Is it just me, or is that needle not resting on the peg?

Also note that accuracy for this type of gauge is often given separately for the middle versus the top/bottom of the range; they're often expected to be more accurate in the middle of the range. If it gets knocked off a little at the bottom of the range, it might have more of an impact in the middle (operating) range.

sbenyo wrote:
I also noticed that the heat light comes on and off every 14secs sharp after the machine is completely heated. Is this the normal rate for heat cycle when the machine is on and idle?

My Semi heater also cycles on for precisely 14 seconds, then shuts off, when the machine is idling; the gauge needle then takes around 50 seconds to float down to the bottom of the green range before things kick in again. The machine tech at 1st Line says this is within normal operating parameters, and I have had absolutely no issues with it functioning this way.

sbenyo wrote:
I am also quite sure my rubber base is kind of glued to the bottom....

You may, in fact, be correct, but it is likely just a build-up of dried-on spilled coffee and/or other liquid detritus. However, it does seem to be a tight seal at the best of time; you'll just have to take a crack at it. Try soaking the entire perimeter joint with warm water from a sprayer first and as DJF suggests, gently work it loose all around with something non-metallic that's not too sharp but long enough to provide some twisting/prying leverage.

I finally found the time and courage to open the bottom part of the machine and adjust the pressurestat. (The pressurestat is a MATER model)

I did a few tests:

1. Turned the pressurestat quarter of a turn clockwise:
The machine heated a bit higher than usual. It reached and stayed on the higher end of the red area.

2. Turned the pressurestat back to original position and a quarter of a turn anti-clockwise:
The machine did not change from original. It reached the lower end of the red area. (Same as original position)

3. Turned the pressurestat full half turn anti-clockwise from original position:
No change. The machine still heats to the lower end of the red area.

In all tests the steam pressure still seems too powerful to me. It creates too much steam when valve is fully open. I still can't steam milk properly and instead of microfoam the pressure creates very large bubbles. The milk seems to be heating too fast and gets to max temperature in about 10-15secs which makes it really hard to control.

I completely replaced the steam wand with a new one to eliminate this factor.
I am still not sure what is wrong. It can be either the pressurestat, gauge or maybe the steam valve itself.
I am also not sure what result I should be looking for and what should be the right steam pressure. Maybe I am getting the right pressure and I am just not using it right... (I really doubt it as everywhere it is stated how easy it is to create perfect microfoam)

I have no idea what to do next. Any recommendations what I should try? Maybe I need to lower the pressurestat more or even replace it.

Install a new pressurestat and adjust it, if necessary, so that the needle on the pressure gauge remains within the green zone at the top of the boiler cycle and so that the heater kicks in again at between .9 and 1.1 bars.

The pressurestat may not be your only problem, but nothing else will be clear until you repair/replace it. It's unfortunate that you replaced the steam wand before addressing your overpressure issue. Unless you can see serious physical damage to the old wand, it was probably unnecessary. If the wand itself was part of the problem, disassembling and cleaning it would have almost certainly have sufficed.

And really, you shouldn't even be operating the machine with that degree of chronic overpressure. The red on the gauge means "warning: stop," after all. Of course, there is a safety valve installed on the boiler, but runaway pressure can't be good for the machine.

Did you descale? I suggest taking the p/stat off and having a look inside via the connections.. If it's scaled up use an eye dropper or something and get some descaler in there. If that doesn't work get a new one for peace of mind like David says. Most regard these p/stats as a maintenance item anyway. .

Edit; Before taking it out try turning the adjuster a full 1/2 turn or more AC and see what happens. Don't let it right out though .

DJF wrote:Did you descale?

What he said! If you haven't yet done a through descale of both the boiler and the waterline to the group, do so ASAP, before swapping out the pressurestat.

FYI: The clear coat on the Semi is prone to damage from the acid in the descaler. Wipe up all spills and splashes IMMEDIATELY, and swab the affected area with a 15% isopropyl alcohol solution to clean and neutralize (avoid getting alcohol on the white paint of the front badge, however).

