Bezzera Duo DE Dual Boiler

[PeterW]

Thanks for the info quester!! I was unaware that the valve could be locked open with the lever being in the off position!!

I am curious as to why you use the Kasa switch as opposed to the machine's own scheduler.

I was going to set up the scheduler on my machine but when I read somewhere that it disables the standby function, I decided against it. Prior to getting the Duo DE, we had a Magica and as my wife has been working from home the past year, the machine would be switched on at 7am and was still on when I got home at 6pm, boiler running all day, water tank in need of filling, etc. She would just forget to turn it off after her second coffee. I love the fact that the Duo goes into standby. I've found that the Duo heats up so fast that I don't really need to use the scheduler anyway.

Thanks for the tip on the group seal. I will order one to keep spare.

I have had my Duo for about a month now and absolutely love it. I still need to tinker a bit with the volumetric settings but it's making great coffee. I ordered some additional kit to go with the machine too - a naked Bezzera portafilter with wooden handle and the Bezzera tamper station with wooden handled tamper.

[quester]

Relatively recently I had the unfortunate experience of having my composite granite bench cracked by the super heated water from my Duo DE and wanted to warn other users to be alert to this possibility. I had programmed the TP-Link Kasa smart switch to come on every morning at 05:50 to ensure the machine is hot and ready to go for 6am....ish, start to the day. More like 06:10 - 06:15. This unfortunate morning, I was greeted by a flooded scullery and a cracked bench...20 minutes after it had switched on (it is plumbed in). The Hot Water Valve had locked in the On position. The machine was 5 1/2 months old when it happened. The hot water valve had been faulty, as evidenced by random acts of dripping and running. In fact, I had to adopt the habit of toggling the lever to ensure it was in the off position. Clearly, this morning the valve had stuck open, though the lever was not in the up/locked position.

The boiler was set to 127 degrees for the steam pressure. The heat of the water coming out, under sustained pressure, cracked the granite bench. Suffice to say, I no longer trust the smart switch approach. The supplier kindly and immediately replaced the faulty valve unit under warranty and the replacement is behaving perfectly. I now leave the hot water wand, at end of use, pointing in to a plastic container I keep under the Portafilter AND take extra care to toggle the lever so as not to have a repeat episode if I am away from the machine.

By the time I had a service agent swap the valves over, the machine was 7 months old. Coincidentally, the Group head gasket (#7496097) was starting to leak. I hadn't realised, also, that this gasket/seal needs replacing every 6 months. It had become extremely hard and brittle. Hot tip number 2, make sure you have a spare seal. I'm not sure whether there is a better replacement seal that the one issued, but Mike has said, in an earlier post, that he likes the fact that this one seals quickly and easily. They are about $8.00 each.

Otherwise, I remain really pleased with the machine and would buy it again in heart beat

[PeterW]

Just to add regarding the operation of the display on the Duo DE... I recently watched a Bezzera factory tour on Youtube and Luca Bezzera mentioned possible upgrades to the firmware in the Duo and Matrix. So I sent some feedback via the Bezzera website today about the temperature display. Hopefully they will read it and consider it.

[PeterW]

pp61 - Hi Pedro. When I first switch mine on, the screen shows TFT: 2.2 FW: 2.4 and it shows the actual temperature. However I am not sure what it shows from standby. Will check that tomorrow.

pp61 - I have checked this morning and confirm that from standby, the digital display only shows the set temperature (i.e. target), not the actual temperature, so you have to look at the coloured lines below the number and wait until they have turned grey. I agree that this is not ideal and could be improved.

[PeterW]

Hi there,

Thanks to all who have posted in this thread. I have just upgraded to a Bezzera Duo DE so the information has been very helpful.

I am a long-time Bezzera user (20+ years), having owned two BZ99's, a Magica and now the Duo DE. I am really enjoying the volumetric dosing and the auto-clean function. And it is so fast to heat up.

pp61 - Hi Pedro. When I first switch mine on, the screen shows TFT: 2.2 FW: 2.4 and it shows the actual temperature. However I am not sure what it shows from standby. Will check that tomorrow.

One thing I have struggled with is using the single shot portafiller, i.e. getting the dosing right. It seems the difference between having too much coffee (hard up against the head) and not enough (resulting in a weak shot) seems very small.

[pp61]

Greetings from Switzerland!

I bought the Duo DE a few weeks ago to replace my Sage Dual boiler system.
Although bought in Dec 2020 the box indicated manufacturing date Oct 2019. Afraid that I still had the initial display, with its humidity problems, I contacted and phoned the Bezzera HQ in Milan.
They did not want to talk to me and send me to the Swiss distributor who indicated the following:

The last main board software version is the 2.4 (the machine in your photo has the 2.2 version). The screen already has the latest software version (2.2).

With the screen having the latest software I assumed I had the updated display and decided not to return the machine.

I also noticed that when the machine comes from stand by it is NOT showing the actual temperature, is this common for everybody in this forum or would updating to firmware 2.4 fix this?

Other question, did anybody already update the firmware themselves?

