On September 16, 2018 at 11:38, Nick-ISI said...
.... the doubling of resistor value may or may not work as you are effectively halving the change seen by the panel, in your example one leg going open circuit will not then show infinite resistance, but 2K instead of 1K. Depending on the panels sensitivity to resistance (voltage) change on the zone this may not be enough to trigger a fault condition. If it doesn’t register this fault then you have a circuit that will not trigger the panel when the detector is triggered as it has an open circuit leg, but the panel is still seeing an EOL on the other leg that is sufficient for it to think it’s all good.
The resistance the panel is looking for is very specific. And it absolutely will trip with a change of 1/2 or 2x resistance. Several alarm panels use to have diplexing on their zones, where you could use 2 different value resisters on different devices and create 2 zones on a 1 zone input. Not sure if any of them are still doing that these days.
One could do resisters at 3x the normal for 3 devices on a single zone. Good chance it would work but as you said, that maybe getting a little to close to the detection threshold for comfort. Even if you did test it and it seemed to work.
