Hello everyone,

I have just purchased a new Rocket Mozzafiota type V which is a huge step up from my old Barista Express and I am hugely excited about it, but I am really having a hard time getting the hang of it (I've had it for almost 2 weeks now). I've read countless articles/watched videos... I generally understand the concept of the cooling flush but am still having trouble with the exact flow over everything. I have a few questions I hope someone can help me with:

1) This machine has a PID and it comes with a conversion chart which shows the equivalent GH temp... so if thats the case and this chart is accurate, why do I need the cooling flush? I use the "flush and go" method and flush until the water stops dancing, but I suppose I don't fully understand why it's necessary when they give you a conversion chart...? I read on here somewhere that rocket machines hardly need a cooling flush at all, is that true? This is more a question about fundamentals.

2) What is the preferred boiler pressure? It was sent to me so that it idles at 1.4, but I can move it up and down with the PID by adjusting temperature. I have read countless times that it seems 1.1 or so it better. I have moved it down that low with the PID set to 245 or so, but then espresso comes out a little on the cool side IMO... is this because I am over flushing? I stop when the water stops dancing/steaming so It seems to me that if you do this, it shouldn't matter what the boiler pressure is, because you are stopping it at the same point, whether the starting pressure was 1.1 or 1.4... is this correct or no?

3) My biggest concern is this, as I am beginning to think there may be something wrong with the machine: If I pull a shot and steam at the same time, I lose pressure pretty quickly until it sitting at about .6 and the milk won't even swirl any longer, but it steams beautifully coming out of idle. I just don't understand this, as I thought the whole point of the HX design was to allow both simultaneously. This is why I am trying to run the boiler at a higher pressure at the expense of a longer flush, as I am trying to compensate for this loss or pressure, however, it only keeps the pressure higher for a few extra seconds.

Im guessing it's my technique that is off and not my machine, but I can't figure out what else to change. Here is my technique:

Grind
Flush till water calms
Begin pulling shot
(If milk) start steam- the steam will fatally lose pressure at about the last 1/3 of the shot
Stop the shot
Steam until finished

I don't know, can anyone help me? I was hoping to avoid buying a thermometer, but perhaps there's no way around it? My biggest concern though is the loss of pressure, I just don't understand that.

Thanks.

Nice machine!

Pull your shot first, then steam the milk. The HX is designed to allow espresso extraction and steaming to be accomplished from a single boiler, but not necessarily at the same time. Some larger HX machines are capable of doing this, with their larger boilers and heating elements.

Your PID doesn't control the group temperature directly; it controls the boiler temperature. The cooling flush is intended to set up the conditions for the shot to occur at the target brewing temperature, accounting for the losses that happen as the water moves through its circuit. These losses are intentional, of course--everything is supposed to work together to deliver as stable a temperature as possible during the shot. If your cooling flush is too long or too short, the temperature profile will differ from the indication on your conversion chart.

Were the references to a preference of a boiler pressure of 1.1 specific to your machine? If not, my suggestion would be to stay with 1.4 for awhile and try to dial in the other factors (grind, extraction flow rate, etc.). When you change the boiler temperature, the optimum cooling flush duration will change as well, in theory.

You should at least have a thermometer for your steaming pitcher. My favorite is the Thermapen, available from thermoworks.com.

FWIW, my Evoluzione with pretty much similar specs than your machine, has no problems steaming (for two cappuccinos at the same time) while pulling a shot. My machine is set at 1.2bars.

E: Removed thoughtless ideas.

E: One difference between our machines is that I run mine with 230V. That should boost the heating quite a bit, I guess.

Also, make sure that the holes in your steam nozzle are clean and unobstructed.

I wonder if a possible cause of the steam problem may be that the water level in the boiler could be too high, limiting the volume of steam available ? Sometimes level probes can get moved accidentally.

I presume the boiler has a thermistor/PID setup which monitors and controls the temperature ? If so, unlike mechanical pressurestats these can be slower in detecting the need to activate the heater. 1200w into a 1.8 l boiler isn't overgenerous, so if anything else is off a bit, the combination of things may be causing a problem.

Does the machine have a "heater active" indicator ? if so how quickly does it seem to react ? Have you changed any other PID parameters ?

If you are not pulling a shot, how long will the steam last ? does it still run out or continue as long as you keep the valve open ?

In an HX machine the brew water doesn't come from the boiler of course, so it isn't anything to do with depleting the boiler. As you pull the shot the HX will extract heat from it - but the machine is designed to handle that.

I think a chat with your supplier would be helpful anyway.

Sorry I'm of no help with the brewing side, except that it's the taste that should tell you whether you have the brew temperature nailed or not. I have tried domestic HX machines, and did own one for a while, but they remain a closed book to me requiring a level of skill I just don't have.

Other love them though.

