Who is responsible for the controls on a packaged unit?
By Bassirou Thiam, building automation engineer · Updated
On a packaged unit with factory controls, everything inside the box belongs to the manufacturer: components, internal wiring, the controller and its logic. The BAS contractor connects to a small set of terminals (start/stop, status, alarm, setpoint) and to the network, where it must set the right address, device instance and baud rate.
Draw the line at the box
Electricians, pipefitters and sheet metal all connect to the unit, but none of them makes it run, and neither does the controls contractor. The interface is what the BAS owns: a handful of hardwired points and the network connection.
What to ask for before you wire
- Written wiring instructions from the manufacturer. Until you have them, pull your cables to the unit and leave them coiled, not terminated.
- A certified points list for that exact unit, with the network objects and their meaning. Do not map from a generic document found online.
- The network settings expected on the unit: protocol, address, device instance, baud rate.
Where it is written
The controls responsibility matrix in the specs decides who furnishes, installs and wires each item. Read it before bidding: on packaged units it is a common source of disputes. The submittal checklist lists where these interfaces must appear.