Pedro

[mikef]

Re Duo pre-infusion, it's not what we might assume. Pre-infusion is all about wetting or soaking the puck prior to extraction. Most assume that pre-infusion is at low pressure, say 4 bar, roughly line pressure. That's how many machines produce low pressure, but line pressure is only available if you are mains connected. E61 produces a bit of pre-infusion from the pressure driven by thermo-syphon. Not sure what level of pressure that is. The Duo, in an attempt to provide pre-infusion does not use line pressure because they want to market the machine as having pre-infusion from either line or tank by simply applying full pump pressure (say 9 bar) for one second, then waits for the set 'Pre-Infusion' time (settable up to 5 seconds) and then applies full pressure for extraction. So the question is, "is there any difference between high-pressure and low-pressure pre-infusion?" I can't tell. So I'm happy. I actually set the pre-infusion to zero seconds ie no pre-infusion. Then I simply load the portafilter and then run the pump for about 2 seconds (2 seconds completely wets the puck without losing any extracted coffee through the OPV). Then I wait for as long as I like (say 10 seconds) then extract my shot for the programmed volume. It works beautifully.

[hillside]

Just did some more searches and figure the John Guest tubing is rated to 15 Bar. Just purchased Apex FMP600 pressure reducer and backflow prevention to replace current lower version. Should be all good.
Still interested in an answer to my original Q re pre-infusion.

[hillside]

Correct that current pressure is 3.5 bar- 350KPA

[hillside]

Just waiting for my DE to arrive today. Upgrading from an Alex Duetto 2 after 13 years of good service-it is plumed in with severe flow reduction, nowhere near the 6 bar the DE can take...lucky to be 1.
My question is about "pre-infusion". If machine set to plumed does it use the pump for pressure or switch to using Mains pressure. If the latter I will need to change all my plumbing as the current low pressure line goes under floor across room.
Cheers

[level3ninja]

From memory it varies and the newer the design the more likely it is to be at the group head.

[mikef]

Hi level3ninja,

I agree with you completely; except one thing I don't know is the location of the thermocouple in a typical saturated head - on the boiler or near the group head? The boiler is probably insulated and the jacket and head are not, so the head is lossy compared to the boiler. There is also some differential from the top to the bottom of the boiler. These drive the thermosyphon action to circulate the boiler water through the jacket to the head. So the boiler is (a bit) hotter than the head. If the thermocouple to closer to the head then less the need for an offset. You are right that we are talking about small temperature deltas. I'm certainly not needing to justify my machine. I was totally surprised when I measured the BZ stability. To get that for a $4800 machine compared to the expensive big boys is impressive. PS I have no connection with Bezzera.

Just for balance, I agree with noidle22 that the Duo DE's pre-infusion is rubbish. I almost thought that it was misleading to describe the Duo DE and Matrix DE 5-second wetting as pre-infusion. But then after investigation and confirming with an 'expert' mate, I'm told that the Gaggia and Bezzera have well-document 'pre-infusion' and it can be implemented by either by (1) low pressure for a duration (eg E61 pre-infusion at the pressure generated by the thermosyphon, or line pressure for a duration (typical 4bar) or (2) full pressure for a short period and then a delay at zero pressure prior to full-pressure extraction. The Duo applies full pressure for one second then waits for up to five seconds (settable). It does a lousy job.

[mthomas87]

Wouldn't it be pretty similar to the integrated brew groups of Breville Dual Boiler or Linea Mini? They're both pretty hard to beat for temperature stability and have relatively tiny brew boilers. Way easier to control something with a smaller thermal mass.

[level3ninja]

The overall brilliant feature of the Duo IMHO is the BZ head. You can pay $12,000 to $16,000 for a La Marzocco or Slayer to get a huge fully-saturated head (or a Rocket Nine One for $10,000). They are big and it is expensive to fabricate such a substantial stainless steel jacket to maintain the boiler temperature around the head. Because they are large, they need single bigger boilers, bigger heating elements and take a lot longer to reach temperature stability. All this because they are using water as the medium to move heat/energy to the group head. The PID controller (probably with an offset) in these machines must maintain the optimum balance between boiler temperature and head temperature, but this might involve some compromise. Compared to the BZ head, this is so old-school and clumsy.

The BZ uses electrical energy to move heat to the group head (as opposed to hot water) by a 120W double heating element controlled by its own PID. It's smaller, more efficient, means you can have a tiny (0.75L) coffee boiler and it heats up super fast. It's much cheaper and smaller to transport heat/energy over electrical wires compared to hot water through stainless steel jackets. Dare I say it, I'm sure that the BZ head has better temperature stability due to group head having it's own dedicated PID while the boiler has its own separate PID. This means if the head cools, it heats the head only. So no offsets needed. Brilliant. On this basis, with all the other minor gripes about the machine, makes the Duo for me, "Best In Class".

The whole point of a saturated group head is that it is at exactly the same temperature as the boiler, because it is essentially in the boiler. The reason offsets are required are because the hot water coming out of the boiler travels through small pipes with large surface areas and lose significant heat. The pickup pipe for the saturated group is down within the boiler but it travels through the 'arm' of the boiler going to the group. There might be a degree difference between the dead centre of the big part of the boiler and the group, or there might not. Given that the 'arms' of the boiler come off the main boiler in an upwards direction to the group heads I'm inclined to think that natural convection will reduce temperature differences to tenths of a degree. The huge thermal mass of all the water in the boiler and all the metal the boiler is made of will provide greater temperature stability than a cartridge heating element in a group head. That being said, I would argue you are correct that a cartirfge heater is a more efficient way to heat up a domestic machine with a single group and small boiler. Not trying to bash the Duo/Matrix here, it just sounds like you're trying to justify your machine choice and working backwards to some questionable engineering.

[Martino]

Well said mike! Those are some of the reasons I was interested in the Duo DE in the first place. Had it been on the market just a year earlier, I would have had it in my kitchen.