Just received my new Alexia a few days ago and I have had issues generating decent shots. When I pull a shot it looks normal for a few seconds and then it turns into a gusher. While cleaning the grouphead I noticed that there seemed to be a large amount of steam coming from the grouphead when the brew lever is activated. I have tried adjusting the pid temp with no change in results. I checked to make sure the boiler is completely full by using the instructions given in the HB Alexia review and from the Chris's Coffee instruction manual. I have used other machines and never had a problem generating a normal flowing shot.

Boiler pid showing a value below boiling Boiler pid showing a value above boiling Typical shot. Except on the Rocky Doserless I ground it finer than normal, at 4, trying to see if I could get a normal flowing shot. Any suggestions would be greatly welcomed.

A few questions:

• In the first video, the PV (current temperature, or process value) is 12 degrees below the SV (setpoint, or set value) at the beginning of the flush. Unless the machine has just been turned on, or if you have very recently pumped an amount of water through the boiler, the PV and the SV should be within 1 degree.
• Your SV is 208F, which is very high for a brew temperature, but very low for a boiler temperature. If your PID is setup to display target brew temperature, then your SV is too high by at least 5F; flashing of steam would be expected with a brew temp this high. At your locale, boiling point is probably around 210F.
• In the second video, the PV is 222F, compared with a SV of 208F. Was the steam switch used to raise the temperature? Certainly, flashing would be expected at this temperature.
• In the 3rd video, the PV starts at 211F, which again does not match the SV as closely as it should.

The first step in troubleshooting this would be to determine whether or not the PID is controlling the boiler temperature correctly. After warming up, while sitting idle the PV should only very rarely, if ever, depart from the SV by more than 1 degree. If your machine is not behaving this way, then PID tuning may be an issue.

The second step would be to determine whether or not an offset has been programmed into the PID to allow direct input (through the SV) of desired brew temperatures. If so, then I would immediately reduce the SV to 200F and try again.

If there is no offset programmed, and if the SV represents the actual boiler temperature, then something else is going on. Depending on the location and type of boiler temperature sensor used on the Alexia, there should be a difference of approximately 24F between the actual boiler temperature and the resulting brew temperature. But I would never expect steam at the grouphead from an Alexia with a true boiler temperature of 208F. So this would be a real head-scratcher if there's no programmed offset.

Jim

Jim,

Thanks a ton for the quick reply.

From your questions I realized that the pid temp value is really an arbitrary value and doesn't tell you what the temp is coming out of the brew head. For some reason I thought that the pid set temp would be very similar for all pid'ed machines but now I realize that is not the case.

The videos were not taken at ideal times because I was trying to record and brew at the same time so many attempts were made in a short period of time; this caused the large difference between PV and SV. The PV of 222 was after a number of example shots had been made and the pid overshot the SV (didn't activate the steam switch).

To answer the first troubleshooting question I have not seen the pid, at idle, vary from the SV by more than 1 degree. For the second question I realized that I needed to figure out what the water temp was coming out of the brew group. So, I headed to the grocery store and picked up some styrofoam cups to do a styrofoam cup test. I used a Fluke multimeter with a Type K probe to measure the water temp in the styrofoam cup. By doing ~2 ounce shots and waiting a few minutes between each shot its seems that there is roughly a 10F difference between the SV and water in the styrofoam cup. At 205 I am sitting at ~195. Which, from what I have read is fairly close to ideal. At a SV/PV of 205 I do not have a problem with steam as long as I do not run more than two-three 2 ounce shots. If I run more it causes steam to come out of the group head. When I am conducting the tests there is no coffee involved. As a side note, I do not have any pressure released from the valve below the group head (I believe this is normal because there is not build of of pressure). But, I do see water drip out of the pressure value.

I am going to continue to test to see how the pid responds to multiple shots. The steam issue is under better control but there still seems to be quite a bit of steam if I pull more than a few shots. Thanks again for the help.

ShaggyJ wrote:For some reason I thought that the pid set temp would be very similar for all pid'ed machines but now I realize that is not the case.

Especially true for machines with tallish boilers with the temperature sensor located inside a thermowell. The vertical position of the sensor makes a big difference with respect to the temperature it reports back to the PID.

ShaggyJ wrote:The PV of 222 was after a number of example shots had been made and the pid overshot the SV (didn't activate the steam switch).

That's a lot of overshoot (~15F). You may wish to contact your PID provider and ask about tweaking the tuning.

ShaggyJ wrote:I used a Fluke multimeter with a Type K probe to measure the water temp in the styrofoam cup. By doing ~2 ounce shots and waiting a few minutes between each shot its seems that there is roughly a 10F difference between the SV and water in the styrofoam cup.

That should be useful data, but the delta (10F) between PV and brew temp is way less than I would have predicted. Could be a matter of sensor position inside the thermowell, though. If your sensor is at or near the bottom of the well, then it will report a lower temperature than a sensor positioned higher up.

