What Are The Main Components of An RTU?

In the HVAC context, where RTU stands for Rooftop Unit, the main components vary depending on whether it is a heating-only, cooling-only, or combination heating/cooling unit (common in commercial systems). Below is a breakdown of the key components found in a typical packaged RTU (heating + cooling system):

Core Components of an RTU (Rooftop Unit)

1. Heating Components

Gas Furnace or Boiler (for warm air or hot water systems):

Uses natural gas or propane to generate heat.

Common in colder climates for winter heating.

Electric Heaters:

Use electrical resistance to produce heat (simpler but less energy-efficient than gas systems).

Heat Exchanger:

Transfers heat from the fuel source to the air without mixing combustion gases with the conditioned air.

2. Cooling Components

Refrigeration Cycle Components:

Compressor: Drives the refrigeration cycle by compressing refrigerant gas.

Condenser Coil: Releases heat from the refrigerant to the outdoor air.

Evaporator Coil: Absorbs heat from the indoor air (located within the RTU’s air handling unit).

Expansion Valve: Reduces the pressure of the refrigerant, allowing it to absorb heat in the evaporator.

Chiller (in larger systems):

Produces chilled water for cooling, often paired with an air handler in the RTU.

3. Air Handling Unit (AHU)

Blower/Fan:

Distributes conditioned air through the building’s ductwork.

May include a supply fan (pushes air into the building) and an exhaust fan (removes stale air).

Air Filters:

Clean incoming air to remove dust, pollen, and other contaminants (replaceable or washable).

Dampers:

Control the flow of outdoor air (for ventilation) and recirculated indoor air.

4. Controls and Sensors

Thermostat or Digital Controller:

Monitors indoor temperature and sends signals to adjust heating/cooling output.

Humidity Sensors:

Measure moisture levels and trigger humidifiers or dehumidifiers (in systems with humidity control).

Safety Switches:

Shut down the unit if issues like overheating, gas leaks, or fan failure are detected.

Variable Frequency Drive (VFD):

Adjusts fan speed to optimize energy efficiency (common in modern RTUs).

5. Ventilation System

Outdoor Air Intake:

Brings in fresh outdoor air to meet ventilation codes (required for indoor air quality).

Exhaust Air Outlet:

Expels stale indoor air to the outside.

6. Condensate Management

Condensate Pan and Drain:

Collects and removes moisture produced by the cooling process (e.g., from the evaporator coil).

Condensate Pump (if needed):

Pumps condensate to a drain if the unit’s elevation makes gravity drainage impractical.

7. Structural and Protective Components

Weatherproof Enclosure:

Shelters internal components from rain, snow, and UV rays.

Sound Attenuation Features:

Reduces noise from fans and compressors (critical for rooftop installations near occupied areas).

Mounting Pads or Vibration Isolators:

Minimize vibration transfer to the building structure.