I own my Rocket for ten years now. The idle temperature of my grouphead used to be 208F with boiler pressure set to 1.15. During last winter it dropped to 205F which I found pretty obvious due to lower room temperatures. I covered the grouphead with a cloth to increase temperature again to 208F. However, it kept lowering to 200F. Therefore I inspected the grouphead for scale and found the mushroom was blocked with a small piece of limescale. Once removed, temperature was back to 205F.

It is summer now and temperature has not reached 208F anymore. Grouphead inspected again, a lot of limescale, thought the mushroom was not blocked. I decided to descale whole system, replacing also some o-rings, infusion valve, brass lever and expansion valve, cleaning and lubricating hot water and steam sections. Everything is running smoothly like out-of-the-box, though idle temperature is 200-202F which drives me nuts. I could increase the boiler pressure, but I want to solve the problem.

Some observations made, also taking into account similar topics on HB:
- there is no moisture observed in the portafilter when the machine is idle (of course there is some after the flushing). There is no water dropping from the bottom of grouphead, thus I assume it is well sealed
- there are some limescale pieces coming from the hot wand steam when opened
- flushing the system several times does not change temperature
- releasing some steam and water from hot-steam wand couple of times increases idle grouphead temperature to 207-208F

Any suggestions what might be wrong, and why temperature sometimes increases to the (almost) desired value upon releasing steam/hot water? Some ideas of mine for next steps:
- to inspect mushroom for any clogs
- to inspect restrictor for any clogs
- to increase the boiler pressure to 1.3
- to descale again to get rid of remaining clogs (if any)

kulka wrote: Any suggestions what might be wrong, and why temperature sometimes increases to the (almost) desired value upon releasing steam/hot water? Some ideas of mine for next steps:
- to inspect mushroom for any clogs
- to inspect restrictor for any clogs
- to increase the boiler pressure to 1.3
- to descale again to get rid of remaining clogs (if any)

When you "descaled the whole system", you mean you descaled the HX circuit and the boiler circuit, correct?
I would take out the boiler fill probe and look at it to make sure it's shiny. If you can see inside the boiler through its hole, see what it looks like in there.

If you start with the boiler filled and take the mushroom out (You don't want the pump coming on for boiler fill with the mushroom out), and push the brew valve off center with your finger to drain the head a little bit, and re-center it to stop the head from draining...
Then turn the machine on, you will be able to see how much thermosiphon flow is occurring. (add a little cold water to the open head until it's just slightly lower than the upper port at the back of the E61 head)... The water should be visibly flowing to the head through that upper port. A spoonful of citric acid also lets you see if there's any chemical reaction occurring (as in, there's still more calcium).

kulka wrote:- releasing some steam and water from hot-steam wand couple of times increases idle grouphead temperature to 207-208F

That's the sign of false pressure. From Can someone please explain false pressure?

another_jim wrote:"False pressure" is air pressure rather than steam pressure. Air expands and hits a level that will fool the pstat before the water even reaches boiling. A temperature PID would not be fooled and would not need a vacuum breaker (although the initial steam output would be thin). I have no clue where the air comes from if there is no vacuum breaker and the system stays sealed; but if the pressure isn't from water, it has to be from air.

In other words, the steam boiler needs to be only saturated steam. If there's a mixture of air and steam (water), then the pressurestat will stop heating prematurely.

Additionally, and sorry if it's none of my business...
The Evo is the plumbable machine, is it not? You really should get a decent (sodium exchange) water softener for that thing. Having to descale it often isn't much cheaper and certainly more stressful to the machine.

Yes, the HX circuit and boiler circuit were descaled.

The false pressure idea is interesting, but if I understand correctly it may happen to the machines not equipped with vacuum breaker, correct? Mine is and it was recently replaced. Moreover, releasing the steam and hot-water works just to some extent - sometimes to 207-208F, sometimes just to 205F.

I was using water softener from the very beginning. Two years jug-system with additional filter inside water tank. Then I switched to more fancy sodium exchange, still with water tank. Now the machine is plumbed with BWT Mg+ filter I am really pleased with, however the problem started before it was plumbed. I also checked whether switching back to tank would make any chance and no, it did not.

Yet another observation - I'm pretty sure the water flow is different for one brew and another. Previously I blamed grinder setting/weather combination, but today the same grind level, tamp force, water pump pressure and brew time resulted in quite two different yields. Could it be because some clog is running through the system?

Today I inspected the grouphead and there is even more limescale than before descaling. The mushroom holes were a little bit clodged, perhaps this is the reason why the grouphead did not reached its max temperature. The water flow rate is different almost every time - one it is a continues flow, another time the flow is interrupted with steam splashes. And each time there is a lot of limescale in the water. I'm definitely not happy with the 'professional' service I had.

In addition to the all good point already mentioned,
in many, if not all EhEx machines
there is a restrictor (in addition to the gigleur)
sometime located in the connection and in side the fitting from boiler to pipe or from pipe to HeEx grouphead incoming fitting,
when scale is present, that restrictor,,,, will get restricted even more so,
again I do not know if your specific model has one but is possible.

kulka wrote:I decided to descale whole system

Was this the first descale since you owned the machine?

If so, it would be well worth it to syphon the boiler and flush the HX tube both ways, i.e. running water into top, then bottom holes in the group.

cafeIKE wrote:Was this the first descale since you owned the machine?
If so, it would be well worth it to syphon the boiler and flush the HX tube both ways, i.e. running water into top, then bottom holes in the group.

Indeed this is the first descale ever. Do you mean to inject water into top hole in the group, and then to the bottom hole in the group? Of somehow from the inside of the machine?

I will check for the restrictor but first I need to remove completely limescale. And I need to do this on my own. This is how much limescale is the after several cups of coffees made. And this is how much limescale comes when the water pump is on (mind empty grouphead). What worries me is that the limescale has different colours, is this normal or are these some minerals? The limescale is spitted out every time hot-water wand is opened or the water pump is on, but there is no correlation between amount of water and amount of limescale (i.e. more water does not mean more limescale is spitted out). However, there is much more limescale coming from the group than from hot-water wand. Any suggestions of what could I do without too much 'engineering' are much appreciated. I'm thinking on:
- flushing the whole system until there is no limescale coming out
- repeat descaling (with citric acid this time, previously Dezcal was used)
- take out all the tubes and descale them in a bath (not really happy with that)

The restrictor that Stefano mentioned is in the upper fitting of the HX to group tubing on the EVO v2. That fitting can be easily removed for inspection. See E61 HX Choice - Profitec Pro 500 PID or Rocket Giotto/Cellini Evoluzione V2?. It's an appx 3 mm orifice, but can clog and cause a cool group. The tiny 0.7mm gicleur at the top of the mushroom clogs more easily, but is not part of the thermosyphon loop.

Pure limescale is white, but scale inside the machine may have other colors - brown for traces of oxides and blue-green for traces of copper corrosion.

When scale gets bad, dismantling and descaling in a bath is always best. I think you could get away with removing a fitting like the anti-vac valve and doing repeated descaling and rinsing of the boiler, with strong spray and siphoning until its clean of all loosened scale, maybe remove the pressurestat and make sure that pipe is clear, then finish up with a final conventional descale or two. Others with professional experience (Stefano or JRising for example) would know best about that.

As JRising said, you need to use softer or softened water.