I am having a hard time figuring out how/where to install my recessed window sensors (TANE STB-3/8 TC). More specifically, I am building a house using mostly double hung Pella windows (mix of Architect series and Pro series). I don’t want to degrade the window by drilling into the window cavity itself. I searched for pictures/videos to install recessed contacts in windows but have seen very few. Is there a best practice for installing hard-wired recessed sensors in Pella windows?
Were all of the sensor locations pre-wired?
Sensor wiring should be run through (typically) the base of the frame. Small recessed contacts can typically use thin surface mount magnets glued to the bottom of the window proper.
Nothing has been wired yet. I have the small neodymium magnets that have a small screw. I didn’t know if the base/bottom of the frame was the normal location to install the sensor, or if the side of the window frame was normally used.
Two additional questions about the GC3:
If the TS1 secondary panel doesn’t work with the GC3, when will a compatible secondary screen be available?
How large (exact dimensions) is the transformer power supply for the GC3? I want to mount it flush on a wall and would like to recess the transformer in a box.
Thanks
Currently, you can use the 2GIG PAD1 but all that offers the user is a keypad to arm/disarm the system. While 2GIG has stated that they are working on a dedicated secondary panel, there is no ETA at this time. 
The power supply for the GC3 is:
3" 3/8 L x 1" 5/8 W x 1" 3/8 D
I didn’t know if the base/bottom of the frame was the normal location to install the sensor, or if the side of the window frame was normally used.
Typically for wired sensors it would be the base (recessed sensors anyway) as installing a recessed magnet on the side would necessitate removal of the window and cutting into/around the track.
Surface mount sensors go pretty much anywhere.
For double hung windows, keep in mind a recessed wired contact cannot be made to monitor both sliding panes. Multiple sensors would be required.
Smaller wireless contacts can sometimes be placed on the top of the lower pane, with the magnet next to it on the upper pane if the magnet is small enough to allow either pane to slide.