Hi everyone!  I am having a bit of a problem with my Nuova Simonelli 2 group Appia Compact.  The pump pressure(the bottom half of my pressure gauge) keeps going up to about 12 or 15 even at rest.  I adjusted it back down manually a couple of times back to 3 - 5 bars at rest and 9-10 while pouring and it seemed to work fine for a couple of weeks each time.  Now it just won’t stay where it should when adjusted anymore.  A friend of mine suggested it might be that the solenoid valve went bad but I certainly don’t know.  Any suggestions or ideas would be greatly appreciated.  Thanks so much!

Views: 6130

Reply to This

Replies to This Discussion

Sad I missed this discussion. It cannot be the internal pump if it goes down to 9 bar when pulling. When you are not pulling shots the gauge shows the incomming pressure, nothing in your espresso machine effects that pressure.

It it likely because you have a check valve and a faulty pressure regulator installed before the machine, or in your building. In NC and many other states we are required to install check valve to prevent possibly contaminated water from getting back into the water system.

The problem is, if you dont open your lines and release the pressure often enough, eventually that check valve in combination with a faulty pressure regulator will cause a build up of pressure on its stop side. Normally this goes unnoticed because people use there water.

A pressure regulator looks like a brass icecream cone with a long screw it. Adjusting it is counterintuitive. You tighten to increase your water pressure.


Eli Masem said:

Thanks guys. this gives me a good base of troubleshooting knowledge to go on.  Tomorrow I'll be testing everything from my flojet to the connections, to retrying the pump after taking the spring out for some spring squeezing. I have a feeling, though, that it comes down to the internal pump. time we'll tell and so will I when i finally get it back to go.  :)

Sorry I didn't see this thread sooner too!  The real question here (as previously mentioned by Mickael and seemingly ignored) is what pressure you get while pulling shots, because resting pressure varies quite a bit and doesn't really matter.

Every espresso machine has a check valve to keep water from backing out of the machine into the plumbing system when the pump is off and the boiler is heating - heating the water causes it to expand and builds pressure above and beyond the incoming line pressure. Every machine also has an expansion valve to relieve that buildup of pressure when it gets too high (usually set around 12 bars.)  Check valves and pressure regulators external to the machine aren't going to be your problem. If the internal components are working properly you won't see unsafe pressures on your gauges.

It's perfectly normal for the "pump pressure" gauge to climb from incoming line water pressure up to anywhere from 9-12 bars while the machine is resting and the water in the heat exchanger is heating.  In fact, if you DON'T see that rise pretty regularly after pulling shots, it probably means that your expansion valve is releasing pressure too early and not holding like it should.

The first step is to adjust the expansion valve such that it holds pressure (no water comes out the drain/exhaust side of it) up to at least 10-11 bars (it needs to be set at a higher pressure than the desired pump pressure) and so that it releases pressure above 12 bars so that you don't have unsafe pressure building in the system.  Again, this pressure is not coming from outside of the machine, nor from the pump.  This pressure builds as a result of heating water.

Once the expansion valve is set to work properly (and if it isn't adjustable or won't adjust as it should, it needs to be replaced) you can look at pump pressure.  The reason it's critical to verify expansion valve function before messing with the pump is because if you set the expansion valve to keep resting pressure at 3-5 bars, then it's going to be releasing water down the drain and bleeding pressure every time the pump kicks on.  On many machines, the pump can run so much faster than the expansion valve can drain that you'll still be able to set 9-10 bars of pump pressure even with the expansion valve opening, but you'll be wasting tons of water and get much less consistency on your pump pressure.

So, once the expansion valve is set properly and/or replaced, set the pump for around 9 bars of pressure.  When everything is working properly, you should see 9 bars of pressure anytime the pump is running and anywhere from line pressure (typically 3-6 bars) to 12 bars at rest.

As usual, I've written way too much and I apologize.  Hope this helps and it's not too late.  If I've misunderstood the description of the problem, sorry.  I'd love to hear what finally fixes things for you.

Reply to Discussion


Barista Exchange Partners

Barista Exchange Friends

Keep Barista Exchange Free

Are you enjoying Barista Exchange? Is it helping you promote your business and helping you network in this great industry? Donate today to keep it free to all members. Supporters can join the "Supporters Group" with a donation. Thanks!

Clicky Web Analytics

© 2022   Created by Matt Milletto.   Powered by

Badges  |  Report an Issue  |  Terms of Service