# FCT with an External window Open/Close sensor ## Introduction The Fan Coil Thermostat (FCT) comes with an input that can be connected to an occupancy sensor in order to make heating/cooling more efficient. This optional functionality can be used in order to reduce energy expenditure in times where there are no people in the room/space. To further optimize the use case one could use the Open/Close sensor in order to control the FCT. For example if a window is open you would want to stop heating as it will be inefficient. This is an Enterprise level feature and all you need to do is configure the devices to communicate to each other through the platform in order to take benefit of it. ## Prerequisites This article assumes that you have the necessary devices and functionalities implemented into your Building already, which are listed below: * Fan Coil Thermostat * Open/Close Sensor If you have not onboarded and/or configured the devices, you can look at our [Quick Start guide](https://docs.mclimate.eu/mclimate-enterprise/getting-started) section. Make sure your FCT is installed well, properly wired in accordance with your desired application and is connected to the LoRaWAN Network Server (LNS) and it is connected to Enterprise.

## Configure the Open/Close Sensor Go to the *Control* section of the Open/Close Sensor and expand the *Advanced* settings. Select the FCT you want to control and move it to the right via the arrow button. {% hint style="info" %} In case you have other devices that can be controlled by the Open/Close sensor, like a Vicki for example they will be listed at the top, so you might need to scroll down to get to the FCT section. Refer to the image below for an example use-case. {% endhint %}

In this example we are controlling a single FCT, however you can have as many as you need. If the Open/Close sensor and the FCT have been properly paired, the FCT should move to the right table.

## FCT in Open Window mode Now that the FCT and the Open/Close sensor have been paired, a change of state (open to close and vice versa) will trigger a response in the FCT. Let us look at the event of the sensor reporting changing state to "Open". This is done by separating the two portions (the LED blinks to indicate it), which in our case would be when the window is open.

The "Open" event, triggers a Status change in the FCT, effectively turning it off. In this state the display will be off and the unit will not be heating the room.

This is also indicated in the Monitor tab for the FCT in Enterprise.

{% hint style="warning" %} You can still manually turn the FCT ON, if it has been turned OFF by the integration with the Open/Close sensor. This can be done either via the power button or via Enterprise/command. {% endhint %} ## FCT back to normal operation Let's look at the events' triggered by the sensor changing its state back to closed.

The Open/Close sensor instructs the FCT again, causing it to change its status, which again is reflected in the Command logs of the FCT.

At this point the FCT switches to its status in the Monitor tab and resumes operation as per the settings it was last using (all settings are preserved). If it was utilizing a Heating profile it will set the target temperature in accordance with the time slow that it currently is in (this might be different than the one it was when the window was opened).

This process can be repeated as many times as needed in order to limit the waste of heating energy when a window has been opened and the FCT will remain OFF until it is turned on via the Open/Close sensor integration