Hello everyone,
After an intense troubleshooting session with my Brewtus (dual boiler),
I’ve reached the end of my knowledge — and I especially can’t explain the
behavior from a physics standpoint. So I’m relying on your help. Maybe
someone has an idea or can explain something to me.
to put it briefly, the questions in general:
- Shouldn't the brew and steam boilers be separated in terms of pressure?
Or are they actually "connected" somewhere?
- Could someone check for me if the preassure of the brew boiler is at
about the same as the steam boiler (1bar).
- Should the expansion valve and the air relief valve remain sealed when
there is a pressure of 1 bar in the return line?
*Problem:*
-
Hot water/steam flows back into the tank via the return line
-
After a few hours, the brew boiler gradually empties — water gets
refilled during extraction and it takes some time untill water reaches the
group head
This issue has been ongoing for about a year. I initially suspected a leaky
valve due to scale build-up. So I descaled and also disassembled and
cleaned the solenoid valve, expansion valve, and air relief valve.
Today I replaced the parker solenoid valve but this doesn't stop the
backflow.
*Observations:*
1.
The issue only occurs when the steam boiler is turned on → Only brew
boiler heated: no backflow
2.
Pressure from the steam boiler transfers to the brew boiler → Steam
boiler heats to 1 bar, shortly after the brew boiler also shows 1 bar
-
Note: the brew boiler is filled via a pipe that passes through the
steam boiler
-
Question: Shouldn't the brew and steam boilers be separated in terms
of pressure? Or are they actually "connected" via that line?
3.
Steam seems to push back from the brew boiler (filled from above) → The
steam boiler (filled from below) doesn’t empty
4.
Steam escapes via the expansion valve → OPV is set to 10 bar, at just 1
bar pressure it should normally remain closed
-
Question: Or is that only true for water pressure and not for steam
pressure?
5.
Steam also escapes through the air relief valve toward the tank → Return
line to the tank gets hot, condensation drips through the vacuum hose
*Possible causes (only if the valves should be closed at 1 bar):*
1.
Expansion valve (Expobar 30400055) leaking or seal surface damaged
-
The OPV is only supposed to open above 9 bar during extraction —
which it does
-
If it’s venting already at 1 bar steam, then it’s leaking (backflow
possible via steam pressure)
2.
Vacuum valve leaking
-
The vacuum valve (Expobar 65000215) is supposed to open during
heating, then close?!
-
If it doesn’t close, steam/water escapes continuously → backflow into
tank
Thanks in advance for all your answers! 😊
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