BAS Drawing Standards and Best Practices

BAS Drawing Standards and Best Practices

Well-designed BAS drawings reduce installation errors, speed commissioning, and make long-term maintenance easier. This guide covers essential standards for control system documentation.

Drawing Types and Purposes

Sequence of Operations (SOO)

The written description of how the system should operate:

• Control narratives for each piece of equipment
• Setpoints and parameters with ranges and defaults
• Alarm conditions and required responses
• Mode descriptions (occupied, unoccupied, morning warmup, etc.)

Points List

Complete I/O schedule including:

• Point name/address
• Point type (AI, AO, BI, BO, etc.)
• Engineering units and range
• Sensor/actuator model
• Associated equipment
• Network segment (for BACnet MS/TP)

Control Diagrams

Schematic showing control relationships:

• Controller locations
• Network topology
• I/O connections
• Integration points

Wiring Diagrams

Physical connection details:

• Terminal assignments
• Wire colors and gauges
• Conduit routing
• Power supply connections

Point Naming Conventions

Consistent naming is critical. A good convention includes:

[Building]-[System]-[Equipment]-[Point Type]-[Description]

Examples:

• BLD1-AHU-01-SAT (Building 1, AHU 01, Supply Air Temp)
• BLD1-VAV-201-DMP (Building 1, VAV Box 201, Damper Position)
• BLD1-CHW-PMP1-SS (Building 1, Chilled Water Pump 1, Start/Stop)

Best Practices:

• Maximum 20-24 characters for BACnet compatibility
• No spaces (use hyphens or underscores)
• Abbreviations should be documented in a legend
• Be consistent across all projects

Common Abbreviations

Abbreviation	Meaning
SAT	Supply Air Temperature
RAT	Return Air Temperature
MAT	Mixed Air Temperature
OAT	Outside Air Temperature
DAT	Discharge Air Temperature
SP	Setpoint
DMP	Damper
VLV	Valve
SS	Start/Stop
STS	Status
ALM	Alarm
CMD	Command

Wiring Diagram Standards

General Requirements

• Show all wire colors and gauge sizes
• Label terminal block numbers
• Indicate shielded cables and grounding
• Show power supply locations and voltage

Analog Inputs (AI)

• 4-20mA: Show loop power source (2-wire vs 4-wire)
• 0-10V: Note signal ground requirements
• Thermistors: Specify type (10K Type II, etc.)
• RTDs: Show 2/3/4-wire configuration

Analog Outputs (AO)

• Indicate voltage or current output type
• Show end-of-line resistors if required
• Note floating point actuator connections (24V, COM, direction)

Digital Points

• Show interposing relays for high-voltage loads
• Indicate normally open vs normally closed contacts
• Label supervised vs unsupervised circuits

Network Diagrams

BACnet MS/TP Segments

• Maximum 64 devices per segment
• Show trunk and drop lengths
• Indicate termination resistor locations
• Label MAC addresses
• Note baud rate (typically 76800)

BACnet/IP Networks

• Show IP addressing scheme
• Indicate BBMD locations
• Document VLANs and subnets
• Show router/switch locations

As-Built Documentation

Every project should include updated as-builts with:

1. Verified I/O assignments - What was actually installed
2. Final setpoints - Values after commissioning
3. Network addressing - Actual device IDs and IP addresses
4. Software backup - Program files and database exports
5. Graphics screenshots - Current operator interface

File Naming and Organization

```mermaid
graph TD
    ROOT["ProjectName/"]
    SPEC["01_Specifications/"]
    DRAW["02_Drawings/"]
    SUB["03_Submittals/"]
    PROG["04_Programming/"]
    AS["05_AsBuilts/"]
    
    ROOT --> SPEC
    ROOT --> DRAW
    ROOT --> SUB
    ROOT --> PROG
    ROOT --> AS
    
    SPEC --> S1["Section_230900_BAS.pdf"]
    DRAW --> D1["M-601_ControlDiagram_AHU1.dwg"]
    DRAW --> D2["M-602_ControlDiagram_VAVs.dwg"]
    DRAW --> D3["M-603_NetworkRiser.dwg"]
    SUB --> SU1["PointsList_Rev2.xlsx"]
    SUB --> SU2["SequenceOfOperations_Rev3.docx"]
    PROG --> P1["Controller Backups"]
    AS --> A1["Final Documentation"]

## CAD/Drafting Standards

- Use manufacturer-provided CAD symbols when available
- Layer naming: M-CTRL-EQUIP, M-CTRL-WIRE, M-CTRL-TEXT
- Include revision block with date and changes
- PDF exports should be searchable (not flattened)

## Coordination with Other Trades

BAS drawings should cross-reference:
- **Mechanical** - Equipment schedules, airflow diagrams
- **Electrical** - Panel schedules, power availability
- **Fire Alarm** - Interface points, shutdown sequences
- **Plumbing** - Domestic hot water, medical gas (if applicable)

## Quality Checklist

Before issuing drawings, verify:
- [ ] All points from SOO appear on points list
- [ ] Point names are consistent across all documents
- [ ] Wire gauges match signal types and distances
- [ ] Network segment device counts are within limits
- [ ] Terminal assignments dont conflict
- [ ] Sequences match specification requirements