Help me understand the nuances- HX vs boilers

Recommendations for buyers and upgraders from the site's members.
Vindibona1

#1: Post by Vindibona1 »

I understand that an HX machine has a single boiler, usually on the steam side (I think) and somehow the heat gets to the other side to brew espresso. The boiler is pretty self explanatory. I called one of the retailers to discuss selection of a new espresso machine but they were kind of vague as to which would be better for me and left me a bit confused and wondering if I should eliminate HX machines in my search.

As I go through all the specs I see one machine that has a boiler, go to the next model and then see in the specs it's an HX. Example is the Profitec Pro 300 (dual boiler) and the next step is the 600 with HX. Now throw in the ECM Classika PID Espresso Machine single boiler and wonder if that's all I need? And then looking at other brands they all seem to offer boilers and HX models. Do I avoid HX or lean into them? Also, do the E61 brew groups come into play with either one?

To help understand my situation, I don't do much milk, only pull one or two shots daily. I have to think the most important thing (not certain) for me is the stability and precision of brew temp. PID and pressure brew gauges seem essential. If recommending a model, while the $1800 range would be welcome, if the right machine were $2400 I could hold my nose and write the check if the value warranted.

So, what's the deal with HX and why should I want one- and are there any standout models?

Nunas
Supporter ♡

#2: Post by Nunas »

Vindibona1 wrote:I understand that an HX machine has a single boiler, usually on the steam side (I think) and somehow the heat gets to the other side to brew espresso. The boiler is pretty self explanatory. I called one of the retailers to discuss selection of a new espresso machine but they were kind of vague as to which would be better for me and left me a bit confused and wondering if I should eliminate HX machines in my search. As I go through all the specs I see one machine that has a boiler, go to the next model and then see in the specs it's an HX. Example is the Profitec Pro 300 (dual boiler) and the next step is the 600 with HX. Now throw in the ECM Classika PID Espresso Machine single boiler and wonder if that's all I need? And then looking at other brands they all seem to offer boilers and HX models. Do I avoid HX or lean into them? Also, do the E61 brew groups come into play with either one? To help understand my situation, I don't do much milk, only pull one or two shots daily. I have to think the most important thing (not certain) for me is the stability and precision of brew temp. PID and pressure brew gauges seem essential. If recommending a model, while the $1800 range would be welcome, if the right machine were $2400 I could hold my nose and write the check if the value warranted. So, what's the deal with HX and why should I want one- and are there any standout models?
A single-boiler-dual-use (SBDU) machine is the simplest. It has a single boiler and usually two thermostats on it, although these days sometimes a PID controller. One thermostat is set for steam and the other for brewing. The water in the boiler is used for both steam and brewing. They are simple and effective. The biggest disadvantage is that when one wishes to switch from brew to steam or vice versa, there is a brief waiting period for the machine to heat up or cool down. An HX also has a single boiler, which is regulated most often by a pressurestat, but again PID controllers are becoming more common. The pressure stat (or PID) is set to provide steam at a given pressure (or temperature). To brew, a pipe passes through the boiler. Because it's immersed in the hot boiler, water passing through the HX tube picks up heat along the way. So, in an HX, the water in the boiler can be used for hot water, via a spigot and for steaming, via another spigot. The brew water travels from the reservoir, through the HX tube, to the group. The biggest advantage is that one needs not wait to steam, and can even steam while brewing if desired. A third main type has two boilers (DB), one for steaming/hot water, and another for brewing. Inherently, a DB is more temperature stable than an HX. This can be a blessing or not, depending on what you want. Folks that like to vary the brew temperature can do it easily with either an HX (by flushing) or a DB, but changing temperatures is faster with most DBs, as one does not have to bring a brew boiler up or down to a new temperature. So, in your case, since you usually drink straight shots, you could be happy with any of these machines. I hope this is of some help. I realize that it does not provide a "buy this not that" recommendation; as you can imagine, the decision can be complex. On the other hand, a quality machine of any of the three types can produce excellent espresso.

Vindibona1 (original poster)

#3: Post by Vindibona1 (original poster) » replying to Nunas »

Thank you. A good start in helping me understand. I can truly understand some of the advantages of the HX, but I'm concerned about the precision, but for boilers, warm up time becomes an issue. The Bezzera BZ13 has 8 minutes of warmup time. Very fast. But others are noted at 25 minutes. It seems excessive if I'm only pulling one or two shots in the morning.

