HX vs. double boiler temperature stability

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Ltrain5000

#1: Post by Ltrain5000 »

There seems to be a long standing debate or discussion on what's better-- A PID'd DB machine or temp surfing on a heat exchanger. There are people vigorously defending their positions on both sides. From my understanding, since many of these machines have the same rotary pumps and OPV configuration, the pressure stability during shot extraction is not nearly as much of a variable as the temp stability since temp stability can be influenced by so many different things.

I was wondering if the entire question could be simply answered by showing temp swings on both types of machines during shot extraction. I know on my La Marzocco GB5, a temp swing was as close to non-existent as it could get. And on my SB PID'd Silvia, the temp swing is closer to 19 degrees if I don't add preheated water to the reservoir. Obviously, these two machine are on opposite ends of the spectrum, but I sold my GB5 and am considering a $2-3K home machine to pair with my Robur-E. I know people will say "This machine is great because...... But actually seeing the swing (or non-swing) in action is the real proof isn't it?

Does anyone have video of their prosumer machines (HX or DB) showing the PID during extraction to show whether or not the machine's temperature changes? to put it in a nutshell, isn't that the entire goal of an espresso extraction once the pressure stability is controlled?

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HB
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#2: Post by HB »

Ltrain5000 wrote:There seems to be a long standing debate or discussion on what's better-- A PID'd DB machine or temp surfing on a heat exchanger.
Operationally, it's hard to argue that a double boiler's flush routine isn't less complicated. Heat exchanger espresso machines, by their nature, demand that the barista pay closer attention to temperature management than a double boiler. Whether a given barista considers the heat exchanger flush routines burdensome is like trying to convince someone who has driven cars with manual transmissions for years that an automatic transmission is "better" than manuals. It's not just about which demands more or less from the barista (or driver), it's also about a feeling of control: Some enjoy it, others consider an unnecessary burden.
Ltrain5000 wrote:I was wondering if the entire question could be simply answered by showing temp swings on both types of machines during shot extraction.
If two espresso machines produce the same temperature profile every time, whether it's rising or humped, who's to say one is better than the other, except by blind tasting the results? The reason the question of which makes better espresso, an HX or double boiler, keeps coming up is because it's asking the wrong question. It would be like asking a group of car enthusiasts which is better, an automatic or manual transmission. Good luck getting consensus on that one.
Dan Kehn

Ltrain5000

#3: Post by Ltrain5000 »

HB wrote:If two espresso machines produce the same temperature profile every time, whether it's rising or humped, who's to say one is better than the other, except by blind tasting the results? The reason the question of which makes better espresso, an HX or double boiler, keeps coming up is because it's asking the wrong question. It would be like asking a group of car enthusiasts which is better, an automatic or manual transmission. Good luck getting consensus on that one.
I understand your point, but I guess I misstated my question. Which one is best is obviously a matter of opinion. My question was intended to ask which one has more stability as opposed to which ones have consistent humped or rising profiles. - If we are talking profiles, which ones would have a flat temp profile? and if it's not totally flat, which ones are the closest to being flat? Meaning not straying from the temp at which the boiler is sitting before the button is pressed to begin an extraction.

I can get a very good tasting shot with my Robur and my Silvia. Is it on par with my GB5? No, but I have had some pretty damn close. Is the temperature profile consistent on the Silvia in regards to a curve? yes, but the brew boiler temp profile is not flat during extraction like it is in a GB5. I hope that clears up what I am asking.

As to your point about control, I guess I am still a bit confused as I have never used an HX machine. But I have read people saying surfing / flushing gives them "control" as you mention. Control over temperature? Please don't take this the wrong way, if one must flush / surf, etc and guess where you're at and have a rising or humped curve during extraction, isn't that indicative of the user not having control? Wouldn't programming a PID give more definite control over temperature if you could rely on a flat curve?

I've not used a whole lot of different roasters, but do roasters give a temperature profile during extraction to try to achieve while pulling a shot? I've only seen a target temp and have always assumed the goal is to stay as close to that from point A to Z during the pulling of the shot.

Thanks for the reply.

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sversimo

#4: Post by sversimo »

A HX machine will never have a flat temperature profile. I have a Izzo Vivi PID HX machine, In order to have some control its fitted with a k-type for temperature reading during brewing and its NEVER flat.

Ltrain5000

#5: Post by Ltrain5000 »

What is the swing? Is that why you're modifying it to be a DB?

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HB
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#6: Post by HB »

Ltrain5000 wrote:If we are talking profiles, which ones would have a flat temp profile? and if it's not totally flat, which ones are the closest to being flat?
I understood your original point, but reject the assertion that flatter = better, though I do agree flatter = easier to reproduce. As a matter of interest, the water entering the brew chamber of a double boiler is the same, but that's where it ends. The temperature delta between the bottom of the puck and the exit is significant, as this chart shows:
HB wrote:Years ago I did measure the temperature difference between the top and bottom of the puck for hot/cold baskets:

Image

The distance between the lines indicates the cold/hot basket delta; the distance from the 0 axis represents the top/bottom delta. It shows that indeed cold/hot baskets do have a measurable effect on the first seconds of the delta between the top/bottom, but the effect falls below the boiler's natural temperature variance shortly thereafter (measured on a La Marzocco Linea without PID controller).

From Can hot portafilter burn the coffee even before brewing?
Engineer-types like to talk about "flat" brew profiles, but no such thing exists beyond measuring with a Scace thermofilter. Hence why I speak of repeatability, not stability (whatever that means).
Dan Kehn

Ltrain5000

#7: Post by Ltrain5000 »

Dan, thanks for the reply-- apparently you were typing your reply and I was editing my post at the exact time to add a question about control. I wasn't trying to change anything up, but just hoped to get your knowledgeable opinion on both questions in one fell swoop.

Ltrain5000

#8: Post by Ltrain5000 »

HB wrote:though I do agree flatter = easier to reproduce.
HB wrote:Hence why I speak of repeatability, not stability (whatever that means).
So, if as close to flat means easier repeatability, in your opinion is the DB setup easier to reproduce since they seem to closer to flat than an HX? (from what I gather)

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Randy G.

#9: Post by Randy G. »

I am no scientist, and as close as I got was teaching 7th grade biology. But I went from four years with a Vibiemme Domobar Super (HX) to two years with a Vibiemme Double Domobar (dual boiler PID controlled). Both were in conjunction with a Mazzer Kony. The big difference between the two designs is that the brew boiler in a double is filled with water and does not have to also hold steam. The temperature of the brew water as displayed by the PID is a direct reading of what will be SENT to the group. The PID allows one degree changes in this water to be made. "Consistency" comes from being able to hold that water at a user-desired temperature without the swings that a pressurestat creates with its deadband. So if considering design differences alone, each design is capable of great results in the cup. For a home user who isn't brewing ten (or 100) pulls consecutively, the predictable results in the double boiler design are far easier to work with. All this is based on my limited experience, but the repeatability and control with the double has been evident from the start.
Espresso! My Espresso! - http://www.EspressoMyEspresso.com
LMWDP #644

Ltrain5000

#10: Post by Ltrain5000 »

Ive been looking at the VDD DB machine. So, when brewing a shot, what does the PID show?