control specialties
control specialties
...
First thing to understand is when you're way in the deep end, there's lots of variables, design decisions, and liability for life safety system performance.
In a refuge area like a stairway you could have supply fans at the bottom and exhaust fans at the top. Both run at the same time on signal from the fire alarm system. Positive pressurization of the refuge area on signal.
In a rooftop AHU you could have separate supply and return fans in the same unit, or one fan with separate supply air, return air, mixed air dampers. On signal trip from the FA you might shut everything off or shut off supply air while running exhaust, smoke evac., negative pressurization of the smoke zone.
It's a potential nightmare for the wrong person, it's a specialty. IMO, a PE should supply sequence of operation at a minimum and/or wiring diagrams, signed and stamped, and pick up liability for operation. There are lots of ways to wire it wrong. I'm very sure most of the guys trying something like this are not grasping the subtleties, approaching this analytically, what happens when and why
