La Marzocco Linea with random steam boiler over-pressure problem

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duke-one
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#1: Post by duke-one »

Hi All: My one year old Linea is going over pressure in the steam boiler but only once and a while. I have it set at 1.5bar and most days all goes well. It has over pressurized 2-3 times since new (I use it every day). I think they should have put a more serious pressurestat in such an expensive machine but it is what it is. The tube that feeds it is U shaped; is that to keep condensate from building up? Could "water-lock" cause intermittent problems? Have other Linea owners replaced the pressure control with a more robust unit?
Thanks, Duke Masters

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erics
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#2: Post by erics »

That pressurestat (likely a MA-TER) controls a secondary relay if I remember correctly.

The U shaped tube intentionally keeps condensate in contact with the pstat diaphragm.
Skål,

Eric S.
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stefano65
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#3: Post by stefano65 »

yes some years back they went from full size psat
to small (CEME for a while now MATER)
and a big contactor (in Italian called teleruttore)) that takes the load off of the pstat
Stefano Cremonesi
Stefano's Espresso Care
Repairs & sales from Oregon.

duke-one (original poster)
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#4: Post by duke-one (original poster) »

My single group has the smallish p-stat feed the heater directly. I turned it down a bit and exercised the adjustment a bit. I hate these problems that happen 2-3 times a year then go away. I should get a replacement p-stat to have it on hand.
Duke

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stefano65
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#5: Post by stefano65 »

I didn't notice you where talking about a 1gr
the contactor will be on 2 groups and up
Stefano Cremonesi
Stefano's Espresso Care
Repairs & sales from Oregon.

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erics
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#6: Post by erics »

Thanks for correcting me on the pstat operation, KDM. When I was initially responding I wanted to say CEME but somehow that came out as MA-TER. The new MA-TER I have in front of me (XP110) is stamped with a 15A rating at 125/250 VAC so it should be able to handle that steam boiler electrical load fairly easily.

But . . . a pstat failing so infrequently as yours seems a little strange to me so I would simply replace it and keep the original as an emergency spare.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

duke-one (original poster)
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#7: Post by duke-one (original poster) »

Eric: Yes, that it goes wild once in two or three months and then back to normal is a bit odd. I will get a replacement and either install it on arrival or wait till the next incident. Probably will tear up the original looking for the fault, to no avail.
Duke

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Paul_Pratt
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#8: Post by Paul_Pratt »

I've seen this before, like Eric says p-stats don't usually fail like this. Either all or nothing.

You may want to check that your pressure gauge is accurate. It could be off by a few 0.1 bars. Having it at 1.5 it may be closer to 1.8 open value than is indicated on the gauge which is why it opens the valve.

I have also seen faulty safety valves that open below 1.8.

Just a thought.

duke-one (original poster)
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#9: Post by duke-one (original poster) »

Paul: I think the gauge is OK, it showed the overpressure when the p-stat was sticking and the safety was blowing off, showed the 1.5 I had it at and now shows the about 1.3 I reset it at. Thanks for the idea.
Duke