'94 La Pavoni Europiccola: long time to heat up, then trips fuse - Page 2

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RobAnybody

#11: Post by RobAnybody »

landdogger wrote:Descaled the heating element sleeve and reattached, but unfortunately no luck.
Does it heat up faster with the sleeve in? I wouldn't expect it to stop the thermofuse from tripping, the old fuse used around '94 cuts off at 152°C https://www.espressocare.com/products/i ... ofuse-152c so your new one ~25°C earlier.
landdogger wrote:I'm getting resistance across the terminals, so I don't think the element is burned out.
You would also expect the cirquit breaker to flip with a burnend out element, it would create ground fault.
Does the resistance acros the terminals come close to what you would expect for a 200/1000 watt element? and when the element is still warm? (machine unplugged of course)
LMWDP #647

landdogger (original poster)

#12: Post by landdogger (original poster) »

Thanks, Rob. Will check resistance again and note the readings.

If I were to replace with a new stainless steel element, would the 127C fuse do the trick?

Am I correct in understanding that the 152C is for the brass / copper element?

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RobAnybody

#13: Post by RobAnybody »

landdogger wrote:Am I correct in understanding that the 152C is for the brass / copper element?
More like around the time of the last brass/copper heating elements this thermofuse was used.
Brass does have a higher thermal conductivity than steel, so it could well be the reason la Pavoni switched to the 127°C thermal switches around the introduction of the stainless steel heating elements.
Replacing the heating element will probably work, but changing the thermofuse is a lot easier (and less costly)
cheers,
Rob
LMWDP #647

landdogger (original poster)

#14: Post by landdogger (original poster) »

Following up re resistance across the terminals. I'm getting 12.5 and 58.5 ohms, which I'm guessing are the 1000w and 200w elements respectively.

Is my math correct if I calculate that the 1000w should be at 14.4 ohms and the 200w element should be at 72 ohms?

If so, then these values likely explain things heating up more quickly.

RobAnybody

#15: Post by RobAnybody »

landdogger wrote:Is my math correct if I calculate that the 1000w should be at 14.4 ohms and the 200w element should be at 72 ohms?
That would be correct though the measured values I found reported here vary a lot, for the 200W element (that one stayed the same in all build years) it ranges from 65 to 75 ohm.
The ratio between the two somewhat works out.
Even if the 1000W element has more output, this would mean the water should also heat up faster (which, as you pointed out earlier, is not the case).
Do you get infinite resistance from the terminals to the heating element base?, also when the machine is warm? (and unplugged).
LMWDP #647

landdogger (original poster)

#16: Post by landdogger (original poster) »

I was able to get the machine up and running again. The problem was [as these things usually go] the result of my own error.

The device stopped working right after I had replaced the safety valve. The old ball bearing was getting stuck (suddenly releasing steam instead of gradually) so I swapped it out with a the new teflon cap. I didn't realize that there were two different springs to choose from, and I incorrectly replaced the old spring with one for a Millennium model (mine is pre-millenium, '94).

These springs for the Millennium models are stiffer, so it takes more pressure to release steam out of the safety valve. As a result (this is my hypothesis), on the first run with this new spring, my machine heated up and then tripped the thermofuse because it couldn't let out any steam before reaching max temp. I'm guessing maybe the pressure stat on newer models helps manage this temperature / pressure balance automatically?

(I didn't realize the connection at first, and was bummed when the machine wouldn't turn on because I couldn't test the new safety valve I'd installed! :oops: )

I replaced the fuse with a new resettable one, but as Rob pointed out, the old fuse was rated for 152°C and the new resettable ones are rated at 127°C. Even after I swapped the safety value spring back to the original, my machine's brass and copper element was tripping the thermofuse.

I've now replaced the old heating element with a new stainless steam one, reverted back to the original spring (with the teflon cap) and everything works as expected. I've certainly learned much more about this machine after the experience, and now know to look for details about which models each part can be used for!

Thanks to Rob for his help in debugging over the past few weeks.

RobAnybody

#17: Post by RobAnybody »

landdogger wrote:Thanks to Rob for his help in debugging over the past few weeks.
You're welcome!
I hadn't realised you also changed the spring in the steam valve :oops:
good to see you have her running again!
I hope you kept the brass heating element around! They tend to be more quiet than the new steel elements. And if you're not going to use it yourself I bet someone will be happy to have it.
cheers!
Rob
LMWDP #647