Hey Gary!

I have heard that cooling the grouphead might be a nice way to control overheating, but never done it properly. I actually did not get around to think of a clean and easy way to cool the grouphead.
I normally switch off the machine between shots and use a cold wet towel on top of the grouphead but this is not enough (I have a millennium Pro). The main problem is that the third shot is very hot and the taste starts to get a bit bitter. Any suggestions on how to cool the grouphead properly without making a pond out of my kitchen ?

Cheers,
Angelo

Angelo,

Since you've got a Millennium model, the answer should be very easy. On my Millennium, I only need to cool the portafilter. That entirely works. If you haven't gone there, see my thread where I demonstrate this. La Pavoni Millennium Owners, Are Temperature Problems Solved? (I don't mean to pitch my thread in particular. Who cares? But peaceup challenged me to actually demonstrate my claim, which I did there and in the hope others would get over the belief that these always overheat. They don't. For blends needing a hotter pull, I sometimes even do a heating flush.) I also showed my cooling method to fellow HB members, including yakster on his Millennium rebadged as Gaggia Factory, when we had a get together at my house. I'm claiming witnesses because those shots really are dialed in, not burned!

I use a stock portafilter, not one with the bottom cut out. This gives me enough metal mass to cool the shot effectively by plunging it in water or running it under the tap. To check the temperature, I also don't do anything fancy. I touch the portafilter with my finger to see if it is room temperature, body temperature, very warm or hot. This gives me all the information I need without a temperature strip on the group. The variations here can be a lot, considering you're balancing out the heat of the rest of the metal mass in the group. If that doesn't work for you, you may have the PSTAT set too high. I did some speculation on my other thread that my machine may be easier to regulate because it has a brass piston instead of a plastic one. But Christopher Cara says no, it's the PSTAT setting that works. He replaced the piston and services his customers' machines all the time. I don't know the exact setting for mine, but the shot-pulling temperature is effective and there's plenty of steam for milk drinks.

Let us know if these suggestions work. If they don't, I've seen others who time turning the elements on and off. But with a Millennium and a stock portafilter, you shouldn't need to do that.