Izzo Alex Duetto - Tips for best performance

Getting the Best out of your Duetto

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Performance and temperature stability is about man AND machine (click to enlarge all diagrams and photos). The Duetto has a simplicity of design that does not “fight” the efforts of the control system, Izzo incorporated many things into the design, some are not implemented as well as I would like and can be improved. It also explains some of the thinking behind the design and will help you develop your own personal “routines” This “fine tuning” is valid whether your Duetto is a US or UK version and covers:

  • Insulation
  • Ventilation
  • PID & Brew Stability
  • Best way of using the machine

Insulation (Steam Boiler) & Ventilation

This is very important to ensure that the heat from the steam boiler 124-128C is not transferred to the interior of the machine and the components inside. The objective is to ensure as stable an internal machine environment as possible with a lower overall internal temperature. …This is for 3 reasons.

  1. Economy
  2. Internal Components last longer, both electrical, electro mechanical and mechanical (if you doubt this look at components above/near the boiler on any HX prosumer machine after a few years)
  3. Electronic circuits are more stable and accurate (more consistent readings)


The early Duettos had no insulation prompting me to immediately insulate my steam boiler, later machines come with factory fit insulation, but although it helps it’s insufficient for our purposes. I have advised people to use a polyester pond liner fleece (about 3mm thick), it’s cheap, very effective and easy to fit see here. http://coffeetime.wikidot.com/boiler-insulation-duetto-steam-boiler

It is not critical to insulate the bottom of the steam boiler (and it’s really difficult), but the top should definitely be insulated and insulated as well as possible. On mine I left the safety relief valve and the vacuum breaker showing. I actually intend to loosely cover the safety relief valve (because if it does vent, it will have the advantage of not spraying all over the interior) and a raised covering over the vac breaker.


Has been improved on later model Izzo machines, with a hole in the inner wall of the case and extra ventilation slots in the edges of the cup tray, plus a heat deflector for the PID….but more can be done (and on earlier models, this keeps everything much cooler inside). The cup warmer tray should be placed on 4mm (I used small felt furniture pads) standoffs, not enough to leave a gap at the front, but enough to allow the ventilation holes under the cup tray to work MUCH more effectively. Drill extra Ventilation Holes above the PID, these are NOT drilled in the cup warmer tray itself, but in the panel underneath it as shown. When drilling, use a centre punch, start with a small hole and make progressively larger ones finishing with a chamfer using a much larger bit to finish the edges on both sides….(use a lubricant when drilling)

Use Optimum PID Settings

Use the Wiki article to get the best set of http://coffeetime.wikidot.com/izzo-alex-duetto-pid-settings PID settings that suit you. Currently for UK and US customers…these machines come with factory default settings that can be improved on a great deal (in fact it’s essential to tweak them). The Wiki article here covers the UK/Europe models and has some settings in for US models. Insulating the brew boiler will result in a machine that is slower to recover, because you cannot afford to let the brew boiler temperature overshoot. This means VERY conservative PID settings and a machine that is less responsive. At this time I would not recommend insulating the brew boiler. The simplified diagram below shows what can happen when the temperature overshoots the setpoint and should help illustrate why this is important:


Brew Water Stability & Preheat (steam boiler on)

The PID shows:

actual boiler temperature – offset1= assumed/calculated brew temperature

Short term variations in boiler temperature (e.g. pulling a shot with no-preheat) does not appreciably vary brew temperature. In this case the brew boiler might not look very stable (the temperature displayed on the PID) as shots are being pulled, but overall the system will deliver a stable brew temperature at whatever you set the PID to obtain see izzo-alex-duetto-temperature-studies. This is due to:

  • The relatively large thermal mass of the total brew system
  • Positioning of the thermal sensor
  • Convection currents within the Brew Boiler (due to well positioned cold feed)
  • Size of the Brew Boiler
  • Relatively low flow rate during a shot.

Shots with preheat have very little difference in brew temperature stability than shots without, however the boiler temperature will become far more stable during the shot. The message here is that “capacity” has increased. You will be able to make continuous rapid back to back shots, and be unlikely to overcome the Duettos ability to maintain a stable brew temperature.

