I believe the offset is 24F for my evaluation model, but it will vary depending on the thermowell probe placement. Next on my list is to post a plot of the typical temperature profile. I've been using the Alexia as my evaluation setup for the Titan Grinder Project and noted how it recovers very quickly; I'll measure a series of thermofilter pulls to quantify intershot variance later tonight.

As promised, below is the brew temperature profile of the PID'd Quickmill Alexia. This was the first 30 second pull after being idle for an hour. To warm the group, I drew 3 ounces, let the boiler recover two minutes, then recorded:


The PID setpoint value is 221F

For the Schomer disciples out there, the raw data is below:

185.3
187.9
192.7
196.5
197.1
197.3
197.5
197.7
197.7
197.7
197.5
197.5
197.4
197.3
197.3
197.3
197.3
197.3
197.5
197.5
197.6
197.7
197.7
197.7
197.7
197.9
197.9
197.9
198.0
198.1

The target temperature is 198F. There is an ever so slight rise to the temperature profile towards the end. To see how the Alexia performs under load, the series below are the maximum temperatures at different recovery intervals. The draw was for 30 seconds and the datapoint was the maximum temperature recorded with a Fluke 54-II digital thermometer and thermofilter:

1 minute 30 seconds: 198.1, 197.8, 197.6, 197.5, 197.4
2 minutes 0 seconds: 197.5, 197.5, 197.4, 197.5, 197.6
3 minutes 0 seconds: 197.7, 197.9, 197.9, 197.8, 197.9

These are the best intershot temperature consistency measurements I have ever recorded.

Note: This evaluation model is a slightly modified version of the PID kit offered by Jim Gallt / Chris' Coffee. When I did a few quick measurements of the original PID configuration, I noted temperatures would trend upwards. I noticed this same tendency with my PID'd Amica and added a manual cutoff of the heating element to reduce overshoot; I figured it might improve on the Alexia's already impressive performance. I contacted Jim about this and he sent me a cutoff relay for the heating element whenever the pump was engaged. While the difference in intrashot brew temperature is likely beyond the abilities of mere mortals to taste, the cutoff relay has the added benefit of eliminating the "aaaa-eeee-aaaa-eeee" sound of the pump as the PID cycles the heating element on and off during an extraction. At this price point, I believe the enhanced usability and elimination of the pump pressure zig-zap due to heating element cycling is worth it, but Chris/Jim haven't decided on the cost of this option.

cafeIKE wrote:As the 30 second shot time starts at first drops, not pump on, the 30 second series is only 2/3 of the way through the shot.

I don't understand your comment. Let me elaborate on the details behind the measurements posted above.

These measurements were taken using a thermofilter and the first "drops" show up in around five seconds. The thermofilter yields 70 mls in 30 seconds from pump on. But just for giggles, I tried a 50 second pull just to see how much the tail end temperature would rise. Specifically, I did a warmup flush of 3 ounces since the machine was idle for over an hour, let it recover for a few minutes, then ran the pump for 50 seconds. The cup contained 124 mls and the finishing temperature was 199.1F. A couple minutes later, I double-checked that a 30 second pull was 70 mls and the finishing temperature was 198.0F.

cafeIKE wrote:The 30s series initially posted would be about 10s shy of the end point of an actual shot.

I suppose it depends on whether you measure by volume or time. As discussed in the thermofilter review, the thermofilter was designed to measure the boiler's output, not precisely recreate the coffee's brew temperature profile during a real extraction. Its strength is the standardization of where and how it measures.

Comparatively speaking, the Alexia's shot to shot brew temperature consistency is on par with the La Marzocco GS3 IF you're moving at a leisurely pace. The Alexia would fail miserably if subjected to the WBC Procedure for Measurement of Brewing Water Temperature protocol, excerpted below:

5.3 Testing pattern:
Specification: The length of the idle interval for item A of the Test Procedure shall be:

But for the less hurried espresso only drinkers who prize inter and intra temperature stability, the PID'd Alexia eliminates brew temperature management concerns.