a HX it will always be a bit hit or miss and I'm happy to be in the ballpark. Do you have any advise on the second shot after first shot? Thanks for the work.

*Well, it certainly doesn't need to be hit & miss at all. I have performed over 40 tests so far & I am pretty much able to hit whatever temp I want within 1°C.*

*As far as the second shot there are a lot of variables at play & you only have one reference point (your GH thermometer). Fortunately we can clearly see that this is the only variable we really need to worry about if we want fairly **accurate & repeatable shots.*

*Ensure your GH temp is rising, pull the PF, prep the puck & lock back in at the same temp every time, initiate the shot at the same (rising) GH readout every time. This is about as accurate as you are going to get.*

*If your GH readout is too high you will need to either 'Fan & Wait' or 'Flush & Wait'. *

*It is worth considering that a first shot after a long idle will produce a higher HX hump than a second shot pulled after either a recovery from a cool group or a cool down (with the fan) from a hot group. This is likely due to a hotter machine on shot one & 'overheated HX water', this is discussed in the video. A way around this would be to flush for a little longer before a first shot vs a second shot.*

*If your group is cool after a first shot & requires 'some time' to recover back to 'pulling temp' you could consider bumping your boiler pressure/ PID up, dropping post shot screen flushes may also help.*

*If your group is hot after a first shot & requires cooling via flushing or fanning you could consider dropping your boiler pressure/ PID or implementing a longer screen flush post shot. You may still require additional cooling but the above process are just things that may get you closer to where you want to be, this all depends on what temp you are trying to hit also.*


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## kennyboy993 (Jan 23, 2017)

Howard - what affect is the foil having on temperature reading do you think, and why do you need to do that as opposed to just using bare thermocouple end.

I'm looking to fashion one of these myself

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## NJD1977 (Dec 16, 2014)

Great guide and very interesting.

Out of interest, how long do you use the fan for to get to the target GH temperature?

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## HowardSmith (Jan 21, 2018)

kennyboy993 said:


> Howard - what affect is the foil having on temperature reading do you think, and why do you need to do that as opposed to just using bare thermocouple end.
> 
> I'm looking to fashion one of these myself
> 
> Sent from my iPhone using Tapatalk


 Little to none would be my best guess but this would not be my area of expertise... Considering the GH thermometer has a stainless casing around it I would say the 'at puck' thermometer its more responsive.


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## HowardSmith (Jan 21, 2018)

NJD1977 said:


> Great guide and very interesting.
> 
> Out of interest, how long do you use the fan for to get to the target GH temperature?
> 
> Sent from my SM-G973F using Tapatalk


 Not long, but it all depends what the GH temp is.

Put it like this. If the group is up to full temp, lets say 98°C, I put the fan on, weigh my beans, get the grinder going, get my milk etc... By the time I am ready to go I may only have 20 seconds or so until the GH is at the correct temp.

It is surprising just how little airflow is required to drop the temp of the group. Try it out & report your findings here.


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## HowardSmith (Jan 21, 2018)

Here is the video showing the automated set up. It's not pretty but this was more as a proof of concept... works really well.

E.g PID set to 90°C, walked up to my machine this morning, prepped shot, screen flushed and got 90.1°C at the puck.






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## HowardSmith (Jan 21, 2018)

Here is the final set up made a little less ugly, no exposed wiring...























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## terio (Oct 17, 2017)

This is a really awesome effort. Something I will have to look into playing with in the future.


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## kennyboy993 (Jan 23, 2017)

I'm sure some of the guys over on HB would love this also

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## HowardSmith (Jan 21, 2018)

kennyboy993 said:


> I'm sure some of the guys over on HB would love this also
> 
> Sent from my iPhone using Tapatalk


I have already shared all the same info over there too mate.

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## GazRef (Dec 30, 2019)

Outstanding thread H. Thoroughly appreciate the rainman approach. 👍


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## KTC (Apr 18, 2020)

Hello Howard, thank you for laying out that guide & for the comprehensive documentation. It's been fun following along & implementing your method. I got my machine, the Mara (not X) a short while back. As much as I would have loved to get the X, it just wasn't a possibility.

