To be clear, technicians can continue using traditional HFC systems while taking the time they need to get comfortable with the mildly flammable A2L refrigerants. With similar service procedures (same oil, piping, and brazing), minimal training is needed for a smooth transition. 

Right Selection 

For a mechanically controlled evaporator, the distributor nozzle selection is key, so do your homework. The technical bulletin is a critical reference needed to make the right nozzle section. For mechanically metered systems, the TXV must feed the correct volume of liquid through the distributor tubes. 

The good news is that a package of nozzles (including ones for the A2Ls, R-454A, R-454C, and R-455A) is shipped with each evaporator. Using the nozzle sizing table, the installation technician can then select the correct nozzle. As a reminder, add the nozzle retaining ring to secure the nozzle in the distributor as shown in Figure 1. After nozzle selection, the rest of the physical installation steps have not changed when applying the equipment with an A1 refrigerant. 

FIGURE 1: After selecting the correct nozzle, be sure to add the nozzle retaining ring to secure the nozzle in the distributor. (Courtesy of Heatcraft)

When applying the same evaporator using an A2L refrigerant, there are a few more considerations. For example, refrigerant leak mitigation methods must be employed, which means isolation and potentially ventilation of the conditioned space. Even mechanically controlled evaporators must be equipped with a refrigerant detection system (RDS). Kits can be ordered as a “shipped loose” option with all the components needed to install the sensor and isolation valve to comply with mitigation requirements. 

In addition to the mitigation components, the installation technician must mount the isolation valve on the liquid refrigerant line and suction line check valve outside the walk-in cooler or freezer, as close to the evaporator as possible. This will limit the amount of releasable charge that can enter the conditioned space. A sample piping layout of what an isolation arrangement could look like is shown in Figure 2. 

FIGURE 2: A sample piping layout of what an isolation arrangement could look like. (Courtesy of Heatcraft)

For electronically-controlled systems, the distributor, nozzle, and EEV are brazed together, requiring three nozzle configurations per A2L. Ordering the correct size unit with the A2L of choice ensures proper performance and desired temperature difference (TD). Remember, the EEV cannot compensate for mass flow alone. 

Heatcraft makes the selection process very straightforward. For example, there are specific preferred option packages that apply the A2L that Heatcraft has chosen to work with cold storage applications: 

• G0210: Standard base with RDS + intelliGen (R-455A); 

• G0211: Standard base with RDS + intelliGen (R-454C); and 

• G0212: Standard base with RDS + intelliGen (R-454A. 

For more information about mitigation requirements for A2L refrigerants, visit www.heatcraftrpd.com/resources/news/a2l-essentials-issue-3-mitigation-requirements.