P&ID extraction for building automation.
In building automation the "P&ID" is rarely a classic process diagram. It arrives as a set of mechanical control schematics, one per air handler, chiller plant, boiler plant, or VAV riser, usually paired with a points list table and a written sequence-of-operation narrative. These come from the controls contractor or MEP consultant during design-build or a controls retrofit, often as vendor-formatted sheets that mix ISA-style bubbles with equipment-relative sensor callouts and no loop numbers at all. The engineer's job is to turn that pile of per-equipment sheets into one coherent BMS points register that the DDC integrator can actually build against.
What building automation drawings carry.
- Points are typed as AI/AO/BI/BO (analog/binary input/output), the building-automation cousin of the process AI/AO/DI/DO. The type maps to a BACnet object (Analog Input, Binary Output and so on) with an instance number, engineering units and often a change-of-value threshold, so the points list carries protocol metadata a process I/O list never would.
- Tagging is equipment-relative, not plant-relative. A sensor is named by the unit it serves (supply air temperature on AHU-1) rather than a hyphenated ISA loop number, and many controls sheets carry no loop numbering at all. Extraction has to preserve the equipment prefix as the key.
- The sequence of operation drives which points must exist. ASHRAE Guideline 36 sequences (economizer high-limit lockout, supply-air-temperature reset, trim-and-respond static pressure and duct-temperature resets) each imply a specific set of sensed and commanded points that the schedule must account for.
- Network topology is on the drawing. Devices sit on an MS/TP RS-485 field trunk or on BACnet/IP, and the sheet shows which controller and trunk each device lands on. A points list without the trunk assignment is incomplete for the integrator.
- Control elements are dampers and two- or three-way valves. Actuators are modulating (0-10 V or 4-20 mA) or two-position, spring-return, and the normally-open versus normally-closed fail state is a safety-relevant attribute that belongs in the valve/damper schedule.
- Life-safety interlocks are frequently hardwired outside the DDC. Low-limit freezestats, duct smoke detectors, high-static cutouts and firestats are shown as hardwired trips, sometimes on a separate sheet from the DDC point list, and must be captured as interlocks rather than ordinary AI/BI points.
- Packaged equipment integrates over a gateway. Chillers, boilers, VFDs and packaged rooftop units arrive as vendor equipment exposed through a BACnet or Modbus RTU/TCP integration points list, so the register mixes hardwired field I/O with mapped integration objects and needs the protocol noted per point.
- European and Dutch practice uses its own conventions. A regeltechniek puntlijst (control points list) follows NEN/ISSO habits with letter-based device codes rather than ISA loop numbers; that market is served by the dedicated Dutch page at /solutions/regeltechniek-puntlijst and should be linked, not duplicated.
- VAV terminal boxes repeat one point pattern across dozens or hundreds of zones (damper command, zone temperature, reheat valve, airflow). The value is in extracting the repeated per-zone schedule cleanly, not in one hero diagram.
What the extraction delivers.
- BMS/BAS points list (I/O list) with signal class (AI/AO/BI/BO) and the BACnet object type per point
- Instrument/device schedule for field sensors, transmitters, actuators and switches
- Control valve and damper schedule (fail position, actuator signal, two-position vs modulating)
- Equipment list for AHUs, chillers, boilers, pumps, cooling towers and VAV terminals
- DDC controller and panel schedule with point count and network trunk per controller
- Field cable/wiring schedule between devices and their controllers
Instrument tags on a building automation drawing.
- TT-AHU-201Temperature transmitter reading supply air on air handler 201; equipment-relative naming rather than a loop number
- RH-AHU-201Relative humidity sensor on the same air handler, sharing the equipment prefix
- DPT-FLT-201Differential pressure transmitter measuring pressure drop across the filter bank of unit 201
- CV-HW-VAV-114Hot-water reheat control valve on VAV terminal box 114; modulating actuator
- DMP-OA-201Outside-air damper actuator on AHU-201; economizer control element with a defined fail position
- FS-AHU-201Freezestat / low-limit safety on AHU-201, typically a hardwired interlock rather than a DDC point
Regulatory context.
- ANSI/ASHRAE 135, published internationally as ISO 16484-5 (BACnet), defines the data communication protocol and object model for building automation and control networks, which is why the points list is expressed in BACnet object types.
- ASHRAE Guideline 36 gives standardized high-performance sequences of operation for HVAC systems (VAV air handlers, chilled-water and hot-water plants) and defines the points and functional tests those sequences require.
- ASHRAE Standard 90.1 sets the energy requirements that mandate specific controls such as air-side economizers, demand-controlled ventilation and supply-air reset, each of which adds required sensing and command points.
- ASHRAE Standard 62.1 governs ventilation for acceptable indoor air quality and drives outdoor-air and CO2 sensing points used in demand-controlled ventilation.
- NFPA 90A covers installation of air-conditioning and ventilating systems, including duct smoke detection and smoke-damper interlocks that appear as hardwired life-safety trips on the control drawings.
Which discipline reads it.
HVAC and MEP EngineersPrimary persona. Speak to turning a per-unit control drawing set plus points tables into one equipment list and BMS points register that the mechanical design intent can be checked against.Controls EngineersFocus on DDC point counts per controller, BACnet object typing, MS/TP versus BACnet/IP trunk assignment, and the points implied by Guideline 36 sequences.Commissioning and Startup EngineersThe points list is the backbone of functional testing. Frame around verifying that every sensed and commanded point in the sequence of operation exists and is addressable before Cx starts.Electrical EngineersAngle on the field cable and panel schedule: device-to-controller wiring, actuator signal type, and separating hardwired life-safety trips from network points.
Common questions
Our set is control schematics and a points list, not ISA P&IDs. Does that even fit?
That set is exactly the building-automation deliverable. The register you receive is a points/I-O list keyed to each piece of equipment, built from the control sheets and the accompanying schedule tables rather than from a process P&ID.
HVAC uses AI/AO/BI/BO and BACnet object types, not process AI/AO/DI/DO. Is that respected?
Yes. Each point carries its building-automation signal class and the BACnet object naming the integrator expects, so the list drops straight into a DDC build without re-typing.
Our sensors are named by the equipment they serve, with no loop numbers. Will that survive?
The equipment-relative tag is preserved as the key. A supply-air sensor on AHU-201 stays associated with AHU-201 rather than being forced into an ISA loop convention it never had.
A packaged chiller shows up as an integration points list over a Modbus or BACnet gateway. How is that handled?
Integration points are captured alongside hardwired field I/O, with the protocol noted per point, so the register reflects both the physical wiring and the mapped vendor objects.
We work in Dutch puntlijsten. Is that a separate thing?
Dutch regeltechniek points lists follow NEN/ISSO conventions and are covered on the dedicated page at /solutions/regeltechniek-puntlijst, which handles that tagging convention directly.
Are hardwired safeties like freezestats and duct smoke detectors captured separately from DDC points?
They are flagged as hardwired interlocks rather than mixed in as ordinary AI or BI points, so the life-safety trips stay distinct in the schedule.
Run it on your building automation drawings.
Upload a P&ID set and see the instruments, equipment, and lines it reads before committing to a plan.