The one thing I was most concerned about, before comitting to an HX, was temprature management. Given that I don't have a group head thermometer & no means of aquiring one either, I assumed temprature to be a black box for me. The idea of flushing, & potentially wasting much water everyday just didn't appeal. Then I found your post on HB, and suddenly, there was a ray of hope! Soon as I got the machine, I sourced that parts and this is where I'm at today -









And this is it's (second) brain -









Ever since I started reading up on modding the Gaggia Classic, I was fascinated with Arduino & the whole DIY electronics ecosystem. Sadly, the Gaggia never graced our lives. But then, little Mara came along & I found your post & finally, I had the oppurtunity to dabble with Arduino! There's a k-type thermocouple taped to the chopstick, that slides in behind the group. The fan is hooked onto the relay. It turns on once the temp crosses the pre-set hight & goes off once there's a dip below the low. It's not the neatest setup, but I'm still learning.

I'm very new to espresso, there's a lot I don't yet know. But I'm able to clearly discern the difference in flavour at different tempratures. I've been trying out different coffees, at different roast levels and the temprature control has made it possible to pull shots optimally. Best of all, no cooling flushes necessary, no water wasted!

As much as I've been learning & enjoying the whole process, there's a lot I don't know. The thermocouple reading is all I have to gauge the group temp, with no way of knowing what's happening at the puck. Before, I was using a cooking thermometer to check the temp -









Don't know about it's accuracy, but this thermometer would settle at around 93 C after warmup. The thermocouple settles at about 100 C. This doesn't make sense, 100 would be too hot, but the shots don't come out burnt. I have no Idea of how a reading of 100 C taken from behind the group, would corelate to the reading of a group head thermometer. My temprature reading before & during extraction remains almost constant, since the thermocouple isn't coming in contact with water, unlike a grouphead thermometer.

I've seen that in your automated setup, you've stuck the thermocouple behind the group too. Could you shed some light on this mystery?

You mentioned in the first post that you have another approach to this whole thing in mind. How's that coming along? I'll be tuned in to know more about it.


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## HowardSmith (Jan 21, 2018)

KTC said:


> Hello Howard, thank you for laying out that guide & for the comprehensive documentation. It's been fun following along & implementing your method. I got my machine, the Mara (not X) a short while back. As much as I would have loved to get the X, it just wasn't a possibility.
> The one thing I was most concerned about, before comitting to an HX, was temprature management. Given that I don't have a group head thermometer & no means of aquiring one either, I assumed temprature to be a black box for me. The idea of flushing, & potentially wasting much water everyday just didn't appeal. Then I found your post on HB, and suddenly, there was a ray of hope! Soon as I got the machine, I sourced that parts and this is where I'm at today -
> <img alt="mara.thumb.jpeg.988bbbf19acce7f0608863aba54038fa.jpeg" data-fileid="40540" data-src="<fileStore.core_Attachment>/monthly_2020_06/mara.thumb.jpeg.988bbbf19acce7f0608863aba54038fa.jpeg" src="https://www.coffeeforums.co.uk/applications/core/interface/js/spacer.png">
> And this is it's (second) brain -
> ...


I'm glad you have found the info useful and are using it effectively.

Firstly your 100c temp behind the group may be correct, most likely. Temp varies in different locations on the GH. The top of the group is much hotter than the lower end because the thermosyphon only really circulates through the top section.

My findings were that with my machine brew water temp would be around 2.5c above the temp displayed on my GH thermometer prior to initiating the shot. With my automated set up with the thermocouple fixed to the flat section on the underside of the e61 where it attaches to the machine the temp displayed almost matched my GH thermometer. I think I needed to program a small offset, maybe 0.5c for it to match up.

Numbers really do not matter if you can distinguish differences in taste at different settings. I can nail whatever temp I want now consistently without flushing but really knowing what temp it is at is irrelevant, I simply dial in to around a roasters recipe at 93c and then play with pushing the temp up and down 2c each way. This could be as simple as saying 'let's try a hotter shot, or let's try a cooler shot'.

