boy_lah wrote:Remember you need to grind EVEN finer to compensate for lack of pressure in the boiler.

I was under the impression that the boiler pressure is irrelevant to espresso extraction; once the water is in the chamber, it's your lever pull that pushes the water through the grounds.

How does boiler pressure relate to the grind size of the coffee?

gegtik wrote:I was under the impression that the boiler pressure is irrelevant to espresso extraction; once the water is in the chamber, it's your lever pull that pushes the water through the grounds.

How does boiler pressure relate to the grind size of the coffee?

When the grind is more fine, there tends to be more back pressure due to sealing of the puck. This can prevent water from entering the group head, if the boiler pressure is low. When you grind more coarse, you can definitely feel the water fill the group more quickly.

Ray

uyeasound wrote:Out of interest, what range of brewing temperatures do people operate; what is the coolest temperature you feel suits any particular coffee you use, and what is the hottest temperature you use for a different coffee you also use?
I let my pavoni regulate the boiler pressure and temp, but i flush the brew head until it is the temperature i want - dependent upon what bean i am using.
My range is about 97C to about 102C on the metal of the brew head. That's the temp of the head before i start the brewing by letting the water in.

Some like it hot.

I've tried everything from 225 to 245 in the boiler (using the PID controller on my La Pavoni). In my experience, 234 is about ideal (which equates to 10.0 PSI on my machine). When you start getting down around 230 to 233, the shots tend to be sour. In some cases (depending on bean), I have had good luck clear up to 238 to 240, but that's the exception, not the rule.

10 PSI / 234.0 degrees works pretty well for me. There's a faint hint of sourness at times, but that can be adjusted out with the grind usually. I run my machine at 234.0 and the controller keeps the boiler to within 1/10th of a degree of that. That's the best temperature I have found for most beans I have tried.

Ray

hi Ray, I'm a newbie so can you explain where is your PID measuring? Is it the group or ?
And since I (and I think most LP users) don't have a PID installed, we need to find the equivalent of your 112'C/234'F using the OE temp strip. And it seems like people agree placing on of the group and just before the first bar (90'C/194'F) lights up is optimum.

I've been my usual shots and I've re-dialled in my routine slightly from original post. I now boil till just over 90'C/194'F, do 4-7 flushes to warm up the group, grind/prepare my basket, then re-boil again until just over 90'C/194'F again then pull. Its winter here where I am and things cool pretty quickly so this way I'm compensating for the cold but also taken into the feedback around needing to warm up the head. The danger here is my first cup is usually better at the risk of second cup maybe borderline too hot. Whereas before I was probably brewing too cold but I had easily 2 cups and the second being the better one.

Finally, I think in addition of whether a brew is too hot (bright) or cold (sour), there is also personal preference. I used to prefer much hotter drinks since I grew up in Australia but since living in HK, I now lean to a cooler drink which brings out more layers of the bean flavours. Cooler however doesn't mean sour...just the cooler end of the 'still good' range. And by the way, i'm anything but technical, i go by taste and that's very personal of course.

cheers,
Clinton

boy_lah wrote:hi Ray, I'm a newbie so can you explain where is your PID measuring? Is it the group or ?
And since I (and I think most LP users) don't have a PID installed, we need to find the equivalent of your 112'C/234'F using the OE temp strip. And it seems like people agree placing on of the group and just before the first bar (90'C/194'F) lights up is optimum.

I've been my usual shots and I've re-dialled in my routine slightly from original post. I now boil till just over 90'C/194'F, do 4-7 flushes to warm up the group, grind/prepare my basket, then re-boil again until just over 90'C/194'F again then pull. Its winter here where I am and things cool pretty quickly so this way I'm compensating for the cold but also taken into the feedback around needing to warm up the head. The danger here is my first cup is usually better at the risk of second cup maybe borderline too hot. Whereas before I was probably brewing too cold but I had easily 2 cups and the second being the better one.

Finally, I think in addition of whether a brew is too hot (bright) or cold (sour), there is also personal preference. I used to prefer much hotter drinks since I grew up in Australia but since living in HK, I now lean to a cooler drink which brings out more layers of the bean flavours. Cooler however doesn't mean sour...just the cooler end of the 'still good' range. And by the way, i'm anything but technical, i go by taste and that's very personal of course.

cheers,
Clinton

The PID controller measures the water temperature inside the boiler (down around the heating elements; however once it's up to temp, the heating elements are only on 25% of the time).

Basically when my machine is at 234.0 degrees, it's 10 PSI on the pressure gauge. So if you have a pressure gauge, you can go by that.

Ray

Ray - after your PID gets to 234'F/112'C...what is your routine from cold? Do you leave your boil 'on' after it hits 234'F/112'C but pull quickly or do you turn it off? Do you flush the head to warm it up, do you just go for pull from cold group? Or do you leave it essentially leave the boil on but only 'pull' when the temp drops back to 234'F/112'C? Mind sharing a bit more about your routine beyond the temp in your boiler being 234'F/112'C?

