Home-Barista.com

Jeff wrote: I've read about other machines that try to have a "PID HX" controlling brew temperature like this. It might be that they intentionally restrict the thermosiphon to keep the group from drifting up a lot.

If your HX is 7-8 years old you may not have any thermosiphon restriction.. There is a tube from the boiler to the group and another tube back from the group to the boiler that forms the thermosiphon. On mine, the restriction is in the "top" part of the thermosiphon that brings hot water to the group. You can take off that tube to see if there is any restriction. Ive read about anything from 3 to 2mm. The smaller the restriction, the slower the water circulates. This means less idle temp and less need for flushing.. AND .. slower rebound.. (I have 2.5mm restrictor and have to wait up to 15 min for the group to get hot enough between drinks 2 & 3). On my particular machine, it is unusable for parties.. again.. a bit annoying for a few thousand dollar machine.. Lelit actually provides the user with a few different restrictors that the user can use.. so you can tailor for your use.. (another thing they don't tell you about HX designs). Now maybe yours used to have a restriction and it opened up.. and so now you have a 'hot' system. You'd have to do some research on that model and on its thermosiphon design.

If you have zero restriction, then you will have to flush a lot to cool the group. These system are generally designed for cafes where you are pulling shots ever few minutes so the group doesn't overheat.. With zero restriction you will need to go through a bunch of water.. is it plumbed in?

Now, remember I only have a few years in this theory.. there are HB guys here with decades more and better experience with HX designs.. HXes are like DOS.. easy after you've beaten your head up learning the commands.. but they ain't click and drag ..

Didn't get to use my machine today for myself. Made wife a quick drink as I ran out of the door this morning. I normally work from home.
Her drink was "acceptable", not as good as yesterdays. I'd increased the boiler temp by +2C and did a long flush to 89C. Shot was 88->86C on EricsT.
I'm guessing that with a higher boiler temp I need to aim lower on the ET.

Bluenoser wrote: Yeah if your PID has an offset programmed into it.. like a DB does.. it can really throw a monkey wrench into your expectations. You should be able to find out all the Gicar parameters through its user interface.. such as it is.. (one or 2 buttons).

I've got the full manual from Gicar for it. It's very very basic. No display just an 8 way DIP switch.
You set the desired temp (in C) using the bottom 6 bits (7th is a ghost bit that is always on. e.g. (1)011111 = 95C.
It can be viewed here under the name "Termosteco board for coffee boilers or cup warmers"

I dislike it enough that I'm considering switching it with a Sestos PID like this guy here did in his blog on adding a PID.
It should be an easy straight swap, I've already got all the parts which were inexpensive.
My only concern is that the Sestos will over shoot by too much on start up and cause the over pressure valve to vent too much due to it being a surface mounted heat sensor. The Gicar manual does state that it aims for 10C below its target and then takes it easy after that to get there.
I wouldn't use the Gicar thermocouple I'd use a K thermocouple with the same ring connector for surface mounting. Got it in the post yesterday.
I'm holding off for now to see if I can live with it as it is first.

Bluenoser wrote: Not having been in espresso for a long time.. and being an electronics guy.. I'm into data.

My under grad is Electronics/Comp Sci. I've spent my career working in software but still dabble in electronics from time to time.

Bluenoser wrote: You'll find the E61 really influences the final temp. Anything from seasonal changes to air currents can cause a significant temp fluctuation in the brew water

My previous machine, which was also a Sanremo, wasn't an E61 and was made in the mid-90's. I had, at the start of this year, after several years using it finally figured out how to pull a good shot from it using a temp sensor and a flushing technique. Then summer came and the ambient water temp ruined it and I decided it was time to go E61 thinking it wouldn't suffer the same problems. How wrong I've been...

Bluenoser wrote: If you have zero restriction, then you will have to flush a lot to cool the group. These system are generally designed for cafes where you are pulling shots ever few minutes so the group doesn't overheat.. With zero restriction you will need to go through a bunch of water.. is it plumbed in?

