Looking back at old relay logic versus modern controllers

Worked on a 1970s Otis unit in a Boston office building last month. The relay panel was a maze of wires, maybe 200 contacts. Took two days just to trace a single fault. Newer jobs with microprocessor controllers, same fault takes an hour tops. The diagnostic screens show you exactly which safety circuit is open. Miss the old days sometimes, but the time saved is real. Anyone else have a story about switching from relays to solid state?

3 comments

3 Comments

jade8853mo ago

Wow, my old foreman called relay troubleshooting a "thinking man's game" for a reason.

julia_burns93mo ago

Tell me about it. I've spent more time staring at a ladder diagram than I care to admit.

tessacarter2mo ago

What was the hardest relay logic puzzle you ever had to figure out? I remember tracing a single bad connection through three different cabinets once, felt like solving a mystery.