Here's a fairly simple test, that doesn't rely on boiler sensor position, for finding a good SV for an Alexia:

• Using a hex key, temporarily remove the M6 grouphead screw.
• Push your beaded thermocouple probe into the socket to a depth of around 3/4 inch (this dimension is not critical when no water is flowing).
• Put a little bit of packing around the thermocouple wire, just to seal up the hole a little (I use a bit of paper towel)
• Adjust the SV until the multimeter/thermometer reading from the grouphead is 196F at stable idle. Expect it to take ~10 minutes for changes in SV to be communicated to the group, BTW.

At normal room temperature (say 75F), your brew temp should be ~3F higher than the group thermocouple reading, so you can adjust accordingly.

Be sure you remove the t/c and packing, and replace the M6 screw, before running any water through the group

Jim

Jim,

From playing around last night it seems that the brew temp and SV converge when multiple shots are pulled. So, at idle (30 min) after pulling a shot there is a 10F difference between SV and brew head temp. But that difference between SV and brew head rapidly decreases when multiple shots are pulled and eventually the brew head temp becomes greater than the SV. Today, using the styrofoam cup test without the portafilter here are the results of the test.

SV: 198
Time period between shots: ~2 min
Shot time/volume: 5-8 sec/2-3 ounces

# Temp PV Notes
1 188.7 198 No sputtering
2 192.7 198 No sputtering
3 197.9 200 Slight sputtering
4 200.9 203 Sputtering very noticable
5 206.2 204 Sputtering very noticable

When I say sputtering it is the noise coming from the grouphead because of the steam being released.

Next step, remove the M6 grouphead screw and figure out what the proper SV should be. Thanks a ton Jim for the help.

Jim,

With a SV of 198 the grouphead temp is 186.9. So, I am going to increase the pid temp to 207 and see what effect that has on the grouphead temp.

Here is a pic of the setup


Thanks,
Jad

ShaggyJ wrote:SV: 198
Time period between shots: ~2 min
Shot time/volume: 5-8 sec/2-3 ounces

# Temp PV Notes
1 188.7 198 No sputtering
2 192.7 198 No sputtering
3 197.9 200 Slight sputtering
4 200.9 203 Sputtering very noticable
5 206.2 204 Sputtering very noticable

A few observations:

• This is an imperfect test, because the flowrate does not match a real shot very closely. Don't want to draw too many conclusions based on these results.
• Still, I am concerned that your PV has not settled back closer to SV after 2 minutes.
• Also, your brew temperature seems to be rising significantly as you go through a series of shots.
• During development of a different PID system for the Alexia, I saw similar behavior when the sensor was placed low in the thermowell. This is because the lower part of the boiler is slower to react to the heater, causing the PID to "overdrive" the system.

Your PID system is not one of my designs. So I'm not sure what type of sensor you have, and I'm not sure where it is located. Hopefully once you get the SV established by referencing the grouphead temperature, you'll see the kind of performance the Alexia is capable of.

Jim

Jim,

An SV of 207 results in a grouphead temp of 195.7. Now the dilemma that I am faced with is at this higher SV it is very prone to producing steam from the grouphead. For example, I placed the M6 bolt back into the machine and pulled a ~2 ounce warming flush (no steam from grouphead), then I attempted to pull a shot after about 2 min and there was the noticeable steam gurgle during the shot. After the shot I cleaned the machine with a quick portafilter wiggle and swipe of the brush and steam was rolling out of the grouphead. The PV then overshot to 213. So, I think my next step will be to undress the Alexia and try to figure out where the temp sensor is located. Any other suggestions would be welcomed. Thanks again for the help Jim.

Jad

Here are some of the pics of the undressed Alexia...

Back of PID


Top view of thermowell


Probe removed from thermowell


So, the distance from the top of the thermowell to the bottom of the probe was roughly 3.5 inches. This would place the probe slightly below the middle of the boiler. Should I move the probe up an inch, or is the placement correct?

Thanks,
Jad

The person you purchased your Alexia from, presumably Dave Blaine - Hitechespresso, has gobs of experience in applying PIDs to espresso machines, as does Jim G. I would certainly feel safe in assuming the temperature sensor placement is correct for the particular parameters embedded in the PID. But, you might want to send him an email and reference this thread.

Your overshoot to 213 when Sv is 207 is, IMO, NOT CORRECT. I would see what values are embedded in the controller for P, I, & D at present. Write them down. Next I would do an autotune on the controller and see what values come up as a result. Keep these settings for the time being.

When you change Sv, you (obviously) also change grouphead temperature and I would give the machine a good 30 minutes to respond to this. This is probably a bit conservative but better you have a stable temp to work with. The typical operation with Alexia is to do a short flush (as you did) and then pull the shot - NOT to wait two minutes as you did. In addition, I would count on pulling shots at 2.0 to 2.5 minute intervals with an edge towards 2.5 minutes.

The idea here is to relate a particular Sv setting to a "how pleasing is the taste" for a particular bean.