Here is my descale method:
If I remember correctly, it takes about 1.5 liters of descaler to do the Semi, so mix this up and have it ready in a vessel with a good pour spout. Mix up a little more if necessary.

Best to start with a cold machine. Unplug the machine, remove the steam wand, open the steam valve, and completely drain the boiler into the sink. Turn off the steam valve and add all the descaler to the reservoir. Proceed immediately to descale so that the solution spends a minimum amount of time in the reservoir.

Turn on the machine and IMMEDIATELY refill the boiler all the way. CAUTION: Failure to immediately refill can result in ruining the heating element, as per the manufacturer's warning in the manual. When the solution reaches the top of the sight glass, continue to fill for 10 seconds. Draw off water through the group until you see the solution start to come through; this should take abt. 4-5 ozs. Turn off the machine and let sit for several hours. As soon as you shut off the machine, check the reservoir and remove any excess descaler; rinse and wipe out the reservoir to remove all traces of solution.

Drain all the descaler into the sink through the steam valve. Shut off the steam valve and refill the boiler with clean water; continue filling up to a count of 12 seconds after the water reaches the top of the sight glass. Leave some clean water in the reservoir and run this through the group, about a cup at a time, turning the machine off and waiting a few minutes between flushes. Do this for about a half hour, for a total of about six group flushes. Unplug the machine again and drain the boiler into the sink.

Repeat the rinse at least twice more. This may seem like tedious overkill, but it takes a LOT of flushing to purge all traces of descaler from the lines.

The first thing I tried is to adjust the pressurestat more. I took it full anit-clockwise turn from original position.
It has now finally settled on the middle of the green area, even after waiting enough time for it to heat up!

That's a good start. Then I tried again to froth milk, turning the steam valve all the way as recommended here. This time it seems to me that I had more control over the steam. It is not as hot or strong as it used to be. It is still heating quickly to max temp but I think I have to give it more chance and practice before I can say if it's functioning properly now.

One thing that did happen is that after frothing milk the temperature raised a bit over the green area into the yellow. After a while it settled back to the high end of the green area and stayed there. I am not sure this is how it should be but I will definitely give it a try now!
In addition the heat cycle has jumped from every 14secs to every 42-45secs. I hope this is the normal rate and a kind of sign temperature and pressure are right.

thankfully the pressurestat is tuned tight, and while the machine cycles often (roughly every 25 seconds), the cycle time itself is short (about 9.5 seconds). What does this mean? It means the machine's electrics are very much on top of maintaining boiler temperatures and the heating element, at only 800W, does the job efficiently; that said, the machine does lose a lot of ambient heat by nature of its design.

From this; https://www.coffeegeek.com/proreviews/d ... erformance

Thanks. I missed it when I read this review.
I seems that it is OK that it is having short heat cycles. I took another half turn on the pressurestat. It did not really change. Now it is on the green area and after steaming on the high end of it. It cycles now every 10 or 20 seconds.

I am still working to the my steaming skills. It does seems better but I still find it hard to steam properly. I will keep practicing before I give up and go for other options like descaling or replacing the pressurestat.

Looks like the good Dr. had the right idea on continuing to fiddle with the existing pressure stat. Only time will tell now if it is really o.k. It should stabilize longterm into a steady range cycling within about .2 bars. If it cycles erratically or starts to climb higher than normal consistently, it will need further maintenance or replacement. Choose one of the suggested ranges and stick with it for a while to let everything settle in while you observe.

Descaling: It's not just an optional troubleshooting step. If you purchased this machine secondhand, it should have been one of the first things you did as a routine part of taking ownership. Short of an initial stripdown, you really have no way of evaluating the existing scale buildup, which can wreak havoc with many aspects of machine performance. So, just do it!

After descaling, you may well need to readjust the pressurestat.

After that, it still needs to be done routinely as maintenance. The frequency and method will depend on the kind of water you are running through the group and the boiler respectively.

Don't expect to perfect your milk steaming by tinkering with the machine alone. Clean, descale, and adjust till the machine functions normally; then, as has been suggested, practice, practice, practice!