I'm interested in PIDing my Cimbali M20L Lever and have two unused & plugged holes in the boiler. Both holes are above the water line so to use them whatever probe I use would be immersed in steam rather than water. A pressure transducer - which could be more expensive than a standard PID setup - is certainly an option.

I'm wondering if it's possible to use a standard RTD thermocouple immersed in steam? Bill Crossland - of GS3 and CC1 fame - suggests its quite possible, and possibly better than a pressure transducer, in the below link, but I cannot find any more details or any examples of people doing this. Has anyone done this and can you give any details on how it worked?

PID pressure sensor instead of thermocouple?

Sure.
Many newer machines now uses RTD, for example GS3 and Strada. The key is finding liquid tight sensor and cant be remotely installed like p-stat as the temperature would be inaccurate.

But are their sensors immersed in the liquid or in the steam? That's my real question. Seems like it should work, but want to confirm.

But are their sensors immersed in the liquid or in the steam?

It should be "immersed" in steam.

Bill explained the reason they should be immersed in the vapor here:

Replacing steam boiler seals on the La Marzocco GS/3

In a nutshell, you are looking for the Ideal gas law (pV=nRT) to relate temp directly to pressure. Measuring water temp would add the lagging relationship between vapor temp to the water mass temp.

Awesome! Thanks for your help, gents!

As a follow up, does anyone have suggestions on how to figure out the size of the fittings? I know the anti vac valve on top of the sight glass uses 1/4" BSP so I could always try that to assess size. If that doesn't work, what should I do? Are these things standard? In other words, if one fitting is BSP they all will be?

If it's the case that it's BSP, I know I can measure the whole to arrive at the right fitting size. But where can I find BSP RTD probes? Auberins only has NPT, M14 & M16.

Finally, the boiler element has 6 poles. Can I just use a normal two pole SSR, wiring 3 lines to each pole? Our I need a tri-pole SSR?

Any suggestions on where to find this stuff?

A few pics of your machine, especially the heating element connections would be helpful. Otherwise you should expect suggestions from any other owners of this La Cimbali lever.

Certainly I have adaptors to accept 1/8" RTD probes but you need to do a little homework on what ports may be available on your boiler.

Thanks @erics.

This picture is not my personal machine, but it does the job. In this picture you can clearly see the six contacts on the boiler. Hope that helps.

https://www.flickr.com/photos/97011464@ ... 726790536/

As for fittings, there is a port high up that I was able to fully seal with a 1/4" BSP fitting. It currently has a converter to a male 1/8" BSP, so it seems like I could fit either, although I'm not sure if a probe will fit in 1/8" male since the opening is quite small. I think I'll go for a 1/4" BSPP male fitting to 1/4" NPT female and put the probe in there.

Actually just read on Auberins website that their 1/4" NPT will thread well into BSPP so I'll try that first.

I found this:

This Pt100 RTD temperature sensor is for applications that need liquid tight seal such as beer brewing or biodiesel production. It can be easily installed either on the tank or on the pipeline (with a T joint). The probe body is made of stainless steel. The mounting is 1/4" NPT thread. (it threads well into 1/4" BSPP and BSPT too). This probe has a detachable connector with a spring lock. The detachable cable is convenient for systems that need to be moved for cleaning. It reduces the possibility of breaking the cable when the tank is moved around. Recently, this probe has been redesigned with a thinner diameter tip. It reduces the flow restriction when installed on a pipeline.

here: http://www.auberins.com/index.php?main_ ... cts_id=189

Looks like it needs a sealing ring.

Probably a PTFE washer or at the very least Viton. A car gasket maker compound may also work but I am not sure it is good safe.

(Of course don't be tempted to use a neoprene seal at these temperatures...)