Building automation articles from the field
Practical write-ups on the problems that cost the most time — organised by the layer of the system they live in, so you can go straight to where the evidence stopped agreeing. Free, no signup.
Getting into the trade
Where to start if you have no background, and what the path pays.
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No Technical Background? Here’s the Real Path Into Building AutomationNew
What controls work pays at each stage, where it leads, and the free-first path in — in order of how much each step actually moves the needle.
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You Just Inherited an Undocumented Building. Now What?
No as-builts, no point list, no passwords, previous contractor gone. What to inventory first, what to trend immediately, and the three faults to check before anyone asks.
Equipment layer
Is the equipment actually doing what the point says?
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The 8 Parameters You Need From Any VFD
Every drive needs the same eight things from you, regardless of brand — plus the two-source trap that makes a perfectly working network look broken.
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Sensor Drift: When Every Control Decision Downstream Is Wrong
Temperature sensors drift a degree or two a year. The BAS keeps reporting normal while every decision downstream of that sensor is quietly wrong.
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Test an Economizer in Twenty Minutes
A stuck damper or drifted outdoor air sensor throws away hundreds of free-cooling hours a year, silently. A twenty-minute verification procedure.
Network layer
Did the value arrive — and is it the value that was sent?
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How to Connect to Any Manufacturer’s Controller
Nine manufacturers, one table: the exact port, cable, software and gotcha for each — so you pack the right thing before you drive there.
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MS/TP Max Master and Max Info Frames: The Two Settings That Decide Who TalksNew
How MS/TP token passing and Poll For Master really work, why a Max Master set too low silently skips devices, what too high costs, and how to set Max Info Frames for routers and supervisory ports.
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MS/TP Wiring: Termination, Biasing and the Meter Checks That Find Most Trunk FaultsNew
The four meter checks that find most BACnet MS/TP trunk faults: powered-down resistance, idle DC voltage, common-mode voltage and polarity, plus spurs, shield grounding and loose landings.
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BBMDs and Foreign Devices, Explained for the Tech Who Has to Make Discovery WorkNew
Why BACnet/IP Who-Is doesn't cross IP routers, how BBMDs and broadcast distribution tables fix it, how foreign device registration works, and the common BBMD failures that break discovery.
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Device Instance vs MAC Address vs Network Number: Three Addresses, Three Different JobsNew
BACnet gives every device three addresses. Which must be unique where, what breaks when each one is duplicated, how routers use network numbers, and how to check a site before it bites.
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Ping Works, BACnet Doesn't: A Layer-by-Layer ChecklistNew
A controller answers ping but not BACnet. Why ICMP proves less than you think, and a layer-by-layer checklist: firewalls, UDP 47808, wrong port, subnets and BBMDs, network numbers, your laptop's NIC binding and port conflicts, and NAT.
Troubleshooting method
When the screen, the meter and the equipment disagree: how to find out which one is lying.
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Why “Offline” Isn’t Always OfflineNew
A front-end offline status is a conclusion, not a measurement. How to tell a dead controller from a timeout, an expired COV subscription, an overloaded supervisor or a wrong binding, and prove which one you have.
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The Command Is On, the Equipment Isn’t: Tracing a Command That Produces No OutputNew
How to trace a BAS command that produces no output: priority arrays and stale overrides, HOA switches, relays, safety strings, VFD modes and proof, with a meter reading at each link.
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Intermittent Problems: How to Catch a Fault That Won’t Happen While You’re WatchingNew
A field method for intermittent BAS faults: define it with timestamps, trend before you touch, correlate with time, weather and other equipment, leave a trap, and prove it on demand.
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Interlocks and Enables: Why the Equipment Won’t Run When Everything Says It ShouldNew
Why BAS equipment won’t run when commanded: hardwired safeties versus software interlocks, enable chains, lockouts, minimum off timers and latches, and how to walk the chain in order.
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Everything Looks Normal, but the Equipment Isn’t WorkingNew
When every BAS point looks normal and the building is wrong: sensor location, plausible misconfiguration, actuators that move without the damper, mechanical failures the controls can’t see, and the go-look rule.
Logic layer
Is the program deciding what you think it’s deciding?
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Hunting Valves and Dampers: PID Without the Math
A loop that never settles wears out actuators and destabilises everything downstream. What each tuning term actually does, in field terms.
