PID on a HX...this is my thinking, is it flawed? - Page 2

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espressme

#11: Post by espressme »

jimoncaffeine wrote:jesawdy,
Thanks! I had a great time writing the articles and doing the rebuild.
The PID is indeed on the lsm. I have done some documentation and another (single) article will be written.
snip
It will cover:
- PID selection
- SSR selection
- Thermocouple choices (including some ideas for placement.)
- Installation and ideas about how 'permanent' you want it to be (I made mine so I can uninstall, leaving no traces, in about 10 minutes.)
snip
Jim
Hello Jim,
Please post it here! Or, at least a URL to it!
I have a PID and SSR of correct ratings in the mail to me and am looking forward to having at least one machine PID'd. I have the basic idea, but the CG Ham Beach article was lost.
I have a used, dirty, but basically sound 1993 1 group Salvatore commercial HX to overhaul that could really benefit by the PID. Salvatore checked it out!
I look forward to your posting and article!
Sincerely
Richard / espressme
richard penney LMWDP #090,

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HB
Admin

#12: Post by HB »

jasonmolinari wrote:Given that the water dance is necessary because water in the HX tubing is sitting at above boiling point, since the boiler is under pressure, could one replace, or augment the pressurestat with a PID, which takes readings from the boiler water (just like Ken's), but instead of setting the PID to 240 or whatever, you would set it to espresso brew temp. The water now idle in the HX would equilibrate with this boiler water (which is accurate, and repeatable given enough stabilization time between boiler water and HX water, which i think should be less than 4-6 minutes), and would be at espresso brew temp. At least for the 1st 4-6 ounces (or however much is in the HX tubing inside the boiler). This is more than enough for a shot. No dance necessary.
Have you read MOSFET's Six Million Dollar Expobar? He "de-HXed" it by adding a PID and insulated preheat coils.
jesawdy wrote:If it was a simple 1/4" diameter copper coil in a heat exchanger shell, I might agree with you that cold water is just pushing hot water out, but it is a goofy looking test tube shaped reservoir that "dips" into the boiler water.
You're thinking about the Cimbali Junior's HX. The Tea's HX is a straight horizontal copper tube (it's pictured in JimP's article Single Boiler vs. Heat Exchanger?).

Back to the original question, I'm interested in hearing if others can reproduce Ken's results on a prosumer E61. When it comes to thermal memory, the Cimbali Junior is an elephant, which plays well to the PID'd steam boiler strategy. I'm not sure the smaller HXs (110ml) of a prosumer E61 and lesser thermal mass will benefit as much. From the machines I've seen, the other extreme of the "thermal memory" range is the Gaggia Achille. My gut feeling is that HX machines whose thermal memory are at the extremes will benefit most from precise control...

Another approach I've been mulling over is to automate the cooling flush. That is, combining an E61 thermocouple adapter, an inexpensive PID, and a SSR controlling the pump. Non-lever type E61s would be good candidates for this modification (e.g., Valentina and the Expobar Pulser).
Dan Kehn

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coffee_monkey

#13: Post by coffee_monkey »

Jason,

I have done exactly what you proposed on a very similar machine (Rituale... should be almost same as Tea w/ some minor layout differences) with a very important addition.

What Jeff said pretty summed up the missing link in your proposed setup. To achieve what you want, you basically want to get as close as a "perfect" HX as possible. What I did was to created a pre-heater loop around the boiler and insulate the boiler+loop. The length of the loop was calculated to give me at least 3 oz of pre-heated liquid which is heated close to boiler temp such that the HX is not doing any further heating during pulling a shot. You basically increased the size of your HX so that it has enough capacity to get you thru a shot (commercial HX are much different and have much larger capacity... some also are heated by steam only and will not work w/ this setup).

I then calculated/tested to get a minimum rebound time needed to get to steady state again, and make sure I do not outpace the machine when I use it.

The result is basically a pretty crappy single boiler machine with no ability to steam. Also, there is the issue w/ the vacuum breaker valve. If you set temperature crosses the threshold temperature (210 on my machine), the boiler will go from close to open (and vice versa). It takes more energy to close the valve so whenever this happens, the rebound time will become non-linear and became a bit random. It also will spit some water when it goes from open to close. Normally this is not an issue as it only happened once during initial ramp-up. But if it does that everytime you pull a shot, you will get water all over the inside of the machine (Which is very bad...). I learned this lesson the hard way (valve got stuck while I was at work and steam came up for hours which warped my cabinet above the machine...) and have since re-routed the exit steam to the drip-tray.

Despite the limitations, the machine is quite consistent currently. My wake-up shots are consistent within 2 degrees and no more cooling flushes are needed. In fact, I need to pull a blank to warm up the head before the wakeup shot. I can also converge on steady state much sooner (about 2 to 3 shots) and intrashot stability also improved.

