The relay coil voltage mismatch that cost me a callback in Phoenix

Last month I wired up a new commercial panel and used 12V relays for a door strike circuit that was actually running on 24V. Everything tested fine on the bench, but once the system went live, the relays were buzzing and dropping out after about 20 minutes. I traced it to the coil rating, swapped in 24V relays, and it's been solid since. Cost me a 90 minute drive back to the site and a grumpy customer who said "I thought you guys checked this stuff." Now I always verify the circuit voltage before grabbing a relay off the shelf, even if it looks like a standard install. Has anyone else had a similar hiccup with relay coils and how do you catch it before leaving the job?

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henryf5318d ago

That Phoenix sun does a number on patience, trust me. Saw a similar thing years back where a guy used 48V coil relays on a 24V fire alarm loop, they'd test fine cold but drop out when the panel warmed up after lunch. The real kicker is bench testing with a variable supply, set it at the actual site voltage and let it run for an hour before you button things up. Also, those little sticker labels on the relay body are easy to misread when you're in a hurry, so I started double checking with a multimeter right at the coil terminals, not just trusting the box. Your callback story is the kind of thing that makes guys swear off cheap parts, but it's really about the 10 extra minutes of verification.

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