autonut843 wrote:
Once again, I should have Googled first and I would have found my
answer. The Firex manual for one of their interconnected smoke
detectors says...


This smoke alarm should be installed in accordance with the NFPA's Standard 72 (National Fire Protection Association,
Batterymarch Park, Quincy, MA 02269) and any local codes that apply.

When interconnecting, use #18 AWG minimum solid or stranded wire. Maximum wire length between any two is 1,500
feet for #18 AWG or 4,000 feet for #14 AWG (20 OHMS loop resistance).

DO NOT connect to any other type or model of heat or smoke alarm. Connect smoke or heat alarms to a single AC
branch circuit. If local codes do not permit, be sure the neutral wire is common to both phases.



So, I think that explains why I haven't found a commercially available
relay module to do what I was looking for.

Does anybody have a good idea for a passive way to monitor if the smoke
detector is going off? I guess I'm thinking something like a sound
pressure level sensor or something like that. Obviously it wouldn't be
foolproof. Any other ideas?


You can buy smoke detectors that provide dry contact closure on
activation. They are available in interconnected models but they are
not cheap. If you want smoke detectors that can be reliably monitored
from a remote location you should install a listed automatic fire
detection system. Since that is work I have done as an electrician I
can assure you that it would be both cheaper and more reliable then
anything you would jury rig. Systems are available that are wireless.
Those systems meet the requirements for interconnected detectors.
--
Tom Horne

Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.