CO detection driving a solenoid valve
I have a design challenge that perhaps some of you can help me with. I've got 4 CO detectors, connected into the FA system as Supervisory Signals. And if any one of these CO detectors goes off, I need to have a solenoid valve shut the gas off to the hoods in this area; this is a commercial kitchen.
I wanted to have the Fire Alarm control Panel send that signal but am told that the Honeywell panel is not listed for control.
Gameplan B is to operate the solenoid off an aux contact on the CO detectors. Now here's the thing, if I use N.O. aux contacts on all 4 CO detectors, wire them in parallel and then in series with a 24V source and the 24V solenoid, that works except that the system is not fail safe. i.e. if the power supply fails and/or there is an open circuit, then no one would know of the problem.
I could wire N.C. aux contacts in series but then the solenoid valve would be constantly energized and that can't be good. So what is the best approach for a fail safe system?
Mike Shields, PE