Using the Duetto

I found the Duetto requires around 45 minutes before pulling a shot. I usually wait an hour before pulling any shots…the machine has a large thermal mass that needs to heat up….but it’s this thermal mass that gives you stability. There is a shortcut to warming the Duetto up that will cut this down to 25m in an emergency…see warming an E61 quickly. Before any series of shots it is best to give the Duetto a 1oz flush to stabilise the temperature, then grind and tamp etc… If you are pulling multiple shots further flushes should not be necessary, as the delay between shots will only be a minute or two. At the end of each shot I give the Duetto a 0.5-1 oz cleaning flush to remove grinds from the screen.

So a typical shot might look like this:

  1. 1oz flush
  2. Remove portafilter, dry, fill with coffee and tamp
  3. Pull shot
  4. Remove portafilter, knock out, clean
  5. 2-3oz cleanup flush

The gap between step1 and 2 is long enough for the boiler to return to the setpoint value, whether the steam boiler is on or off (with the steam boiler on it will most likely not have changed).

A multi shot series might look like this:

  1. 1oz flush
  2. Remove portafilter, dry, fill with coffee and tamp
  3. Pull shot
  4. Remove portafilter,
  5. 1oz flush
  6. knock out portafilter, dry, fill with coffee and tamp
  7. Pull shot
  8. Remove portafilter,
  9. 1oz flush
  10. knock out portafilter, dry, fill with coffee and tamp
  11. Pull shot
  12. Remove portafilter, knock out, clean
  13. 2-3oz cleanup flush

The above protocols were designed to work well whether the steam boiler is on or off…but are especially helpful in ensuring stability with the steam boiler off and ensure you are not flushing too much non-preheated water into the brew boiler. With the steam boiler on, it pretty much doesn’t matter what you do and you cannot overheat the brew boiler.

Note: the brew water preheat system is designed to deliver preheated water at normal coffee brewing flow rates to the brew boiler. It will also handle the much higher intermittent flow rates of cleaning (flushes of a few oz) etc.. Under these circumstances, the preheat system should never overheat the brew boiler. However it is specifically designed to drop the temperatures during prolonged flushing. This maximises the use of the heating element in the brew boiler and ensures the steam boiler is not “over” cooled…in effect creating “balance” between the two systems

Steam Boiler: On…or Off

Last, but not least, an important piece of advice, keep the steam boiler OFF if when you are not using it. This means once a set of Lattes is finished, switch it off. Even if you will be using it again 10 minutes later, there are benefits and the warm up time 10 minutes later is only a handful of seconds.2

The steam boiler on ALL models of Duetto, except mine the prototype can be switched on or off by the user as a standard feature. I actually added this modification to mine on day 2. I felt this was a modification that should be in place on every machine Izzo sold….rather than something added much later e.g. after the first 10 or 20 machines, because it is important.

Heat is required to make espresso, but heat ages/stresses all components over time. The less heat energy you can put in a thing the better. Insulation helps, but over time there is a gradual creep upwards as temperatures begin to equalise…reaching the point at which insulation capability and ventilation capability are in balance. Getting into a Habit of switching the steam boiler on when you need it and off if you don’t is a good one. Even if you have a party with only Latte drinkers, you can switch the steam boiler off when you’re not using it….Even if you have to go out and make a Latte 20 minutes later. If your boiler is insulated as per this Wiki article, the steam boiler will be up to temperature again before you have ground and tamped the 1st espresso shot. After 1 hour, the warm up time is only a few minutes, after 2 hours it’s less than 5 minutes. This has huge advantages:3

  • Accuracy of temperature detection and hence brew water temperatures is much higher, because electronic components are kept in a far more constant and smaller heat range. The accuracy of temperature detection devices can change with environmental temperature
  • Thermal stress on all components is massively reduced and their lifespan is increased. Your vacuum breaker, pressure stat, high power relays, steam boiler heating element all last much, much longer. e.g. If a machine is on for 16 hours the pressure stat switches on/off nearly 1000 times, but only 100 times or less, when using the steam boiler only when required.
  • It’s better for the environment
  • Should a failure ever occur in that High temperature 127C, high pressure component, you're very likely to be there and able to take action to ensure damage is minimised.
  • If you have Kids, the whole machine is safer, as high pressure steam and 100C water from the hot water tap is a hazard.
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