Oh, make sure you put in voltage regulation or replace the vibe pump w/ a rotary pump if you choose to PID the TEA. The voltage drop as result of the PID will cause the pump pressure to pulse at PID interval (1 sec usually) and the clarity of the shot will really suffer...


Ben

jasonmolinari (original poster)

#14: Post by jasonmolinari (original poster) »

Thanks to all.

Dan, i will check the post on CoffeeGeek when i get a chance. I've also mulled the idea of automating the flush, but can't think of a good way to do it with a levetta machine

Ben, thanks for the details..it sounds like a lot more than i was looking to do, so i might pass on this mod, but it is interesting that someone else had the same idea.

Hrmm..maybe i'll just have to keep dancing until someone comes out with a sub $1000 rotary dual boiler PID machine:)

jason

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hbuchtel

#15: Post by hbuchtel »

coffee_monkey wrote:What Jeff said pretty summed up the missing link in your proposed setup. To achieve what you want, you basically want to get as close as a "perfect" HX as possible. What I did was to created a pre-heater loop around the boiler and insulate the boiler+loop. The length of the loop was calculated to give me at least 3 oz of pre-heated liquid which is heated close to boiler temp such that the HX is not doing any further heating during pulling a shot. You basically increased the size of your HX so that it has enough capacity to get you thru a shot (commercial HX are much different and have much larger capacity... some also are heated by steam only and will not work w/ this setup).
Ben
Ben, after you added the extra length of HX tubing did you notice any effect on your extractions? Maybe a longer time between turning the pump on and first drops of espresso, or a slower flow, something like that?

Thanks,

Henry
LMWDP #53

jasonmolinari (original poster)

#16: Post by jasonmolinari (original poster) »

I've read the coffeegeek post mentioned by Dan, and it is similar to what you've done Ben.

I was inside the machine last night, and i don't see much space, or really ANY space to put coils of copper tubing around the boiler, let alone 6 of them as the guy on coffeegeek did!

Not only that, how did you bend the copper tubing cleanly to go around the boiler making good contact with it? And what insulation did you use? I've seen this mentioned a few times, but the only stuff i've seen at home depot is rated to about 150deg. F, which is well below where we'll be.

thanks
jason - still thinking about doing it:)

coffee_monkey

#17: Post by coffee_monkey »

Henry,

There was no difference in flow with the pre-heater loop. Upon adding the rotary pump, my built in pre-infusion drop down to about 1sec or less as pressure come up to full almost immediately. I added a needle valve between the machine and the pump which allowed me to adjust the water debit down to 70~90ml/10sec. This make the pre-infusion goes back to the original 6~7. There is a good discussion of this on coffeed right now...

Jason,

You have to clear some spaces around the boiler but there are enough space to get at least 7 loops in. What you do is to start your first loop and put a hose clamp on it. Then do your second loop (or 3rd if you can pull it tight enough) and put another hose clamp on it. Pull on the loop REAL hard/tight before putting the clamp on it. The contact is not perfect but it's as good as I can get it. Another way the I seen the silvia folks did was to prebend the loop into a coil (that is smaller than the diameter of the boiler) and slip it on like a spring. But that won't work very well since there are many ports around the Isomac boiler. This is actually the hardest part of the entire project... changing plumbing is a real major pain in the ass and expect some leaks on your first try... I put a 3 way between the pre-heater loop and the original route. This allow me to bypass the loop and put the machine back to its original config when I need to steam again.

I used the ceramic paper sheets that some ppl used (do a search on CG or HB... I forgot where). Very good insulation but pain in the ass to use as the ceramic fibers are quite sharp and brittle....


Ben

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jasonmolinari (original poster)

#18: Post by jasonmolinari (original poster) »

Interesting Ben, i read up the stuff on your blog, pictures would help for sure, specially in seeing how you wrapped the coils, i can see that being a major pain..

Why install a 3 way? If you just add length to the HX, which is wrapped around the boiler, you could still turn the boiler temp back up to make steam in the boiler, and keep using the extended HX, couldn't you? Obviously your flush would be much much longer...but a 3 way isn't necessary to run in steam mode....

coffee_monkey

#19: Post by coffee_monkey »

If you revert back to the normal HX mode, the extended HX will make your flush ridiculously long. Also since there are more cold water to heat now, the recovery time will be excessively long as well. Basically you just make your life that much harder...

Plus, if you go all thru all that much trouble changing the plumbing, a couple more valves/fittings is not going to hurt.

jasonmolinari (original poster)

#20: Post by jasonmolinari (original poster) »

Agree, adding a couple of valves isn't the problem, but accessing them easily is. Since i'd only go back to HX mode to make steam drinks, i don't care about the flush length.

You mean if you wanted to revert to HX mode to actually use it as it was before, maybe to sell the machine or whatever? Then yes i agree, putting a valve in it is fine, since you wouldn't be switching it every day anyhow.