Steam boiler size versus pressure

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ak_brian
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#1: Post by ak_brian »

Hello H-B,

I've got a question I haven't quite sussed out an answer to, and I'll try to give you the short version, and if you feel like it, you can read the longer part.

What is more effective, or efficient, in steaming larger quantities of milk: steam pressure, or steam boiler size? If I want to set a larger 24oz pitcher of milk to the steamer and, after stretching, just let it churn - would it matter more to have a larger boiler or one that produces more pressure? I've been trying to stay at or under $3500. Thus far I've been leaving towards the Profitec700/ECM Sync with their 2 liter, 2 bar pressure, or maybe a La Spaz Vivaldi II with its 2.5l steam boiler, with (according to the manual) 1.4 bar max. I'm not loving the 53mm portafilter though, as I have some 58mm accessories already with my manual lever setup.

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The long version:
I've been trying to decide on a semi-automatic machine, with an emphasis steam endurance. Before the last couple of crazy years we regularly had our close friends over a few times a month, which put us at seven coffee drinking adults and four cocoa drinking kids. While myself and another enjoy espresso and coffee as it is, the rest prefer anywhere from 6oz lattes to big 'ol mochas and the like. I'd like to be able to just stick a 24oz/~700ml pitcher of milk on the steamer and let it rip while I focus on pulling shots. When the immediate family is over for our holiday rotation, it's 15 people minimum. I have zero hope of keeping up with that on anything short of a commercial setup, but again it would be nice if I could maintain a steady workflow of a bigger pitcher of milk while getting shots split.

The answer I see most commonly for this situation is a Linea Mini, but I just...can't bring myself to pay $5400 plus shipping to Alaska (spoiler: it's brutal), especially given some of the more interesting features out there, like pressure profiling, require either modifications I am not confident I could do, or an even bigger jump in price to something like a GS/3 MP or the like. I think they'd never find my body if I told my wife I spent $7300+ on an espresso machine haha.

The other aspect is I'd still need to get a grinder, so while I could conceivably go for a LMLM, the difference between a ~$3000 machine and a $5400 would let me invest in a good grinder. I hand grind at the moment and would not like to do that forever haha.

Thanks for the help and consideration :)

Nunas
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#2: Post by Nunas »

It's more complex than you may realize. There are three main elements, static boiler pressure (or temperature if PID controlled...they're directly proportional). The boiler size has nothing to do with static pressure; but it is only one of two factors in how long the boiler can produce a given pressure. Finally, the heater size; this controls the recovery time; it also has to do with how long the boiler can sustain a given pressure.

Take the Profitec/ECM machines, for example. They now have 2-bar static steam. That is, the pressure will rise to 2-bar and stay there. They also have a largish steam boiler (for a prosumer machine). They run on 15-amp circuits (in North America), which limits the size of the heater. When you open the steam control, you instantly get 2-bar of pressure. However, this nearly immediately begins to drop, the temperature drops along with it, and the PID switches on the heater. However, due to the small size of the heater, relative to the demand for steam, the pressure continues to drop. So, while a bigger boiler gives some additional steaming capability, in a home machine, it is limited by the size of the heater.

In contrast, consider a big, multi group commercial machine. Not only will it have a massive boiler, it will also have a big, often 3-phase, heater. Given enough intensive steaming, it too will poop out, but it will take much longer to happen than in a prosumer machine.

I don't know if there's ever been a steaming comparison between machines here on H-B; that might be an interesting thing to pursue. We could start with a commonly large steaming jug size, put in a given amount of water, and measure the time taken to heat to 60-degree C, registering time and pressure drop at given intervals, perhaps 5-seconds.

I almost forgot, the steam tip has a significant effect. To run a reasonable test, we'd have to settle on a given total aperture for the holes.

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ak_brian (original poster)
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#3: Post by ak_brian (original poster) »

Thanks for the reply! One of the reasons I fell into this hobby was because there's complexity and experimentation, and I get to drink the results haha.

That makes sense though, I had noticed when researching machines that the p700/ecm duo no longer did a 20amp option after the steam upgrade came about. That's too bad, as I have that as an option in the spot I'd planned for the machine. I figured a larger boiler gave better endurance, I guess, compared to a smaller one. But I hadn't thought much about the heating elements, as most I'd looked at in the dual boiler realm seemed to be either 1200w.

I debated a heat exchanger machine with a large capacity boiler, I'd even looked at buying used or new commercial machines. it would make the milk side of things easier, but I really wanted to stick to something with more accurate temperature control so I could experiment more with a variety of coffee. At the end of the day, it's my hobby and everyone else gets to enjoy the benefit, right? :D

I've watched a member here, and I'm sorry I've forgotten the name, but he did some videos of him serving at Cars and Coffee (a man after my own heart!) and at a steady pace it seemed like the rebound time on smaller, consecutive, milk drinks seemed pretty reasonable, so I am confident I'll be okay preparing at a steady pace, but being able to do a larger pitcher at a time might make things a little easier. I'm just not sure haha, I've been researching everything so much I've kind of got myself in an indecision loop. And I might genuinely just be over thinking it at this point. I doubt I'd be disappointed with any number of the dual boiler options, but trying to size/spec based on the larger groups has made that more difficult.

