# door sensor on alarm



## s.kelly (Mar 20, 2009)

A community center I am involved with got an alarm call this morning. I went to check it out, and as ususal it was the front door. 

The front door is an aluminum storefront door, alum. frame, mostly glass.

It has an electric strike with key fob openers. There is probably 1/4 to 3/8" play when the door is closed.

As heavy trucks come by we think it rattles the door and sets the alarm off.

Sensors are in the side of the door and the frame. I do not know much about this so I wrote the numbers down. Both have BP547 on them. One is an F1 and one is an E4.

Looking for some help in how to reduce false alarms. Different sensors, better sensors, tighter door, or a combination. I will call the compnay and talk to them this week, but I want to have some thoughts going in.

Thanks


----------



## sarness (Sep 14, 2010)

They make wide gap sensors, same issue myself one time except that jet planes were shaking things up.


----------



## don_resqcapt19 (Jul 18, 2010)

Fix the door, it should not have that much play.


----------



## niteshift (Nov 21, 2007)

I agree tighter door. Just went thru this. Had to replace push bar and hardware. bottom and top pawls wore out.


----------



## CDN EC (Jul 31, 2011)

My home automation setup has a magnetic door sensor that was a real pain when first installed. It's wireless and just screwed to the outside of the door and frame, but the play in the door made it trip constantly whenever the wind blew.

I put weather stripping on the inside of the frame and repositioned the sensor and magnet slightly to make it work and it's been fine since.


----------



## BBQ (Nov 16, 2010)

We do alarm repairs and most of the door jamb switches are not that sensitive. Break the circuit at the door, hook up your continuity meter to it, lock the door and go nuts on the door to see if wiggling the door breaks the circuit. Also unlock the door, open and close it slowly noting how far it can move with out breaking / making the circuit. If wiggling the door does make the switch change state I would get a better mag set up. _(I agree with Don the door should be tighter but that is not my job)_ You could have a bad splice in the door jamb where the cable spices to the mag switch.

You should also check the loop resistance with the end of line resister in place and make sure you are within the specifications. One of my coworkers fixed an intermittent false alarm call by replacing the EOL resister once he realized the loop resistance was wrong.
.

That said .......in my opinion the number 1 cause of 'false' alarms from the main door is operator error.


----------



## B4T (Feb 10, 2009)

Wide gap door contacts are very common.. ADI has them up to 1.25"..

Also try moving the location of the contacts closer to the hinged side where there is less play..

Some guys put the contacts on the widest part of the "door play" and you have trouble from the get go..


----------



## BBQ (Nov 16, 2010)

I can't say I have ever run into a front door as described by the OP to need a wide gap contact. 

Even very small contacts are good for almost 1"

As far as placement, from a security standpoint you want them mounted on the latch side of the door. 

BTW, pretty sure these are what the op has. 











If so it would take a hell of loose door to be an issue.


----------



## B4T (Feb 10, 2009)

BBQ said:


> I can't say I have ever run into a front door as described by the OP to need a wide gap contact.
> 
> Even very small contacts are good for almost 1"
> 
> ...


I don't think those magnets would work on an AL frame door.. not enough material to hold the magnet in place..

But I have only used them in wood frame doors.. so not really sure..

Most likely surface mounted magnets mounted too far apart and too close to latching side..


----------



## McClary’s Electrical (Feb 21, 2009)

B4T said:


> I don't think those magnets would work on an AL frame door.. not enough material to hold the magnet in place..
> 
> But I have only used them in wood frame doors.. so not really sure..
> 
> Most likely surface mounted magnets mounted too far apart and too close to latching side..


They work just fine on aluminum frames


----------



## s.kelly (Mar 20, 2009)

Thanks all for the replies. 

I am not sure how much I can tighten the door without causing binding on the electric strike. Anyone have experience with these? I was looking at it and I think I could tighten it up, but have no experience with the latch.

I will disconnect next time I am up there and see how much it takes to open the contact. Resistor must be in the locked jb that the alarm company supplies. Maintenance get keys for this usually, or is that considered their property?


----------



## Awg-Dawg (Jan 23, 2007)

I assume you tried this but,


Try bigger,wider magnets.


----------



## s.kelly (Mar 20, 2009)

Have not tried it yet, alarms are not my thing, and likely I'll have the alarm people handle it, just trying to get some background. Some earlier posts mentioned the wider magnets. I was not aware of the option, but I will certainly check on it.


----------



## LARMGUY (Aug 22, 2010)

Number one question, Are you alarm licensed?



> *EDIT: I did some digging and found a contact, surface mounted with BP 547 on it.*
> *It is a polling loop serial numbered contact used in a V=Plex system. If it's serial numbered, call the alarm dudes.*


 
They make them in 3/4" and 1" with terminals or pigtails. They are designed for steel doors. If you can find a rare earth magnet, replace the existing one.


















If you can't drill a new hole for the door magnet they make these. Just squeeze them and adjust as necessary.












You said it was a reader with keyfob. Is it a software system to a controller or just a keypad / reader combo only at the door? Most access control systems are separate from the alarm system so there would be two contacts per access controlled/alarmed door.
Check the alignment of the contact to the contact magnet. Use a pencil to mark the centerline of the door contact on the jamb. Then mark the centerline of the magnet on the door. Close the door and see if the marks align. Check the air gap between the magnet and contact. Sometimes the magnet settles a bit into the door. If the contact has ever come loose and been hit by the door it could be faulty. Bad resistor, faulty connections, faulty alarm motherboard, hundreds of reasons. Pictures speak louder than words.


----------

