Securitron PSM_Series - Manual (Page 3)

PN# 500-16200
Page 3 Rev. D, 08/11
and automatically take the batteries off the load. At that point the "on battery" contacts will
switch back to normal condition and a red "system disconnect" LED will illuminate on the panel
enclosure cover. The system disconnect condition will also terminate the low DC signals (LED,
pulsing Sonalert and "trouble" contacts) as the PSM no longer has the power to operate these
functions. The PSM itself is dependent on the battery power which has now been terminated.
There are two reasons for this system disconnect. Once the batteries are close to the end of
their capacity, there is no reason to throw them into deep discharge as this is somewhat harmful
to the batteries. The more significant reason is that security equipment designed to run at 12 or
24 volts will begin to fail in hard to predict ways as the operating voltage drops below 10.5 or 21
volts. Operating an installation at this sort of indeterminate voltage can even create a
safety hazard. For example, consider a perimeter security installation that employs magnetic
locks and control devices for the locks such as timers or powered exit devices. With declining
system voltage, a situation could arise where the locks were still largely holding but the control
devices were failing because of low voltage. This would render the doors unusable. It is
therefore safer to abruptly cut power when voltage falls into an indeterminate range.
When the PSM has disconnected the batteries, they still supply a small amount of power
sufficient to illuminate the red LED. There are also some leakage currents such that a battery
pack in system disconnect will continue to be drained at roughly 50 mA. While quite small, this
current will eventually deep discharge the batteries, so the user should always try to restore
normal charging as soon as possible.
System disconnect is accomplished by a set of 10 Amp rated contacts on terminals F1 and F2 in
the PSM which will open in system disconnect. These terminals are wired in series with the load
(see Section 5.2).
5. WIRING
5.1 BASIC WIRING WITH SECURITRON POWER SUPPLY
"Basic" wiring permits the PSM to perform all of its monitoring functions but does not include
system disconnect. This is because system disconnect wiring may be done in two different ways
depending on whether there is a second system disconnect switch. See Section 5.2.
FIG. 1: PSM BASIC WIRING WITH SECURITRON POWER SUPPLY
NC NC NO C NO C B+ F1 F2 NC C NO
TROUBLE
SPDT
OUTPUT ON BATTERY
SPDT
OUTPUT
SYSTEM
DISCONNECT
SPDT
OUTPUT
(NORMALLY
ENERGIZED)
B+ F1 R1
PSM
BATTERY
PACK
SECURITRON POWER SUPPLY
For basic wiring, refer to Figure 1. This shows all of the PSM terminals and the basic four wire
hookup to any of the Securitron power supplies called out in Section 2 of this manual. Be sure
that the voltage of the PSM (12 or 24) matches the voltage of the power supply.