Neilo Posted July 1, 2008 Share Posted July 1, 2008 Can anyone help? I have a Scantronic 9452 (or rather my customer has) which was giving false alarms on one zone only. I checked the system was all as it should be (battery checks etc.) so figured that, failing any external influences on the zone, the detector was probably on it's way 'out'. I therefore installed a new cheapie Honeywell PIR in it's place which seemed to be working ok. I did a quick walk test and set the alarm and activated it in an armed situation. All as it should be. However, and I didn't notice this but my customer rang me later tell me that all the LED's on ALL the PIR's except the one I 'd changed were permanently on. The new one was going on and off as expected. When I returned I did a full walk test and full armed and activated test and the system seems to work as it should do, although I haven't left it for any length of time becuase the owners are away and I have to liase with the next door neighbours for keys etc. I have searched all the forum and can't find anything remotely like this fault listed. I've thought about powering down completely (mains off, battery disconnected) but don't want the system to go into default (I do have the installation/user manual). Any ideas? Thanks Link to comment Share on other sites More sharing options...
Chorlton Posted July 1, 2008 Share Posted July 1, 2008 Hi Neilo I'm no help I'm afraid as I only do fire but other members may be along soon who can. As this is a public forum the information provided will be limited to that we don't want falling into the wrong hands (burglars !!!) If you are in the alarm/CCTV/fire industry have a look around make some more posts so you can get to know us and us you and once your post count is upto 10 you can apply (FOC) to access the trade side of the forum where alot more detailed information is available. Use the link below. Take care, C. Link to comment Share on other sites More sharing options...
antinode Posted July 1, 2008 Share Posted July 1, 2008 Sounds like a bizarre fault. Do any of the detectors in question have the latch wired up? I would try disconnecting the Aux supply to the detectors for a minute or two then power back up to see if that will clear it. Also may be worth checking any settings/links/DIP switches inside these detectors. Do you have a make/model or description of the PIR's in question? Trade Member Link to comment Share on other sites More sharing options...
luggsey Posted July 1, 2008 Share Posted July 1, 2008 Sounds like a bizarre fault. Do any of the detectors in question have the latch wired up? I would try disconnecting the Aux supply to the detectors for a minute or two then power back up to see if that will clear it. Also may be worth checking any settings/links/DIP switches inside these detectors. Do you have a make/model or description of the PIR's in question? Yep sounds like old latching PIR's, must have put the latch wire in the +ve by the sound of it. Some were wired up cleverly to only flash when user code is entered and an output triggers so an output may be locked on as well. ----------------------------------------------------------------------------------------------------------------------------------- Life is like a box of chocolates, some bugger always gets the nice ones! My Amateur Radio Forum Link to comment Share on other sites More sharing options...
Wooly-bobs Posted July 1, 2008 Share Posted July 1, 2008 Last time i had that it was low AUX to the passives. Link to comment Share on other sites More sharing options...
morgan306 Posted July 1, 2008 Share Posted July 1, 2008 As Chris says, some PIRs leds stay lit when the supply to them is low. They may still function normally though. What was the voltage at the detector? Link to comment Share on other sites More sharing options...
lawandorder Posted July 1, 2008 Share Posted July 1, 2008 As Chris says, some PIRs leds stay lit when the supply to them is low. They may still function normally though. What was the voltage at the detector? First thing to check is supply voltage to detectors, many detectors will light up permanently if supply voltage is low. Having said that most PIRs will go into alarm condition at this point so you would not have been able to set the system. Check the wiring of the old PIRs, as already suggested look for a latch wire. Are all the detectors powered from the same output on the panel? Link to comment Share on other sites More sharing options...
