Windows partially open

[Bzncrewjr]

So my idea is to mount 2 sets of switches for the magnets on the windows.  
One for full closed and one with the window open a few inches (to allow some air in)
 
My idea is to be able to leave the windows open a few inches and arm the alarm.
 
I'm thinking to make this work, I would need 2 zones or whatever you call them.   So I could alarm it with the window full closed or armed and the partially opened armed ignoring the first (fully closed window) position.
 
Is this possible or am I in the wrong ball park?
 
 
--Russ
 

 

[tmbrown97]

It's easier than that - you just use two magnets along the slide side (as opposed to the end).  One magnet for fully closed and one in the partially open position.  You can use a very subtle line on the window frame to mark the location of the second magnet.
 
I've had this in a few homes and it works well. 

 

[alarmguy]

I have used a number of GRI VS-06 contacts on many windows and they have worked well.

 

[Bzncrewjr]

It's easier than that - you just use two magnets along the slide side (as opposed to the end).  One magnet for fully closed and one in the partially open position.  You can use a very subtle line on the window frame to mark the location of the second magnet.
 
I've had this in a few homes and it works well. 

 
Doh!   That's too easy. 
 
Thanks!
 
--Russ

 

[Del91574]

When using surface contacts to install what is called "venting" in the trade, you need to invert the second magnet 180 from the mounting orientation of the original. Part of the reason why they put manufacturer's labeling or design features on most contacts (identify the poles)
 
Keep in mind, you don't want the window to be much more than  6 or 8" open in the vented height.....the goal is security and ventilation.

 

[johngalt]

When using surface contacts to install what is called "venting" in the trade, you need to invert the second magnet 180 from the mounting orientation of the original. Part of the reason why they put manufacturer's labeling or design features on most contacts (identify the poles)
 

DEL-Just out of curiosity, but can you explain why?

 

[Del91574]

With strong enough magnets or installed close enough together, you have N-S N-S, effectively creating what appears to be a large magnet to the reed switch and allowing the zone to set up if it's marginal to the "sweet spot" on a contact, as you never want to put a contact in the middle of a magnet, only at the pole or literally completely linear, never a "T". False alarm issue. Had an install about 15+ years ago I was troubleshooting (someone else installed) and couldn't find the issue and it only occurred when the owners opened the windows.
 
Noticed when working on the basement windows (doublehung) and was able to access the splices and watch what was occurring with a good quality analog meter. Was able to move the window about 10"+ linear without the system seeing any difference in the location of the sash, but the meter told a slightly different story.
 
You want separate and distinct areas on the window/magnetic flux areas. There's a reason why the "real" manufacturers pay attention to the orientation of the magnet in all of their contacts, surface and recessed.
 
Same alarm guys ended up with a bad magnet batch, somewhere in the 100's of contacts.....wasn't good for their business and troubleshooting wasn't their forte.

 

[johngalt]

Thanks Del.

I hadn't thought of that but it makes perfect sense.

 

[giansiro]

Here is a good resource of hardwired door contact, http://www.lowvoltagesupply.com/category-s/1829.htm