Problem with ECM Giotto pressurestat?

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by dubsea »

First time poster. Im hoping I can get some advice on a problem Im having with an older ECM Giotto Machine at our office.

The issue is nearly identical to what was covered in this old thread: Problem with ECM Giotto pressurestat

We have now had the pressurestat replaced 3 times by our local esspresso technician company. Each time the issue returns in a matter of 3-9 months. The last time the technician came out, they replaced the single circuit pressurestat with a larger one that had 3 circuits and said if the issue reoccurs, just move the wiring to the next circuit.

Aside from the new large pressurestat being too big for the machine and requiring that a heat shield was removed and the water tank sits crooked, I cant help but feel like there is some issue that is causing the pressurestat to malfunction.

Basically once the boiler heats up the pressure release safety valve is nearly constantly sending out steam and hissing.

Even when it is working correctly after a new pressurestat is installed, it's still nearly impossible to pull a nice shot from the machine. I have a Rocket Cellini at home and use the same beans to get consistently great shots, but simply cannot get the machine at work to play nice.

Couple of possibly relevant points:
-I recently did a full descale and unlike the user in the post I linked above, it did not seem to make any difference.
-I checked the line from the pressurestat to the boiler and it is not clogged.
-Some of the wiring looks a bit old and questionable but I verified the connections are tight.

Any suggestions on what might be causing the pressurestat to be going haywire? or am I on the wrong track here?

User avatar

#2: Post by stefano65 »

Well with out really going too deep into this
if the safety valve is always open can be weak or the pressurestat
can be adjusted too high,
do you have a steam gauge that reads correctly?
Stefano Cremonesi
Stefano's Espresso Care
Repairs & sales from Oregon.


#3: Post by PhilthyCoffee »

I'm certainly not expert like Stefano's, but first thing I'd take the plastic cover off the pressurestat and see if the terminals look burnt where the wires are connected. It should be noticable without having to remove any wires. If so, maybe there's a short or damaged wire causing the issue and damaging the pressurestat. Issue doesn't sound pressurestat related, those Sirai's are supposedly stout, should probably be good for at least 5 years I would think. I just replaced mine on my Rocket Giotto maybe a year ago after it started making a bad connection due to age.

dubsea (original poster)

#4: Post by dubsea (original poster) »

Thanks for the reply Stefano.

To clarify, when the new pressurestat is installed in seems to function fine with the exception of me having a really hard time pulling anything close to a descent shot.

In it's current not-functioning state, the safety valve is nearly constantly on. I dont have a steam gauge and was thinking about playing with the pressurestat adjustment on the current 3 circut pressurestat....but considering the history of the repeated issues, it makes me think something else is going on which is causing the repeated pressurestat failures.....and terrible shots.

dubsea (original poster)

#5: Post by dubsea (original poster) »

Checked connections on the pressurestat and they look good. This is not a Sirai pressurestat but rather its one meant for a larger machine that the tech said would give me less problems. I was thinking about moving the wires to the next circuit but at this point after being on the 4th pressurestat in ~3-4 years, continuing to mess address this by dealing with the pressurestat is starting to feel like im addressing the symptoms and not the cause.

Team HB

#6: Post by JRising »

dubsea wrote: In it's current not-functioning state, the safety valve is nearly constantly on.
If you can rig some sort of way of measuring the boiler pressure (I really thought all Giottos had a gauge) that would be best. Even just a very tight hose over the steam tip and a gauge held tightly for a few seconds while you open and close thre steam valve.

You'd be able to confirm whether or not the safety valve is working = relieving because the boiler is > 1.5 bar...
Or leaking = relieving despite being below 1.4 bar.

Additionally, it would help you find a good pressure at which to set the p-stat, maybe bring the boiler down to the 1.0 to 1.2 range if the deadband is tight, it might help with the nasty burnt coffee flavour.

dubsea (original poster)

#7: Post by dubsea (original poster) »

Sorry about the confusion, this machine does have a gauge. Currently the pressure relieve valve is activating well below 1 bar on the gauge. This was not the case when past issues were occurring and the valve would only release around the 1.5 bar range.

Im going to pull appart the valve shortly and see what I find.

Team HB

#8: Post by JRising »

Replace the Safety valve.
I do recommend taking apart and trying to clean and fix components that don't have the word "Safety" in their name. Things that do have that word should be replaced with new. If you rebuild it to not leak at 1.5 Bar, you can't be sure it will relieve at 1.8 or wherever it your boiler starts to become a pipe bomb.
★ Helpful

dubsea (original poster)

#9: Post by dubsea (original poster) »

So it is actually the Vacuum Breaker valve which is leaking. Not the safety valve. I took it apart and it appears the an oring is torn. Im gunna get that replaced and replace the pressurestat again and see where I get after another descale.

dubsea (original poster)

#10: Post by dubsea (original poster) »

Quick update here - After replacing the oring on the vacuum valve and installing a new normal sized pressurestat we are back in business! 1 month + with no issues.

I suspect the torn oring in the anti-vacuum valve was letting pressure seep from the boiler which was repeatedly triggering the pressurestat and likely over-working it which caused it to fail prematurely.

More than a bit disappointed in my local (and seemingly well respected espresso repair company) who replaced the pressurestat 2x before installing the industrial sized one which also eventually gave up the ghost.