La Pavoni Europiccola power cycling, can't reach 1 bar

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wash_chris

#1: Post by wash_chris »

Hi all. First post after a long time lurking on these forums. This has been an invaluable resource searching for a machine and rebuilding after I found one. I picked up a pre-millennium in decent shape at auction and have spent a few weeks cleaning and rebuilding (as described below) and I've already pulled some really good shots (and more than a few bad ones). I believe my machine is from around 85-90 based on the original (damaged) badge, screw hole in base, and dual switch with black trim. I don't recognize my heating element and wiring from any online resource, but all appears to be in working order, apart from the problem I describe below.

When trying to get the machine up to 1 bar for steaming. At about 0.75-0.8 bars, regardless of the second switch setting (I or II), the machine cuts off - I hear an audible click and the light in the red on/off button light turns off. After the pressure drops to around 0.5, the machine clicks back on (power light illuminated) and builds pressure to 0.75-0.8, and the cycle repeats. The machine never reaches 1 bar. I get quite a bit of steam from the safety valve, but nowhere else I can see as I'd expect if there was a leak. Steam from the wand is decent and I can froth milk if I choose to, so this is more a mystery than a showstopper. My understanding of this generation of machine is that it has a thermal fuse but not a pressure stat, which is confirmed by the pic of the element wiring. Is this normal behavior?

For background, since getting the machine I've torn it down completely, cleaned everything and descaled twice, replaced all seals except the internal safety valve seal, the two boiler spacers, and heating element gasket (which are on the way). I still have the original steel ball and spring in the safety valve that will be replaced soon. I've fitted an aftermarket pressure gauge atop the sight glass which is how I'm getting the pressure reading. I've tested the boiling capability without the cap on and in position I water boils in about 20 minutes, about 8 in position II.

Any ideas would be appreciated, or clarification if this is expected behavior.

Thanks!

Chris







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homeburrero
Team HB

#2: Post by homeburrero »

wash_chris wrote:At about 0.75-0.8 bars, regardless of the second switch setting (I or II), the machine cuts off - I hear an audible click and the light in the red on/off button light turns off. After the pressure drops to around 0.5, the machine clicks back on (power light illuminated) and builds pressure to 0.75-0.8, and the cycle repeats. The machine never reaches 1 bar.
That sounds like a malfunctioning thermofuse. Normally that model opens at around 120℃ and stays open (does not reset -- you have to replace it). It's easy to troubleshoot - just temporarily bypass that thermofuse and verify that the machine then works normally, with the light and the heater being continuously on, and when on the II setting it hisses more vigorously. Don't run the machine unattended with the bypassed thermofuse.

It may be difficult to find an exact replacement. You could MacGyver in a new resettable thermoswitch, or go back to the old fashioned one with a melting thermofuse soldered into a wire inside an insulating sheath. Francesco has a nice page related to bypassing and replacing these: http://www.francescoceccarelli.eu/La_Pa ... to_eng.htm

P.S.
Your machine has a somewhat unusual element, with terminals placed a little differently, but does look properly wired, functionally the same as this '88-'89 on F.Ceccarelli's site: http://www.francescoceccarelli.eu/La_Pa ... p88-89.JPG. Your heatup times indicate that both elements are working.
Pat
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XS750AU
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#3: Post by XS750AU »

It sounds like the thermal fuse has been replaced by the wrong part, or the previous owner was wanting to reduce the boiler temp. The thermostat on the neutral side sounds to be cutting supply to both heating elements. The part circled in red needs to be replaced with the correct spec part.

wash_chris (original poster)

#4: Post by wash_chris (original poster) »

Thanks for the guidance and pointers. I was able to bypass to validate that the thermofuse is the culprit. Without it in play the machine would happily steam away and built pressure before I cut power and let some off with the wand.