My initial goal was to come away with the ability to produce a 'hot' 'medium' and 'cool' shot. It turns out that the fan method is so reliable that we can realistically reproduce almost identical shots, shot after shot at any temp we like by simply managing the GH temp.

I'm currently not using the automated set up because the relay/fan kicking in and out kind of drives me nuts. I simply fan down with the small fan and pull the shot on the rebound. Good luck with your set up, it certainly looks more complex than mine and looks like you have had a bit of fun tinkering, which IMO is what it's all about so keep it up.

As for the other automated method.... Temperature controlled solenoid valve in the thermocouple to completely bypass the e61 once temp is achieved. Some kind of override controll via the pump switch.

Not done it yet, may not do it but that's how u would automate this in a more professional way.

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## KTC (Apr 18, 2020)

HowardSmith said:


> Temperature controlled solenoid valve in the thermocouple to completely bypass the e61 once temp is achieved. Some kind of override controll via the pump switch.


 This approach seems so much simpler than, as you mentioned, the Mara X way. There would be some kinks to iron out along the way, I suppose.

One thing that comes to mind, if the thermosyphon bypasses the E61, water in the HX might tend to superheat much, much faster, without dissipating heat to the group. This might need additional management.

It would be so much fun if some sort of temprature management modding kit for HX machines existed, much like what MrShades has done for the Gaggia Classic. This is an oppurtunity I've missed out on by not getting a GC, getting deep inside a machine's guts and tinkering around.


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## MarkM (Jun 5, 2020)

Great detail. But.... did any of this affect the actual flavour of the shots?


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## HowardSmith (Jan 21, 2018)

MarkM said:


> Great detail. But.... did any of this affect the actual flavour of the shots?


Definitely.

I am not a 'super taster' and drink all my shots in milk. I can clearly taste a difference even in a milk drink when the temp it too hot or too cool.

For a long time I was running my shots way too hot and not getting what I wanted. My shots are now way more consistent.

What machine do you have?

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## Nikko (Aug 20, 2014)

A novel approach to HX temp management is used in the Xenia to drain the HX after each brew to start afresh each time. So predictable conditions always.


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## kennyboy993 (Jan 23, 2017)

Nikko said:


> A novel approach to HX temp management is used in the Xenia to drain the HX after each brew to start afresh each time. So predictable conditions always.


This sounds interesting, so the hx is almost behaving like a thermocoil where brew water heating is only happening at brew time?

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## HowardSmith (Jan 21, 2018)

kennyboy993 said:


> This sounds interesting, so the hx is almost behaving like a thermocoil where brew water heating is only happening at brew time?
> 
> Sent from my iPhone using Tapatalk


It's worth bearing in mind that the Xenia design is very different to the standard e61 HX machine with thermosyphon.

Look at this diagram. My understanding is that the group is also actively heated with PID controlled cartridge heaters.

Draining the HX on an e61 HX machine after each shot would not produce the same results that the Xenia achieves.

But you are correct, if you look at the diagram you can see the relatively small capacity HX which coils through the steam boiler. I think once the solenoid opens post shot, gravity will simply drain the path. The only issue I can see with this would be the potential for an introduction of steam at the beginning of a shot since the brew path (hx pipe) will be empty of water and likley full of superheated air/steam. In reality this may not cause an issue and may not even happen, I don't know the ins and outs of the machine.









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## kennyboy993 (Jan 23, 2017)

Thanks Howard, very interesting machine - group head heating adds another level of sophistication


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## HowardSmith (Jan 21, 2018)

kennyboy993 said:


> Thanks Howard, very interesting machine - group head heating adds another level of sophistication


It does... check this out from the coffee machinist on Instagram...

He fitted two cartridge heaters to this ECM machine and I think it boasts an 8 min warm up time.... The heaters are PID controlled, you can see the thermocouple, drilled and tapped in the centre I'd assume. This is the same location as my thermocouple although mine is simply surface mounted with heat sync glue.

