fateagk Senior Member Joined: 2 Jan 2004 Posts: 102 Location: Tampa, FL Expertise: I love coffee
Espresso: Andreja Premium, Pid'ed... Grinder: Mazzer Mini Roaster: iRoast
Posted Fri Dec 3, 2004, 4:09pm Subject: Re: Fine Tuning Brew Temperature on a Heat Exchanger Machine
boby Said:
Thanks for posting this topic. I have an Andreja and would like to find an easily repeatable way to know what the brew temps are like I did on my PID'd Silvia. To that end I was interested in your post because I've heard that the GP is similar to the Andreja and in fact that they share many of the same components. But the amounts of water you are flushing seemed too high to me (maybe there are more differences between the two machines than I thought, particularly the length of the HX) so I made some data-logged measurements of my own and found that my initial reaction that the flush amounts are too high [for my machine] was correct. For example, after sitting idle a period of time longer than "16 & over" a flush of 8 oz. takes the temps from a max of 210 deg F down to 185 deg F. Even if I wait 35 secs, the next pull brings water with a maximum of 192 deg F and not 202 F. I'll bet a flush of 8 oz. will empty the HX and bring in some not-yet-heated-enough water.
I wonder if you have, and would share some of the flush water temps and your pstat setting. That may help me to understand the large difference in our brew temps using this method. And again, thanks for your work and for posting this.
Bob, IIRC, you have adjusted your Andreja Premium's pressurestat to much lower than the OP's stated 1.2 average. If he has a deadband of .2, that would put it roughly at 1.1-1.3 for the cut off and cut on times. In your review you stated that you had adjusted yours to 1.05 at the top of the boiler cycle. While there are probably several contributing differences, do you think this may be the most significant? It seems like it is hard to give anybody a reference, even between two machines of the same model, for doing cooling flushes because of variations in pressurestat settings (deadband and max pressure). I need to dig out my TC because I have my pressurestat set at around what the OP states. His messurements seem to be more close to what I am observing. Before, when I had my pressurestat set closer to yours, his figures would surely be too high. Either way, if there were an easy way to determine flush time as a function of boiler pressurestat settings and idle time, that would be very useful for sure!
Posted Fri Dec 3, 2004, 5:04pm Subject: Re: Fine Tuning Brew Temperature on a Heat Exchanger Machine
tom_b Said:
The method of measuring brew temp will make a big difference. I found that before I got a 36 gauge tc and ran it 'over the lip and under the screw', I didn't get very reliable results, as differences in pressure from using a single basket with a hole poked in it (putting tc up thru spout) made for different results. Even with the under the screw method I get different readings for a 20 second shot than a 30 sec one. The thing I like about the method is that you can make your normal shot and test a 1.5 oz ristretto in 30 secs or what have you. tom:) 'this year's gift for my coffeekook habit - an omega hh501at!!'
I'm fortunate to have the use of Jim Schulman's PF with the TC mounted so that it is rigid and mounted in the basket with the cable going through the bottom of the basket by way of a tiny hole drilled into the basket. It exits out through the spout.The TC junction sticks up from the bottom of the basket to just below the shower screen. I then surround it with sponge to limit the flow, somewhat. That way it is in the perfect place to measure the water just as it streams out of the shower screen but more importantly, it is in the exact same place for every measurement.
Posted Fri Dec 3, 2004, 5:18pm Subject: Re: Fine Tuning Brew Temperature on a Heat Exchanger Machine
Abe_Carmeli Said:
Bob,
I can see three parameters that may produce different results, and as I mentioned in my post, the flush quantities may differ between machines due to those differences. The parameters are:
1) Water temperature in the tank 2) The heat exchanger design. 3) Accuracy of your temperature measurement - how accurate is your thermometer reading?
I used an OMEGA HH506RA with a 24 Gage thermocouple. I snaked it into the portafilter through the bottom of a single spout, and then through a hole I drilled in the portafilter gasket and into a sponge. The exposed end of the thermocouple was slightly above the top of the sponge. The sponge simulates ground coffee. I have found that using a different thermometer, and even a thinner gage thermocouple, gave me less accurate results. Also placing the thermocouple in a different location gave a different reading.
Water Tank Temperature: It ranges from 86 f to 110 f. After the machine was off all night and then on in the morning for 30 minutes, the temperature in the tank will be around 86 degrees. If it is idle for an hour or more thereafter, it may reach 110 degrees. Flush quantities will change slightly if you are refilling the tank with cold water. That is: flush less, about 0.5-1.0 oz less depending on idle time, and add 5 seconds to the recovery time.
If I find the time this weekend, I will run some tests which will include tank water temperature, and update my chart.
I have confidence in the measurements. I use an Extech digital with high accuracy and a data logging output directly into a laptop. As you can see in my post above, I think our PF's with embedded TC are somewhat similar. The junction on mine never changes position because it's rigid inside the basket and surrounded by sponge like yours except that it sticks up above the sponge and just below the shower screen.
