Tech Tips: Why You Need a Refrigerant Detection System for R-454B and R-32

As the HVAC industry transitions toward low-GWP refrigerants like R-454B and R-32, safety measures must evolve to meet both performance and code requirements. One key component in these systems is the Refrigerant Detection System (RDS) — essential not just for compliance, but for protecting people and property.

R-32 and R-454B Refrigerant Cylinders

Why Is an RDS Necessary for R-454B and R-32?

1. Low Flammability Risk (A2L Classification)

Both R-454B and R-32 are classified as A2L refrigerants, meaning:

  • A = Lower toxicity
  • 2L = Mildly flammable

While they don't ignite as easily as hydrocarbons, these refrigerants can become hazardous in confined or poorly ventilated spaces.

2. Leak Hazard and LFL (Lower Flammability Limit)

In a sealed environment, a refrigerant leak may allow gas to accumulate. If concentrations rise above the LFL, even a small ignition source can cause a fire.
An RDS helps prevent this by:

  • Continuously monitoring gas levels
  • Triggering alarms or initiating ventilation before dangerous concentrations are reached

3. Code Compliance

Refrigerant detection isn't just good practice — it's required.
Installation of RDS is mandated by:

  • ASHRAE 15
  • UL 60335-2-40
  • ISO 5149

These codes demand gas detection systems in A2L refrigerant installations to ensure life safety and automated shutdowns if LFL thresholds are approached.

4. Safety for Occupants and Technicians

An RDS protects:

  • Building occupants from flammable gas exposure
  • Technicians from health risks and fire hazards during maintenance

RDS Solutions at Hercules Industries

Hercules Industries offers two RDS kit options tailored for compatibility with A2L systems:

1. ADP Brand RDS

Hercules Part Code: 27A05ADP

  • Pre-wired sensor and control board
  • Plug-and-play integration with ADP coils
  • Compatible with R-32 and R-454B
  • Basic alarm and system shutdown functions
  • Ideal for simplified installations

2. Allied Air Brand RDS

Hercules Part Code: 27A06

  • Designed for Armstrong, Concord, and other Allied Air systems
  • Includes advanced control module, sensor, and pre-configured harness
  • Integrates with furnace or air handler controls
  • UL-listed for full code compliance
  • Factory diagnostics and more customization options

Five Rules for RDS Installation

Follow these guidelines to ensure proper RDS application:

  1. -01 Multi-refrigerant Coil + Non-RDS Furnace
    → You need both an RDS control and sensor
  2. -71 R-454B Coil + Non-RDS Furnace
    → Only the RDS control is needed (sensor is factory-installed)
  3. -01 Multi-refrigerant Air Handler
    → Both control and sensor are required
  4. -01 Coil + 2025 RDS-integrated Furnace
    → Only the RDS sensor is needed (control is factory-installed)
  5. -71 R-454B Coil + 2025 RDS-integrated Furnace
    → No RDS kit needed — both components are pre-installed
RDS Decision Tree - Air Handler and Coil/Furnace Requirements

Installation Requirements at a Glance

  • RDS is required for A2L refrigerant charges > 4 lbs
  • Coil manufacturers provide the RDS
  • RDS is included by all major HVAC brands
  • Compatible with A3 thermostats for system alerts
  • Uses secure screw terminals (no wire nuts)
  • Backwards-compatible for field installation
  • Protection Pro™ is factory-installed on all low-GWP models

Conclusion

When working with R-454B or R-32 systems, an RDS isn't just a recommendation — it's a requirement for safety, code compliance, and peace of mind.

Hercules Industries offers both ADP and Allied Air kits to meet your installation needs. Choose the right system based on your equipment, installation scenario, and desired feature set.

For assistance selecting the correct RDS kit, contact your local Hercules representative — or refer to our RDS Decision Tree.