[quickthrowman]

> You have no clue what you're talking about. You are correct in that low cost PLC hardware can replace relay and pneumatic controls, but HVAC systems aren't just basic relays and pneumatics.

The person you’re replying to was saying that the old method of HVAC/process control, prior to digital controls, was pneumatics and relays. Old HVAC control systems were indeed pneumatic systems, I’ve seen some in the wild in the last few years in the US.