Hello tech people,

I have recently checked my Simonelli Appia with a Scace to determine a good flush routine. When it has been at rest for some time, the water starts at 220F and doesn't go down much from there. After purging 12oz of water (until there was no steam or hissing), the water still doesn't reduce far past 208F.

I have checked the thermometer with other machines and it showed proper.

The boiler pressure is set just a hair above 1, any lower and I couldn't steam any milk.

Any suggestions for further troubleshooting?

Troy

Did you measure immediately after flushing. Big HXs can recover extremely fast.

Yes I did. It is a single group, so the boiler is not huge. However, I have heard many times that the Appia is prone to overheating.

Following another post, somewhere in the coffee forum universe to replace the gicleurs (flow restrictors in the group head) with the smaller ones that are stock in the WBC Aurelia. I did this well before getting a Scace, and didn't notice any significant difference.

T

hello,

What kind of gicleurs did you use?

Where did you put them?

There are two sets of gicleurs in these machines. One at the flowmeter and two in the group head. The one in the flowmeter wasn't replaced because I do not wish to alter the water pressure entering the machine (Part no 07300125).

I replace the two gicleurs at the grouphead, because i was interested in altering the rate of water circulation through the heat exchanger (Let me know if you need more information about the hydraulic system is structured and how it works). The gicleur that restricts the water entering the group (part no. 07300127-2,5) was replaced with the WBC Aurellia gicleur (part no. 07300126 (Ø1,5)). The gicleur that restricts the water leaving the group is the same on all machines so it wasn't changed.

Note, I am a very handy person and really enjoy taking things apart. I took apart and rebuilt my entire machine to descale it, and replaced a lot of parts in the process. Replacing flow restrictors is not a simple job. Unless you are willing to make some potentially expensive mistakes, as the brass fittings are fragile and VERY fussy, I would not recommend this sort of modification.

However, since i have done it and don't mind the frustration of building, taking apart, putting it back together another way, taking it apart, asking for help, putting it back together another way, troubleshooting, asking someone with more experience, taking it apart, etc. I will continue to develop myself as a tech, because it is very rewarding. At least it is before finding out that the machine is still running too hot to brew good espresso.

T

Hi Troy.

Do you know the size of the injector on the Appia? That could play a important role, as it define how hot will be the water that comes from the bottom part of the thermosyphon, when brewing a shot. I think the Aurelia injector was shorter but they change to a long one on the WBC, but considering the restrictors and the water level.

So, other crucial thing is the water level. As far as I know, they change the level from 50-60% to 80% at Aurelia WBC, and the boiler pressure to 1.15-1.2 bar. This one is easy to change. Maybe you could start from that and later check the injector. If the water level higher still don't give you a "colder" group head, than maybe the injector could be shorter to drop the bottom inlet water temp.

Márcio.

Hello Márcio,

I am trying to understand what you are saying and how it will affect the temperature of the brew water. I will paraphrase and then comment.

I am not sure what the injector is. I have searched the Appia part schematic and cannot locate this part. I think that you are referring to the Teflon tube exchanger, which attaches to the bottom fitting inside the heat exchanger. That part is still the OEM part that the machine was built with. As I understand it's function, it is to insert water into the centre of the HX (seemingly to avoid temperature variations in the HX itself). The length would probably be dependent on the size of the HX. I don't understand how changing the length would effect the water temperature because of flash boiling.

Water level is an interesting idea. Many steam issues can be traced back to either pressostat set too low or not enough space in the boiler for steam production. I am uncertain about the water vs steam temperature inside a boiler, but I am sure that steam is hotter than water. So lower levels of water will produce greater steam production and a hotter water in the HX, and higher water volume will produce less steam and relatively cooler water in the HX. Hopefully by increasing the boiler pressure will offset the steam production.

Hmm.. I will check that out this week and tell you the results.

You are right! The amount of steam at the boiler can change the stability point of the thermosyphon/group. And yes, the injector is the teflon tube that let the water enter at a middle position inside the HX.

I just think that the a short injector would add a less hot water to the bottom part of the thermosyphon, as the portion overheated will be quickly flushed and the fresh water will have less hot path to exchange heat. The HX on Appia and Aurelia is huge, 1L as far as I remember. So with the injector you have to flush the monster 12 oz and still get hot temperature, as when you do that, you heat the group. This kind of setup, with the restrictors and big HX, is aimed to keep the group at a lower temp, so it can work as a effective radiator during the shot. So you have to find the sweet spot for a small flush that just brings you to the balance and then you can pull the shot.

Take Oscar as a poor comparison. The HX is small, about 120 ml. But there is no injector. So I got a good thermal stability with 1.2-1.3 bar at the boiler, 3.0mm at the bottom inlet and 3.2mm at the upper inlet. Just a little more water from the HX (upper) as the bottom is directly from the pump->copper tube. If I could inject the water right at the middle of the HX, for sure things would be different.

So, for you to compare to Aurelia WBC, as they are very similar, the injector they use are 13cm teflon tube, and the other parameters are the 80% fill, 1.15-1.2 bar, and the restrictors (smaller one at the hot inlet, 1.5 or 1.75).

One thing to note about this machines is that after you find your balance, and get for instance, 93°C at the group head, I don't think it's easy to flush and get 90°C, considering the huge HX size. The machine should have some way of divert the flush to keep the group at the lower temp. Maybe two 3-way valve at the thermosyphon tubes could do that?

Márcio.

How long past flash boil are you flushing and what is your finished flushing to pulling a shot recovery time?

The gicleurs, if you have a single group machine, there is only one group jet (assumption based on other machines, never used your machine). I am assuming based on your description that the other are actually thermosiphon flow restrictors which you would change to regulate the flow of water through the thermosiphon for the group head heating. Changing those will alter the machines grouphead idol temperature and have an effect on the shot temperature by altering the heat synch effect the grouphead has but the heat exchanger water will still need flushed to the proper brew temperature.

Changing the water level in the boiler will change the steaming performance. While lowering the boiler water will produce more steam, it will have a lower velocity. Increasing the boiler water will reduce the amount of steam produced but it will have a higher velocity. So if you are running out of steam, then lowering the boiler water will get you more steam. If you have plenty of steam but that steam does not have enough velocity to get the milk moving in the pitcher, increasing the boiler water level will help.

Some good information on gicleur sizes and other stuff are in those posts :
Flush routine for Nuova Simonelli Appia
and
Nuova Simonelli Appia Tour