Accurex’s XDGX make-up air units use packaged direct expansion (PDX) technology to cool air using refrigerant. They are also direct gas-fired, meaning that they provide 100 percent outdoor air heated over a gas flame. The HVAC industry is moving away from refrigerants classified as A1, meaning that they cannot spread flame but have high global warming potential (GWP), and is transitioning to A2L refrigerants, which have a low GWP but also some potential for flammability. Accurex is proud to feature the A2L refrigerant R-454B in its direct gas-fired make-up air units, and has just passed a third-party safety inspection to ensure that its direct gas-fired technology meets safety standards without compromising high standards of air quality and energy efficiency.

Adapting to Deliver Advantages to Commercial Kitchens

Direct gas-fired make-up air units can heat, cool, and ventilate busy commercial kitchens. They are an ideal solution when only sensible cooling (the cooling of the air temperature) is needed, not latent cooling (the cooling of the air moisture, which isn’t felt). They have a smaller unit footprint than alternatives that provide dehumidification, as well as lower operating and energy costs. Additionally, the direct gas-fired technology eliminates the need for a heat exchanger, an add-on that increases upfront and maintenance costs and can lead to issues such as air leakage and frost buildup.

Some manufacturers have declined to update their direct gas-fired make-up air offerings to comply with the requirement from the U.S. Environmental Protection Agency (EPA) to transition to environmentally friendlier A2L refrigerants. But Accurex has redesigned its units to safely integrate R-454B refrigerant and continue delivering the benefits of direct gas-fired, 100 percent outdoor air ventilation, cooling, and heating.

Acing the Test

Third-party tester Intertek inspected Accurex’s XDGX unit for compliance with the fourth edition of UL standard 60335-2-40, which governs refrigerant detection and leak mitigation. After multiple days of testing, the unit fully passed, meeting the following requirements:

• Published power consumption is accurately rated
• Lower temperature rise in each component than the minimum set by standard
• Lowest possible risk of refrigerant entering a potential ignition source through an opening
• Leak detection sensors and mitigation sequence fully operational and effective

Microchannel Coil Technology for Superior Performance

In addition to advanced safety features, the XDGX and other make-up air units now incorporate microchannel coil technology in their condenser coils. Figure 1 below shows the unique design of microchannel coils, which have wavelike fins. Refrigerant runs from their headers through tiny vein-like channels in their parallel flow tubes.

Figure 1

Originally developed for the automotive industry, microchannel coils are on average 40 percent smaller than standard tube and fin coils and use 50 percent less refrigerant. Their all-aluminum design also increases surface contact between the refrigerant and the metal, leading to improved heat transfer that makes them 40 percent more efficient than standard coils.

Have more questions about direct gas-fired make-up air with PDX technology? Your local Accurex expert has the time and knowledge to talk about the needs of your project.