I thought I would share the recent upgrade since there are few installs of PIDs on commercial machines let alone levers. Some argue that it isn't worth it but so far I would disagree. The temperature stability and ease of adjustment is very nice. Of course the true factor is the quality of espresso and so far it has made repeatable shots much easier.
Notes on the install and goals:
The machine is a 240v model which is nice for speed of response by the element and the gauge wire required when running a new dedicated line. I have it on a dedicated 20amp breaker. I had several goals in mind when taking on the upgrade, improvement in repeatability of shots was top on the list but I also wanted to cut down on the noise a bit and improve the reliability. The Sirai pressurestats need to be rebuilt or replaced every so often to ensure a consistent deadband. My preference was to have one that varied even less:)
First up is the before picture with the pressurestat and hookup to the boiler indicated.
Here is a side picture of the same with the pressurestat removed. Some of what you can't see is the wiring which is in the panel that is in the bottom of the picture. 3 wires come in from the wall. A white, black and green. The white and black carry the power that eventually run into the element. voltage across the two is 240v. The stock wiring runs 3 wires to the pressurestat from the black incoming wire and the white is run directly to the heating element and other electronics. A relay controls power when the power and heating switch is turned on. I reused an available terminal on this relay to pull power for the pid so the pid would only be turned on when the heating switch was on.
The probe is a RTD type with a 1/8 npt thread. I needed something small enough that it would work in a 3/8 BSPP plug once it was drilled and tapped. Finding an adapter isn't easy when going from npt to bspp and I had the tapping set. Brass is easy to work with:)
Here is the mounted SSR and probe. The probe is installed where the pressurestat would go on the boiler. For those wondering, the probe measures temp from the steam and not the water. This seems to be working fine and it adjusts quite quickly to temperature changes. The single group version of this machine has limited options as far as adding a probe. The SSR is mounted to a heatsink upside down to protect the ssr from water. It is drilled and tapped and then mounted to the frame of the machine is roughly the same location as to where the pressurestat was. This made it easy since all the original wiring was reused with connectors and all.
Finally here is a picture with the setup running. I have it set to 243F right now which is about .95 bar of pressure. This seems to be just about right but it is very easy to adjust according to the bean. I have a project box from auber instruments ordered that the pid will be installed in and mounted to the bottom of the machine. I figure I will drill and tap the box for a solid mounting.
While I was at it I rebuilt the group and lubed the spring and all contact points with food safe silicone grease. Dow 111 was used on the seals.
The lever pull is much smoother now.
