Posted Sun Jan 1, 2012, 10:28am Subject: Re: What's your Colling flush time and averge brewing temperture
I have an Alex Hx machine as well. It's not the Alex II but I'm pretty sure they should perform similarly. I struggled for a while trying to figure out how to regulate the brew temperature on my machine. I finally achieved good control after a purchasing a group thermometer renting a Scace thermofilter. By using the Scace, I was able to determine precisely how much water to flush to dial the brew temperature within 1F of my target temperature. Further more, the temperature during the extraction is stable within 1F throughout the shot using my method. I have my pressurestat set at 1.3 bar at the top of the cycle on my machine, but I have also tested this method at 1.0 bar with the same results. The amount of water you need to flush is dependent on the temperature you are aiming for and the current group temperature (which is dependent on the boiler temperature and how long since a shot has been pulled last).
I made a chart to show exactly when to stop to flush for different brew temps and different group temps. The way you use it is simple. First, make sure the group thermometer is stable at 200F or higher (increasing temp on the thermometer is ok, decreasing is not). Next, simply match the temperature on the group thermometer to the nearest temp on the chart under the column named Idle temp. Determine the target brew temperature (between 198F and 203F) and match up the temperature from that column with the row matching the reading on the group thermometer. This will give you your target temperature that you want to end your flush. Next start your cooling flush and continue until the temperature on the thermometer reads the temperature from the chart. (For example, if my group thermometer reads 210F and I want a brew temp of 200F, I will end my cooling flush at 203F on the thermometer) After stopping the flush, the thermometer may continue decreasing a degree or two, this is normal. Now lock in the portafilter and pull your shot. I usually allow about 10 seconds from ending the flush until beginning the shot. If you want to pull subsequent shots, the group temp will be lower, but by following the chart, the ending flush temp is higher which gives you a shorter flush to compensate. I can easily pull shots about a minute apart with my machine with completely consistent brew temps.
P.S. I noticed that you said you were aiming for a 196F brew temp. My chart only goes to 198F. I would simply subtract about 4 degrees from the 198F flush end temp and that should get you around 196F (which is actually lower than I've gone before).
Posted Sun Jan 1, 2012, 1:01pm Subject: Re: What's your Colling flush time and averge brewing temperture
Yeah. The Alex does require quite a long flush. I would estimate 8-10oz from idle. I know some machines require a much smaller flush. I think this may be because I don't think the Alex has a thermosyphon restrictor. Before I plumbed in my machine it seemed like I was constantly refilling the reservoir. It makes things much easier with a plumbed in machine. I've thought about trying to source a thermosyphon restrictor to reduce flush volumes, but I don't know how that will affect using my chart and I'm pretty happy with the results I'm getting now.
A 224 F. Grouphead temperature? Read using the thermometer that mounts in the E-61 group? That is REALLY hot! Way too hot, even for a HX machine on an extended idle time. At idle I would expect to see something more in the range of 202-203 with a flush temp up to around 206-MAYBE 208 tops after an extended idle temperature. Maybe the Duetto works differently than the two E-61 machines I have had, but that is a temperature that would produce nothing but steam for an extended flush time.
I hope that was a typo or that the thermometer was either mounted incorrectly or is defective...
ggenel Senior Member Joined: 16 Dec 2011 Posts: 63 Location: Concord, MA Expertise: Just starting
Espresso: IZZO Alex II Grinder: Baratza Vario
Posted Sun Jan 1, 2012, 1:24pm Subject: Re: What's your Colling flush time and averge brewing temperture
Machine was idle for a couple hours and the group temp was 224. I did a 10oz flush and temp went down to 198. About 5 sec. of steam. My settings are as follows.
The PID is set to 255 which sets the boiler preassure at 1.3. I can set the PID to 250 and that will set the boiler preassure at 1.1 and will lower the group temp to about 210 give or take a couple degrees.
My Alex @ 1.3 bar idles between 222F and 224F depending on ambient temperature as well. So, I don't think this is abnormal for the Alex. Yes, it is hotter than other E61 machines, but I think it is because of an unrestricted thermosyphon. The group temperatures and flush volumes are actually almost identical to my last machine an Expobar Pulser, another E61 machine. I'm sure I could get it lower by dropping the p-stat, however I love the steam power at 1.3 bar and the flush volumes don't bother me as my machine is plumbed in.
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