Was wiring a panel today and found out UL 681 has a hidden clause about cellular backup monitoring time

I was reading through the new standard while waiting on a customer and saw that UL 681 now requires cellular backup to report a trouble signal within 4 minutes if the primary path goes down. That actually shocked me because I've been installing dialer backups for years that only ping every 24 hours for a check-in. Found this in the fine print on page 47 of the 2023 revision. Has anyone else's AHJ actually enforced this yet or is it still flying under the radar?

2 comments

2 Comments

noahbaker1mo ago

Hold up I think you might be reading that wrong. I pulled up my copy of UL 681 from the 2023 revision and page 47 talks about dual path requirements for communicators not cellular backup specifically. The 4 minute thing is for the primary path to report a trouble on the secondary which is a totally different deal than your dialer check in. My old school dialer checks in every 24 hours for a heartbeat and passes inspection every time.

the_thomas1mo ago

Yeah I read something similar in a trade magazine a few months back. It was talking about how UL 681 gets misinterpreted all the time, especially the part about backup paths and timing. The article pointed out that a lot of inspectors and even some installers mix up the 4 minute window for trouble reporting with the actual dialer check in cycle. It made me double check my own work because I was guilty of that too. But you're 100% right, the 24 hour heartbeat on a standard dialer is still totally valid and passes fine, at least around here.