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Mixing Nest Protects with an existing wired interconnected smoke alarm array

Community Member

I have a vacation home that was built eight years ago, which has an interconnected wired smoke alarm system, and I'm considering replacing the two CO/smoke detectors with Nest Protects this winter, and the remainder in two years when they hit ten years old. What issues do I have to be aware of if I do this?

Will the smoke detectors (they're First Alert brand) be able to interconnect with the Nests properly, i.e. will the Nests be able to send and receive signals to the other alarms? Or would I have to leave the Nests disconnected (i.e. the interconnect wire capped) until I replace the remaining alarms in two years?

My primary home also has an interconnected wired system, installed seven years ago when I bought the house, this time with Kidde brand units. This house has three CO units and four smoke units, and I'll want to do the same replacement schedule with those units, so I'd like to know if Kidde plays well with Nest, too.


Platinum Product Expert
Platinum Product Expert

If you mean can you have a standalone conventional detector or detectors and install Nest Protect separately, then yes. However, if one of your Nest Protects sounds an alarm, your conventional detector will not sound unless it also detects the issue and vice versa if the conventional detector senses something that Nest Protect hasn't yet.

If you mean interconnect Nest Protect with a conventional detector then no and that's pretty standard. Each manufacturer uses proprietary detection algorithms meaning there’s no industry standard. What that means in practice is if alarms from different manufacturers were to be connected together, they may not warn you properly in an emergency. The NFPA actually prohibits the connection of alarms from different manufacturers without special testing. As far as I'm aware, there's no manufacturer that sells a detector that is designed to interconnect with a device from a different manufacturer and some manufacturer's even state in their documentation not to try to connect their device to that of a different manufacturer.