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 Posted: Friday Oct 5th, 2012 01:46 pm
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ComfortGeek
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I have three PIRs on one circuit which have been operating fine for months.

Suddenly, they have started causing false alarms when in night or away mode (but not in walk test / security check mode)

There's definately nothing moving in the rooms, the heating is not on, the wiring has not been changed, I've taken cover off the PIR and checked no insects are inside.....

Any idea what might suddenly start this false alarm?

Only thing that has changed is the bell box has been added and 2 x RIOs added to control some TWSO2s. The problem started the day I fitted the RIOs and TWSO2s.



 Posted: Friday Oct 5th, 2012 05:13 pm
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wiredhome
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Well the first thing you need to do is split them on to a zone each so you can work out which one is causing the problem

is it happening at the same time each day?

do any of them look at a
window? the sun is lower in the sky now
mirror? refelection of the sun

are they pirs only or dualtecs?

is it possible you disturbed the connections in the panel when fitting the rio etc?

It's a case of working thru it bit by bit






 Posted: Saturday Oct 6th, 2012 01:39 pm
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ComfortGeek
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Thanks WiredHome

I've measured the resistance in the circuit. It is 2.7k when closed and 7.4k when open - so the circuit resistance seems to be ok, the resistors seem to be ok, the wiring is ok.

So, I think the issue is either a) a faulty PIR opening it's contacts at random, or, b) something else is effecting the resistance of the loop momentarily, causing it to trigger the zone.

What I do have is a normally open zone sharing the same common as this PIR zone - could that be it?

Interestingly, the normally open zone (which is a break glass call point) is on the same wall as a PA zone which also triggers at random (but is normally closed) - so I wonder if there is electromagnetic interference becuase of 230v wires close to the 12v wires - and this is feeding back into the common and effecting the PIR zone....

Could this be it?

I've disconected the normally open zone to try and rule it out....but, is there any reason why a comm terminal cannot support both a normally open and normally closed circuit? i.e. two zones sharing the same comm terminal, but one is normally open circuit, the other is a normally closed circuit - is this probelmatic?



 Posted: Saturday Oct 6th, 2012 06:13 pm
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wiredhome
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Hi
The mains could be the cause of your problem
especially if the pa is having problems as well
mains and low voltage should be at least 6-8 inches apart

Can you rewire?

regards
Niall



 Posted: Sunday Oct 7th, 2012 02:08 am
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ident
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Normally open zones sharing the same Common terminal with normally closed should not cause any problem.

If you short the PIR and leave the wires in place, that may show if it is a PIR or interference problen



 Posted: Sunday Oct 7th, 2012 05:05 pm
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ComfortGeek
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Ok

I removed the normally open zone that shared the same com terminal as the faulty zone and it still went off, so we know it's not that!

Now I have put a wire in each of the 3 PIRs across the alarm terminals to see if it alarms tonight - if it does, we know it is interference from 230 v wires not the PIRs themselves.

I have also wired the PIRs to latch if they are triggered, so we can see if it is a faulty PIR. Luckily the type of PIR can latch the light even if the alarm contacts are shorted - so I can test for a faulty PIR and interference at the same time.

Another thought......Could it be anything to do with the battery test? I read that when battery test is done, AC is removed for 2 mins (as set in comfigurator)

Funny that the problem only started when I connected 2 RIOs and 5 TWS02s....could the battery not have enough power when it goes into test and this stops power to the PIRs and set them off?

Funny thing is it does not remove power to other PIRs or fire detectors.....but perhaps there is enough power for them just not for the last thing drawing current on the circuit.

I'll let you know how the testing goes!



 Posted: Sunday Oct 7th, 2012 05:08 pm
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Hi Niall - thanks for advice

I cannot see any mains and 12v wires close to each other for the PIR circuit.

It went off again last night so we know its not the other circuit sharing the same com terminal (as it was removed).

I have now shorted the alarm contacts on the PIRs and set up teh latch feature to see if we can ID if the issue is a faulty PIR, something triggering movement at night or interference from mains wires.

If that's not it, god knows!

(Thought it could also be something to do with battery check - have asked Cytech to look into this)



 Posted: Monday Oct 8th, 2012 04:17 am
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ident
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Battery Test will occur at the same time each day, for 2 minutes
In that time, the battery will power the system, so there is a voltage drop from 13.8V to 12V (or below if the battery is not good). The voltage drop should not affect a good PIR. A battery can supply enough to power all the modules, PIR, TWS etc
Check the event log if the false alarm occurs at the same time each day



 Posted: Tuesday Oct 9th, 2012 07:26 pm
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ComfortGeek
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Thanks, since I put a wire across the alarm contacts in the PIRs, there have not been any false alarms for 2 nights running, so we'll now unloop them individually until we find the PIR that is faulty / giving the false alarm.



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