The tank temperature may have something to do with it but I also suspect that there is a difference in the size of the HX, yours being larger and thus needing more water to be flushed out. If you are doing more measurements, I would appreciate knowing the beginning and ending temperature of the flush, giving the amount of flush used. That will give me a basis for comparison. Thanks so much!!
Posted Fri Dec 3, 2004, 5:22pm Subject: Re: Fine Tuning Brew Temperature on a Heat Exchanger Machine
fateagk Said:
Bob, IIRC, you have adjusted your Andreja Premium's pressurestat to much lower than the OP's stated 1.2 average. If he has a deadband of .2, that would put it roughly at 1.1-1.3 for the cut off and cut on times. In your review you stated that you had adjusted yours to 1.05 at the top of the boiler cycle. While there are probably several contributing differences, do you think this may be the most significant? It seems like it is hard to give anybody a reference, even between two machines of the same model, for doing cooling flushes because of variations in pressurestat settings (deadband and max pressure). I need to dig out my TC because I have my pressurestat set at around what the OP states. His messurements seem to be more close to what I am observing. Before, when I had my pressurestat set closer to yours, his figures would surely be too high. Either way, if there were an easy way to determine flush time as a function of boiler pressurestat settings and idle time, that would be very useful for sure!
Right you are - I do have it set to 1.05 max and that may have an influence on this whole business. I'll be looking into this in depth and report back.
Posted Fri Dec 3, 2004, 6:43pm Subject: Re: Fine Tuning Brew Temperature on a Heat Exchanger Machine
Another variable for those of us using a plumbed in water supply: seasonal variation of the water temperature coming into the house. In the winter, my cold water supply is noticeably colder than during the summer.
Posted Fri Dec 3, 2004, 7:39pm Subject: Re: Fine Tuning Brew Temperature on a Heat Exchanger Machine
Abe_Carmeli Said:
The problem with Dan’s method is that on my machine, watching the water flow to determine water brew temperature still leaves a margin of error of 4-5 degrees.
Four or five (!) degrees of variance really surprises me, unless you're speaking of the "hump" rise. In that case, an extra 10-15 seconds of rebound time can push you over a few degrees, but the last two-thirds of the shot should nonetheless track within two degrees or less.
boby Said:
To that end I was interested in your post because I've heard that the GP is similar to the Andreja and in fact that they share many of the same components. But the amounts of water you are flushing seemed too high to me (maybe there are more differences between the two machines than I thought, particularly the length of the HX) so I made some data-logged measurements of my own and found that my initial reaction that the flush amounts are too high [for my machine] was correct.
For what it's worth, the Giotto Premium that I tested required a longer flush than the Andreja Premium at the same pressurestat setting. The HX of the Tea and Andreja are the same 110ml; I don't know the volume of the GP's. That's one factor, plus the thermosyphon lines are different lengths. Andreja's are very short, especially the top one. There's also the boiler orientation / amount of HX exposed to steam versus water... lots of variables. Of the machine's I've tried, the Expobar Lever is the flush-and-rebound king. You'll go through a lot of water with that machine, especially since it vents the OPV into the huge driptray.
I like to "recalibrate" my intuition with an in-basket measurement a couple times a week, less often if I know the machine well. The bottomless portafilter bug bit me and that's provided very useful feedback.
-- Dan
PS: For yet another interpretation of HX temperature stability, see Jim Schulman's results on alt.coffee (link).
Posted Sat Dec 4, 2004, 12:04am Subject: Re: Fine Tuning Brew Temperature on a Heat Exchanger Machine
HB Said:
Four or five (!) degrees of variance really surprises me, unless you're speaking of the "hump" rise. In that case, an extra 10-15 seconds of rebound time can push you over a few degrees, but the last two-thirds of the shot should nonetheless track within two degrees or less.
As I mentioned in my original post, your method is excellent. The problem is with me - lack of experience. I am sure that if you looked at my water flow, you would be able to pinpoint brew temperature.
PS: For yet another interpretation of HX temperature stability, see Jim Schulman's results on alt.coffee (link).
Jim in that post believes that narrowing the brew temperature to something less than 5 degrees Celsius is not practical on H/X machines. From my own experience it is possible and practical, as I now do it on every shot, and without any additional gadgets.
Posted Sat Dec 4, 2004, 12:13am Subject: Re: Fine Tuning Brew Temperature on a Heat Exchanger Machine
boby Said:
The tank temperature may have something to do with it but I also suspect that there is a difference in the size of the HX, yours being larger and thus needing more water to be flushed out. If you are doing more measurements, I would appreciate knowing the beginning and ending temperature of the flush, giving the amount of flush used. That will give me a basis for comparison. Thanks so much!!
Posted Sat Dec 4, 2004, 12:22am Subject: Re: Fine Tuning Brew Temperature on a Heat Exchanger Machine
I did some more testing tonight and updated my flush chart with the new data. I also added some comments of how to apply the chart to other machines. See attached.
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