Neilo Posted July 2, 2008 Author Share Posted July 2, 2008 First thing to check is supply voltage to detectors, many detectors will light up permanently if supply voltage is low.Having said that most PIRs will go into alarm condition at this point so you would not have been able to set the system. Check the wiring of the old PIRs, as already suggested look for a latch wire. Are all the detectors powered from the same output on the panel? Many thanks to everyone who has replied so far. Firstly I'm a Locksmith who occasionally gets asked to look at alarms so forgive me for being a tad naive! However, the system works as it should do, setting, activating, walk tests, the whole nine yards apart from the fact the LEDS on the old, existing detectors are permanently on. There were six wires, a + and - ; the two tamper wires; and NC and C. There wasn't a latch wire. I think I'll try to power down, disconnect the battery, leave for a while then see if the PIR's restore to normal. Unfortunately I can't get in the house until the weekend but thanks once again for the posted replies so far and I will respond early next week to keep you posted. Link to comment Share on other sites More sharing options...
luggsey Posted July 2, 2008 Share Posted July 2, 2008 Many thanks to everyone who has replied so far.Firstly I'm a Locksmith who occasionally gets asked to look at alarms so forgive me for being a tad naive! However, the system works as it should do, setting, activating, walk tests, the whole nine yards apart from the fact the LEDS on the old, existing detectors are permanently on. There were six wires, a + and - ; the two tamper wires; and NC and C. There wasn't a latch wire. I think I'll try to power down, disconnect the battery, leave for a while then see if the PIR's restore to normal. Unfortunately I can't get in the house until the weekend but thanks once again for the posted replies so far and I will respond early next week to keep you posted. If there is no latch wire then as mentioned start checking voltage to detectors and look for a possible high resistance connection. ----------------------------------------------------------------------------------------------------------------------------------- Life is like a box of chocolates, some bugger always gets the nice ones! My Amateur Radio Forum Link to comment Share on other sites More sharing options...
Neilo Posted July 4, 2008 Author Share Posted July 4, 2008 Hi, Many thanks to everyone who gave me the benefit of their experience. I have just come back from the house having disconnected the mains and removing the battery and then reconnecting again and lo and behold the LEDS have gone off and are acting as LEDS should do (or LED's on PIR detectors anyway!). All your replies were very gratefully received. Rgds Neilo Link to comment Share on other sites More sharing options...
lawandorder Posted July 4, 2008 Share Posted July 4, 2008 Hi,Many thanks to everyone who gave me the benefit of their experience. I have just come back from the house having disconnected the mains and removing the battery and then reconnecting again and lo and behold the LEDS have gone off and are acting as LEDS should do (or LED's on PIR detectors anyway!). All your replies were very gratefully received. Rgds Neilo Glad you got this problem sorted but it would be interesting to know why it happened in the first place. My guess (and it is only a guess) is that the existing PIRs had the option to be wired as latching and that at some time during your initial repair the voltage to them dropped to a level where the latch initiated. (perhaps during battery test?). As I say, just a guess but it does seem strange that they all "appeared" to latch. Link to comment Share on other sites More sharing options...
Neilo Posted July 5, 2008 Author Share Posted July 5, 2008 I think you might be right about the latching. To be honest I changed the detector on the 'faulty zone' without powering off etc. (hence the expression a little bit of knowledge is a dangerous thing!) . It would seem, that thanks to your help and the rest of the replies, I probably got away with it but I'll know to switch everything off next time. Once again many thanks. No longer in a hole I'd dug! Link to comment Share on other sites More sharing options...
mark auto Posted July 11, 2008 Share Posted July 11, 2008 sorry for being a dumbass guys, but could someone explain latching to me? i dont get it Link to comment Share on other sites More sharing options...
lawandorder Posted July 11, 2008 Share Posted July 11, 2008 I think you might be right about the latching. To be honest I changed the detector on the 'faulty zone' without powering off etc. (hence the expression a little bit of knowledge is a dangerous thing!) . It would seem, that thanks to your help and the rest of the replies, I probably got away with it but I'll know to switch everything off next time.Once again many thanks. No longer in a hole I'd dug! BS4737 demanded that there was a way of identifying which electronic detector had triggered so in the event of a false alarm the problem could be recified. Nowadays that usually means fitting a control unit with multiple zones and each detector tends to be wired to it's own zone and when the alarm activates the user can see which zone triggered. In the good old days before you could buy an 8 zone panel for less than the cost of a round of drinks many panels were single zone. To identify which detector had triggered an extra wire was used in each detector which was connected to the latching terminal. As I recall this wire went positive when the system was set and the walk test LED would stay illuminated until manually reset. Many panels still have an output for latching detectors and latching still has it's uses with things like vibration detectors etc. Some detectors even had a remote output to allow an additional walk test/latch indication to be mounted near the panel. If you work for any of the long established nationals you may still come across this type of installation. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.