Why did descaling solve thermosyphon stall issue?

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robc
Posts: 9
Joined: 10 years ago

#1: Post by robc »

I have an Expobar Office Lever that was having daily thermosyphon stalls. The stalls would occur every morning. The machine would heat up to approximately 190 and then temperature would start to plummet. Running water through the group head would solve the issue (until the next morning). I typically only have the machine on for a few hours in the morning. On the days that I would turn machine back on in afternoon or evening, I would not experience the stall, nor would it occur the following morning.

While trying to troubleshoot this I opened up the group head. The mushroom appeared to have some light corrosion or scale which was easily removed with vinegar. The gicleur and gicleur screen appeared unobstructed. I put machine back together and stalls still occurred.

Next, I descaled machine by running dezcal from my water reservoir. This solved the thermosyphon stall issue! It also lowered my group head idle temperature from 202 to 199. Note: My boiler pressure is set at 1.2; there is a 2.5mm thermosyphon restrictor; Erics thermometer is installed.

I am curious to understand why descaling solved the stalling issue and lowered the idle temp. Could someone please educate me?

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LaDan
Posts: 963
Joined: 13 years ago

#2: Post by LaDan »

That's a good question and it deserves it's own thread. But you probable would want to put a link to your other thread about the mushroom's 'rust'/'scale'. If only for the background info.

My thinking with this, when it happens is air bubble. I think that when the machine is off, and getting to room temperature then water in the thermosyphon areas will drain back down to the boiler. Then these chambers/pipes are empty. What I do every morning before turning the machine on, is raising the lever to let the water sip through the grouphead. It always take a little longer for the water to start coming out (plumbed line in pressure of 4 bars, BTW). Ater this "priming", raising the lever will get water out faster. Conclusion? These chambers are empty over night.

Now you turn the machine on, and with the heat, water will start circulating, but if because of some scale it was more difficult for the water to push through the air bubble... ?

The E61 head is always been a bit confusing to me. Even with my technical background I still feel that I am not full understand it, regardless of how many drawings I looked at. So, I might be completely wrong, or maybe 50% wrong. So if more knowledgeable people can correct me, that will be a good thing. :)