Finally, I assume time between the boiler hitting 234'F/112'C and pull is minimal ie. 3-6mins?

thanks
Clinton

My boiler is usually about 110C / 230F and my group between 85-90C / 185-194F for the first shot. There is no easy relationship between boiler and group temp. The latter one can be all over the place (without pid).

boy_lah wrote:Ray - after your PID gets to 234'F/112'C...what is your routine from cold? Do you leave your boil 'on' after it hits 234'F/112'C but pull quickly or do you turn it off? Do you flush the head to warm it up, do you just go for pull from cold group? Or do you leave it essentially leave the boil on but only 'pull' when the temp drops back to 234'F/112'C? Mind sharing a bit more about your routine beyond the temp in your boiler being 234'F/112'C?

Finally, I assume time between the boiler hitting 234'F/112'C and pull is minimal ie. 3-6mins?

thanks
Clinton

With the PID controller, things function a little differently than a stock La Pavoni. I also have an adjustable pressure regulator (bypass valve) on mine, which allows me to fine tune the steam release balance point a little bit too.

Basically it goes like this:

I turn the machine on using the "II" switch setting. This bypasses the PID controller and uses the full 1000W heating element to heat up the machine. The PID controller still monitors the temperature and displays it on the screen, but it's out of the loop as far as controlling anything. The reason I heat the machine up on the "II" setting (which is there for steaming milk) is to take the load off the solid state relay, which normally the PID controller toggles on/off (which in turn controls the power to the heating element).

It takes the machine about ~ 2 minutes to reach 170+ degrees. At this point, I flip it back down to "I", which hands control over to the PID controller. From there, the PID controller stabilizes the temperature to 234.0 degrees.

I generally leave the machine sitting for about 5 minutes or 10 minutes on the counter. This gives the PID controller time to not only stabilize the water temperature in the boiler, but also for the entire machine (including the group head) to warm up to a more or less constant temperature. This helps reduce the differential between the boiler and group head temperatures.

Once the machine is up to temperature, the PID controller keeps the water in the boiler at 234.0 degrees (or whatever target temperature you set) to within 0.1 degrees. The PID controller cycles on 1/4 of a second (to inject heater) for every 2 seconds. So you can think of it like a 25% duty cycle, where the heating element comes on and goes off - just enough to balance the water temperature.

Before the first shot, I usually pull some water through the group head (sort of like the reverse of a cooling flush on an HX machine). Then I pull the shot. During the pull, the PID controller is still keeping the temperature at 234.0 degrees, although sometimes it will maybe move 0.2 degrees (although I usually don't pay a lot of attention to it, since I'm focused on how the extraction is going).

The group head temperature is pretty constant. Because the machine is constantly pinned to 234.0 degrees, it tends to level out the temperature of all the components of the machine, including the group head. So you never really get into a situation where anything over heats. If something were to over heat, it would impact the water in the boiler, which would cause the PID controller to cut power until the water temperature dropped back down to the proper level. So you can think of the PID controller as not only controlling the temperature of the boiler water, but also controlling the temperature of the overall machine (at least to some degree, since everything on the machine is connected).

As long as there is water in the boiler, you can leave the machine on all day and it just stays at whatever temperature you program. With the adjustable pressure regulator, you can increase the spring tension to meet (or slightly exceed) the steam pressure inside the boiler; this achieves a perfect balance between the two and prevents the machine from hissing steam. Except for when I'm steaming milk, the machine runs totally quiet and doesn't make a sound.

For steaming milk, I flip up to "II", which takes the PID controller out of the loop. It takes about 20 seconds to go from 234 degrees to 250+, which produces more than enough steam pressure (around 25 PSI). What I usually do is flip the machine to "II" right as I'm starting the pull. By this time, the water in the group head is heading through the puck. As I'm exacting the espresso, the machine is racing up to 250 degrees. So just about the time the shot is done, the steam is ready to go.

Once I'm done steaming milk (if I'm making a latte), then just turn the machine back to "I" and the PID controller takes over again and brings the temperature back down to 234.0 degrees again (or whatever the set temperature is). It only takes a minute or two for the machine to drop back down to the target temperature typically (especially if you bleed off a little steam).

That's basically the routine.

Ray

cheers Ray. Very helpful. So when should i send my LP over for a PID upgrade?

Else...it's the 'low tech' temp strips and manual on/off i guess

KurtAugust wrote:My boiler is usually about 110C / 230F and my group between 85-90C / 185-194F for the first shot. There is no easy relationship between boiler and group temp. The latter one can be all over the place (without pid).

Kurt - reading Ray's routine and your reply I guess without a PID, our stock LP temp will go up/down beyond a 'set' point. That being the case, we don't the benefit of leaving the machine on and warming everything up to a 'stable' temp. Hence your comment 'boiler and group temp - all over the place".

hmmm....more 'by feel' i guess.