HB wrote:The shorter the cup, faster the thermometer response, and tighter the fit to the grouphead, the more accurate the temperature measurement.

Are paper cups equally suitable for this test as styrofoam cups? Paper cups are a lot easier to find where I live.

They'd probably work if you double them up or maybe just wrapped them in a thick towel. The styrofoam cups aren't environmentally friendly, but they are much better at holding heat compared to paper cups.

HB wrote:The shorter the cup, faster the thermometer response, and tighter the fit to the grouphead, the more accurate the temperature measurement.

One could simply forgo absolute number certainty and brew by taste. On my DB, 103°C is minimum boiler temp, 106°C max. After dial-in, remains unchanged until next coffee. I use the group thermometer so infrequently, batteries last a decade or so.

e61's punish prep inconsistency as the flow rate can affect temperature.

Twenty years or so ago, added Almost a PID to a Solis SL-90 and was very content with ± relative to pot mid position.
Ditto pals for whom I did the mod.



from Solis SL-90 Adjustable Brew Temperature

I wonder if the thermosiphon circuit in Boren's machine is not working properly (e.g. has some blockage or maybe a partial vapor lock)? That could explain the large intershot temperature fluctuation which, if as large he reports are definitely not "normal" for a properly functioning e61 with either a PID-equipped single or dual boiler machine.

Is there a way to test if the thermosiphon is working correctly? And also, what does it mean for it to work correctly in a non-HX machine like mine?

Thanks!

When the thermosiphon does not function, the group temperature drops to a low value

It can happen on an HX with too short a flush. I had the problem on my HX when I first got it.

Buyer's Guide to the Vibiemme Domobar Super - Page 19 (Disregard the "leave the puck" bit. I made two shots in short succession back then.) and E61 Salvatore troubles with low brew water temperature?



There isn't any reason I can see that the same could not occur on an SB or DB given the right set of circumstances. When I do a descale or rebuild, I fill the boiler / HX without the mushroom and cap and a blind basket to ensure the entire water circuit is full.

@HB & @Bluenoser. You were both right. The test I presented in the OP wasn't useful. I now did it again, with actual coffee in the basket and measuring temperature both above the puck, and (in a few shots) also in the cup. The results are much more useful and it turns out my machine temperature stability is not as bad as I initially concluded (though it's far from brilliant).

The new test is here:

SB E61+PID, Episode 2: Tested properly this time, with much better results