Hi All, Since I'm ordering a new lever for my Europiccola, I've also been wondering (for a few weeks now, actually) about changing my piston. I have the Millennium model, which has a plastic piston. There is a brass replacement available, and after using my brass-pistoned Elektra, I wonder if putting a brass one in my Pavoni would be a wise move. My question really centres around heat. The new Millennium model uses a plastic sleeve to insulate the water in the group from the group (which is attached to the boiler, and thus quite hot). I wonder if the plastic piston in the machine is designed to work in conjunction with the plastic sleeve, or if the decision was more based on cost. Given some of the cheaper components used in the new Millennium, I suspect it has more to do with cost. Since the piston never comes in contact with the group; only the gaskets actually touch the sleeve, would anyone suspect a brass group of making the group water hotter than with a plastic piston? Thanks in advance, --Derek -- http://www.novernae.comHome of the Wandering Sloth
Hi Derek- (a) Is there a problem with the Elektra piston? (b) I wouldn't think the water would need isolation from the group. (c) Yes there is a design factor and yes there is probably cost considerations. (d) The group by being in contact with the boiler will dissipate heat to its environment. I would tend to think there would be heat isolation between the group and the boiler to improve boiler efficiency. Brass has the ability to conduct heat much better than plastic. Of course there is a good likelihood I did not understand the question(s).
On 10/26/06, Tom Ulmer wrote: <Snip> Actually, I was just using the Elektra as a comparison. It's my Pavoni Europiccola that I'm having replaced. No, there's no problem with it, although I am concerned that flavour and odour are being absorbed. The shots on my Elektra had a more complex taste, and I wonder if a stained piston couldn't be a culprit. <Snip> With a Europiccola, it does. Because the group is physically connected directly to the boiler, it gets extremely hot; the machine will overheat after only a few pulls, and then it must cool down. By adding the insulating sleeve inside the group, they've managed to lengthen the time you can pull shots for before it's overheated by a shot or two. <Snip> Here you've hit the nail on the head. Heat will dissipate more readily to brass and water. The water (and consequently the brass piston) is isolated from the group by the sleeve. However, the piston will hold heat better, and so could do one of a couple things: it may retain more heat, thus lowering the number of shots before the machine overheats, or it may maintain a more stable temperature at the filter screen and give a more stable shot. It certainly won't absorb odours and oils. I'm leaning toward buying the brass piston. I need to do a gasket job on the machine; a few are starting to go, and buying a set of piston gaskets is half the price of a brass piston, which comes with gaskets. And I'll always have the old piston... I just don't like the idea of plastic pistons. It feels cheap and wrong. Thanks for your help. --Derek -- http://www.novernae.comHome of the Wandering Sloth
Hi Derek, I think that Pavoni used the plastic pistons only for a few years, I have heard that the more recent models come with the brass piston again. A few months ago I have replaced the plastic piston in my 2003 Professional with the brass one and I have not noticed a change in taste or behaviour after that. Generally, overheating is not much of a problem, with the Pavonis. If you want to make more than 2 (or 3) shots in a row, just have her "drink" some cold water in between and rinse the portafilter, wait until the group is at temperature again and all will be well... Cheers, Walter Derek Bradford schrieb: <Snip>
On 10/26/06, Walter wrote: <Snip> That's a shame. If that's true, I just squeaked in at the end. I bought mine last year. <Snip> What made you decide to change the piston? --Derek -- http://www.novernae.comHome of the Wandering Sloth
Derek Bradford schrieb: <Snip> I bought mine last year too. Only when I opened it I realized it had been built in 2003... <Snip> Curiosity mostly ... after someone had recommended it in another BBS. And the fact that I spotted some sort of a hairline crack on it (which in retrospective might have been a scratch as well) Walter