HVAC Plan Symbols

A comprehensive guide to HVAC symbols commonly used in mechanical drawings. These symbols represent air distribution devices, dampers, piping systems, and control sensors.

Supply and Return Airflow

4-Way Ceiling Supply Diffuser

Ceiling diffuser for supply air distribution in four directions

3-Way Ceiling Supply Diffuser

Ceiling diffuser directing supply air in three directions

2-Way Ceiling Supply Diffuser

Ceiling diffuser for bidirectional supply air flow

1-Way Ceiling Supply Diffuser

Ceiling diffuser directing supply air in a single direction

Return Grille (Exhaust)

Opening for air return or exhaust removal from space

Direction of Supply Air

Arrow indicator showing supply air flow direction in ductwork

Direction of Return Air

Arrow indicator showing return air flow direction in ductwork

Door Undercut Size

Notation indicating undercut dimensions for air transfer through doors

Door Louver with Clear Area

Door opening with louver and specified clear area for air transfer

HVAC Dampers

Volume Damper

Device for regulating and balancing air volume in ducts

Fire Damper

Safety damper that closes automatically to prevent fire spread through ducts

Smoke Damper

Damper designed to control smoke movement in ductwork during fire events

Combination Smoke and Fire Damper

Dual-purpose damper providing both fire and smoke control in ductwork

Back-draft Damper

Damper that prevents reverse air flow in exhaust ducts

HVAC Piping

Chilled Water Supply

Pipe line carrying chilled water from chiller to cooling equipment

Chilled Water Return

Pipe line returning warmed water from cooling equipment to chiller

Hot Water Supply

Pipe line carrying heated water from boiler to heating equipment

Hot Water Return

Pipe line returning cooled water from heating equipment to boiler

Vent Pipe

Pipe line for venting air or gases from HVAC systems

Drain Pipe

Pipe line for condensation drainage from HVAC equipment

Make-Up Water Pipe

Pipe line supplying fresh water to replenish system losses

HVAC Sensors

Thermostat

Temperature sensing and control device for HVAC zone control

Humidity Sensor

Device for measuring and monitoring moisture levels in air