1 intrusion alarm technology power supplies. 2 intrusion alarm technology security systems shall...
TRANSCRIPT
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INTRUSION ALARM TECHNOLOGY
POWER SUPPLIES
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INTRUSION ALARM TECHNOLOGY
Security systems shall have a primary power source and a secondary power source.
The primary power source shall be provided by a 20 amp source and it should be a dedicated outlet, if the outlet is not dedicated it shall not exceed combined load of 20 amps.
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THE PRIMARY POWER OUTLET SHALL NOT BE A SWITCHED OUTLET.
If an existing outlet is to be used you should verify that it can’t be shut off by a wall switch.
The outlet should not be a GFCI or an arc fault outlet either, if the outlet trips it will put unnecessary wear on the battery backup.
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Surge protection should be provided to prevent system damage and eliminate false alarms from electrical surges or spikes.
Receptacles for dedicated kitchen, dining rooms, laundry or other such circuits should not be used for alarm systems.
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The primary power for alarm systems is delivered by a class 2 power limiting device like a power transformer.
These transformers are hardwired by the installer.
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INTRUSION ALARM TECHNOLOGY
Typical voltages for burglar alarm systems can range from 9VAC to 17VAC at 20VA to 50VA.
The screw is designed to secure the power pack to the outlet and is not used as a ground connection.
These transformers should be screwed to the outlet to prevent accidental disconnection.
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The cable used for wiring the transformer is called lamp cord or zip cord.
It’s an 18/2 cable and looks like the cords used on traditional lamps, hence the name lamp cord.
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INTRUSION ALARM TECHNOLOGY
Because the transformer is plugged into an AC power source polarity doesn’t matter, so you do not need to use polarized wire.
Polarized wire simply has a white stripe on one side to indicate the ground or negative side of the cord, this mark is also commonly found on speaker wire.
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The power cord from the transformer up to the control panel should be placed in wire mold to protect the cable and keep it from being accidently snagged or caught on anything.
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The secondary power must be an approved generator or back up battery for the intrusion alarm system.
The battery back up must maintain the system in idle condition for four hours.
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If the system is a combination burglar fire alarm system the secondary power must maintain the system in non-alarm mode for 24 hours.
This doesn’t apply to a burglar alarm system that incorporate smoke detectors.
The secondary power must activate within 10 seconds after primary power is lost.
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When the system diverts to battery back up the keypad should indicate that the system is using battery back up.
If primary power is working and the system keypad indicates battery, then the circuit breaker is probably tripped an should be addressed immediately.
Most systems will also indicate low battery.
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Batteries for intrusion systems are typically sealed lead acid (SLA) batteries.
The batteries are rated by voltage and amp hours (Ah).
Amp hours indicate how long the battery will supply power (hours) based on how many amps are being drawn from the system (amps).
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Manufactures will provide the minimum specifications for battery back up, i.e. 12VAC-4Ah.
These specifications will cover the minimum 4 hour back up time.
If the customer wants a longer back up time you will have to calculate the amp hour requirements for the system.
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The installation manual will provide you with the amperage draw of each device connected to the system.
They may even provide a work sheet for determining amp hours.
If you’re using generic devices on a burglar alarm system you can get the specs for each device from that manufactures installation form.
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Bottom line is you want to add up all of the amperages for all of the devices connected to the system.
Multiply the total current times the number of back up hours desired and it will equal the total amp hours needed
AMPS x HOURS = Ah
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Alarm devices typically draw milliamps so you will need to convert milliamps to amps.
A key pad may draw 50 mA or .05 amps, to convert from milliamps to amps you move the decimal point 3 places to the left.
It is easier to add all of the device amperages first and then convert them to amps.
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Here is an example of a current draw worksheet with the part number and the current it uses, notice that you need to indicate how many of each device your installing.
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If we add up all of the amperages assuming we are only installing one of each, the sum equals 785mA (15 & 35mA was used for the two with the subscript ).
The control panel uses approximately 100mA, 785mA + 100mA + 885mA.
885mA converted to amps = .885 amps.
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If the customer wants 24 hour back up for the system then we would multiply .885 x 24 hours = 21.24Ah.
This would require installing three 12VAC 7Ah hour batteries.
In order to increase amperage the batteries will need to be connected in parallel, to increase voltage batteries are connected in series.
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Batteries connected in series and parallel, notice the outputs of each;
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If there isn’t any room in the panel for three batteries then another enclosure will need to be added to house the batteries.
A piece of conduit should be installed between the two enclosures.