Hi there,

I'm a tech in Portland Oregon. I work on commercial machines and have a few Linea Classics on my bench at any given time. I was at EXPO this weekend and was talking with a fellow technician that mentioned replacing the contactor with a SSR in my Linea rebuilds. Besides getting rid of the annoying thumping of the contactor, what purpose would this serve and what are possible risks (if any)? Also, does anyone have a wiring diagram they've found helpful?

*Disclaimer* I've only been a tech for a couple years and come from a coffee background, not technical. And the electrical side of things is my greatest weakness so all helpful information is welcomed.

I used an SSR for the steam boiler on a Linea that I run in a café. Going strong now for alomost one year. You can see how I wired it here in post 29:
La Marzocco Linea 2AV overhaul project

I got the idea from Paul Pratt. He has lots of good info and pics on his website. Here are pics of his SSR instalation on a Linea:
http://espresso-restorations.com/1GLinea3.html

I hope other will shime in with more usefull insights. I am learning as I go aswell!

Thanks trumz! Your rebuild is one I came across and already screen shot your wiring diagram; very helpful. And thanks for the link to Paul Pratt, should prove helpful.

The contactor is actually part of a safety system on the Linea. One major disadvantage of SSR is that it will most likely fail closed, it means that in case of failure it will continue to conduct electricity regardless of of whatever being commanded.
Now you say Linea also has thermal limit switch (no 5 below) on the steam boiler, but keep in mind those are used to act on the control side on the contactor (no 28) just like the pressurestat (no 6). Typically the steam boiler has too much wattage to use the thermal limit switch (15A max) and standard Linea 2GR steam boiler is 3000W which is really near the limit. Which is why it works ok for coffee boiler but not for steam boiler.
So in case of SSR failure then you only relying on boiler safety valve to pop open.....



So my suggestion is to keep the contactor intact but add the SSR inline with the contactor. You can use Fuji PID or pressurestat to control the SSR but let the thermal limit switch to control the contactor. Esentially the contactor will be "on" all the time unless the thermal limit switch pops.

Also SSR would derate at high ambient temperature, which is part of the reason why a lot of commercial machine have the SSR located at control box underneath the machine, i.e GB5, Strada etc so you should find cooler location to mount it.

See this: https://www.espressoparts.com/search?q=linea+pid

I BELIEVE it is a very reasonable task to convert an older Linea to PID control for the brew boiler, ESPECIALLY if the installed PID can be incorporated into a new front panel. It certainly APPEARS that way in the current model.

LM in Seattle offers several technician courses for people in your profession and it would be well worth your time to inquire about same. I just have a "hunch" that they are well versed with those wishing to upgrade older Lineas .

Pra and Eric,

Very much appreciate your input! I am in regular coms with Solutions at LM and when asked about this, they said I'd need a stepdown power supply. After further research, thanks to links provided by Kyle, it seems this would only be needed if using a DC/AC SSR, but going with an AC/AC SSR would eliminate this. True?

boost wrote:Now you say Linea also has thermal limit switch (no 5 below) on the steam boiler, but keep in mind those are used to act on the control side on the contactor (no 28) just like the pressurestat (no 6). Typically the steam boiler has too much wattage to use the thermal limit switch (15A max) and standard Linea 2GR steam boiler is 3000W which is really near the limit.

Also, Pra are you saying I'd have to bypass the high limit switch when using a SSR bc it can't handle the amperage?

erics wrote:I BELIEVE it is a very reasonable task to convert an older Linea to PID control for the brew boiler, ESPECIALLY if the installed PID can be incorporated into a new front panel. It certainly APPEARS that way in the current model.

LM in Seattle offers several technician courses for people in your profession and it would be well worth your time to inquire about same. I just have a "hunch" that they are well versed with those wishing to upgrade older Lineas .

Eric, I've done a few dozen PID conversations on the brew boiler and even built out a Linea Classic with a PID on both the coffee and steam boilers, but it was a lot of work and presented some baffling issues. It worked well during bench testing, but after shipping it to GA the SB would overheat and trip the PSV almost immediately after putting the lid on. They've been rocking a lidless machine for about a year and a half! Solutions still gives me a hard time about it. Someday I hope to get out there and fix it! HA!

And yes, LM does offer classes and I've been talking w Randy to figure something out, he doesn't really have a '200' level class at the moment and the '100' level covers pretty basic stuff.

Well, then applying a PID to the brew boiler . . . case closed.

I'm not a big fan of Sirai pressurestats, especially the lower cost/capacity models used on some prosumer machines. So, I would choose a MA-TER pressurestat and let it control an AC/AC SSR to power the steam boiler. This is an error that a few users have made. PID's typically operate in conjunction with a low voltage DC signal switching an AC voltage. However, pressurestats will utilize a line voltage AC/AC SSR.

As far as safety devices are concerned, they can simply be wired in series with the control signals, not the power lines to the particular boiler's element.

You don't need a DC power supply if you get an AC SSR with pressurestat like Eric also says. Pstat will always cycles so you will hear the clicking but shouldnt be as loud as contactor or full size Sirai p-stat.
Or if you want you could always add PID to the steam boiler, thats how its done in GS3 or Strada. For thermal limit switch you need to wire it with the control signal on the contactor since the load side has too much current for the limit switch. See what Kyle has done on his modification.
What do you mean by tripping PSV on the steam boiler? Overpressure/boiler safety valve? What temperature you set the steam boiler to? What does the pressure gauge reads?
I think it is good idea to have other tech, preferably electrician to double check your wiring plan.

Eric, thanks again for the input. I have a habit of making sure key components are of latest OME standards, thus I replace all old style pstats with LM's newest OME part.

Pra, yes I mean the Pressure Safety Valve or PRV for Relief or Release or etc... It's one of two things, bad probe (10% possibility) or a grounding issue bc the machine is fully powder coated (90% possibility) I'm now very deliberate in making sure I have more than adequate grounding surfaces. Thanks for your advice. I'll draw up a diagram and post to have your opinion.

All the best, gents.

As I am also thinking about finally PID'ing my single group Linea I figured this seems like a suitable thread to ask, where would you recommend placing the SSR's and how best to mount them? I see Paul Pratt put them on the left side of the machine underneath the AC wiring harnesses, is this considered best practice?