Yes, it has a rotary pump which is unusual for a HX E61. I do find I need to empty the water tray every day now.
I think it was meant to be in a cafe and on all day primarily.

I was about to say that I didn't think it had a restrictor and then I realised that I had the exploded diagram of all its parts and that if it did I'd see it there.
Low and behold does it not have a weird looking circular thing labelled part #53 "OT GIGLEUR D 3mm HOLE" that appears to go inside the outlet of the top of the HX on the boiler.
If I was to remove that part what would be the net effect?

I don't think you want to remove the 3mm restrictor and use.. but you might want to see if it is still 3mm.. That is the size the Rocket Appartamento uses.. From what I've read, the Rocket idles about 200-205F and does require a flush of about 3-5 seconds..

Now I think some of the tubing geometry also defines the TS characteristics ..

If you removed it, your TS would circulate too fast.. not sure exactly what would happen.. maybe you couldn't cool the water enough.. If you have some small drills (I used to have some from PCB through-hole electronics work) you can find one with about that diameter to check the integrity of your restrictor.. If someone else removed the restrictor, it may be why you're having issues with your machine,

Now if you could replace with a 2.5 restriction, it might need less flushing.. You'd have to manufacture something yourself.. I am not familiar with the part.. some put a round disk inside with a custom hole diameter.

I wonder if the real purpose of the restrictor is to prevent thermosyphon stall as explained on this web page.

If you go back to post #6 on this thread you'll see I said I did a 2nd de-scale to see if I could improve the thermosyphon.
It feels like the thermosyphon is stalled because the head is really slow at heating up yet when I flush it comes out boiling.

I always believed, or assumed without researching, that part of the design success of the E61 was not just in having the head nice and hot but that the head acted like a radiator and cooled the HX liquid keeping it from getting too hot. If I'm right about this then removing the restrictor should allow for a higher boiler setting, and better steam pressure, while keeping the HX water temperature down.

Pulling out that pipe isn't going to be easy so I'm going to leave it for now as is. I do wonder though if that 3mm hole has narrowed with scale or got scale debris floating about and stuck behind it.

I just made my wife a coffee. Flushed and it took a cup full of water to get it down to where I wanted the ET to read before pulling the shot.
The re-bound is quick enough. I waited maybe 2-3 minutes, the ET read 5C lower at the head but then with a flush jumped back up to a level just above where I'd want to pull a shot. So re-bound seems quick enough for back to back coffees. She's going out, I don't want my morning coffee for another hour yet, so won't know for sure on the back to back today.
Steam pressure is still awful. Isn't that the whole point of these machines? To be able to pull shots and froth milk at the same time? Something doesn't add up.
A fast enough rebound + a slow heating head + low steam pressure = thermosyphon circulating too slowly?

The other part of the thermosyphon piping that I was suspicious of was the injector at the bottom where the cold water comes in. There doesn't appear to be an non-return valve and my machines dual manometer shows the pressure in the HX build up as it heats to 12bar where the release valve prevents it going any higher. After the de-scaling it has occasionally not increased but remained at the mains water pressure of 3 bar. Very strange.

What is "slow" in heating up the head?.. An E61 takes up to 40 minutes to be thermally stable. I am guessing your Thermosiphon is actually just fine.. maybe too fast if anything. The slow warm up is characteristic of an E61 group. If your rebound is 2-3 min, then you have a fast TS. That's why I wondered if the restrictor was present or if it is not now 5mm after descaling.

the boiler (steam) pressure will be there in 10 minutes... but the group thermally stable is 40 min. If someone drops in and I want espresso, I turn on my HX but only use it for steam (milk). I use a manual "Robot" for the espresso.

Yes, I might be a bit too impatient with it sometimes. I've got a timer on it which turns it on 1/2 hour before I want to make a coffee. By the time I've got the beans ground and milk/cups ready it'll be 40min.

