When I was picking up my Salvatore Compact Spring Lever, I asked him why there was a coil in the (thin) copper tubing leading to the pressure gauge (similar to the picture below). He said it was simply to allow the tubing to be longer so as to reduce its temperature at the gauge end, helping to protect the gauge. Nothing about condensation.

Chert wrote:+

I have not seen that in other machines. What would that coil in line to the pressure transducer at the PSTAT do?

The coiled capillary tubing has been standard in almost all the machines I've owned. I used this one when I added a remote pressure gauge to my old Strega.
https://www.chriscoffee.com/Pressure-Ga ... 970cmn.htm

When you buy a generic gauge like that it comes with a length of tightly coiled copper tube. It's easier to leave it than it is to cut it. It can also act as a damper if the pressure changes rapidly.

Ira

I have been having quite a time finding the right set of steam and water taps for the build. Although I know that lever style controls are preferred by some over traditional taps, I would really like to preserve the look of the original design. Personally, I find the lever valves are akin to forelegs on a Tyrannosaurus Rex - out of proportion with the rest of the beast.



Alas, the Brugnetti valve is out of production (although there is still a little new-old stock to be found) and I have not come across any of the handles at all. I combed the databases of a number of suppliers to find a likely candidate and found one from Pavoni:



I ordered the valve body and the handle separately and was surprised to find that the handle wasn't the one in the image (it is actually nicer imho). Also, not such a nice surprise, the outlet of the of valve I received is angled back towards the body of the machine. This makes it unusable in the design and I have to find something else. I am guessing that as the Pavoni Bar 2L is still in production that the straight valves can still be found. In an ideal world however, the valve outlet would angle away from the body so that the assembly can be kept close to the backsplash. The Pavoni actually uses an additional spacer to solve this problem. Any suggestions for something closer to the original from another machine in production would be greatly appreciated. Otherwise, I will just have to sort out a right-angle Pavoni valve I suppose.

I had to install the tap that I received temporarily so that I can go on to other things.







Not right at all, but it will have to do for now.

I think we've turned a corner because it definitely seems like it's time to start on the other kind of plumbing!

Here's one I made earlier...
(Not sure how many here will get that reference).



For those who haven't come across them before, these are modular DIN rail industrial control components - aka Lego for electrical engineers. From left to right, AC distribution, 24v DC (blue) and 5V DC (black) power supplies, DC fuse blocks, DC distribution, 12V (white) power supply in the middle, unconnected terminal blocks and a magnetic contactor for switching large loads. The grey terminal blocks come in various flavours (1x1, 1x2, 2&2 etc) and can be jumpered together, converting them into bus bars for power or signal distribution. The metal DIN rail serves as a ground bar linking all the green terminal blocks together - the equivalent of chassis ground. I put this together a while ago for another project and kept it assembled as it often comes in handy.

The 12v supply wont be necessary and neither will the contactor, but the rest will be useful. The first order of business is the temperature control. I have this nice Watlow controller which I am borrowing from another project. It has a number of features that I want to take advantage of. The first is simply speed - this thing just works: five minutes of mandatory RTFM, specify the thermocouple type, change the set point and away you go. The other advantage is that it has a PID auto tune mode which should obviate the need to empirically determine the coefficients for the three terms of the control expression.



I ordered a few of these $2 thermocouples from China a few months ago (K type if I remember correctly). They are advertised as 6mm but are in fact 1/4-20 (but the nut is metric - what a world). They also don't seal, which is a pain as it means that they can be put directly inside the boiler.



A quick side-by-side test with the thermocouple that came with my multimeter shows that all is well in this particular tiny corner of the world.



The TC is hooked to the input of the Watlow and the output is sent to a solid state relay (SSR) that will control the heating element.



The setup so far, from left to right:

Arduino and protoboard (top left)
Unused contactor (bottom left)
Autofill probe connections
24V DC / 120V low amperage control relay (light blue)
Bidoowee brand 5V to 24V and 24V to 5V optoisolated signal convertor (green IC board)
DC distribution and fuseblocks
DC power supplies
AC distribution
SSR (top right)
GFCI outlet (to the left of and connected to the SSR) (powering the heating element)



A couple of words of warning here. The wire gauge used is technically not adequate for the amperage drawn by the heating element. Also, we are playing with 15amps and lots of water, thus the GFCI (Ground Fault Circuit Interrupter). Out of frame, the whole mess is plugged into another GFCI on a 12 gauge extension cable for belt and suspenders safety.

Today I (nearly) boiled water.

The result of the squirrelly form factor of the thermocouple is this ridiculous adaptor:



I put a drop of heat-transfer grease on the tip of the TC to aid the conduction of the heat and attached the whole lot to the boiler. Then I did a quick test of the controller using a lamp in place of the heating element.



Now for the real thing. I put the multimeter TC probe directly into the boiler so that I can compare it with the controller TC. Time to 'put the kettle on'.



As I feared, the lag created by the thermal mass of the lump of brass in the adaptor and the less than ideal position in which it is installed (close to the bottom of the boiler) is significant. After about 8 minutes, the water got pretty close to boiling but the controller probe was nearly 30 degrees behind. After another ten minutes or so, the gap had narrowed to about 9 degrees, but this is far from ideal. Quite possibly, everything will stabilise once the heat is completely diffused through the entire system and in theory, with some calibration of the set point and proper PID coefficients, the overshoot can be reined in. However, a twenty minute plus sample rate just isn't acceptable. To remedy the situation, I am going to move the TC to the top of the boiler and look for a better form-factor - one that can be installed through the wall of the boiler.

bidoowee wrote:I have been having quite a time finding the right set of steam and water taps for the build. Although I know that lever style controls are preferred by some over traditional taps, I would really like to preserve the look of the original design. Personally, I find the lever valves are akin to forelegs on a Tyrannosaurus Rex - out of proportion with the rest of the beast.


Not right at all, but it will have to do for now.

I have two parts VFA machines. If the steam valve suits, I probably could part with it. ( I have to make sure that I have two complete functional ones which I think they both are; a third one lacks the wand itself - so at least one valve assembly is available). Here is the cafe parts diagram

I really enjoy this thread!

Chert wrote:
I have two parts VFA machines. If the steam valve suits, I probably could part with it.

Thank you for the generous offer. I am not really familiar with the VFA family of machines. I took a look at the parts diagram. The two lugs on the handle side are slightly puzzling - are they just not used? The angled outlet is definitely what I am looking for - is the valve body chromed? From another supplier, it is described as being the "old style" which suggests that it may be out of production. I am keen to find one that is still made so that I have a guaranteed supply.

Many thanks

No, that part would not help you for both reasons I suppose, although maybe this image helps determine yes or no. I mean, is the angle in the image the correct direction? VFA is no longer around but maybe the part is still made.

The link supplied by Flint shows cross references to other companies featuring the same part, including Ascaso and La Cimbali. It may still be manufactured. A web search shows the same photo branded La Cimbali on Amazon.