Strange alarm fault

[coalpit]

Guys about four years ago I installed a Scantronics 965 hard wired system in my rural office premises and in all that time have only had one instance of it having been triggered. According to the log this was due to the vibration alarm on the large glass doors having been triggered at about 2.00 in the morning of a very still night a couple of years ago.

Fast forward to two nights ago at just before midnight the alarm triggered.....I have two Masterblasters, one outside and one inside the building, and I jumped out of bed and armed with a powerful torch and in my pyjamas ran the 100 yards to the office building! No sign of anyone about so I turned off the alarm and reset it. The following morning I looked at the log and it showed that the exit door circuit had triggered. The CCTV system did not show any intruder so I have put the alarm activating down to a fault in the alarm system.

The exit door is the only one on the circuit and is controlled by a magnetic switch let into the edge of the three inch thick oak door. I have tried banging very hard on the door to try to trigger the alarm but without success.

Can any member suggest what may have happened and what I should do to avoid it in the future. Would it be wise to replace the door switch?

Many thanks

Richard

 

[Europlex]

What sort of contact, concealed or surface?

Door opens, outwards or inwards?

 

[coalpit]

What sort of contact, concealed or surface?

Door opens, outwards or inwards?

Thanks for your posting.

Sealed magnetic contact concealed into door jam and door. Door opens inwards. CCTV cameras picked up nothing. Although the gap between the switch and the magnet is 5mm I find that parting them to more than 10mm still allows me to operate the alarm.....just tested this. Also I was able to reset the alarm straight way and have not had any issues in this regard.

The door weighs about thee hundred weight and does not deflect easily being three inches thick. There was no wind the night the activation took place.

Cheers

Richard

 

[bernardgreen]

Could some have slid a thin sheet of steel between the magnet and sensor ? That would shunt the magnet field and prevent it reaching the sensor which then opens.

There is another way it could have happened if someone was trying to defeat the sensor but I am not putting that on a public forum. Did the CCTV cover the outside of the door or could someone have been at the door for a few minutes before the alarm went off.

 

[sparkymarka]

Bernard no no no no ...... Probably a faulty contact... Broken / cracked reed switch .. Not as good as they used to be...

 

[coalpit]

Could some have slid a thin sheet of steel between the magnet and sensor ? That would shunt the magnet field and prevent it reaching the sensor which then opens.

There is another way it could have happened if someone was trying to defeat the sensor but I am not putting that on a public forum. Did the CCTV cover the outside of the door or could someone have been at the door for a few minutes before the alarm went off.

Thanks Bernard for those suggestions.

Yes it would have just been possible to have slid a thin strip of metal over the sensor as there was is a tiny gap where the door stop is fitted. I've now dealt with that! The CCTV camera that covers the approach to the exit door does not actually cover the door itself, however anyone with an interest in gaining access to the building has far more tempting potential access points which are directly covered by cameras and none of these picked up any 'visitors.'

We are very rural and anyone wanting to carry away anything would have had to have got here with a means of transport. As soon a I had reset the system I jumped in the car and drove down to the where a car could have been left and none was there. I was there before an intruder would have had time to have hot footed to get there so I'm inclined to think that this alarm activation was a system fault of some kind.

BTW if you would like to share any private thoughts with me is there an email address I can contact you on? All my addresses have my name as part of them so I would not want to put them here.

Cheers

Richard

 

[coalpit]

Bernard no no no no ...... Probably a faulty contact... Broken / cracked reed switch .. Not as good as they used to be...

That was the possibility I first thought of but the switch has been working fine since that activation. Obviously if it happens again I will change it. Any other suggestions would be most welcome.

Cheers

Richard

 

[bernardgreen]

Coalpit

I have sent you a message explaining how it can be falsed.

Regards

Bernard

 

[coalpit]

Coalpit

I have sent you a message explaining how it can be falsed.

Regards

Bernard

Thanks for that Bernard. I've replied to your off list message.

Cheers

Richard

 

[JM2]

Just replace the contact pair.
Then you'll know it wasn't the one you've binned.

 

[EightyTwo]

Check that the connections on the contact are good and that there's no sign of water ingress. Oak is full of formic acid and any water on the connections is sure to start then rotting away. Did you use a new CQR grade 2 contact - the type with the snap-on cover (RFT)? If so, check the built-in tamper switch and the little plastic clips that hold the cover on. I've known these to pop apart, generating a tamper.

 

[coalpit]

Check that the connections on the contact are good and that there's no sign of water ingress. Oak is full of formic acid and any water on the connections is sure to start then rotting away. Did you use a new CQR grade 2 contact - the type with the snap-on cover (RFT)? If so, check the built-in tamper switch and the little plastic clips that hold the cover on. I've known these to pop apart, generating a tamper.

Thanks for the thoughts. This is the model of contact I have used on the exit door and all the windows. http://tinyurl.com/nvlhw2s The oak door frame is very old oak and is unlikely to get damp where it is however I've just checked and all seems to be well. The unused screws look a bit tarnished on their heads and the two contact screws have the resistor soldered across their heads. When I installed the system I felt that this gave the most positive fixing.

Cheers

Richard

 

[Lectrician]

Those cheapy ones are renown for failing. They don't just "fail", they start to cause issues, as you have found.

 

[coalpit]

Those cheapy ones are renown for failing. They don't just "fail", they start to cause issues, as you have found.

Can you point me to one that is going to be reliable that I can put in the same 19mm hole please?

Cheers

Richard

 

[Lectrician]

I generally fit these.

http://www.securitywarehouse.co.uk/catalog/index.php?main_page=product_info&products_id=3423

http://www.securitywarehouse.co.uk/catalog/index.php?main_page=product_info&products_id=3846

You likely have a 20mm hole?