PTI security systems Falcon XT Installation Manual page 40

If multiple power
supplies are required
to power all of the AI devices
on a site, you must use an RB5
relay at every power supply to
ensure that all devices and power
supplies can be reset from the
main controller circuit board. See
Adding Additional Power Supplies
for more information.
Always power sirens,
maglocks, and door
strikes from power supplies that
are separate from the ones that
power AI devices. Never use the
controller or any remote power
supply that is connected to an AI
device to power these types of
devices (sirens, maglocks, door
strikes) as they have significant
amperage draw and can lock up
the entire system. A remote power
supply can be used to power
these items in some cases, but
it needs to remain separate from
the AI devices. Remember to
take voltage drop and amperage
needs into consideration with
these items also. Refer to
manufacturer specifications for
voltage needs and amperage
restrictions for these devices.
36
Voltage Considerations
Voltage drop is a serious consideration when planning a site. Wire
has resistance that reduces the available voltage the further along
the line that the voltage travels. Additional AI devices on the line also
reduce the voltage. All devices connected to the controller require
a minimum of 12VDC to power them. If the power at a specific AI
device falls below 12VDC due to a long length of wire with multiple
AI devices on it, then the entire system can lock up. Each AI device
must receive at least 12VDC when the system is at full amperage
load.
For this reason, always power sirens, maglocks, and door strikes from
separate power supplies, never from the controller or from a remote
power supply connected to AI devices. Sirens, maglocks, and door
strikes have significant amperage draw as they are initially powered
up to sound or open. This can draw the system below 12VDC during
this short period if they are connected to the same power supply as
the rest of the system, resulting in system failure.
Dealing with Amperage and Voltage needs
While planning the layout of a system, it may become obvious
that the 2 amp power supply in the controller is insufficient for the
number of AI devices or for the wire length. Should this be the case,
additional power supplies can be purchased and placed on the line
as necessary. Refer to Adding Additional Power Supplies for more
information.
Battery Backup Calculation
Battery backup time is equal to the current draw (amps) divided by
the amp hour rating of the battery. For example: if the system draws
2 amps and the battery is rated at 4 amp hours; the battery backup
should last for 2 hours if the battery is fully charged and all other
conditions are right (4 ÷ 2 = 2). Certain external issues can influence
this length of time, such as the age and condition of the battery,
damage to the battery or power supply, power surges, and/or the
level of charge in the battery. Also, each time the AI device is used
while the AC power is out will reduce the total backup time as the
current draw increases slightly when the keypad is in use.