You're describing a situation where the occupancy sensor "defaults to ON" when power is restored. This is a common issue with some occupancy sensors and their intended use cases.Here's a breakdown of why this happens and potential solutions

Why it's happening:
Default State on Power Restore

Some occupancy sensors are designed to turn on the lights (or activate the connected device) when power is restored after an outage. The reasoning is that in a commercial building, you want the lights to come back on automatically after a power failure for safety and security. This is a "fail-safe" behavior in many applications.

Internal Relay or Triac Control

The Lutron OPS2H uses either a relay or a triac to switch the power. When power is applied, it defaults to the "on" state until the sensor logic (motion detection, timeout) takes over.

Solutions


Look for a "Manual Override" or "Inhibit" Input

Some occupancy sensors have an input terminal specifically designed to prevent the sensor from automatically turning on the load when power is restored. This might be labeled "Inhibit," "Manual Override," or something similar.

How to Use It

You would wire this input to a switch (or in your case, the output of your remote control receiver). When the remote sends the "off" signal, it not only turns off the siren but also activates the "Inhibit" input. This would tell the sensor not to turn on the siren when power is restored, even if it detects motion.2.

Use an Occupancy Sensor with a "False-Trip Immunity" Feature

Some advanced occupancy sensors have settings to avoid false triggers or power-on triggers. These may have settings for a specific "start-up delay" or a way to prevent the sensor from immediately triggering on power up. You would have to check the product documentation carefully.3.

Replace the Lutron OPS2H with a Different Type of Sensor



Vacancy Sensor (Manual-On)

These sensors require someone to manually turn on the lights (or in your case, the siren) using a switch. They then turn off automatically after a period of no motion. This would definitely solve your problem, as it would never automatically turn on. However, it would change your interaction pattern. You'd have to manually turn on the siren when you enter the cabin.

Occupancy Sensor with Adjustable Sensitivity and Delay

Look for sensors with highly adjustable sensitivity and delay settings. A very short delay and very low sensitivity might minimize the initial "false" trigger, but this is not a guaranteed solution.

Sensor with "Power-On Inhibit" Feature

Actively search for a sensor that explicitly states it has a feature to prevent turning on the load immediately after power restoration. Read the product manuals carefully to confirm this functionality.4.

Add an Intermediate Relay with Power-On Delay

This is a more complex solution, but it's reliable. You would add a separate relay between the occupancy sensor and the siren. The relay would be controlled by a timer circuit that prevents it from closing for a few seconds after power is applied. This would give the occupancy sensor time to initialize without triggering the siren.5.

Use a Smart Occupancy Sensor and Home Automation

If you're willing to invest a bit more, a "smart" occupancy sensor (Z-Wave, Zigbee, etc.) connected to a home automation hub (SmartThings, Hubitat, etc.) would provide the most flexibility.

How it Works

The smart sensor reports occupancy to the hub. You create a rule in the hub that says: "IF occupancy sensor detects motion AND remote switch is OFF, THEN do NOT activate the siren." This allows for much more sophisticated control and avoids the automatic activation on power restore.

Important Considerations



Safety

Be extremely careful when working with electrical wiring. If you're not comfortable, hire a qualified electrician.

Product Documentation

Always read the product manuals for any occupancy sensor you're considering. Pay close attention to how it behaves on power restore and any features related to manual override or inhibit inputs.*

Siren Power Requirements

Make sure any sensor or relay you use can handle the voltage and current requirements of your 12VDC siren.

Recommendation:

I would start by looking for an occupancy sensor that specifically mentions a "power-on inhibit" feature. If that's not readily available or you're comfortable with a bit more wiring, the "intermediate relay with power-on delay" is a robust solution. The smart home option is the most flexible but also the most complex to set up.Without knowing the exact Lutron OPS2H model version, it's hard to give more specific advice, but look for the documentation. Also, look for a wiring diagram that can guide you through the correct implementation. Flag for review