I hope you get it sorted - and quickly - hate disappointments like this

keepitsimple wrote:In an HX machine the brew water doesn't come from the boiler of course, so it isn't anything to do with depleting the boiler. As you pull the shot the HX will extract heat from it(

True. How silly of me to forget that.

g3dahl wrote:Your PID doesn't control the group temperature directly; it controls the boiler temperature.

Yes, it's a very nice machine!

The PID, as Gary says, controls the boiler temp. But that statement may not make it obvious to you that only the steam temp (which determines the pressure) is being monitored. Having a PID in an HX machine doesn't change much re: brewing - you still have to go through the same HX flush routine. And your PID setting shouldn't have that much effect on the length of your cooling flush because only the first part of the brew water flow is sitting in the reservoir, and none comes from the boiler. Once the overly hot water that was in the HX is flushed through the group, the exchanger is heating water from the reservoir. As I recall, the specific heat of a substance (in this case, water) is independent of temperature - so whether the boiler water is at 220F or 260F won't change how long it takes to raise the temperature of water that starts far below that (after the cooling flush).

There's no relationship between steam time and brew time in a HX machine - whether or not you "pull" a shot while steaming shouldn't affect how long and at what pressure you can steam. With a 1.8L boiler, you should have more than sufficient steam to foam enough milk for whatever drink you want to make. And it's hard to imagine that the flow of 2 ounces of brew water through the HX could make much of a dent in the temp of the 1.8 L in the boiler.

Your machine should steam and brew fine at the same time. You have the same 1200W heater and 1.8L boiler that many of us have. Your boiler pressure may drop a bit - on mine it settles down to around 0.9 bar, which is an equilibrium point determined by the heater and the wand orifice - it's the pressure where the steam flowing out of the orifice matches what can be produced by 1200 watts of heating power.

Cooler water flowing through the HX will impact that, but not normally enough that you would notice it.

One thing that will kill your steam output is cool water flowing into the boiler. If an autofill kicks on while you are steaming, the pressure can easily drop to 0.5 bar or lower. Depending on your controller's logic, if you are brewing, you may not get an autofill until after you drop the brew lever. (That is the case with my Evo V2, but can't guarantee that's the case with the new V5 PID machines.)

My machine will steam and brew perfectly well at the same time. But I do better if I'm only paying attention to one thing at a time, so I brew first, then steam. First thing I usually do is to open the hot water wand to kick off an autofill in order to make sure it doesn't fill right when I'm trying to steam. There's a delay in that autofill system, so to do that I open the tap for a split second, wait a few seconds, then repeat until I get the autofill. Uses a little water, but in theory is not wasted because removing a little boiler water should help prevent mineral concentration in the steam boiler.

I suppose if your machine had a leaky autofill solenoid, then you might see your boiler pressure increase while the brew lever is up and the steam wand is closed, but see it dive if the brew pump runs while the steam wand is fully open. That would also overfill your boiler. (On my machine, I can do blind basket backflushes and see no increases or decreases on the boiler gauge, with the wand closed, and with it open.)

Deebo wrote:This machine has a PID and it comes with a conversion chart which shows the equivalent GH temp... so if thats the case and this chart is accurate, why do I need the cooling flush?

On an HX machine, a chart like that would be misleading. It might show typical group idle temps**, but of course would have no reliable correlation with the brew temp. As you know, this is related to flushing and how long since the last shot. Best to toss that chart. I would recommend getting an EricS group thermometer and practice and learn how your group responds, and how the shots taste with different approaches to flushing and waiting.

** Edit update: I found an online manual for Giotto/Cellini PID here: https://www.seattlecoffeegear.com/asset ... manual.pdf where on page 15 they include a PID vs group temperature table, and say:

" ...Rocket Espresso measures and displays boiler temperature. The table above indicates 'real' group temperature through precise measurement using the SCACE meter."

Of course, we all know that can't be of much use unless you know what flush was used, how long the group has been idle, etc. I suppose this table might be a scace temp for a group that has been idle for 10 or more minutes, then pulling a simulated shot with no flush. This manual does not say. At 250F (~ 1.06 bar at sea level) that table indicates a scace temp of 203F, which to me seems a little low for a no-flush shot from an idle group on a boiler that hot.

Interesting thread here on the topic of steaming and brewing at the same time with an HX espresso machine:

Steaming and brewing at same time with HX espresso machine

keepitsimple wrote: As you pull the shot the HX will extract heat from it(

The heat exchanger adds heat to it. It works by raising the temp of the brew water coming from the reservoir or water line as that water passes through the HX (which is sitting inside the boiler). The cooling flush purges the water that's been sitting in the HX chamber, after which it's heating the stream coming from the source.

The high mass of the brew group and the high specific heat of its metal keep its temp fairly constant, which helps stabilize the water temp at the screen (within limits, of course). Really tight control, e.g. +/- 0.1 deg, can't be had without active group temperature management of some kind. But the combo of HX and thermal mass adds heat to the brew stream and stabilizes temp as it hits the puck.