Breville Dual Boiler, five+ years on - Page 117

November 23rd, 2020, 9:40 pm

Excellent work, pushing back on the boundaries of or community knowledge, there Geoff. Much appreciated.

When you get your new ones, will you do a close inspection of the area around the bottom of the ceramic, where it interfaces with the steel rod? Mebbie we can get to the bottom of the riddle of why/how these things seal at all?

-Peter

November 23rd, 2020, 10:35 pm

Yep, sure will. I'm intrigued! My theory is that the internal pressure of the boiler pushes the flange like base of the probe up into the ceramic sleeve w enough force to seal it. I took off the c-clip washer on the top when I inspected it, enabling me to slide the ceramic sleeve up off its flange base just enough to see that the flange on the rod is stepped, shaped to mate with the bottom of the sleeve. Pressure would be significant. Enough to seal metal against ceramic?

And if the surfaces had some lime deposits, the seal would leak... And then some thick grease might reseal...

I'll post some close up photos when I replace it.

November 23rd, 2020, 11:55 pm

Or possibly descaling the rod and ceramic might also re-establish the sealing surfaces?

Pics, if you can.

This adds up a little bit as to why it never happened to me since I use water that cannot lime scale due to lack of Ca and Mg.

-Peter

November 24th, 2020, 7:52 am

Just to add my two cents to the temp probe issue of steam/water leakage, I experienced this back in the spring of this year. I actually think I caused the leak by leaning heavily on the connector while installing a few o-rings. When I started the BDB back up to check on my repair, water started spritzing out between the probe shaft and the ceramic part. It would start consistently around 175F and stop at around 185-190F. I could push down on the top of it and make it stop, but upon removing my finger it would spritz again. I ordered some food grade silicone grease, as Peter mentioned, placed a dab right where the shaft meets the ceramic housing and it stopped. Still good after six months. Why this works, I have no idea!

November 24th, 2020, 10:58 am

BaristaBob wrote: I ordered some food grade silicone grease, as Peter mentioned, placed a dab right where the shaft meets the ceramic housing and it stopped. Still good after six months. Why this works, I have no idea!

I say it has to do with the tight clearance between the ceramic and the steel, and the fact that silicone grease doesn't melt at ordinary espresso boiler temperatures.

Though I'm interested in Geoff's discovery that there is a circumferential flat in the rod that might get pressed up into a corresponding flat landing in the ceramic, under pressure. BTW, if so, this would be a similar behavior to how the vacuum breaker works.

-Peter

#1166: Post by **walleye** » November 24th, 2020, 5:11 pm

gchapman wrote:I did get a hold of Breville USA today after waiting on the phone for an hour! In spite of a very bad connection I manage to explain my situation and my request for new steam probes. I fortunately had a part number off ereplacement.com, otherwise he would not have helped me.

In order to sell them to me I had to give up my right to have warranty work done on the machine. After owning it for a year, and with all you guys as my back up, I responded to his email with, "I accept". It sounds like Breville is wary of people messing with the internal parts of the machine and then coming to them for warranty repairs. Makes sense.

I don't know if I gave up at the same time the ability to send it back to them for their $299 and we fix it deal.

The part number is SP0001820, and the cost was only $17 shipped! I would've paid $100 to get them shipped from Australia!

Geoff. Thanks for this. I went through the same thing with Breville and they're sending me the probes (for $17). I'll post some updates as I do the replacement.

Also, one thing that happened... in removing the probe, the grounding screw snapped off. I ended up drilling a new hole in the frame and I plan on pigtailing the grounding wires to the new spot. If anyone out there has had this happen, let me know if you found this easy to fix.

November 25th, 2020, 11:41 am

In relation to my latest question regarding the pressure, I now recorded a video of a clean water backflush.
I am pretty sure that the pressure reached 10 bars or more just a few weeks ago (vs 9-9.5 now) - and I haven't tampered with the OPV. The machine is 2 months old.

Also, I have noticed some slight oscillation in the pressure, as you can see and probably also hear from the video:

How do your machines behave during a backflush? Is the pressure 100% stable or does it also oscillate a little? I see no leakage anywhere during the backflush that could explain the oscillation.

November 25th, 2020, 12:24 pm

Pressure always oscillates when it is bouncing off of the OPV, as it would with a blind disc or the gray silicone disc. This is normal. The OPV has a plunger on a spring. You can also see if you look very carefully an upwards, a ripple of water on the surface, in the tank. This is the water being bypassed from the OPV back to the water tank.

-Peter

November 25th, 2020, 1:01 pm

Thanks for always being so helpful, Peter!
I will direct my focus towards the level of the pressure itself, making sure that the OPV setting does not limit my brew pressure. I think it is getting close. When I brew 20g in, 40 g out in 30 secs, the pressure is around 9 bars initially.

November 25th, 2020, 2:29 pm

sorenwrang wrote:Thanks for always being so helpful, Peter!
I will direct my focus towards the level of the pressure itself, making sure that the OPV setting does not limit my brew pressure.

Actually there is no harm in using the OPV as an extraction pressure limiter, and not only as a safety device. A lot of people use the OPV for this purpose these days in fact as low pressure extractions are becoming popular. In fact, lately I rarely do my own extractions even above about 7.5-8 bar.

sorenwrang wrote: I think it is getting close. When I brew 20g in, 40 g out in 30 secs, the pressure is around 9 bars initially.

Another thing that is also natural is that the pressure as indicated on the brew pressure gauge will naturally drop as the shot progresses. What happens is, as the puck erodes its flavors into the cup, it can no longer block the water flow enough for the pressure to remain high. So it drops lower and lower until the shot is ended. So you also have no problems or worries when you see this happening.

-Peter