Wireless window sensors


Active Member
New home construction. I have a M1G that I plan on installing. I don't want to drill and windows recessed sensors, so I plan on using wireless (don't know which ones yet). I have 23 double hung windows. I thought about locating the sensors on top of the bottom sash, so one sensor could be used for both the bottom and top sashes. The top of the bottom sash is flat and wide/thick enough to mount the main part of the sensor. However, when both sashes are closed, the wooden area on the upper sash that lines up with the top of the lower sash is the horizontal muntin bar, which is essentially a small quarter-round.
It looks like the only place the magnet can be located is on the glass (using double-sided tape), but I think that puts it about 1/2" above the top of the other "half" of the sensor that is mounted on the top of the lower sash. It will also put it at a 90 degree angle to the other half.
Before spending $1K+ on the sensors, I would like to make sure they will work. The hard-wired window sensors I've used in the past were easy to test to make sure a sensor was mounted correctly (spacing, etc.) without having to wire it up. Can the same thing be done with Elk's wireless sensors, or do I need to have an M1G, wireless transmitter, etc., all hooked up and running to make sure the sensors are mounted in a way that will work?
Any suggestions on dealing with double hung windows that doesn't involve any drilling?
While putting sensors on both the top and bottom of a double hung window is the highest level of security, I think it is pretty safe to do just the bottom window. 99.5% of the people trying to break into your house via a window are going to raise up the lower portion of the window. It simply takes too much time, agility, and energy to climb in the top portion of the window.

I'm not sure if you can test the sensors without the ELK being hooked up, but the reality is that you don't need to install the sensors until it is. With hardwired sensors, it is obviously important to test them during the installation phase because they generally get covered up after that. Wireless is generally going to be surfaced mounted after construction is already complete, so there really isn't a need to install them until the system is ready to go.

Personally I surface mount the sensor on the casing of the lower window and then surface mount the magnet on the edge of the sash close to the casing, but not on the glass itself. This allows the window to open and close normally (even tilted in to clean, etc) and still helps keep the sensors/magnets out of view from the outside. You could easily put a sensor on both the top and bottom window if needed. The sensors will be visible to anyone inside, but they are small and generally inconspicuous and any window drapes, blinds, etc will help conceal them too. The truth is that no one but you will ever see them or be bothered by them.
Putting the sensor on the bottom of the window only is plan B, but I'm hoping I can make it work for both. I went to the house and took a picture of the sash. Turns out it isn't as bad as I thought. The quarter-round "muntin" on the top sash isn't as tall as I thought it was, so maybe the magnet will be close enough to the transmitter if it is glued to the window above the muntin.
Looks like the magnet can be 1/2" thick, maybe a little more, depending on how thick the tape/glue/silicon is. I guess I can also use other magnets if the Elk ones don't fit the bill.
The Honeywell 5800Mini sensor has a gap spec of 1", so it is possible it would work with the magnet mounted on the glass.  The magnet is pretty small at 1/4" x 1/4" x 1" so wouldn't be too obvious on the glass.  
Other window sensors, like the Elk Mini and Slim sensors, have a smaller gap spec.
Keep in mind that a magnet is a magnet is a magnet.  If the magnets supplied with the wireless sensor are too big, replace them with some smaller "rare earth" magnets, or remove them from the housing and just mount the magnet, etc.