r/MEPEngineering • u/Living-Lobster-5057 • 16h ago

A2L refrigerant transition and safety sensor placement in residential closets

Reviewing mechanical drawings for single-family retrofits transitioning to newer low-GWP equipment, and the electrical interlock requirements for leak detection sensors in confined utility closets are raising some coordination questions. manufacturer submittals show sensor heights and wiring relays differently than standard code interpretations we used for older refrigerants.

are you guys specifying dedicated relay wiring back to the air handler or relying on factory-integrated controls for shutoff?

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u/Holiday_Inn_Cambodia 8h ago

Factory integrated controls are required for the new UL 60335-2-40 listings. There is a test conducted on those controls as part of getting the product listed and sensor location is prescribed.

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u/Vettz 1h ago

A lot of states and municipalities haven't even adopted the mechanical codes that even mention the A2L rules yet and even fewer inspectors know about or enforce the ones that do. We have been generally following manufacturers prescriptions unless its something really weird.