Compressed Air Systems Under Title 24
Where more than one compressor is online and the combined rating exceeds 100 horsepower, the system needs a controller that selects the most efficient combination of compressors for current demand. An acceptance test is required before an occupancy permit is granted.
The trigger has two parts
Both have to be true: more than one compressor online, and a combined rating above 100 horsepower. A single large compressor is outside the requirement no matter its size, because there is nothing to sequence. Several small compressors totalling under 100 hp are also outside it.
"Online" is doing work in that sentence. It describes compressors available to run and share the load, not everything installed in the room. A standby unit that is not part of normal operation is a different thing from a second machine that trims demand every day.
What the controller has to do
It must be able to choose the most energy-efficient combination of compressors within the system based on current air demand. That is a genuine sequencing requirement, not a pressure switch.
The reason is how compressors behave off design. A machine running unloaded still draws a substantial fraction of its full power while delivering almost no air, so two compressors each at 40 per cent are markedly worse than one at 80 per cent. A system without sequencing tends to drift into exactly that state and stay there, because nothing is looking at the combination as a whole.
Why compressed air gets singled out
Compressed air is among the least efficient ways to move energy around a building — most of the electricity into a compressor leaves as heat, and what survives is then lost again through leaks and pressure drop. In a plant with a large compressed air system it is often the single biggest electrical load, and it is usually running whether or not anything is using air.
That is why the code reaches it at all. The equipment has nothing to do with the building, but it can easily dominate the building's consumption.
The acceptance test is a permit condition
This one is worth stating precisely: before an occupancy permit is granted, a compressed air system subject to this section must be certified as specified in Reference Nonresidential Appendix NA7, with a Certificate of Acceptance submitted to the enforcement agency.
Two acceptance forms cover it, NRCA-PRC-01a-F and NRCA-PRC-01b-F. Both carry the -F suffix, so a field technician may perform the test rather than a certified acceptance test technician.
Sequence it into the programme early
An acceptance test tied to the occupancy permit sits on the critical path, and a compressed air system is commonly one of the last things commissioned because it is installed by a specialist contractor after the building is otherwise complete. Discovering the test requirement at that point is how occupancy slips.
Establish the compressor count, the combined horsepower and whether a sequencing controller is in the package. Those answers decide whether any of this applies — and they belong in the equipment specification, not in a late conversation with the plant supplier.