EPA 608 Type III Master 2025: Low Pressure Systems

Type III certification focuses on **low-pressure appliances**, most commonly represented by large centrifugal chillers. These systems are unique because they operate at pressures below atmospheric pressure (in a vacuum).

Operating in a Vacuum

Because low-pressure systems like those using **R-123** operate in a vacuum, any leak in the system allows air and moisture to be sucked *into* the unit rather than refrigerant leaking out. This creates the need for specialized maintenance equipment.

The Role of the Purge Unit

The **Purge Unit** is a secondary system designed to remove non-condensables (air) and moisture from the top of the condenser. A high frequency of purge unit operation is the primary indicator of a leak in a Type III system.

Specialized Safety: The Rupture Disk

Instead of a standard spring-loaded relief valve, low-pressure chillers use a **Rupture Disk**. This disk is designed to burst at **15 psig** to protect the evaporator from over-pressurization during service or ambient temperature spikes.

Leak Testing Requirements

To leak test a low-pressure system, you must increase the pressure by heating the system (using hot water) or using specialized heating blankets. **Never exceed 10 psig** during this process to avoid blowing the rupture disk.