Alarm Troubleshooting: Tips to Reduce False Alarms

IDENTIFYING False Alarms by RFI

Visual Inspection
Go outside and look for close sources of RFI signals, CB/Ham radio aerials, local taxi ranks and police, fire and ambulance stations.

Mobile Phone
Place the aerial of your mobile phone against the PIR cover and standing perfectly still so you don’t activate it, dial a number and press send. This test can be performed on any power detector.

Cover
Mask the troublesome PIR securely with a business card or PVC tape and put the circuit on a soak-test

Finally
If RFI is identified as a potential cause of fire alarms, don’t fit a dual microwave/PIR. Microwave is a receiver of RFI and could give more false alarms than an ordinary PIR

FOUR STEPS To Eliminate RFI

1. Instead of changing the detector with an identical PIR, go through our ‘PIR fault finding checklist’ to prove the cause is RFI
2. Swap the troublesome PIR with another in the same building
3. Fit an ACT 1376 PIR stabiliser inside the troublesome zone PIR and put the circuit on a soak-test
4. If a false alarm moves to the other zone, change the PIR and recover the PIR

FIVE CAUSES Of PIR False Alarms

1. The first cause of PIR false alarms is low or unstable voltage at the detector. Test to make sure the voltage at each PIR is above 13VDC and stable.

2. The second cause of false alarms is sudden infrared movement / heat changes in view of the detector. Check behind and inside the PIR for insects and identify objects that can move or rapidly change temperature (e.g. pets, vermin, fax, mailbox, radiator or boiler etc).

3. The third cause of false alarms is white light momentarily blinding the detector. Always choose PIR’s with genuine white light filters and avoid fitting facing glass with 50% of its operating range.

4. The fourth cause of false alarms is a direct draught striking the detector. This causes air convection inside the PIR. Make sure cable and screw holes are totally sealed and don’t forget the hole where the cable comes through the cavity wall or ceiling.

5. The fifth cause of false alarms is RFI/EMI signals. A mobile phone can be used to test susceptability to RFI by placing the aerial against the PIR casing and transmitting. Fit an ACT 1376 stabiliser inside the PIR to eliminate RFI.