The BAS Settings You Never Touch, But Probably Should

Back when I was managing a large hospital site, the BAS started lagging badly.

Graphics were slow. Commands delayed. Everything felt like it was crawling.

Turns out there were a lot of excessive trends left over from the project team during commissioning, and they’d been there for years. Controllers were dumping data on schedule, but there were simply too many points being logged. The server couldn’t keep up. Everything slowed down.

What followed was a controller-by-controller audit. We applied standard trend intervals and COV settings across the board. The lag disappeared. The system stabilized.

Since then, I’ve never underestimated the impact of BAS config settings.

Here are six that are almost always overlooked, but can quietly make or break a system.

1. Trend Intervals and Storage Limits

Why It Matters: Poor trend settings can silently wreck your system. Too much data clogs servers and delays graphics. Too little, and you miss the patterns that help you troubleshoot.

Most techs don’t realize how often trend data gets lost because the controller’s local buffer fills up before the server pulls it. Once that happens, the data’s gone.

The Fix: Set trend intervals that match the behavior of the point, not just a default. Fast-changing points (like damper position or discharge air temp) should trend more frequently. Stable ones (like OA temp) need far less.

2. Change of Value (COV) Settings

Why It Matters: Too tight, and you flood the network. Too loose, and you miss important data.

The Fix: Stop defaulting to 1.0 for every point. Tune COV thresholds based on the speed and sensitivity of each point. A discharge air temp and a binary occupancy input don’t need the same resolution.

Pro Tip: Audit fast-changing sensors and actuator positions first, you’ll see noticeable performance improvements.

3. Locked Values

Why It Matters: A manually locked point can quietly override logic for weeks, and no one notices.

The Fix: Before rewriting logic or re-downloading programs, check lock status. It's not broken. It's just been manually hijacked.

4. Alarm Deadbands and Delays

Why It Matters: Without deadbands or delays, every little blip becomes an alarm. Important issues get buried in the noise.

The Fix: Add time delays to fast-reacting points and reasonable deadbands to analog sensors. Clean up your logic so real faults stand out, and nuisance alarms don’t overwhelm your logs.

Best Practice: Classify alarms by severity and route them by role (operator, service tech, facility manager).

5. BACnet Priority Arrays

Why It Matters: When a point doesn’t respond, it’s often not broken, it’s just losing the priority fight.

The Fix: Understand how BACnet priority arrays work. Your write might be sitting underneath a manual override from weeks ago. If it’s not higher priority, it gets ignored.

6. Outdoor Air Sensor Accuracy

Why It Matters: A bad OA temp sensor throws off:

• Economizer logic

• Heating/cooling reset schedules

• Energy savings strategies

The Fix: Validate OA readings seasonally. If your sensor drifts even a few degrees, you could lose free cooling opportunities and increase run time.

Final Thoughts

These settings don’t show up in dashboards. They don’t alert. They don’t break. But they quietly shape how well (or how badly) your BAS performs every day.

When things go sideways, don’t just check wiring or logic. Check your settings.

💬 What’s the most overlooked config issue you’ve ever found? Drop it in the comments, let’s trade lessons the next tech won’t have to relearn.

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