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Jeff
Team HB

#4: Post by Jeff »

Brew temperature can impact espresso taste, between subtly for a degree or two C, or a lot outside of maybe 5 deg C. If it is repeatable, it doesn't matter what the knob or dial says, as long at "94" (or whatever) is always close to the same temperature and "96" is always about the same amount warmer.

No matter what the dealers tell you, an HX machine requires you to manage its brew temperature. PIDs don't generally control brew temperature and "games" with the thermosiphon to be able to make that first shot "walk up" can cause significant problems with the second.

Here's one discussion of what's involved -- HX Love - Managing the Brew Temperature

The only HX machine I'd consider buying new these days is the Lelit Mara X. As far as I know, it is the only one that manages the brew-head temperature with its PID, not the steam boiler. With the availability of good, dual-boiler or close-coupled groups in machines under $2,000, it is hard for me to recommend an HX machine new. Used, they can be a reasonable choice, outperforming they typical single-boiler and thermoblock machines in trade for learning a flush routine (and probably a bit over $100 for an EriccS group-head thermometer to make it easier and more repeatable).

There's a good overview of the basic machine types at How to choose an espresso machine and grinder at the "right" price

E61 groups take 30-45 minutes to warm up, in general. There's not much you can do about that with a big chunk of brass hanging out in the breeze (that was designed to spill heat, to make HX systems work). Heaters in there help a little bit, but so would putting a towel over the group. Many just put their E61 machine on a suitable smart plug. Like the PID claims, the warm-up times quoted are to sell machines.

Nunas
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#5: Post by Nunas »

The warm-up time is mostly related to the size of the boiler and the power of its heater. Another consideration is heating the group. Some groups, like the ubiquitous e61 maintain stable temperature by being massive. Even if the boilers heats up quickly, it takes a while to stabilize the group head and the attached portafilter. So, I would not get too beguiled about claims of quick warm-up. For an espresso machine, warm-up time is a simple fact of life. Many of the folks here on H-B power their machines via smart plugs, so that they machine will be ready for them when they want to pull a shot. Of course, this only works for someone who drinks coffee at more or less the same time daily.

If temperature stability and quick warm-up are important to you, then there are other options. Some espresso machines have the group head attached directly to the brew boiler. They are said to be quicker to warm up and more stable. I don't know for sure, as I've never had one. Another option is a thermoblock/thermocoil machine, like many from Breville. They don't have boilers. Instead, thee water passes through an instant heater, like those sometimes used these days instead of a household water heater (but way smaller :lol: They get a bum rap because they are often used in really inexpensive machines, but they are not inherently bad. The major downside of thermoblocks is that using water with low hardness is essential, due to the thin water passages.

I second the view that the Mara-X is a good HX, as suggested above. It is the first of a newer generation of HX machines. I believe, though, that the stability it has is not just due to its PID controller, but also due to careful engineering of the thermal loop.

gobucks

#6: Post by gobucks »

If you care a lot about temp stability, HX machines are not ideal, although as others have mentioned, the Mara X is reasonably good here - the PID has 3 settings with +/-2C temperature. Not as good as a single boiler or double boiler in temp stability, but certainly much better than other HX machines (even those with PID).

If you really don't think you'll do many milk drinks, the Classika PID might be all you need, and does have some advantages - the brew boiler is much larger than the entry level double boiler machines, and build quality is very good. However, at $1600, it's competing with not only HX machines but also several excellent small DB machines. If I were going single boiler PID, I'd probably go with a Rancilio Silvia PID or Lelit Victoria, both of which are ~$500 cheaper than the Classika.

Even if you're mostly a shots person, being able to do back to back milk drinks is pretty handy when you have company, as most casual coffee drinkers would prefer milk drinks. I'm a ~2:1 or 3:1 shots to milk drinks kinda person, and my wife does americanos, so I'm really only making maybe 1 flat white/cortado per day, but even so, I'm really really glad to have a double boiler once a month or so when I have family or friends over.

If you go for an HX/DB machine, there are a lot of good options under $2000 - as mentioned above, Lelit Mara X (HX), Lelit Elizabeth (DB), Rancilio Silvia Pro X (DB), Profitec Pro 300 (DB), Breville Double Boiler (DB), ACS Minima (DB).

