Linea brew boiler overheating

[Stubbie]

Linea AV/2 - Made in 2002

Last weekend, I turned the machine on and let it come up to temp.  When I started pulling shots, I could tell right away something wasn't right.  Started checking, and water coming out of the group wasn't nearly hot enough, and the groupheads were much cooler than I expected.

Took off the cover and was looking around and found a button on top of one of the groupheads was popped up.  Pressed this in and saw that the boiler light was now on and I was gaining pressure.

Pressure continued to build, past the 9 bar mark it usually stabilizes at.  Running some water through the groups would bring it back down, but then it would climb again.

Was pulling some shots, and when running a flush noticed steam was coming from the groupheads - finally popping the button on top of the grouphead again.  Shut it down and started reading.

I really haven't found much on line speaking to this trouble specifically, although I suspect it is a thermostat failing - I really know very little about the insides of these machines and was hoping some of the gurus here would chime in.

I really think that I would like to install a PID to control brew temps if I am going to have to replace parts anyway.  Does anyone have an idea on how to do this on a La Marzocco?  Have some parts laying around they are looking to sell?  I have seen the kits for sale on line, and know I can do it for quite a bit less with a little bit of information on what to source.

I think I need to go ahead and buy the "Orange Book" since there doesn't seem to be a soft copy of it out there either...

-Stubbie

[milowebailey]

Stubbie

Sounds like it might be the pressurestat.  I don't know what happens when one fails, but seems that may be your issue.  Maybe you can adjust it back down to 9 bar.

PIDing is also an option.  Fuji and CALs seem to be the best or most often used on espresso machines.  Installing them is fairly simple.  You'd just bypass the pressurestat and replace it with a Solid State Relay (SSR) and install a thermocouple where you want to measure the temp.. probably on the boiler somewhere.  Let me check when I get home tomorrow and I'll see what I have in my box of parts.  I may have an extra PID and SSR.

[Tex]

I did a complete rebuild of a 2-group Linea a few years back, and the rebuild included a PID conversion. I assembled the parts myself, but they looked like this: http://www.espressoparts.com/cgi-bin/ep.pl?pgm=co_disp&func=displ&strfnbr=71&prrfnbr=3076&sesent=0,0&search_id=330333

This might help too: http://www.espressoparts.com/espressoparts/content/graphics/pagebuilder/EP_PID_INSTRUCTIONS.pdf

[Stubbie]

You guys are awesome!

Yes Tex, that was the kit I had seen on line as well - but I hadn't found the instructions you posted up.  Looks like they use the Fuji like Milo suggested.  Look forward to seeing what you've got in your spares Larry, thanks.

-Stubbie

[Tex]

Regardless of what combo of parts are used to convert your Linea to PID, this is basically how you do it.

The only tricky part might be getting a brass or stainless reducing fitting to go into the boiler where the pstats steam tube went. IIRC, the LM had BSSP fittings and I had to get a BSSP to NPT reducer from McMasters-Carr so the compression fitting I got from Omega would work.

BTW, I put two PIDs on the Linea I rebuilt, simply because I hate pstats!

[lurkerjohnny]

Stubbie, I got my Fuji PXR3 (same one as espressoparts) off of ebay brand new for $65.  I bought the ssr for it for another $10.  I was able to get some hi-temp silicone wiring off of someone on Homebarista.  If you need some of that, I have enough to share.

The part on your machine that seems to be malfunctioning is the thermostat, not the P-stat.  The P-stat is for the steam boiler.  You may want to check if maybe all you need to do is lower the temp on the thermostat by turning the little white screw counter-clockwise I believe.  Double check the manual on the direction though.

If you do decide to go PID, you need to decide if you are going to remove the thermowell from the brewboiler.  Some people have a hard time removing it.  If you can remove it, then go the route that Tex mentioned, either assembling on your own a BSSP to NPT reducer to place in the thermowell, with a thermocouple probe/wire running out of it or buying the pre-assembled one with thermocouple probe/wire from espressoparts   OR.....

You can take a shortcut and leave the thermowell in.  Then you just either insert a wooden dowel (Barry Jarrett) with a hole drilled through the middle or insert a copper/steel plug with hole drilled in the middle.  You place a thermocouple wire with the end stripped off down the hole and have the bare wire hanging over the end so it gets stuck in the bottom of the hole (smear some thermal compound on it).  This way should still give fairly accurate results, maybe a wee bit slower.  But, it will be easier to install if you have problems with the thermowell.

I hope this information helps!! 
PS:  I started a thread about the thermowell and thermocouple on Homebarista a while back.  This info may help you.
 http://www.home-barista.com/knockbox/thermocouple-bare-wire-versus-probe-for-pid-t14336.html

[Tex]

I removed the thermal well and used a reducer to get down to the 1/8 NPT x .125" compression fitting.

You should find what you need here: http://www.omega.com/Green/pdf/RA_RB.pdf. One thing: Have the compression fitting fitted out with a Teflon/BTFE ferrule, so you can adjust the new probe until you find the best depth. Compression fittings come standard with brass or s/s ferrules, and are only good for one tightening.

I use TMTSS-125G-6 - 1/8" x 6" grounded s/s sheathed type T probes when I PID commercial boilers: http://www.omega.com/ppt/pptsc.asp?ref=JMTSS&Nav=tema07.

[Stubbie]

OK, thanks to Larry I now have a PID and SSR.  Decided to bite the bullet and order the thermocouple and correct fitting from Espressoparts - it's on it's way to me now.

I was also able to find the La Marzocco owners manual and technical manual online.  I'm hoping the technical manual will suffice in lieu of the "Orange Book"

Johnny - thanks for the offer of the wire.  I am going to see if I can source it locally and if I can't find it will take you up on your offer.  Do you happen to know the gauge of the wire you have?  I would assume that I really won't need that much of it.  Also, thanks for the links to those other threads...I have learned a lot by reading them.

Slummin' it with the Andreja Premium for the time being   I have to say, it's been fun to go back to the smaller machine for awhile, but I sure miss my Linea.

-Stubbie

[lurkerjohnny]

Hey Stubbie, sorry just got back from a trip.  I think the wiring that I got is 14 gauge.  I can give you 6 feet of black and 6 feet of white.  I still have not finished this project.  When I do, I still need to decide if I am going to take apart part of the machine to get at the thermowell and do the project right or if I am going to just stick the thermocouple into the thermowell hole with a copper/steel plug. 

Shoot met a pm with your info if you want it.
Keith