Pressurestat Creep

Pressurestat Creep
Originally uploaded by pavasm.

I think my pstat is starting to go. About a year ago the original pstat on my machine (Signal Lux) failed. The boiler temp ran away and tripped the high-limit thermostat. I replaced the pressurestat and the thermostat. I took the Signal Lux stat apart, and found the contacts were pretty toasted. I found that the full heating element amperage was running through the stat, which I believe is not rated for 10+ amps. When I put in the replacement Mater stat I also added a relay, so that the full amps do not run through the stat. I also strapped a thermometer probe to the boiler so I would be able to keep an eye on the boiler temp if it changed over time. Well, now that is apparently happening. The temp used to happily idle around 214F. Now it does upon initial warmup (up to an hour or so), but after shots are pulled, the temp climbs up to about 218F. From some forum research, it appears the exposure to the steam on the pstat line evantually degrades the stat (or maybe it is some sort of scale in the line). When I originally replaced the pstat I vowed to switch over to some sort of digital control (PID) if the replacement went. I think the time has come. I also wanted to try adding a dimmer to the pump wiring so that I could control the pressure of the vibe pump, and I thought I could use the same enclosure as the PID/SSR.