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La Marzocco Linea with random steam boiler over-pressure problem

Postby duke-one on Tue Oct 09, 2012 3:40 pm

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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Postby erics on Wed Oct 10, 2012 8:04 am

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.
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Postby stefano65 on Wed Oct 10, 2012 9:59 am

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
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Postby duke-one on Wed Oct 10, 2012 12:08 pm

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.
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Postby stefano65 on Wed Oct 10, 2012 4:05 pm

I didn't notice you where talking about a 1gr
the contactor will be on 2 groups and up
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Postby erics on Wed Oct 10, 2012 10:07 pm

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.
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Postby duke-one on Wed Oct 10, 2012 11:44 pm

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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Postby Paul_Pratt on Thu Oct 11, 2012 6:44 am

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.
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Postby duke-one on Thu Oct 11, 2012 1:37 pm

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.
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