I own a full service espresso bar with a 2-group La Marzocco Gb/5. The machine is 5 years old. We maintain it well with a water softener and we back flush everyday with Puro Caffe. We are guilty of not replacing the water softener as much as we should. About 2 times a year right now but the water in Houston is not that bad. This week we have been losing all the pressure for the steam wand boiler. It will just drop from the 1.5 bars to zero. We have been shutting off the machine, turning off the water valve that fills the boilers that is on the side of the machine and then re-opening the valve and turning the machine back on. It has been resetting that way although it might take 2 to 3 attempts before the pressure starts building again. We have checked the fill probes for the boiler and the first time we experienced this problem a month ago there was some calcium build up on the tips of the probes. We cleaned/replaced them and that seemed to fix the problem, initially. Now this week we're having the same problem but the probes are clean. I'm not sure if the issue is a fuse/electrical problem or a calcium build up problem. Nonetheless the boiler is getting an inconsistent fill and will lose the pressure as stated above. Any ideas? Thanks

It sounds like the steam boiler isn't getting filled to the proper level. Calcium buildup on the level probe wouldn't cause this. More likely, it would cause just the opposite problem -- overfill.

The probe works by conducting electricity through the water to the boiler, which is at ground potential. When the probe conducts, it means water has reached the proper level. When it doesn't conduct, the water level is below the probe and the steam boiler needs to be filled. If the probe is caked with scale, and that prevents conduction (not a given), then the boiler would be calling for water all the time and would overfill (you'd see water streaming out of the OPV.)

My guess would be that there's a partial blockage in the steam boiler intake line, or the solenoid/valve isn't opening reliably. I don't know if your machine uses the pump to fill the steam boiler or relies on line pressure to do that. If the pump is used, then I would think if the boiler wasn't filling that the pump would be running continuously. Do you hear that when the boiler pressure drops? If the machine uses line pressure, then you wouldn't hear the pump when the problem occurs.

The only sense I can make of the problem being reset when you close and open the main water valve on the side of the machine is that the cycling of line pressure is pushing through whatever blockage is in the path to the steam boiler.

You can test steam boiler filling by using the hot water wand to drain water from the steam boiler and observe whether or not it fills properly. If it doesn't fill, you'll run out of hot water.

An inconsistent fill? What do you mean? Is the sightglass empty? If the boiler isn't filling, the overtemp shutoff might be firing...

Loss of steam is probably from low level in the boiler. There is a "security" or low level probe in the steam boiler and once it goes below that one then the steam boiler shuts off.

Is your pump running all of the time? I would definitely check the steam boiler inlet valve. If the boiler level is low then there should be power going to the valve. Take the wire on and off and see if the valve actuates (Clicks).

There is no sight glass on the GB5. On the GB5 the fill probe circuit is a capacitive sense circuit. When water touches the probe it changes the capacitance in the circuit and signals the micro-controller to turn on the fill.

BillC