Vindibona1 (original poster)

#7: Post by Vindibona1 (original poster) » replying to gobucks »

I think in this moment I would lean toward the Classkia PID w flow control if only because of the looks, PID, boiler and flow control- something I haven't had the luxury of playing with. But the logical all featured machine is the Silvia Pro X but the look is so pedestrian. I would have to talk myself into it, but perhaps it's the logical choice? I wouldn't have to choose between single vs double vs HX.

What do you think of the Bezzera BZ13? I know it's an HX but (at least one of) the reviews say it's pretty stable +/- 1 degree. Looks nice w/rosewood accents. Same price as Silvia Pro X.

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Jeff
Team HB

#8: Post by Jeff »

The number on the PID isn't the brew temperature, especially on an HX. I'd worry if it varied more than one degree since its sensor is what it is controlling. I may have missed it, but I didn't see any Scace or other thermometry. This is a common "PID fallacy" -- the number on the display doesn't indicate brew temperature, nor does it indicate when the machine has fully warmed up and stabilized.

Vindibona1 (original poster)

#9: Post by Vindibona1 (original poster) »

Jeff wrote:Brew temperature can impact espresso taste, between subtly for a degree or two C, or a lot outside of maybe 5 deg C. If it is repeatable, it doesn't matter what the knob or dial says, as long at "94" (or whatever) is always close to the same temperature and "96" is always about the same amount cooler.

No matter what the dealers tell you, an HX machine requires you to manage its brew temperature. PIDs don't generally control brew temperature and "games" with the thermosiphon to be able to make that first shot "walk up" can cause significant problems with the second.

Here's one discussion of what's involved -- HX Love - Managing the Brew Temperature

The only HX machine I'd consider buying new these days is the Lelit Mara X. As far as I know, it is the only one that manages the brew-head temperature with its PID, not the steam boiler. With the availability of good, dual-boiler or close-coupled groups in machines under $2,000, it is hard for me to recommend an HX machine new. Used, they can be a reasonable choice, outperforming they typical single-boiler and thermoblock machines in trade for learning a flush routine (and probably a bit over $100 for an EriccS group-head thermometer to make it easier and more repeatable).

There's a good overview of the basic machine types at How to choose an espresso machine and grinder at the "right" price

E61 groups take 30-45 minutes to warm up, in general. There's not much you can do about that with a big chunk of brass hanging out in the breeze (that was designed to spill heat, to make HX systems work). Heaters in there help a little bit, but so would putting a towel over the group. Many just put their E61 machine on a suitable smart plug. Like the PID claims, the warm-up times quoted are to sell machines.
Thanks for all the info Jeff.
The problem is that I'm inclined to want one of those fancy looking machines. The one that aesthetically of the group that is the least pleasing is the one at that price range that more or less has all the features I'd like including small footprint; The Rancilio Silvia X.

I think I've (only now) become aware of a problem with my Gaggia and think it may need a replacement pump. The motor sort of oscillates as it's brewing rather than make a continuous sound. I don't think I want to put another penny into it as it's 5 years old now and I'm ready for something more heavy duty.

So, if I had to pull the trigger today, wanting PID, best temp stability and range, brew pressure gauge, possible pre-infusion capability. excellent build quality, excellent steam capability (on demand as I don't do a lot of milk, but maybe). Great aethetics or at least decent looks (I'd buy the black Silvia X not excited at all by the Mara X or Lelit Liz/Victoria). Budget $2000 a bit less or a bit more... Which one would you buy, Jeff?

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Jeff
Team HB

#10: Post by Jeff »

Personal opinion, reasonably unvarnished, which may not suit you and your tastes, but you asked. I've been making espresso a long time, prefer light roasts, find Italian espresso unrewarding, and am very picky. I can afford to take risks on a machine and neither go coffee-less or hungry if a $1,000 machine isn't as good as I'd hope.

1) Argos Odyssey - I have one on order. Might be great, might be an "also ran". Time will tell.

2) Used Bianca, Synchronika, or Pro 700 w/flow kit

3) Lelit Elizabeth

The Silvia is a non-starter for me, due to lack of PI control, s as well as usability problems with the drip tray having me wonder what else they didn't think about.