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Can a WSD LV work as an override with a CM sensor and PP20?

Short answer: No.

Your PP20 power pack has three low voltage wires; red, which supplies power, black, which is your common, and white, which is a signal wire. This last wire is the key to the function of the PP20 relay; when the white wire receives a signal, it causes the relay inside the PP20 to close and provide power along the line voltage side of the wiring. You can see this in action, by shorting the red (power) low voltage wire to the white (signal) wire; as soon as they touch, the relay will close and your fixtures will turn on. When you separate the wires, removing the signal that the red is sending to the white, it opens the relay and turns off power to the fixtures.

 In the application described, you have two devices that are providing a signal; the first is a WSD LV, the second a CM PDT 10 (or equivalent). Both devices have the same set of wires as a PP20 – a red wire to receive power from the PP20, a black common, and a white wire that sends along a signal back to the PP20. When the device detects motion, its internal relay allows power from the red to pass through the white signal wire and back to the PP20, causing your line voltage relay to latch and provide power to our fixtures. If the PP20 receives a signal from *any* of the devices hooked to it, it is going to close that relay, and your fixtures are going to stay on.

 Now, let’s look at your devices a little more closely, specifically, the WSD LV. The WSD LV has a push button that allows you to override the “signal” aspect of its internal sensor. When you push the button, you can manually choose for the lights to be off, even though the sensor is sensing motion and would normally be sending an “on” signal. HOWEVER, that override is *only* applicable to the WSD’s internal relay – it has no means of communication with the installed CM PDT 10 to tell it not to send a signal as well. Thus, even though the WSD LV is no longer sending a signal, the CM PDT 10 is, and the relay in the PP20 stays closed. Therefore, the WSD cannot work as an override switch for the CM PDT 10, because there is no way for it to interrupt the signal that the CM PDT 10 is broadcasting.

 This is why, in this application, the  sPODM switch is recommended instead. The sPODM has one additional wire that your existing sensors do not; a white with blue stripe wire that acts as a communication pass through. When using an sPODM, your signal wires from your sensors will wire into the white wire of the sPODM, and then the white/blue stripe wire from the sPODM is the only wire that feeds back to the white signal wire on the PP20. This way, when you press the off switch on the sPODM, it overrides the signal on *all* attached sensors, not just its own internal relay.

 

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