La Pavoni Europiccola - pressure _and temperature_ control?

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martinlhoff

#1: Post by martinlhoff »

My Millenium EPC had a busted thermofuse, probably because I work it too hard. With a new thermofuse it works well again, and now seems that _sometimes_ the pressurestat doesn't cut off, and I have a bit of a runaway condition.

I'll clean the pressurestat, tune it a tad lower, have a replacement in hand etc.

But all of this makes me think the design through, and I see now that this overall design hinges on a balance between...

- the pressurestat
- the pressure relief valve
- water/system temperature reached at the pressure from controls, vs heat dissipation of the system - varies on environmental conditions
- thermal fuse as safety catch

Because temp control is indirect, temp variation is large. Does it make sense to add a control thermostat, inline with the pressurestat? Are there aftermarket parts for this?

To be clear - I don't mean the resettable safety thermostat/thermal fuse. I mean adding to the overall system a control thermostat that, together with the pressurestat, controls power to keep the system below a certain temp (but does not need reset).

NicoNYC

#2: Post by NicoNYC »

Pressurestats are at their core a mechanical switch, one in close proximity to steam and occasionally water, and that makes them probe to failure. And occasionally they fail unsafe so the temperature keeps climbing until a relief valve let's the steam out and hopefully the user turns the machine off before it boils itself dry.

I suspect this is a large part of why manufacturers have been switching to PID control in the last decade or so. Especially for steam boilers where the improved temperature stability is largely moot. There are kits out there put together by hobbyist that have all the parts needed to put a La Pavoni onto a temp-probe controlled PID. I couldn't point you to any one in particular, but there are threads here and in FB groups, YouTube videos of modded machines in operation, etc.

As a bonus, you get tighter temp control (pressurestats are usually about .2 bar band, which is about 3°C, a decent PID can hold less than .5°C if implemented well)

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drgary
Team HB

#3: Post by drgary »

Martin,

The main temperature concerns are at the group and with steaming. To get good, repeatable shots without any modifications to the machine, set the pressurestat at 0.8 to 0.9 bar. A working pressurestat is sufficient rather than electronic control. Use half pumps to partially fill the group with water without releasing water into the coffee. This brings the group up to temperature at the start of the shot. You can get a good reference for brew temperature by attaching a thermometer to the outside of the group and assessing by taste, because thermometer locations differ. This technique lets you control temperature for different coffees, so it's great for temperature surfing.

If you're skilled, you can steam at this pressure. Stronger steaming makes that easier, but then it's easy to overheat the group. If you don't want to do modifications, you can power it on and off using the toggle switch and with a higher pressure setting.

For a Millennium aka 3rd gen Europiccola, the overpressure valve is just for that. Earlier versions without a pressurestat have the valve set to release steam as a temperature sink while maintaining sufficient steam power. Those machines have low/high power settings for brewing and steaming, but this doesn't apply to your version.

People are doing many modifications to La Pavoni levers that you can look up in this lever forum; anything from one hole steam tips to pressure gauges, a device that releases the air pocket, which you can do with good technique, heat break gaskets, etc. I fashioned my own PTFE heat break gasket, added a one-hole tip, added a pressure gauge above the sight glass, and found great benefit from adding a group thermometer. For me, the Europiccola is a manual machine, so I didn't go over the top in additional modifications.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

jpaulm

#4: Post by jpaulm »

I agree with Dr. Gary here. I've had a Millennium LP for about 8 years. The temperature of the water contained in the group head is what matters most, since that is what will be used for the next shot. I put a piece of clear tape there and take readings off that with a small infrared thermometer. The tape is because stainless steel will not give good readings, it's too reflective. By reading the same spot for each shot, you will come to know what your preferred temperature is for that particular coffee before commencing the pull.

A also have a pressure gauge installed. But finding a consistent group head temperature has been, for me, the key to consistently good espresso.

martinlhoff (original poster)

#5: Post by martinlhoff (original poster) »

I agree with y'all. I don't want to tweak or overcomplicate the machine. On the other hand, it's my daily driver machine and I'd like to get 3-4 shots over the first half of my workday. An external PID is what I'm thinking of.

baldheadracing
Team HB

#6: Post by baldheadracing »

In my experience, a PID on a Pavoni is not very useful on its own, just as many have previously shown. I took my PID off after testing.

As has been demonstrated, the issue is that a boiler temperature that is low enough to keep the brew temperature reasonable while the machine is on for long periods of time is too low to generate enough boiler pressure to fill the group and nicely pre-infuse the puck. The usual way around that is to put a tee fitting at the top of the sight glass and fit a bicycle pump (or an electric pump) and a boiler pressure gauge. That decouples boiler temperature from boiler pressure and thus you can have both your ideal brew water temperature and ideal pre-infusion (boiler) pressure for brewing all day long. You can also wire in a second switched circuit (a.k.a. alarm circuit on most PID's, or switch to the pressurestat) to deliver a higher boiler temperature & pressure for steaming. It can all look a bit Frankenstein but the setup can work well if that's what you want.

The easier solutions are to either:
- limit the transfer of heat from the boiler to the group with a heat break; or
- limit the transfer of heat with the Bong isolator; or
- increase the heat dissipation ability of the group with a heatsink.
The drawbacks are the the warm-up time without active user involvement is lengthened considerably, and either math or experimentation is needed to determine the optimal size of the heat break or heatsink for your use (or just buy what is sold and hope for the best).

The much easier solution is to turn the machine off after making a coffee :D.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

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drgary
Team HB

#7: Post by drgary »

Heat break: yes!
Also, toggle power on and off.
And, I don't think of it as an always on machine unless I'm using a light roast.

Some people love the Bong Isolator. I don't trust that they won't degrade with the risk of a steam leak over time. In fairness they changed the plastic for more stability. Still, I would be more supportive if it were designed differently, with thin layers of plastic interrupted by stiff layers of metal to stabilize it. Also I've read user reports that the extension of the Isolator makes the machine even more prone to flexing during a pull. And, a La Pavoni can be successfully controlled without one. YMMV
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!