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Reading a Sequence of Operations — and Spotting What It Doesn’t Say
Sequences describe the happy path in detail and go quiet exactly where failures happen. How to read one critically and verify the logic actually matches.
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Simultaneous Heating and Cooling: The Fault That Never Alarms
The single largest energy waste in most VAV buildings, and it never triggers an alarm because everyone stays comfortable. Here’s the trend recipe that finds it in an afternoon.
Cybersecurity
BACnet/SC, segmentation, remote access, accounts and what to do on the bad day. The cybersecurity section →
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BACnet/SC: The Conversation IT Is About to Force
What BACnet Secure Connect changes for building automation technicians: hubs, certificates, network architecture, and how it differs from BACnet/IP in the field.
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How BACnet/SC Actually Works: Hubs, Nodes, Certificates and the Connection SequenceNew
A field-level walk through BACnet Secure Connect: hub function and hub connector, primary and failover hubs, VMAC and UUID, the TLS 1.3 and WebSocket connection sequence, BVLC-SC messages, and how broadcasts and legacy devices get through.
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BACnet/SC Certificates for Controls Techs: CSRs, CAs, Expiry and RenewalNew
Key pairs, certificate signing requests, the site CA, operational and issuer certificates, who should run the CA, renewal planning, clock problems and what an expired or wrong-CA certificate looks like on a BACnet/SC site.
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Troubleshooting BACnet/SC When You Can't Read the TrafficNew
How to diagnose BACnet Secure Connect faults when the traffic is encrypted: the connection-pattern method in Wireshark, a symptom table from DNS failures to duplicate VMACs, device SC status, TLS inspection and useful display filters.
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Planning a BACnet/SC Rollout Without Breaking the BuildingNew
A practical plan for introducing BACnet Secure Connect on a live site: hub and failover placement, the firewall rules to request, DNS or IP in hub URIs, the certificate plan, phased migration through routers, commissioning checks and handover documentation.
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Segmentation and Firewall Rules: How to Talk to IT About the BAS NetworkNew
Why a flat network is the biggest risk to a building automation system, what traffic the BAS actually needs, and how to write a firewall rule request IT can approve.
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Remote Access to a BAS Without Opening the Building to the InternetNew
Why port forwarding to a supervisor or controller is the worst option, and how VPN with MFA, approved remote-access gateways, jump hosts and time-limited vendor access compare.
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Default Passwords, Shared Logins and the Accounts Nobody OwnsNew
Default credentials on controllers, supervisors and routers, shared admin logins, named accounts and roles, least privilege, removing ex-staff and old contractors, and a clean handover.
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Hardening a BAS Supervisor and Its Controllers: A Field ChecklistNew
A field checklist for hardening a BAS supervisor and its controllers: patching, end-of-life operating systems, unused services, HTTPS, tested backups with an offline copy, removable media, allow-listing, time sync and logging.
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Why BACnet/IP and Modbus Have No Security (and What You Do About It)New
Why BACnet/IP and Modbus TCP carry no authentication or encryption, what that means for anyone who can reach UDP 47808 or TCP 502, and the compensating controls that protect them.
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IEC 62443 and NIST in Plain Language for BAS TechsNew
What the main IEC 62443 parts, NIST SP 800-82 Rev. 3 and the NIST Cybersecurity Framework 2.0 are for, what zones, conduits and security levels mean, and how to answer a spec that asks for 62443 compliance honestly.
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Think the BAS Has Been Compromised? The First HourNew
The signs a building automation system may have been compromised, and what a field technician should do in the first hour: keep equipment safe, isolate at the boundary, preserve evidence, call the owner's IT contact and hold off on restoring.
Graphics, trends and alarms
Is the screen telling you the truth — and would you notice if it wasn’t?
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Your Graphic Should Tell You When It Doesn’t Know
A broken binding shows stale data forever with no error. How to design graphics that fail visibly instead of lying quietly.
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Your Trend Interval Is Hiding the Problem
A valve that looks stable at 15-minute intervals can be hunting continuously at one minute. How to pick an interval based on what you’re actually chasing.
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Why Nobody Reads Your Alarms
Systems routinely carry thousands of unacknowledged alarms. Operators silence everything, then miss the one that mattered. The practical fixes.
New articles by email
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Got a correction or a field story that contradicts one of these? I’d rather be told: svdraper@basfieldreference.com