FLUSH: If your second cup tastes better than your first, try running a blank shot as your zero shot to see if your first shot tastes better. Were I in your shoes, I would certainly want consistency between shots before messing with anything else so I can control one variable at a time.
OFFSET: After achieving consistency between shots, you can play with the offset or temp setting (same net result) to dial in the best tasting temp for the beans you're using.
You have a cool, versatile machine, and I hope you have fun experimenting with it to get ever-better shots!
I don't have any experience of the CC1, so can only comment as someone who has graduated from a Silvia (which I PID'd myself), an Expobar Brewtus II and now a Speedster. I have picked up a few hints and tips about temperature control along the way.
Firstly, the reading on the PID is obtained from a temperature probe in the brew boiler. It does not show a calculated temperature which I read on this thread and cannot be changed to reflect temperature at the grouphead. The term 'offset' is a mechanism to deal with PID errors which I also interpreted as the grouphead temperature when I first read about it. What this little PID gizmo does as I am sure everyone here knows, is to pulse incoming power to the boiler in an increasingly rapid manner to smoothen out the temperature curve to the point where the curve is almost non-existent. A flat temperature curve is a stable boiler temperature.
Now ... if you think about it, the temperature of the water sitting right above the grouphead is a few inches from the nice warm boiler and will have likely cooled down a bit. Even if you are running a Speedster like me, there is still a drop of about 1C from the exit point of the boiler to the coffee grinds in your portafilter - only the likes of a Scace device will tell you exactly what that temperature drop is and how stable it remains during the course of the 25 second shot. The nice thing about solid machines is that this drop is reasonably predictable. On an E61 grouphead like my previous Brewtus, it tried to help by employing a thermosyphon to circulate water between the boiler and grouphead to stabilise that temperature differential.
I little 2 second flush will draw fresh, hot water from the boiler and can only help in ensuring that you can predict the temperature that will hit the coffee when you pull your first shot. You don't need to flush for longer than that. If you don't flush, then it is highly likely than the water above the grouphead is cooler than the boiler and that will result in differences between your first and second shots.
Now .... here comes the interesting bit. If your boiler temperature is too hot, then not flushing might result in a nice brew on the first shot and a bitter brew on subsequent shots. If your boiler temperature is just nice, then not flushing might result in the first shot being a little sour, with subsequent shots tasting nicer.
I'm certainly not a PID expert, but just have enough experience to advise that it is only helping to stabilise the boiler temp.
Steve, it looks like we are on the same page, and see the situation the same way, perhaps the OP reading this point of view a few different ways might see what we are talking about. It is easy to get caught in the whole tech thing and to gloss over the basics.
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
MisterJohnnyT Senior Member Joined: 13 Jan 2012 Posts: 59 Location: S.E. Florida Expertise: Just starting
Espresso: Crossland CC1 Grinder: Compak K3 Touch
Posted Tue Apr 3, 2012, 5:41am Subject: What about the portafilter?
Nobody has mentioned the PF yet. Op, are you making sure the PF is preheated? If the PF is cold when you pull the first shot, could that explain this effect?
Somebody had earlier mentioned that changing the PID Temperature or changing the Offset would yield the same net effect. However, I don't think this is the case. Changing the temperature setting does indeed change the boiler temp. However, I think the offset setting simply changes the DISPLAYED temperature, not the actual temperature of anything. Unless you are talking about some sort of "internal" offset setting.
calblacksmith Moderator Joined: 25 Nov 2007 Posts: 5,684 Location: Riverside, Ca, U.S.A. Expertise: I live coffee
Espresso: ECM Veneziano A1 Grinder: Many different commercial Vac Pot: 40s era Silex Drip: Milita, Bunn&Curtis... Roaster: Cast iron pan, gas burner
Posted Tue Apr 3, 2012, 5:51am Subject: Re: What about the portafilter?
Good point.
As the OP stated the warm up time, it was just ASSUMED that the PF was locked in place.
I use a bottomless PF 100% of the time on an E 61 and I really do not see any taste profile difference with a heated PF or not. The cold PF could have an affect on reducing the GH temp upon locking in place and due to the smaller mass of the GH you might drop the temp of the first shot.
Really though, I do stand by my statement, abet slightly modified, NEARLY all machines need a flush, and yes, in mho, ALL home class machines do.
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
While the plural of "anecdote" is not "data," I have an anecdote to relate regarding PID-controlled dual-boiler machines and USBC finalist practices. I took a class and was instructed to flush the group on a PID-controlled MP Linea -- not a big flush, not to pull the temperature up or down; but a shot-sized flush just before locking in the PF.
But the question about initial start-up of home machines is different. Another anecdote: My machine will reach the PID setpoint temperature less than 15 minutes after start-up. That's nice. But it doesn't mean the PF temperature is at equilibrium. If I check the metal stub of the PF handle at that point, it's cool; close to room temperature still. After a few shots (or an hour), the handle stub will be quite warm. The rim of the PF may be in contact with the electrically-heated, PID-controlled grouphead; but the whole PF hasn't gotten to the temperature that it will eventually reach. So I always run water through the PF before using it, until the stub of the handle gets hot. Some will say that's because I'm trying to use the machine before it's completely warmed up. I probably am.
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