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My next step in HX temperature management
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I also wondered if you could vary the restrictor(Gicleur); I thought about putting a solenoid in the HX loop to control the flow ( ie open the solenoid when the group head is to cold and opening it when the group is to hot). But you'd need to find a solenoid that can operate at higher temps and some type of controller; seemed like alot of effort.
If you where to go to that effort you'd be better of looking at the Coffee Machinist's idea of controlling the group's temp with some heater cartidges and a small restrictor( to stop it getting too hot); because you'd get the additional benifet of a quick heat up time. If you haven't already seen the write up here (link was removed ; try googling "Izzo Vivi Plus PID Red Series Coffee Machinist" )it's a good read. I would like to have it done to my machine but can't justify the cost; so the cheap fan option is what I've got.Last edited by maltur; 22 March 2021, 10:18 PM.
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I don't think the override would be needed.
The driving force in a thermosiphon is a pressure difference which in turn depends on the temperature difference and column height. If we assume a column height of 200mm, hot side temperature 125 oC and cold side 92 oC the driving pressure is about 500 Pa. The standard pump pressure (900kPa) is 1800 times higher.
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Nice work!
Having just been reading up on E61 flow control, I wonder whether it would be possible to automate varying restriction of the flow of water through the group to maintain a set temperature? I guess you’d need some kind of (automatic?) override while brewing.
Brett
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I've found that any issues I've had with steam when my P-stat was over 1 was due to the steam tip. The stock tip on mine had two holes (1.2mm I think); which at times clocked up a bit. I've cleaned mine by poking with needle; and seen large improvements. That said; I find that tip slow to steam milk; it does a good job but slow. I currently use the ECM 4 hole tip because I wanted a faster experience. I think my machine isn't powerfully enough to keep up steam to the 4 hole tip; as the pressure slowly drops while steaming; I still use it because I love the speed. I've been considering blocking one of the holes to see if I can find the best compromise.
Only mention this because if your over 1 bar and disappointed with your steam; try cleaning your steam tip and if that does work try a new tip they are not to expensive.
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Interesting - well done.
I have the same machine and have the grouphead thermometer as well. My P-stat is set at 1-1.3 so it idles around 96, requiring fairly small flushes, with slow recovery and the steam is not as good as I would like. For recovery or warm-up speed I found I only have to throw a hand-towel over the grouphead. While my machine will idle around 96, throwing the towel on the grouphead will easily get it to 99/100 in quick time.
Your solution is much more precise.
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I'm glad you got there in the end. Tbh this is a pretty elegant alternative to the group head thermometer. U could leave the box on the top tray when it's unneeded or even add a timer to it
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My next step in HX temperature management
Thought I'd share my attempts at taming my HX machine's brew temperature. It’s nothing new, I'm not claiming to have discovered any magic; but thought someone my find it interesting. It’s a bit of a long story; just skip to the pics if you don’t want the details.
It all started when I first bought my first "real" espresso machine (Technika IV profi). I couldn't get any consistency in my espresso; especially pulling multiple shots. Just couldn't work out how much to flush between shots.
So the first thing I did was to install a brewhead thermometer (which I've written about in a previous post). Things were much better; the thermometer allowed me to flush the right amount, shot after shot and wait for the group to recover if required.
So all good then I hear you say... well something bugged me about flushing so much water (for the first shot) every time; and the fact I was always trying to perform a balancing act between the group temp and the HX water temp; just bugged me.
I mean to get 4kgs of 98 degree brass cooled down to 93ish degrees take alot of cooler water; so I ended up with a hotter group and cooler water... hoping the mix was right for 93ish degree water.
The next step I took was to turn the P-stat down. I figured if I could get the group temperature down; I'd need to flush less water; hence keeping the HX water hotter with the view of making the balancing act a little easier. I tried setting it at 0.7, and then up a bit to 1. The group temperature lower (to 96 I think) the balancing act was easier; but steam pressure and warm up time suffered. But the worst effect was the group recovery between shots... it took too long. That said I lived with a P-stat set at 1 for a long while; happyish with the results.
Wishing to improve the recovery time I started looking for a way to increase the P-stat without effecting the group temperature (or maybe even lowering it). It seemed thermosiphon restrictor might be the answer.
Enter the dark arts. Not being an expert, so I contacted a site sponsor store to acquire a restrictor suitable for my machine. I ended up getting sent a tiny piece of brass with a 1.8mm orifice; I installed it and turned the P-state back up. It cool the group alright (to about 90) but made the group recovery take forever; I think it caused the thermosiphon to stall.
Disappointed; I enlarged the orifice from 1.8mm to 2.5mm. This resulted in a hotter group but still not bad (around 98 ); then turned the P-stat back down a bit ( to about 1.1) and the group was at 96 and I was back to where I started but the recovery time had improved ( marginally)
Then one morning; I went to pull a shot and the group was in the mid 94's, perfect. It took me awhile to figure it out. It had been getting hotter in my house but we'd just been living with it. But on this morning it had gotten hot enough for the air conditioner to get turned on. What should have been obvious to me all along was that group is effected by room temp and air flow. That’s why the restrictor business is a dark art; because you can tune it to one environment (like an air-conditioned store) but in my house with summer/winter/AirCon/No AirCon it is just never going to be right.
This lead me to googled "Fan E61 espresso" and found like all good ideas someone had already done it; Howard Smith to be exact. Howard Smith has done a very good job of investigating the effect fanning the group. So I thought I'd have a try.
I bought a $10 W3230 temp controller of ebay, paired it with an old PC fan I had lying around, and old mobile's charger. It works excellently; I can turn my P-stat up to have quick group recovery and keep the group temp down. In fact I can set the group to the temp I want ( within a degree); regardless of P-stat. It’s a 12V fan running off a 9v supply so runs next to silent; it seems you really don’t need a lot of airflow to effect the group temperature. I liked it so much I decided it would become a permeant fixture; so I 3d printed a little box for it to live in.
The only downside is it’s a bit ugly; but I think that’s fixable. I’m planning to use what I've got (because it’s working so well) until it breaks and then look at an Arduino nano with a PWM Fan and a IR contactless temperature sensor. This would pretty it up (less cords) and enable a PID variable speed fan controller.
Checkout the video of it working here (https://youtu.be/8vVexTZHG1o )

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