I received the new spring and Teflon mushroom to replace the old ball and spring, which was noticeably softer. With those in place the machine now gets to 1.1 bars before cutting off and dipping to 0.5. I can definitely work with that and will leave the thermofuse in place for now.

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homeburrero
Team HB

#5: Post by homeburrero »

wash_chris wrote:I received the new spring and Teflon mushroom to replace the old ball and spring, which was noticeably softer.
Good that it's softer. There are two springs available with that teflon mushroom and the one you want is the softer one with around 12 coils. (e.g., This one at Stefano's https://www.espressocare.com/products/i ... uropiccola.) The strong one, with around 6 coils is only to be used on machines with a pressurestat -- like the Pro and the late 90's and newer Europiccola. The latest LP models have a different spring and a brass anti-vac fitting.

P.S.
XS750AU wrote:t sounds like the thermal fuse has been replaced by the wrong part, or the previous owner was wanting to reduce the boiler temp.
It sure looks like the original thermofuse, which unfortunately is no longer available as a replacement part. I think that the fact that it's currently opening at a somewhat reasonable operating temp, and reliably auto-resetting is just a lucky malfunction.

There is a post (1991 La Pavoni Europiccola thermal fuse removal) about that from someone who replaced it with a newer manual-reset thermoswitch. The new ones require a mounting screw - that's where a little MacGyvering might be required.

If you go back to the old style, which Francesco refers to as 'the following model easily found', you can get the fuse, butt connectors, and sheath from Stefano's: https://www.espressocare.com/products/i ... al-cut-off
Pat
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Nunas
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#6: Post by Nunas »

I think you need to be cognizant of the proper terminology when ordering parts and know what they do. The terms thermostat and thermofuse ore are often used interchangeably, even by a few manufacturers, who should know should better. But they are two different things. A thermostat clicks on and off at a given temperature; that's what you want to keep a boiler at a given temperature. a thermofuse stops working when a given temperature has been exceeded. There are two types of these, one that looks like a little bullet with axial leads; these are a one-shot safety device that must be replaced when it blows. The second form of thermofuse might be thought of as a thermobreaker. Those are resettable, usually by pushing a little plunger. To make matters even more complicated, there is a thermofuse that looks like a thermostat but has an inbuilt delay before it resets itself (no little plunger). Clearly, this won't regulate a boiler very well. Often, appliances have both a thermostat and a thermofuse (usually the bullet-looking kind), with the point-of-failure of the latter being higher than the set-point of the former. Here, the thermostat clicks on and off merrily, regulating the boiler; but if it fails in a closed state, then the thermofuse blows, preventing a possible fire.

wash_chris (original poster)

#7: Post by wash_chris (original poster) »

On further inspection, and googling, this appears to be a thermostat and not a malfunctioning fuse. To be precise, an Elmwood (now Honeywell) T177 2455R (manual https://docs.rs-online.com/f853/0900766b8050feae.pdf), which appears to still be available online.

Anyone know if these stock on any model of Europiccola, or if this was (more likely) an add on by a former owner? With the safety valve replacement getting pressure over 1 bar, I don't see any downside to keeping this thermostat in place. I never leave the machine unattended while on, so no worry of it malfunctioning and damaging anything. Anything I'm missing in that line of thinking?


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homeburrero
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#8: Post by homeburrero »

Very interesting! Looks like XS750AU nailed it!

wash_chris wrote:Anyone know if these stock on any model of Europiccola, or if this was (more likely) an add on by a former owner?
I'm thinking it was never stock, based mostly on F Ceccarelli, and I think this is the first one of these we've encountered in HB posts.

wash_chris wrote:I don't see any downside to keeping this thermostat in place. I never leave the machine unattended while on, so no worry of it malfunctioning and damaging anything. Anything I'm missing in that line of thinking?
Given that, I think you are OK just keeping it. I assume when under normal use, including while steaming, that it's not cutting out the heater. If it did that while you were trying to steam that seems like a major annoyance.
Pat
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