Changing this offset should not have affected anything other than the display temperature value. However, the (almost obvious) next step would be to change the offset back to what it was before the problem appeared and see the results (if any).

If the temperature fluctuations coincided (exactly) with your offset change, that's one thing. If you just happened to notice them at "sorta" within the same time frame as your offset change, it could be that your temperature sensor is a little scaled up and does not look as pristine as the one below:

Ben -

I believe the "white stuff" is a calcium or magnesium salt buildup. Where the wiring enters the thermowell, the "black stuff" is a sealer used to hold the actual sensing element in place - very common practice. I think it would be a good idea to order up some water test strips from these guys: http://www.mcmaster.com/#water-test-strips/=d78hq8 . I have the T41 and T47 even though the T47 seems to do it all. Titration kits from Hach would be more accurate but are also a PITA depending upon the frequency you do same. It might be interesting to temporarily run your Duetto with bottled water (Volvic is one good choice) and see if that makes a difference (in ALL respects). I did run Anita with Volvic a couple of weeks ago and "could have sworn" I tasted an improved difference. I also have 3 gallons of Poland Spring Water if I can ever get off my lazy butt.

I am NOT a big advocate of espresso machine descaling but the idea of pouring a WELL DISSOLVED descaling solution through the sensor port using a small funnel seems pretty reasonable. Give it 5 minutes of heat, let it soak for an hour or so, and then syphon out. I DO advocate knowing the quality of water going in, treating it as necessary, and developing (in one's own mind) a sign when this is necessary.

The temperature sensor used with these Gicar controllers is a 50,000 ohm negative temperature coefficient (NTC) thermistor. It is designated as such because, at 25 C (77 F), the measured resistance is 50,000 ohms. This is one example of a supplier - http://www.alphatechnicsonline.com/index_2.php .



Boiler sizing tends to be overly generous or "they" may have a different definition of what the "boiler" actually consists of. Boiler tops and bottoms are typically 10 mm and walls are typically 2 mm so you can easily do a quick calculation.

Dennis - that's not an unreasonable response from the dealer. All of these GICAR PID controllers have display "filters" and, for the most part, do not display degree tenths. Only whole degrees are displayed and the tenths are simply dropped off, i.e., NOT a round-up or down. So, as an EXAMPLE, say the exact temperature was 215.9 F. The display (with offset = 0) would show 215 F. Now say the exact temperature was 216.1 F. The display would be 216 F. A true differential of 0.2 would display a differential of 1 degree. And by the same reasoning, a true differential of 1.8 degrees would also show 1 degree.

A 17 mm would be very tight (if it makes it) and an 11/16 would be just a tad loose.

Use a plumber's strap wrench on the boiler - you DO NOT want to twist the tubing connections.