La Marzocco Linea Mini PID temperature - running low?

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nuketopia
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#1: Post by nuketopia »

EDIT:

This was a case of user error on my part.

The temperature dial can be misread, or appear to be incorrectly installed - when in fact, it is as intended. I think the owner's manual should point this out. Also, the dial on the thumbwheel could be marked in a way that would eliminate any confusion. There are some pics later in the thread to show this.

In any case, the Linea Mini makes good consistent shots.

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While dialing in shots this weekend, I'm finding that the temperature setting dial on my new Linea Mini seems to be running lower than I would expect. I'm used to the beans I'm using, roasted only a couple of days ago (Blue Bottle and Chromatic). Despite great looking extractions, I was getting sour shots. So, holding everything else constant, I ran the PID wheel up until the shots were pretty good. But I have to say, I'm pretty near the top end and only just getting balanced shots.

It's also not at all clear what "points" to the numbers on the dial, but it would appear to be the front edge of the machine where the wheel is. That's where the low and high stops on the potentiometer stop, so that seems to be the indicator. In any case, I'm sitting at 212 on the dial (ranges from 185 - 221) so I'm wondering about the calibration.

It is perfectly consistent. I took off the cover and put a thermocouple probe on it where the drain valve comes out. If you set it, it stays there, so the PID is definitely working. I just think the range is shifted towards the cold side a bit much.

Beezer
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#2: Post by Beezer »

Do you have access to a Scace device? Without one, it would be hard to know for sure whether your machine is running cold or not, although it does sound like it might be. I wonder if it would be worth calling LM or your vendor to check it out.

Is this a new machine, or one you've had a while? Is this behavior new or an ongoing thing?

You might also want to try some other beans and see if you get the same kind of results. I suppose it could be a quirk of the beans you're using, though it seems unlikely since you're having to set it for such high temps.
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keno
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#3: Post by keno »

nuketopia wrote:It's also not at all clear what "points" to the numbers on the dial, but it would appear to be the front edge of the machine where the wheel is. That's where the low and high stops on the potentiometer stop, so that seems to be the indicator.
The reading is at the bottom of the wheel at the 6:00 position.

nuketopia (original poster)
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#4: Post by nuketopia (original poster) »

It can't be. Not all the numbers will reach that point.

Kipp
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#5: Post by Kipp »

keno wrote:The reading is at the bottom of the wheel at the 6:00 position.
+1

Your wheel must be in the wrong position. :oops:

nuketopia (original poster)
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#6: Post by nuketopia (original poster) replying to Kipp »


It could be!

So - let me ask those of you have a Linea Mini, does the min and max temperature marks line up at the 6-o'clock position when the wheel is at min/max rotation? Do all the in-between numbers pass through the 6-oclock position?

Because it sure doesn't on mine!!!


EDIT:

Got home, pulled the top cover off and had a look at it. The pot's wire terminals are straight up, but the number wheel is not correctly positioned. It seemed easiest to loosen the nut on the pot and rotate it about 40 degrees. Now the numbers on the dial correspond with the 6-o'clock position, i.e., the 185F minimum now mechanically stops at 6'oclock, as does the maximum 221F. Also, 203F at 6'oclock corresponds to the electrical center of the pot as measured with an ohm meter.

On the top frame the numbers, "198.3F + 12" are written. Presumably, this has something to do with the factory calibration.

But - I don't think this solves the PID being calibrated low. It just moves the numbers into view. I'd still need to set the temperature to 212 to brew a normal shot. It's just that 212 will be at the 6-o'clock spot, not the 3-o'clock spot where it was before.

My guess is that the dial was put on incorrectly, then it was probably calibrated in that position in the factory.

Beezer
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#7: Post by Beezer »

It does sound like the machine has been miscalibrated. I would call LM or the vendor and see if there's a way for you to fix it at home, if it needs to be professionally serviced.
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nuketopia (original poster)
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#8: Post by nuketopia (original poster) »

Had an interesting conversation with La Marzocco today. I'll post more detail later, but I understand their calibration process now.

I need a scace device. Or I need to ship this thing back. I haven't decided whether they have a point or this is a load of bs for a machine this expensive.

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keno
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#9: Post by keno »

I would be curious to hear what you found out. I'd bet someone on HB has a Scace device they would be willing to loan you. So that might be the best route unless the rest of the adjustment is very complex.

Why do you think this is a load of BS?

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weebit_nutty
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#10: Post by weebit_nutty »

Well considering the fact that if you can't rely on the dial and the only other way to be told you need a $600 tool, then yeah screaming BS isn't exactly uncalled for.

Anyway, this machine is clearly not for folks that obsess over the temp labels. I've tested my unit with my own diy tool similar to the SCACE (cost me only $20 vs the ridiculous asking price). The bottom line was that it was very stable and consistent from shot to shot. That was my take away. I did not need to rely on the silly dial setting, other than to rotate it incremently, pull a shot and taste.
You're not always right, but when you're right, you're right, right?

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