I have considered it, but I'd like to find an old knackered e61 HX machine instead of machining holes in mine TBH. If I ever come across one it would make a great project.









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## Border_all (Dec 19, 2019)

Most enjoyable thread thank you


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## KTC (Apr 18, 2020)

HowardSmith said:


> My understanding is that the group is also actively heated with PID controlled cartridge heaters.


 I think the way the group is being heated is through what they're calling a 'Thermal Bridge', where the boiler is thermally connected to the group.









As mentioned on this page - https://xenia.coffee/thermische-eignung/.


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## Nikko (Aug 20, 2014)

There is both a "thermal" connection to the boiler and 2 electric heaters in the group head. I believe a choice of either 100W or 150W per heater is available.


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## cuprajake (Mar 30, 2020)

Having just progressed to a hx e61 machine, this thread gives so much info, shall bookmark it for future reference

Great work


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## Rakan (Oct 5, 2020)

Howard, thank you for this great work, and sharing it with us.

Been doing your fan method for a couple of days.
I'd like to ask, why do I not experience the temperature hump?
extraction starts @88.5c "rebound", and the sensor shows exactly 90.3c constant.
Seriously, 90.3c constant till the end of the shot, did not fluctuate, and no hump, just constant.

I got Appartamento factory set @1 Bar
with E61 sensor by "coffee sensor (black version)"

The numbers I'm getting are ridiculously constant.
for example, rebound @89.5c it hits 91.6c constant till the end of the shot.

Am I missing something, or these are an actual real readings?


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## Rakan (Oct 5, 2020)

It's a "Duplicate post"


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## Rakan (Oct 5, 2020)

Rakan said:


> Howard, thank you for this great work, and sharing it with us.
> 
> Been doing your fan method for a couple of days.
> I'd like to ask, why do I not experience the temperature hump?
> ...


 Follow up,

I got a temperature sensor on the basket with 17.5g of coffee

GH stand by temperature 96.5c, fan method cool down. No flush before or after extraction. Zero flush.

Started the extraction doing the same numbers which is 89.5c rebound.

Temperature in GH sensor is 91.7c constant with zero fluctuation!

and temperature on the puck is 91c, with extraction time from the start 40 seconds.

Puck temperature was solid 91 with 2 fluctuations, first one @10 seconds of extraction for 5 second to 92c then back to 91c

, and second one was at the end of extraction for 2 second to 90c, and then back to 91c

beside that, the entire extraction was spot on 91c.

Bare in mind, the puck sensor is thick, and it was leaking a bit, nothing major, and maybe it was the reason of the puck sensor fluctuating.

yet, GH sensor did not fluctuate it was 91.7c constant.

Truly, those numbers are amazing. I did this method 7 times, and all were spot on constant Temp numbers.

Mr. Howard, what do you think about these Temp readings, and should I change something in my routine?


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## HowardSmith (Jan 21, 2018)

Rakan said:


> Follow up,
> 
> I got a temperature sensor on the basket with 17.5g of coffee
> 
> ...


 Really late reply, not been here for ages...

Your results are almost exactly what I would expect based on my own testing. Your machine being set to 1 bar enables it to brew a 'flatter' profile at 91c because the initial rush of water at the start of the shot it cooler in comparison to say water from a 1.3 bar boiler. The HX hump is affected by the HX water temp, average brew temp is determined by group head temp with this method.

If you're happy at 1 bar keep it there. You will get flatter temperature profiles, but you will also have less steam power & slower recovery times. Set the boiler pressure based on your routine really.


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## Kyle T (Jan 6, 2016)

Hi, only discovered this thread today and read through it. Is this really the extent you have to go to with a HX machine? Having just sold my dual boiler I've been considering a HX machine as I've never had one. I figured I had to make sure to give it at least 30mins to heat up, pull a shot and then flush for 4-5 seconds if I wanted to pull another shot. Is this not the case? Could you not get a decent shot with a random flush or is this more about avoiding the flush all together? Also, how much does the size of the boiler affect things on a HX? I've seen machines from 1.1L boilers up to 1.8L. Does this affect much?