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HB
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#4: Post by HB »

ak_brian wrote:When the immediate family is over for our holiday rotation, it's 15 people minimum. I have zero hope of keeping up with that on anything short of a commercial setup, but again it would be nice if I could maintain a steady workflow of a bigger pitcher of milk while getting shots split.
When I am making cappuccinos/lattes for a crowd, I consider 45 seconds the fastest drink-to-drink time with 60 seconds being more reasonable. The only way to reduce that time is two baristas (one pulling, one steaming) and a commercial-grade steam monster. Unless you're making 16 ounce "big gulp" lattes, the steam time isn't the gating factor for most semi-commercial espresso machines, it's the brew group restabilization time. All the semi-commercial espresso machines that I've used need a minimum of 60 seconds recovery time, otherwise the brew temperature will trend up or down, depending on the design.

If I was serving 15+ people with a home setup and they're impatient, I'd use traditional cappuccino cup sizes (~6 ounces) or even consider splitting the shots for mini-cappuccinos. When I worked cars and coffee events, I used the dealership's regular cups, which are typically in the 9 to 10 ounce range. The milk for that can be steamed in less than 30 seconds, so you can start the pour and finish steaming before the pour is stopped.
ak_brian wrote:I've watched a member here, and I'm sorry I've forgotten the name, but he did some videos of him serving at Cars and Coffee (a man after my own heart!) and at a steady pace...
Voila:
From Installation tips for ECM Synchronika / Profitec Pro 700 steam upgrade
Dan Kehn

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homeburrero
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#5: Post by homeburrero »

Nunas wrote:I almost forgot, the steam tip has a significant effect.
Yes. I think it may be useful here to reference a 2013 post by the late Robert Pavlis relating optimal steam tip size to the heater wattage: Optimal steam tips.
Pat
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#6: Post by Auctor »

Only thing I'd add to some really great advice in this thread is very process-oriented - after you're done steaming a large amount of milk, listen for the boiler's auto-fill. If it doesn't automatically refill itself, use the hot water tap to force a bit of water out of the boiler, thereby ensuring that the boiler fills back up.

Many a time I made one cap in the morning, and another cap in the afternoon, and because the boiler failed to auto-fill in the morning, halfway into steaming my second cup the boiler senses low water, filling itself with cold water, and ruining my steam power.

ak_brian (original poster)
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#7: Post by ak_brian (original poster) »

Thank you for the great information everyone. And thanks HB, I feel dumb for not remembering it was you haha.

The video definitely seemed to show no issue working at a continuous pace to turn out appropriately sized drinks, I think that's as good as a result as I can expect for the money.

A follow-up question, if you will? I understand this is a bit of a hypothetical, but presuming I stuck a big ol pitcher under the wand, after the initial stretching/airation step, would it matter terribly much if the pressure is gradually falling off? As long as it's maintaining a good roll, if the pressure drops to say 1.5 or even 1, by the end of it, would it make for bad microfoam?

What I can ultimately see for doing a crowd is splitting shots and steaming enough for the two drinks at a time, and that would be fine, but I'm still curious about the possibility of going larger. Worst case scenario I'll be ordering soon and will report back :)

Thanks!

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HB
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#8: Post by HB »

ak_brian wrote:...presuming I stuck a big ol pitcher under the wand, after the initial stretching/airation step, would it matter terribly much if the pressure is gradually falling off? As long as it's maintaining a good roll, if the pressure drops to say 1.5 or even 1, by the end of it, would it make for bad microfoam?
Do you mean a 24 ounce pitcher? I don't use one larger than 16 ounces and prefer 12. My guess is that if a 24 ounce pitcher is much more than half full, the final pressure would be too low to roll the milk and the result would be subpar.

Generally speaking, semi-commercial espresso machines can handle a 90 second drink-to-drink pace comfortably and handle bursts of 60 seconds, assuming 8 ounces of milk or less. Their brew temperature falters and the steam boiler times become unmanageable if you push harder.

For perspective, a two group La Marzocco Strada has a 8+ liter steam boiler and runs on 220V / 35A circuit. You can steam non-stop and the pressure never drops. I'm sure the superautos at Starbucks have similar steam performance given their customers' penchant for 20 ounce "lattes". :?
Dan Kehn

ak_brian (original poster)
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#9: Post by ak_brian (original poster) »

Alright, great to know. That will do well enough for my purposes. I'm not that fast anyways! Thanks for the help everyone, it was basically my last question before deciding on what to order. Fortunately most everyone is fine with a small latte, and I'll enjoy learning how to pull straight espresso for myself. I won't hold it against friends and family for the occasional big gulp blasphemy hehe.

Much appreciated everyone :)

ak_brian (original poster)
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#10: Post by ak_brian (original poster) »

Just wanted to say thanks again for the help. After some more consideration I went ahead and ordered a Synchronika yesterday along with the Mignon SD. We'll see how the latter shakes out but the Sync I am confident will be a great experience.

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