Revisions to UL 541, the Standard for Refrigerated Vending Machines

By Barry Karnes, principal engineer, refrigeration products 

UL announces the publication of significant updates to the Ninth Edition of UL 541, the Standard for Safety for Refrigerated Vending Machines. This Standard addresses the electrical shock, fire and casualty hazards of refrigerated vending machines.

These updates were published within UL 541 on Nov. 19, 2020, and involve a revision to Paragraph SA6.2.3 in Supplement SA, “Requirements for Refrigerated Vending Machines Employing a Flammable Refrigerant in the Refrigerating System.”

Background

In the late 1980’s, environmental concerns drove the need for a global agreement called the Montreal Protocol. This agreement provided protection for the earth’s stratospheric ozone layer by phasing out the production of ozone-depleting substances. A number of these substances included chemical refrigerants. By 2010, demand to greatly reduce these chemicals gained momentum and low Global Warming Potential (GWP) refrigerants started being considered as acceptable alternatives to the chemical refrigerants that had been used for decades. However, many of these low-GWP refrigerants had increased flammability.

A flammable refrigerant is defined as having a flammability classification of A2L, A2 or A3 as specified in the Standard for Designation and Safety Classification of Refrigerants, ANSI/ASHRAE 34. Although flammable refrigerants had been used in certain applications for many years, the growing demand for low-GWP refrigerants created the need for their more widespread use.  

In 2011, based on the growing demand for low-GWP refrigerants, revisions to UL 541, Eighth Edition, included the addition of Supplement SA, “Requirements for Refrigerated Vending Machines Employing a Flammable Refrigerant in the Refrigerating System.” Supplement SA aligned with similar supplements in other UL Standards, such as UL 471, the Standard for Commercial Refrigerators and Freezers. At the time, Paragraph SA6.2.3 in UL 541 required the installation and operating instructions of a refrigerated vending machine having a flammable refrigerant to specify that component parts be replaced with like components and that servicing be done by factory-authorized service personnel.

ANSI/ASHRAE 15, the Standard for Refrigeration Systems, is typically used by code authorities for the field installation of refrigeration equipment, including vending machines. However, requirements in ANSI/ASHRAE 15 did not allow refrigerating systems — which could include refrigerated vending machines — to be installed in a public corridor or lobby if the systems used flammable refrigerants. The rationale for this requirement related to the need to allow building occupants to have free and unhindered access to the exits in the event of a fire within the building. It seemed reasonable at that time to assume that vending machines located in a public corridor, lobby or similar area could vent flammable refrigerant during a fire, potentially restricting occupants from escaping the building and hindering fire service personnel from entering.

In 2013 and for consistency with ANSI/ASHRAE 15, an addition made to Paragraph SA6.2.3 required the installation and operating instructions to state that a vending machine having a flammable refrigerant could not to be intended for use in lobbies or locations of egress such as a hallway or a public corridor.

But some in the industry theorized that vending machines with relatively small charges of flammable refrigerants could be installed within lobbies, egress locations, hallways or public corridors without substantially impeding a building occupant from exiting the building during a fire. Based on this theory and in response to the ANSI/ASHRAE 15 and UL 541 requirements, research was conducted to confirm or refute the theory. The research demonstrated that for refrigerated vending machines located in a public corridor, lobby or similar area, limiting the flammable refrigerant charge amount to no more than three times the refrigerant lower flammable limit (LFL) as expressed in kilograms per cubic meter (kg/m³) would not substantially increase the risk to an occupant needing to escape from a building during a fire. In English units, the flammable refrigerant charge amount would be limited to no more than 106 times the LFL expressed in pounds per cubic foot.

The following provides an example calculation of the flammable refrigerant charge size. If a refrigerated vending machine uses R-290, i.e., propane, which has an LFL of 0.038 kg/m³ or 0.00237 lb/ft³, as the flammable refrigerant, the vending machine could be installed in a public corridor or lobby as long as the refrigerant charge size within the refrigeration system, as marked on the vending machine nameplate, does not exceed 3 x 0.038 = 0.114 kg or 114 grams. In “English” units, this would be 106 x 0.00237 lb = 0.25 lb or 4 oz. If the vending machine refrigerant charge size of R-290 were to exceed 114 grams (4 oz), the vending machine would not be suitable for installation in a public corridor or lobby.

Requirement updates

Based on the research in 2020, requirements in ANSI/ASHRAE 15 were updated to allow the use of refrigerating systems — including refrigerated vending machines — to be located within a public corridor or lobby if such systems limit the amount of flammable refrigerant.

Also in 2020, revisions made to UL 541 aligned Paragraph SA6.2.3 with the requirements in ANSI/ASHRAE 15. Paragraph SA6.2.3 still requires the installation and operating instructions of a refrigerated vending machine having a flammable refrigerant to specify that component parts be replaced with like components and that servicing be done by factory authorized service personnel. But it now also requires the installation and operating instructions to state that a vending machine is not intended for use in lobbies or locations of egress, such as a hallway or public corridor if the flammable refrigerant charge size exceeds three times the LFL (expressed in kg/m³) or 106 times the LFL (expressed in lb/ft³). In addition, Paragraph SA6.2.3 also now requires that the LFL of the flammable refrigerant marked on the vending machine nameplate be specified in the installation and operating instructions. These new requirements in Paragraph SA6.2.3 enable an installer to perform the calculation (as shown in the example above). The installer can then determine whether a vending machine located within lobbies or locations of egress can be installed in accordance with ANSI/ASHRAE 15.

These new requirements to UL 541 became effective on the publication date of Nov. 19, 2020.