Well, I'm interested to hear Todd's perspective on this. The thread you linked to below is from Oz I believe, but a 220V place in any case. That is a whole different animal--as one guy said, he has plenty of power at 1 bar, but with a 17 liter boiler behind him!!! That's like having a low-horsepower engine, with tons of torque. With our 110V setup, we don't have the torque, and I believe we need the horsepower (higher pressure) to have a decent amount of steam. As I said, my steam boiler came from the factory at 1.45 bar, and I wish most every day that I had more oomph--stretching goes fine, but getting milk to roll in the pitcher is basically impossible for a 10 oz. latte. I can get a decent vortex, but that's about it. Nothing remotely close to a commercial machine. As to the concerns about the p-stat failing above 1.2 bar, my machine is over 4 years old now, turned on by timer every day from 0600 to 1600, sitting at 1.45 bar, and the original p-stat is still working fine (knocking on wood...).
The discussion about offset is interesting, but I think it's a bit of smoke and mirrors. Here's how I see it, someone out there correct my thinking when I miss the mark. By raising the steam pressure, you are requiring the steam boiler to fire longer and therefore it gets hotter. This in turn raises the temperature of the water moving through the HX to the brew boiler. In theory this raises the group temperature, and changes the espresso. I can see this being true if you are pulling tons of back to back shots or are flushing water, but the beauty of our double boiler machines is that the HX has little to do with espresso temp in "normal" use. So here's my question--when the water headed for the brew boiler exits the HX, is it already at brewing temperature, or is it just warmed somewhat and still needing heat from the brew boiler? My understanding is the latter--which means the steam boiler should have little to do with this, except that the brew boiler won't have to work as hard to get the brew boiler up to temp if you have the steam pressure set higher. Even if the brew group does in fact rise in temperature, however (changing the offset that would be needed to have the group temp be reflected on the display), I would argue that most of us have no idea whether our displays reflect the group temperature currently anyway. What is your voltage? Is your insulation the same as mine? Is your assembly the exact same parts? Etc. Etc. As several of us have said over and over, your tongue is the most accurate way to decide whether your shots are "good" or not. So if my display reads 201 and I'm really getting 211, I will notice a dramatic bitterness in my shots and reduce the temp to something that tastes good to me. I will then learn what range tends to be good on my machine, and play within that range. If you can adjust offset, and it's important to you, then by all means do so. But if you can just be satisfied with good coffee, then it is unnecessary (and so far, I don't know how to change the offset on my new PID controller anyway--I think it takes hardware that I don't have). Below, I am going to copy in a post from KittJ from a couple of years ago. The numbers don't all apply because he's talking about non-PID controllers for most of it, but have a read and get the theory. It is a more detailed version of what I'm saying. Finally, even without a scace device, I have found that I can get pretty good readings of group temperature by using a $30 infrared thermometer from Radio Shack, and aiming it a the bottom of the blind PF while flowing water. I'd bet it's accurate to within a couple of degrees, which at least gives me some idea of where my machine actually is when it says 201 or whatever. That gets me in the ballpark, and then my tongue does the rest. And if I flush a lot of water through, as Kitt says, the temp rises. Anyway, always curious to hear what other experiences have yielded, so keep us posted! All the best, bmc ---------------- (From September, 2009): Richard, My experience matches Dennis's observation: 1. 7 usually works well for most people and 2. rapid successive shots slowly rise in temperature. And perhaps some ancient history might help you get comfortable with how you could get to where you want to be without spending a lot of money on anything but beans. Just playing with the offset based on E-mail comments can be a little frustrating ... you need to insert some tongue testing into the process. You should also be aware that the machines vary slightly from unit to unit and will be affected by things you do, such as add insulation or jack up the steaming pressure/temperature. But the factory setting is a good place to start. And keep in mind that the whole offset thing is not an "error; it's just an adjustment that is not currently helping you achieve the result you want. Initially, the controller display issue was strongly influenced by manufacturing considerations. The "offset" was especially useful because it helped keep the displayed read-out to two digits (e.g.below 100C) ... which made the part cheaper to buy, even though the boiler may sometimes be over 100 C and measuring things in F would be a lot nicer for folks in the US. An offset's task was to "translate" the boiler water temperature, which was needed in a feedback loop for heater management, into a best estimate of the puck temperature ... which is what affects the taste. To my knowledge, no one has developed an actual puck sensor arrangement that is durable enough to survive routine kitchen use, ... although some people have placed a sensor in the group's water path in order to get closer to the puck. If you have not changed the "off-set" from the way it was set when your B-x arrived from WLL, then the reading on the controller display and what you could measure at the puck should be "about" the same (as Dennis reports) and the pattern will at least be very stable/consistent from day to day. If your shots taste bitter, you should try dropping your "displayed" temperature several degrees, since that is the first suspect in bitter shots. You should decide if the shots then taste less bitter ... and perhaps more sour. Note: You are going to need a lot of testing shots because the temperature will vary a little depending on how much time and water has flowed since the last heat cycle (red dot on.) When Abe and I PIDed our supposedly identical machines, we found that they needed different offsets ... more cooling occurred on my machine on the way from the center of the boiler (where the probe sat) to the face of the puck (where we had a PF with a probe) than occurred on his. As I recall, the difference was about 5+ degrees F. We also used a 5 digit display and no offset in order to deal with actual temperatures that were accurate to within a tenth of a degree F. (It does still feel a little weird to say to my spouse, "Gee, I think I need to jack this blend up to 212F for decent shot.") At one point, WLL experimented with changing the offset for all the machines on hand or in transit to a different number. (Since the B originally was only for the US market, WLL could specify a particular value for future production.) So some units went out with an offset of 5 for a period and then they went out with 7. But I don't recall where all that stands at the moment. RE: the Scace: My understanding from parties involved is that the Scace was originally developed in the context of measuring temperatures in big commercial (LM) machines with massive boilers, IIRC. There is a highly specified protocol for taking the "official" measurement. It involves lots of shots and water flow. The original intent behind developing the unit was to assure that the machines used in competition were producing exactly the same water temperature at the puck. (No competitor should be disadvantaged by having an "off" machine in the practice area or at a competition station. Competitors have actually insisted on having the temperatures checked because the felt they had been penalized by their unit.) The Scace has always seemed a little "slow" to me (I have one) and Sean built a similar puck based unit with a slightly faster probe that we used for our puck measurements. Bottom line here is that since the Scace (and a Fluke) is an expensive addition to your coffee toys, there is a way around it. You should ignore what the actual number on the controller reads and discover what number needs to be there to make the coffee taste just the way you like it ... consistently ... over several shots ... at varying intervals ... with whatever flush you deem appropriate. When you find that displayed number, then you can begin to play with the offset to create a displayed number that looks like the recommendation. If you like Belle at 96 on your readout and Klatch says it is best at 201F (93.888 ... C), then change your offset to make the readout say 94 and see if that makes other coffees taste pretty good at the roaster's recommended setting. If so, then be like Dennis and quit worrying about that issue. Regards KittJ -- You received this message because you are subscribed to the Google Groups "Brewtus" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. 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