Well, we're not planning to change our title, but we make no excuses for concentrating on this subject. In the current climate brought about by ACPO 2000, installers are, undoubtedly, even dreaming about false alarms … or is that having nightmares?
Everyone is ready to lay the blame at someone else's door …the apathetic end user, the poorly designed system, the sub-standard installation, fault prone kit, the weather, the time of the month, bad feng shui …
It's generally recognised that end users are the biggest cause, but how much of their ignorance and uncaring attitude to alarm systems is down to the installer not being forceful enough when it comes to explaining alarm responsibilities?
ACPO 2000 means that all installers should now write to their customers (you probably have already) pointing out the dangers of lowering their level of police response, or losing it entirely.
Customers have to be made aware of their responsibility to inform even their newest, lowliest member of staff of correct alarm procedures. If you've taken the initiative in this (perhaps providing a free system survey) they've got less reason to blame you if they drop to a Level 2 or 3 police response.
According to David Grant of ACT Meters (tel 01744 886660), next to end user error, the biggest cause of false alarms is electro magnetic interference (EMI) when alarm cables run alongside mains, phone and other service cables.
In our opinion, EMI and false alarming PIRs are a lot easier to tackle than end users … who are subject to that highly fault-prone and unreliable piece of kit, the human brain.
And using the practical fault finding techniques in the Control Panel Checklist detailed in the next few pages, could reduce your false alarms immediately.
We are as indebted to David for supplying the material for this feature as he must be to us for the free product placement! And other manufacturers … if you've got products specifically aimed at reducing false alarms, let us know about them.
Twenty top tips to prevent false alarms
Control Equipment:
- Take the mains supply from the consumer board;
- Charge batteries overnight before using them;
- On larger systems, power PIRs from an independent PSU;
- Make sure PSUs come off the same phase/earth mains supply;
- Always eliminate induced AC by fitting a 12V spike suppressor.
Alarm Cables
- Don't run alarm cables next to mains or any other service cables;
- Connect unused spare wires down to earth;
- Always use screened cable for keypads, Lim's (line interface module) & iD circuits;
- Never run data and sounder circuits in the same cable;
- Use insulated staples in staple guns;
- Always solder twisted joints on EOL & iD circuits.
PIR Detectors
- Choose PIRs fitted with genuine white light filters;
- Don't fit PIRs within 50 per cent of their range facing glass;
- Don't place PIRs close to radiators, boilers etc;
- Make sure all windows and doors are closed;
- Seal PIR entry holes, especially where cables come through the wall;
- Use dual technology where insects and rodents are a problem;
- Make sure the DC supply is above 13Volts and stable;
- Fit a PIR stabiliser to prevent false alarms caused by RFI.
ACT's seven solutions to false alarms
1 Next to user error, induced AC voltage caused by electro-magnetic interference (EMI) is the biggest cause of false alarms. Alarm cables running alongside mains, telephone and other service cables, induce high voltages and electrical 'spikes' onto 12VDC wires feeding PIRs, keypads and lims. The ACT1313 12Volt Spike Suppressor can be connected between the 12VDC auxiliary supply and earth, eliminating induced AC voltage and clamps the DC supply against electrical 'spikes'. They can be fitted as standard to your control panel and each PSU.
2 Ideally, you should take your mains supply to the alarm from the consumer unit. This is normally the 'cleanest' mains supply available.
If you come off a wall socket (never from the lighting), your alarm system shares the mains supply with every electrical appliance plugged into that ring circuit. To prevent mains interference feeding into the alarm panel, you can fit an ACT230MSF. This is a 230Volt Mains Spike Filter fitted with EMI/RFI and lightning protection. It will work continuously to prevent false alarms, and in the event of a direct lightning strike, will 'self sacrifice' to protect the panel and equipment.
A frightening thought!
3 If you're using a 'metal boxed' control panel, 0Volt of the 12Volt supply may be connected through the box to mains earth. Just imagine, the 0Volt of the control panel and every PIR connected directly to water pipes and all electrical appliances in the building. A frightening thought! To prevent interference feeding back onto 0Volt to the alarm system you can fit an ACT1166 High Frequency Earth Line Choke.
4 It's a good idea to use 'screened cable' for keypads and Lim's (in other words, 12Volt and data). After all, you wouldn't use ordinary alarm cable to network computers - or would you? Takeovers on the other hand can be a problem. Existing unscreened cables can be protected by fitting ACT2468 EMI/RFI filters. Potentially troublesome wires should be connected to the input side of the filter. The filtered output should be connected to the control equipment. The powerful filters can be used as required to protect 12Volts, data, iD, bell, speaker cables.
5 Sometimes, you takeover a real troublesome system, or perhaps your 'first-fix' wires have been damaged by other workmen. Provided they're normally closed circuits, an ACT4201 Opto Isolator can prove to be a life saver. Once connected, circuit resistance has to exceed 20,000 Ohms before an alarm condition, and damaged or earthed wires are no longer a problem.
6 If you've just one troublesome zone or tamper, you can use an ACT120L Transistorised Relay. Simply connect to the 12Volt supply and wire in the troublesome circuit. The 'clean' relay contact output is then connected to the panel and is said to be a quick "guaranteed" cure.
7 Instead of changing a PIR after a false alarm just to keep the customer happy, you could fit an ACT1376 PIR Stabiliser inside the detector. It's quicker, and will eliminate false alarms caused by the alarm cable picking up radio frequency interference (RFI). Try using your mobile phone to test RFI susceptibility by placing the antenna against the PIR casing and, whilst standing still, dial a number and press send.
Next to end user error, induced AC voltage caused by electro magnetic interference (EMI) is the biggest cause of false alarms ... fit a ‘spike’ suppressor as standard to your control panel
You might be amazed at the results – and don't forget dual technology is much more susceptible to RFI.
False alarming PIRs
There are five causes of PIR false alarms … and they can all be eliminated during one service visit.
- The first cause is low or unstable voltage at the detector. Test to make sure the voltage at each PIR is above 13VDC and stable.
- The second cause 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, boiler etc.).
- The third cause is white light momentarily blinding the detector. Always choose PIRs with genuine white light filters and avoid fitting facing glass with 50 per cent of its operating range.
- The fourth cause 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.
- The fifth cause of false alarms is EMI/RFI interference. A mobile phone can be used to test susceptability to RFI by placing the aerial against the PIR casing and transmitting. You can fit an ACT1376 stabiliser inside the PIR to eliminate RFI.
The attacthed pictures are a step-by-step guide to control panel fault finding. Always perform the tests in the order shown.
When the illustrated checks have been performed to Step 10, a number of other tests should be undertaken in a control panel checklist in the following order:
11 Battery test: Record temperature, voltage and capacity available. Replace battery when reading falls below 65 per cent of Ah capacity.
12 Circuit resistance tests: Record all circuit resistances. Circuits must be removed from control panel before testing.
13 Circuit earth leakage test: Check for resistance between zone, tamper and earth. Test with metre on highest Meg Ohm range.
14 Bell tamper return test: record resistance between OV and removed tamper return. Check for stable resistance. Ring bell to induce vibration.
15 Panel zone walk test: Walk test all detection zones to confirm operation. Check each circuit operates normally, especially after lightning.
16 Self-activating bell test:Remove hold-off voltage to confirm operation. Replace if defective.
17 Bell and strobe test: Activate bell and strobe to confirm operation. Replace if defective.
18 Communicator test: Activate communicator to confirm operation. Confirm correct operation with alarm receiving centre.
Wiring and connections: Check panel for incorrect or loose wiring connections. Check all cables are marked and connected correctly.
Source
Security Installer
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