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?
Yes, separate. No they are not connected! Brew boiler never boils, it just
feeds brew temp water to the group head. The brew boiler output goes in a
tube through the steam boiler, but they are sealed from each other.
- Could someone check for me if the preassure of the brew boiler is at
about the same as the steam boiler (1bar).
No, not the same as steam boiler. Steam boiler is at pressure (1-1.4bar
depending on your pstat), brew boiler is not boiling, it is pretty much at
room pressure.
- Should the expansion valve and the air relief valve remain sealed when
there is a pressure of 1 bar in the return line?
Return line... there is an OPV before brew head. When brew pressure is too
high the OPV opens a bit and bypasses brew pressure (water) back to the
cold water reservoir (assuming this is a unit with a reservoir and not
plumbed.) The return line itself between OPV and tank cannot be at 1 bar
because the return line is open to the water reservoir.
Expansion valve? There is an emergency over pressure valve on top of the
steam boiler. That should never be open unless youve got a serious problem
like if the pstat is stuck open. It will whistle like a steam engine and
gorge steam. The reverse pressure relief valve on the steam boiler should
also not be leaking, like... ever. It sets and seals itself every time the
steam boiler comes up to pressure.
*Problem:*
-
Hot water/steam flows back into the tank via the return line
If you mean that the return line to the cold water reservoir is bubbling
with steam then yeah thats not good at all. Having brew boiler at steam
pressure is bad.
-
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
There is a switch to cause brew boiler fill. When brew boiler gets low the
pump will activate to fill it. How low is the brew boiler getting? Not good
if brew boiler is actually emptying. Or do you mean it takes a while for
brew water to reach 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?
Yes separate. Never the two shall meet.
1.
Steam seems to push back from the brew boiler (filled from above) → The
steam boiler (filled from below) doesn’t empty
2.
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?
Do you mean the think on top of the steam boiler? Or the adjustable thing
between the pump and brew head? I've no idea how it handles steam. If its
able to hold 7 bar brew pressure then I would expect it would be tight
against steam.
1.
Steam also escapes through the air relief valve toward the tank → Return
line to the tank gets hot, condensation drips through the vacuum hose
I am not sure what you mean by air relief valve. The reverse pressure
relief valve? That is sealed when steam boiler is at pressure. If it leaks
it leaks steam into the enclosure, no tube to collect its output.
*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! 😊
I'm sorry I can't be more help. It sounds like you might have a leak in the
brew pipe that passes through the steam boiler. Either that or some of your
tubing is routed incorrectly. Is this new behavior? Did you ever see this
machine work correctly?
I would try and debug how the pressure is getting from steam boiler to brew
circuit because it really shouldn't. You could maybe rig up a fitting with
a bike pump to pressurize the steam boiler, then undo stuff and see where
the pressure is going?
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