Hi,
I’ve been having a hard time getting a nice high strength and extraction from my espresso (GB5 semi-auto). I realized that, though I have the coffee boiler temp set to 203F, the water exiting the group might not be hot enough. So after much deliberation I decided to buy a scace to figure out what the difference in temp from boiler to group on my machine actually is. Turns out it’s about a 10 degree difference.
I pushed the temp in the coffee boiler to 207 (water boils at 204.3F at my elevation, so this shouldn’t even be possible) sure enough the boiler says it’s at 207 but the scace is saying 196. So I turn the coffee boiler temp up more, and I kept doing this until the water exiting the group was steam (this began to happen around 210.5)
What kinds of temperature swings are common, and is there anything to do about this? It seems to me like a problem with the temperature probe in the coffee boiler, but that’s just a guess.
What else would it be if not the espresso machine? My thermometer has been calibrated, so I’m pretty sure it’s not that but I am going to experiment again with a different thermometer just to be sure.
Please correct me if I’m wrong, but if there is steam coming out from the group, that should tell me that the water in the boiler has reached it’s boiling point (around 204 at my elevation) yet the GB5 says it’s at 211 degrees, but that can’t be possible, right?
Hey Nick,
I do know that because there is pressure built up in the coffee boiler, the temp can be much higher than boiling point. In other words, water boils at your location at 204.3 at atmospheric pressure, increase that pressure in a saturated boiler and the boiling point rises. As soon as the water leaves that system, it immediately boils.
I don’t know for certain how any other machines compare to the gb5 in terms of difference between boiler temp and water leaving the screen, I do know that the kvdw spirit and speedster have a much larger neck between the boiler and group head. This is theoretically designed to allow better temp stability. Whether this is actually true or not I don’t know, but it makes sense! Then there is the va black eagle. It doesn’t use a saturated boiler to maintain group head temp, but rather a heating element, which allows some easy adjustment of water temp.
Also, there may or may not be an offset programmed on your gb5, making the difference your experiencing more dramatic, and maybe your high elevation is affecting it too. I don’t have any experience high altitude, but I here it makes things difficult.
Lastly, if steam is leaving the group head, it definitely means the water is near 204.3. Don’t worry about brewing espresso with this water. Once you begin pulling a shot and pressure accumulates above the puck, the water will stop boiling as the boiling point will rise again. It’ll be only a second of steam hitting the puck, and I wouldn’t be concerned about that.