Insulated boiler yes or no - Page 2

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HB
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#11: Post by HB »

Ken Fox wrote: <snip> <snip> <snip>

I don't think that having the boiler insulated has any great impact on this phenomenon, one way or the other.

While I do think that insulating the boiler probably does lead to modest temperature overshoot in a PID'd machine, I would submit that the observed decrement in shot temperature consistency is not likely to be noticed by (approximately) 99.999% of the human population.
Your Cimbali is a heat exchanger, albeit one whose steam boiler is running at lower than usual pressure. My comment about the potential impact of boiler insulation applies to dedicated brew boilers and I assume Chris meant likewise. That said, I wouldn't expect the loss of responsiveness for a dedicated insulated/uninsulated brew boiler to be measurable except under load, e.g., faster than one shot ever 2 minutes.
Dan Kehn

Ken Fox

#12: Post by Ken Fox » replying to HB »

I've spent a little bit of time looking at the PID display on the front of both of my machines when they are at idle. There is very little temperature fluctuation, 0.5 degree F. at the very most. Under load this increases to maybe 1 degree. We are talking here about boiler temperature only, and for these purposes a boiler is a boiler is a boiler.

Even in the case of a machine with a dedicated brew boiler, the actual brew temp is not going to exactly mirror the boiler temperature; there will be some attenuation, so, if the boiler temp varies a degree under load, I'd expect the impact of that on the shot temperature to be less than that.

In the end the only way to really be sure about any of this is to test it with a reproducible methodology such as Scace testing. Only then will one really know if any of this matters (boiler temperature overshoot in a PID'd system due to the boiler being insulated).

Were I to do such an experiment comparing a machine with an insulated boiler to an identical machine without insulation, my working hypothesis would be that the observed differences in measured shot temps would be minuscule, probably below the level of variation that could be tasted by the vast majority of people.

ken
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Alfred E. Neuman, 1955

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HB
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#13: Post by HB »

Ken Fox wrote:Were I to do such an experiment comparing a machine with an insulated boiler to an identical machine without insulation, my working hypothesis would be that the observed differences in measured shot temps would be minuscule, probably below the level of variation that could be tasted by the vast majority of people.
Hard to say. For example, the difference may be pronounced for a small-boiler Quickmill Alexia and immeasurable for a multi-group La Marzocco. Whatever the espresso machine in question, I think it's worth trying boiler insulation, if only for the energy savings and cooler interior temperature. For the typical home barista's shot pulling pace, I agree with you, the chances of a meaningful difference between insulated and uninsulated brew boilers are slim.
Dan Kehn

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cannonfodder
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#14: Post by cannonfodder »

I insulated the boiler on my machine but I did it to simply to lower the heat cycles. I run it 24/7 so if I can take a quarter off the cyclic rate, it adds up over a year. It is also a heat exchanger and I believe the added insulation makes next to no impact on the temperature stability due to the design of the machine. Would I let the insulation/no insulation issue dictate which machine I purchase, no. It is a very minor issue when selecting a machine.
Dave Stephens

Ken Fox

#15: Post by Ken Fox »

HB wrote:Hard to say. For example, the difference may be pronounced for a small-boiler Quickmill Alexia and immeasurable for a multi-group La Marzocco. Whatever the espresso machine in question, I think it's worth trying boiler insulation, if only for the energy savings and cooler interior temperature. For the typical home barista's shot pulling pace, I agree with you, the chances of a meaningful difference between insulated and uninsulated brew boilers are slim.
Of course a "working hypothesis" is by definition a guess :mrgreen:

If it were me, I would definitely not go to the trouble to insulate the boiler on any machine I did not expect to have on the majority of the time or 24/7. The energy savings in a machine operated off a timer are going to be minuscule and it is unlikely that one would even recoup the cost of the insulating material in lowered electrical cost.

Likewise, I have no idea how a machine running off a pressurestat or Tstat will behave if it has aftermarket insulation wrapped around the boiler. My guess would be that one would widen the deadband considerably.

ken
What, me worry?

Alfred E. Neuman, 1955

mrmekmek

#16: Post by mrmekmek »

re: PID and boiler insulation:

My understanding information I have read here and elsewhere, is that a PID on a single boiler system with an insulated boiler can have a very narrow controlled temperature. The PID install for the Alexia includes boiler insulation. While I have read historical comments that this helps protect the PID from the boiler heat, I have also read that this configuration still holds temperature very closely (as described in the Bench Buyer's Guide to the Quick Mill Alexia thread). My own experience is that the PID does not overshoot the desired temp very easily, and therefore there is no apparently problem with the boiler insulation preventing the boiler from cooling down. The PID shuts off the heating element before the desired boiler temp is reached as it knows that the system will "coast" up in temp based on the residual heat in the heating element. It cycles the heating element in little flickers as it gets close to the desired temp. At most I've only seen it overshoot occasionally by a degree for a minute or so (as listed on the PID thermocouple reading).

I understand these comments only apply to a dedicated brew boiler PID system, but I'd like to know if my understanding of how the PID limits overshooting the desired temp is incorrect, and how this affects the desired "narrow deadband". If it was possible to eliminate the boiler insulation without damaging the PID, it would seem to increase the natural heat dissipation and increase the temperature change compared to an insulated system. But from the comments above I seem to be missing something?

- thanks, Hans