Building Automation

A network of controllers and sensors that runs the mechanical equipment to a written sequence, plus a front end where a person can see it and change it. In practice that means schedules and optimal start, temperature and pressure setpoints with reset strategies, staging across multiple pieces of equipment, economizer changeover, alarms when something drifts, and trend logs so you can prove what happened last Tuesday. On a small site it might be one supervisory controller and eight rooftop units. On a campus it is hundreds of points across several buildings.

Modbus is older and simpler: it exposes numbered registers, and you need the manufacturer’s map to know that register 40012 is discharge air temperature. BACnet was written for buildings specifically, so a device describes its own points with names, units and priorities, which makes integration far less error-prone. Most whole-building systems are built on BACnet, and Modbus devices — drives, meters, burner panels — get brought in through a gateway. You will meet both on almost any real site.

Most of it can stay. A rooftop unit with a working BACnet board joins the new system directly. A VFD on Modbus comes in through a gateway. Even pneumatic zones can be brought under supervisory control without ripping out actuators. What genuinely has to be replaced is anything proprietary and unsupported, and anything whose manufacturer will not release a way to expose its points. We produce that list from the inventory, with a reason next to each item.

Not on a system we build, and this is worth asking every bidder directly. The questions are: who owns the licence for the programming tool, can another certified integrator reprogram these controllers, and do we receive the points list, sequences and graphics database. Get the answers in writing before award. Open protocols alone do not guarantee it — a BACnet system can still be programmed with a tool only one company holds.

Three, and they are usually staged rather than chosen once. Keep the pneumatic actuators and add electronic-to-pneumatic transducers under a new supervisory controller, which is the least invasive and gets you scheduling and monitoring quickly. Replace zone by zone with direct digital controls as floors are renovated. Or do the plant and air handlers first, where the biggest energy waste sits, and leave the zones for later. The compressor and air dryer condition often decides the order, because a wet, dirty control air supply undermines whatever you keep.

Because the alarm limits were left at defaults and never tuned to the building. An alarm list that scrolls is an alarm list nobody reads, and it hides the one that matters. Fixing it is a review job rather than a purchase: retire alarms for conditions that are normal here, set limits and delays that reflect how this equipment actually behaves, route the genuine ones to a person who can act, and check the underlying sensor before trusting any of it.

Yes, from the start, on any system using BACnet/IP or remote access. They will want the controls network segmented from the business network, they will decide how remote access happens, and they will need addressing and switch ports arranged before installation week. Bringing them in early turns a two-day problem into a ten-minute conversation.

Where the system is open and we can be given proper access, yes — including sensor calibration, sequence corrections, graphics fixes and alarm cleanup. Where a system is locked to its original vendor’s tool, we will tell you honestly what we can and cannot touch rather than discovering it halfway through. In those cases the useful work is often adding independent monitoring alongside it.