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## HowardSmith (Jan 21, 2018)

Kyle T said:


> Hi, only discovered this thread today and read through it. Is this really the extent you have to go to with a HX machine? Having just sold my dual boiler I've been considering a HX machine as I've never had one. I figured I had to make sure to give it at least 30mins to heat up, pull a shot and then flush for 4-5 seconds if I wanted to pull another shot. Is this not the case? Could you not get a decent shot with a random flush or is this more about avoiding the flush all together? Also, how much does the size of the boiler affect things on a HX? I've seen machines from 1.1L boilers up to 1.8L. Does this affect much?


 Hi, only discovered this thread today and read through it. Is this really the extent you have to go to with a HX machine?

*Well this was the extent that I decided to go to since I was frustrated with not knowing what was going on. You wouldn't need to go to this extent now, just read this thread.*

Having just sold my dual boiler I've been considering a HX machine as I've never had one. I figured I had to make sure to give it at least 30mins to heat up, pull a shot and then flush for 4-5 seconds if I wanted to pull another shot. Is this not the case?

*That's not a simple question to answer. It will depend on the machine, the group head temp, what temp you want to be brewing at, how long you leave between shots, ambient temp, the boiler temp. All these questions can be answered by using the methods in this thread in conjunction with a group head thermometer.*

Could you not get a decent shot with a random flush or is this more about avoiding the flush all together?

*Again, not a simple yes no answer because your 'decent' may be different to my interpretation. If you told me you like your espresso brewed with as flat profile as possible and at exactly 93c I could pretty much give you that with my method. With a random flush and no group head thermometer you would be stabbing in the dark. Would that be decent enough for you, I dont know.*

Also, how much does the size of the boiler affect things on a HX? I've seen machines from 1.1L boilers up to 1.8L. Does this affect much?

*I dont have much experience across a range of machines but thinking from a logical perspective a larger boiler will most likely reduce recovery time between shots, may increase group head temp a little vs a smaller boiler which could mean more group head cooling is required, improve steaming performance for large jugs of milk.*


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## pandabear (Feb 12, 2014)

Just came here to say thank you for your efforts, it was a very interesting read and watch!

I share your concerns over the inherent wastefulness of flushing in HX machines so the cooling GH method helping with that whilst giving more accurate and repeatable shot temps seems to be a win/win. I tried it this morning and my Mara (not X) warmed up from off to 88.5c on the thermometer in 20 minutes, shot pulled and temps stabilised slightly above 92c on the thermometer.

Lucky for me that I only have 1/2 shots a day so catching the first one on warm up and then only having to do this possibly once more a day isn't a huge issue!


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## HowardSmith (Jan 21, 2018)

pandabear said:


> Just came here to say thank you for your efforts, it was a very interesting read and watch!
> 
> I share your concerns over the inherent wastefulness of flushing in HX machines so the cooling GH method helping with that whilst giving more accurate and repeatable shot temps seems to be a win/win. I tried it this morning and my Mara (not X) warmed up from off to 88.5c on the thermometer in 20 minutes, shot pulled and temps stabilised slightly above 92c on the thermometer.
> 
> Lucky for me that I only have 1/2 shots a day so catching the first one on warm up and then only having to do this possibly once more a day isn't a huge issue!


 Good to see your mara responds in a similar way to the appartamento (based on the readings)...

I think this comes down to basic physics really. E61's all weigh about the same, boiler temps are about the same, flow rate is about the same. YMMV but the overall concept is the same for e61 HX machines.


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## Wasi (May 30, 2021)

Hello Howard. I also want to thank you for your great work. I also use Fanning for a few days and am thrilled with, how easy and effective it is. I use a Rocket Mozzafiato, with PID and a Rotary Pump. In all previous attempts, I have found, that I do not get a hump at a pressure of 1.2 bar, as is the case in your measurements. For me, the temperature reaches the target temperature relatively quickly and levels off there, with a fluctuation of +/-0.2°. Do you have any idea why that is? Is that rather good or rather bad?

Greetings

Wasi


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