Can I ask a dumb question - or two?
I imagine/guess that the restrictor helps heat up the water quickly inside the part of the HX that's inside the boiler by slowing down its exit which is why it is placed just at the top of the boiler.
So if the restrictor was removed the water would cycle freely.
If I do have a restrictor in place and I'm finding that the water is far too hot that I need a whole cup full flushed out then surely the restrictor is having a negative impact on both water wasted as well as forcing me to work with a lower boiler temperature and lower amount of steam?
It's a big boiler at 1.8L with a 1500W heating element.

If I removed the restrictor then, yes it would take longer to rebound, but I could compensate with raising the boiler temp which in turn would give me the steam I'm looking for.
Based on all this logic (which may be flawed) I'm thinking that the restriction in my HX is too much, not too little?

Remember I keep referencing my friends old (15+ years) Rocket HX which just knocks out perfect shots one after another with no flushing?
That's what I'd like to aim for. (when did they start putting in restrictors?)
I guess I'm struggling to understand the benefit of the restrictor when I've got too little steam and too hot water?
I think I'm talking myself into cracking it open and putting an eye ball on that restrictor to see what is really going on there!

EDIT:
I had an idea. I dismantled the top of the E61, removing its mushroom which take 30secs, then with the HX inlet pipe exposed stuck a copper wire down it to "feel" the end at the top of the boiler.
I can confirm there is something there that stops the wire and after a lot of wriggling I got the wire through whatever it is that's there.
So I think that confirms the existence of a restrictor but not the width.
I'd guess it would be copper/brass, I've seen posts elsewhere that suggest some are plastic (to stop scale build up?)
Felt like metal I was hitting and the hole felt large enough and free. I used 1mm wire.

"Can't get there from here"

Any E61 HX will eventually drift up in temperature until the back of the group head is close to steam-boiler temperature. The temperature of the group head will be set by the thermodynamics of E61 casting (effectively the same in all machines) with some changes due to ambient temperature, air flow over the group, and the like.

Adding a restriction slows down the flow, so slows the rate of upward drift, but not the end-point temperature in a significant way. The E61 HX was designed as a solution for cafe use, with shot after shot being pulled with a constant rhythm. Some machines had adjustable valves that could "tune" the rebound speed to be a good match to the barista's speed. They'll still drift up if not used for a while (minutes) and need a flush to restart the rhythm.

A restrictor in a home setting often just sets the rebound time "painfully" long for a manufacturer trying to make a box that's seemingly more friendly for non-production settings.

The MaraX is the only viable "flush-free" HX I know of. It achieves this by toggling the steam-boiler temperature between very hot and a bit cool and monitors the thermosiphon temperature.

Edit: How close the back of the group head gets to steam-boiler temperature is related to the losses in the path (piping, for example) and the self-limiting nature of the thermosiphon (needs temperature difference to run). You can crank down the flow so much that you're trying to balance the heat loss through the group head with the flow through the thermosiphon, but that approach has several practical problems including stall and slow heat-up times. These challenges are among the reasons high-end commercial machines moved to dual-boiler, saturated-group approaches in many cases.

I have seen the head temperature drift up very high (close to boiling point) when I've left it on for more than an hour.

There's something else I realised that needs to be considered with a restrictor being used and that's the rule of water always taking the path of least resistance. What's to stop the water flowing in the reverse direction when you open the head with the lever on the E61?
I'd guess the answer to that is the difference in circumference of the injector to the HX pipe that it is inside of.
So just removing the restrictor alone probably doesn't make it a completely free flowing system.

You're right, there really isn't an "in" or "out" when you start to brew, both are effectively inlets to the group head when you turn on the pump and water is flowing into the head. As you note, restrictions may cause the flow to prefer one over the other. Once you stop brewing, the thermosiphon eventually reestablishes itself as the cooler water sinks toward the bottom of the chamber inside the group head and the warmer water in the HX is rising.