Hi folks,

I have a GS3 AV.

I haven't paid attention to it for a long time, but I just noticed that the pressure continues to rise above 9 bar (about 12 bar to be exact) during extraction (with coffee).

When empty, however, at free flow the pressure remains at 9 bar.

If I adjust the pressure while extracting (with coffee) to 9 bar, I have 7 bar when empty (free flow).
The amount of water when set at 9bar during free flow is around 500ml/min.

Can someone help me here?
Is that normal? Or how do I set it up correctly? Internet and operating instructions contradict each other here.

Thanks and Greetings
r

Sounds like your expansion valve isn't adjusted properly, or has gotten out of adjustment, or is clogged with scale.

When the pump bypass valve and expansion valve are adjusted correctly, the free-flow (no puck) pressure should be 9 BAR, the max pressure when re-heating after running the group should be 12 BAR and the pressure when pulling a shot should be about 10-10.5 BAR (there's about a 1-1.5 BAR pressure drop at the puck caused by the flow restrictor -- gicleur -- in the group head, so pressure there should be about 9 BAR during a pull.) Backflush pressure with a blind basket should be roughly 10.5-11 BAR.

First step is to adjust the expansion valve. The normal procedure is to run the group for about 15 seconds, then watch the pressure as the boiler reheats. You turn the part of the expansion valve that sticks down into the drain box so that the pressure reaches 12 BAR -- and no higher -- during the reheat cycle (see CAUTION note below.) Then check the free-flow pressure, which should be 9 BAR. If it isn't, the adjust the pump bypass valve so the free flow pressure is 9 BAR, then repeat the expansion valve adjustment. You might have to go back and forth between the two adjustments a couple of times.

CAUTION: Given that you haven't done the adjustment in a long time -- or ever -- the expansion valve threads may be jammed by scale. If you attempt to turn the expansion valve when the threads are jammed, you'll bend and twist the tube that connects the expansion valve to the coffee boiler. Most likely the tube will have to be replaced. To avoid this, you'll need two wrenches or a wrench and pair of pliers. Open the right side cover. You'll see the expansion valve screws into a male-male fitting that you can grab with a wrench to keep the tube from turning while you turn the lower part of the expansion valve with another wrench or pair of pliers. Which one depends on which version of the expansion valve you have. Newer versions have a couple of bevels at the bottom that allow you turn the tube with a wrench. Older versions have a smooth tube that requires a wrench. Best to cover the wrench with electrical tape and squeeze it very gently when turning. Otherwise, the tube will deform or get crushed.

If you can't turn the expansion valve, try wrapping the thread area with a rag soaked in distilled vinegar to dissolve the scale. If worse comes to worse, you may have to replace the expansion valve. The machine should be off and cold when you remove the valve, and use two wrenches to remove it so you don't damage the tube.

If you can turn the expansion valve, but the pressure still rises to 12 BAR during a shot, it's likely that the expansion valve is clogged with scale. You can try removing it and soaking it in distilled vinegar to remove the scale. If that doesn't do the trick, replace the valve.

Hi,

its me again - having problems with the GS3 brew pressure.

I am wondering what the right brew pressure now is.

According to the GS3 manual:
The water pump is factory set at 9 bar pressure. (....) The water pump pressure should be adjusted when the machine is operating and coffee is present in the portafilter.

My first question is: is that true because of the pressure drop in the gicleur? Or do they mean pressure after the drop, meaning there is more pressure as seen on the built-in readings?

So, I read in this forum that the pressure at free-flow should be 9 bar - meaning no coffee and portafilter present - and then it should rise to about 10-11 bar when coffee is present.
So i followed your advice as it sounds more logical to me..

And this is what happens:
Pressure at free flow is set to 9 bar, but brew pressure when pulling a shot rises up to slightly over 12 bar with water drops from the expansion valve.
My conclusion: pump pressure is set to high.

So what I can do now is set the free flow pressure to around 8 bar and then is should work.
But isnt there something wrong within the system? Or do I get something completely wrong.

Help is very appreciated
Thanks

UPDATE:
i recently had the same problem before and solved by readjusting the expansion valve again. Seems now that it is clogged again....
So sorry seems to me i have posted here too fast...
I am letting you know if it works.
thanks @peppersass for your help with my problem last time

Hi all,

Now I cleaned the expansion valve and tried everything again.
Unfortunately, nothing changed:
When pressure is at 8 bar (instead of 9 bar) during free flow, I get the the 10-11 bar. When pressure is at 9, it increases to over 12 bar- almost 13 bar.

Other than having leakage problems at the expansion valve that i solved temporarily with a tape, I have no explanation for that.
Does anyone have any ideas what the problem could be? I hope it is not the pump after all...

Anyway, I decided to buy a new expansion valve, but I think this wont solve the problem...
The expansion valve should be set right at 12 bar. I did the test mentioned above and also experience significant water outflow when the pressure reaches 12 bar...

Thanks

Hey Jules,

Can you measure the flow rate from your group head during free flow?

Thanks!

- Jake

Hi Jake,

free flow is about 500ml / min.

Thanks,
r

Strange.

That's in the correct ballpark.

So here's the thing: when you set the bypass on the pump, you are setting it to a fixed pressure. Whatever the pressure is at the pump when you set the pressure on the bypass is what it stays at, unless your bypass is misbehaving.

So if you are seeing 9 bar at free flow, and 12 bar when pulling a shot, that means your pump should be generating 12 bar or more during free flow. The 9 bar that your panel gauge is registering is a function of the flow rate through, and the pressure drop across the gicleur in the group. If your free flow was quite high, you would need to turn the pump pressure higher than normal in order to generate 9 bar during free flow, and I would expect the pressure to behave as you are seeing when you pull shot. But I would also expect your free flow rate to be significantly higher than it is.

The other alternative would be that you have a significant pressure drop across the gicleur in the flow meter, which is before the brew boiler and the panel pressure gauge. If this were generating an excessive pressure drop during free flow, you might see the same issue, where free flow pressure is much lower than when brewing. But in this case, I would expect your free flow rate to be much lower than what you measured.

So that leaves a misbehaving bypass valve on your pump.
The bypass valve works by rerouting all the water that isn't flowing through the group back to the inlet of the pump. If the path back to the inlet has an obstruction in it, the bypass may not be able to lower the brew pressure sufficiently when you are pulling a shot.

The pump in your machine should be a 70LPH pump, which is 1,167 ml/min. Since it seems that your bypass is working correctly in free flow, which is ~500ml/min, that means it is able to flow at least 667ml/min back to the inlet of the pump. But when you pull a shot, the flow rate plummets to 120ml/min or even less, and it appears your bypass is unable to circulate over 1,000ml/min without the pressure rising.

I would recommend removing the pump bypass and cleaning the passages. It may be easiest to remove the pump from the machine to do this, and in either case, only work on it with the machine cooled down, powered off at the main switch and unplugged. Good news is that pump issues are easier than issues in the flow meter or group. Also good news is that your pump is over-achieving on delivering pressure, so while the bypass may be causing your grief, the pump itself is likely quite healthy.

Sorry for the long post, hope this helps.

Cheers!

- Jake

Hi Jake,

thanks for your help.

Your explanation seems consistent! I like that.

Is there a smart way to remove the pump? I never did it, so do you have some recommendations which parts need to be removed before or can be removed together?

Regards,
Julian

Just the cup warmer grate and tray.

Then you can loosen the clamp that holds the pump to the motor from above (after you remove reservoir fitting and the stainless braided discharge hose). That clamp is the only thing securing the pump.