Buyer's Guide to the Quick Mill Alexia - Page 5

Behind the scenes of the site's upcoming equipment reviews.
Beavis

Postby Beavis » Jul 04, 2007, 6:22 pm

Great clip, Dan. Does the PID read 222? What is the reading on the PID when you hit "BREW"?
Thanks, Beavis

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jesawdy

Postby jesawdy » replying to Beavis » Jul 04, 2007, 9:19 pm

The Alexia PID kit manual indicates that the set value (SV) will be approximately 26°F higher than the actual brew temperature. The kit comes preset with an SV of 230°F and suggests adjusting by taste to a lower SV setting if you prefer a lower brew temperature (I'm sure Dan has determined his temp via a Scace thermofilter).
Jeff Sawdy

Beavis

Postby Beavis » Jul 05, 2007, 6:31 pm

independently verify the water brew temp and let us know the exact temp differential between the SV and the brew water temp. I'm thinking this may be the machine to upgrade to from dear miss Silvia.
Thanks, Beavis

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HB
Admin

Postby HB » Jul 05, 2007, 6:55 pm

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.
Dan Kehn

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HB
Admin

Postby HB » Jul 05, 2007, 11:07 pm

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:

Image
The PID setpoint value is 221F

For the Schomer disciples out there, the raw data is below:
Code: Select all185.3
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.
Dan Kehn

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cafeIKE

Postby cafeIKE » Jul 06, 2007, 12:42 am

Mind running a series or two out to 50 seconds?

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.

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HB
Admin

Postby HB » Jul 06, 2007, 1:19 am

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.
Dan Kehn

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Marshall

Postby Marshall » Jul 06, 2007, 2:48 am

HB wrote: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.



I never thought of using it that way, but Michael Teahan built the same capability into my Zaffiro, when he added an independent pump switch. As long as the levetta is up (to divert the water flow to the brewhead), I can flick off the main switch and flick on the pump switch to get the same effect. Must give it a try ....

Up to now I've just used it to empty out the boiler for descaling without risk of burning out the heating element.

"Bionic Zaffiro" here: http://home.earthlink.net/~mrfuss/.
Marshall
Los Angeles

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cafeIKE

Postby cafeIKE » Jul 06, 2007, 11:21 am

HB wrote:
cafeIKE wrote 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.


Timing clarification:
First drops appear about 9-10s after pump on for an actual shot.
Typical shot runs about 30s for about 60ml. 30s begins after first drops appear, for a total of about 40s.

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

Thanks for the additional runs.

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HB
Admin

Postby HB » Jul 06, 2007, 11:40 am

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:

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