No problem taking it apart.. Took the group completely off. There was no cruft that I could see in the restrictor.. but hard to know as you knock it a lot taking the restrictor pipe off.. Took a 3/32 drill (no metric sizes local) and attempted to clean the orfice and make the 2.5 somewhat equiv to 2.6. (this is obviously not a fine science )

Even if there were some cruft in the mushroom, I don't think that would affect the TS loop.. Looks like it just goes in and out of the group with lots of room. So I won't take that off to clean. However, that thermal loop may be very sensitive to pipe bends and overall volume. So I'm wondering if tuning the hole (ie: making it slightly larger until I get the performance I want) is necessary in my instance.

It is relatively easy to take that restrictor pipe off.. I'll test performance and I might have to order some small metric drills and then attempt to open it more precisely to see its affect.

If anyone can think of any other characteristic or pipe that might cause slow rebound, let me know.. but looks pretty straight-forward.. I did see some green color, but no amount of scale anywhere.

Good to hear, 3/32 will give you approx 2.38mm gap, 7/64 will give you the 2.78mm gap (check with caliper). I made the 2.6mm using both 3/32 and 7/64 on a bench and measured with caliper.

I always wanted to try the 2.9 - 3.0mm to see if it was any better.

So likely my last word on this thread..

Pulled shot today and rebound is still upwards of 10 minutes. If I want to get a second shot at 200F, It actually seems slightly faster but that could be my imagination. But certainly rebound is still slow. My best strategy for now is to set the PID high and pull the first shot at about 202-201 and then the second shot can be about 197.. Then I could do a third shot in 10 minutes and that gives me 3 shots in somewhat a reasonable time. 6 shots would still be a 15 minute wait in the middle. For experimenting with temperature on taste, the best strategy would be to go hot on the first one, and then the natural declining 4-5F drop in temp would be automatic for successive shots..

My suspicion is that as soon as you add a small restriction in the TS loop, it becomes very sensitive to many attributes in that path; bends in copper pipe, level of steam in boiler, etc. Unfortunately, I doubt that Profitec and their suppliers do any type of performance measurements on each machine that pertain to rebound and so each machine behaves slightly different. (In fact, it is unlikely there is even any performance 'standard' that exists for their HX product). Most machines may behave acceptably. But certainly there are posts on HB of slow rebound on HX-restrictor designs from Profitec and other manufacturers. I'm surprised that the manufacturers don't attempt to set some parameters for performance on their machines. When you look at 'specs', they generally only list the mechanical specs, like boiler type, capacity, etc.

From what I've gleaned watching all the WLL videos, it seems they helped Profitec develop the HX restriction-PID design and maybe their tests were conducted on their "prototype" machine which, obviously, would perform according to their desired design specs. Or maybe there is something else wonky in my specific machine.

I feel I can use this machine effectively now.. However, it did require significant additional measuring tools and expense to get to a point where I feel comfortable about knowing where the brew water temp is at.

It may be that I can enlarge the restriction from 2.5mm to something like 2.8 and get better rebound performance. And maybe this is the only practical way to tune the performance on this machine. That is for another time.

UPDATE: There is a definite improvement in the rebound after taking off the restrictor pipe and reaming out and enlarging the hole. My guess is that it might effectively be 2.6-2.7mm now. (Originally 2.5mm) My group is returning to the 200F idle much faster that before (I got 4 minutes today, compared to 10 minutes previously; but I'm using the double spouted portafilter which has more mass than the bottomless and my PID is slightly higher (258F). I had to do 2 cooling flushes before the first shot; and I've never had to do that before. For anyone with a slow rebound, this was a very simple mod on my machine. Don't have exact data points as I've returned SCACE.

Update: June 22, 2020

I written quite a bit about the issues on low brew water temp with the Profitec Pro 500 PID.. I just watched a video from:
http://www.youtube.com/watch?v=pTDWMQr9SlQ. Now I had to auto-translate from German, so if anyone reading this speaks German, let me know if I got it wrong.

Seems they recently tested a Pro 500 PID. Set the machine to the manual recommendation and voila.. bad espresso. You can also see them testing the machine for shot after shot and getting low readings.. about 90C when they are going for 93C.. They eventually get up to 93-95 and better tasting drink, but only after they raise their PID and use a SCACE, which no user would have access to.

Their machine seems to exhibit the same type of performance as what I measured and have come to observe over 2 years of its use.
a) a manual with wrong information (you think they'd want to write a better manual)
b) very slow rebound .. I think in this video they were discussing making espresso for a party of 8. This would be almost impossible for a reasonable time frame.
c) a requirement of a group head thermometer to use this machine properly

I think in the video the two testers are wondering if their machine is a "Monday machine".. maybe mine is too..

Also, if anyone has this machine and the heater 'dies' within a few years.. it is likely the SSR which should be relocated to a cooler place underneath as it is likely being thermally overloaded and failing open.

Yup, didn't listen to the entire thing, but you got the right idea from the video. They basically say that without the extra tools available to them, they'd have been lost what to do and how to fix the issues. And yea they definitely considered this machine could be faulty. Gotta say, that was a pretty insightful review.

I have the non-pid version of the profitec 500 and have been struggling with the temperature inconsistency here as well. My rebound time is certainly quicker than yours, but getting consistent temperature readouts is really hard. Without eric's thermometer I was running completely blind. I am really beginning to think these machines were not very well designed.

Bach

yes.. not only poorly designed, but the manufacturing tolerance from machine to machine in the TS loop may be too loose.. and contributing to very differing performances..

On top of that, Profitec seem very uninterested in connecting with customers (I contacted them twice) and the largest vendor in Canada, that I am aware of, does not really know the technical ins and outs of the unit to offer any assistance.. And I can't believe Profitec does not have better technical info on how to use their HX on their site, with the info in their manual just being wrong.

It has certainly given me a totally different perspective on Profitec/ECM.. I've actually started to use my Robot more for extractions and the Pro500 as a very over-priced steamer.

Sorry to hear that... how is the robot working out for you? i was contemplating getting one as well.

What is your work flow for the robot? What kinda water and how hot do you use for it?

Cheers

Robot works well. I can use straight tap water but often use RO with tww crystals. Same as for HX. I preHeat the piston if using a lighter roast there is a thread here about preheating the robot. I use 17g. Preinfusion for about 10 seconds then pull a lever type of profile. I find results good but I'm not an experienced pure espresso drinker. My friend has a flare pro v2. That can be preheated a touch hotter. Both give great results.

I should have one in a day or so, so will play with it before giving it back to my friend.

I read the thread, how are you heating the piston, just hot water in a cup/container and piston down or ?

Hot water in a tall glass will work. I taped the inside ofcthe double spout to block holes and added boiling water to that. You learn how much. Too much it will overflow. Soak fir a minute or two. Make basket. Tamp. Put screen in and push down 2fingers on each side of centre. Get pf and remove double spout. Install basket. Gently fill near top wait 30 sec Then gently pur 90% out. Refill and pull shot
You dont need both types of preheat. Med beans i only preheat basket.