Securitron PSM-24, PSM-12 Installation Instructions

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SECURITRON MODEL PSM-12, PSM-24 POWER SUPPLY MONITOR

INSTALLATION AND OPERATING INSTRUCTIONS

1. DESCRIPTION

The Power Supply Monitor is a microprocessor controlled product which provides comprehensive
monitoring of a strictly regulated battery charging power supply. Separate versions are
available for 12 and 24 volt power supplies. The PSM performs a series of continuous and
periodic tests to detect possible problems with the power supply and battery pack. Failure of
any of these tests is reported by both local and remote signals. The PSM can therefore be used
as a stand alone monitor or it may be connected to an alarm system.

The PSM also reports any time the batteries are switched into the load circuit (from a local
power outage for instance). Finally the PSM will disconnect the batteries from the load when
their output falls below 88% of nominal. This is to preserve them from going into deep
discharge and to prevent the load receiving a low voltage that may cause operational problems.

2. APPLICABLE POWER SUPPLIES

The Power Supply Monitor is qualified for use with Securitron power supplies models: BPS-12-3,
BPS-12-4.5, BPS-12-6, BPS-12-9, BPS-12-15, BPS-24-2, BPS-24-3, BPS-24-4, BPS-24-6, and
BPS-24-10. It is not qualified for use with Securitron 1 Amp power supplies. There are
two reasons for this. First, the PSM requires power to ope rate: 200 mA @ 24 volts; 250 mA @
12 volts and therefore reduces the total capacity of the supply. It is hard to justify its use with a
small capacity supply. Second, Securitron 1 Amp supplies are not "strictly" regulated. This
simply means that their output voltage varies somewhat with the load. While this does not
cause operational problems (the variation is low), it would create con stant "false alarms" on the
part of the PSM, which expects strict regulation.

The issue of using the PSM with non Securitron power supplies is uncertain. The
general type of supply that can be used with the PSM is one that will operate the load with or
without batteries. When batteries are added, they are continuously trickle charged and
automatically take over the load (generally through a diode), only when the normal DC output o f
the power supply drops out. The specific supply, however, may have some operating
characteristic that makes it unsuitable for use with the PSM. Check with the factory.

3. TESTS

3.1 VOLTAGE LEVEL TESTS

To properly charge the batteries, the power supply should out put a precise voltage: 13.65 volts
for a 12V battery pack and 27.3 volts for a 24V battery pack. If the voltage is too low, the
batteries will never get fully charged. If it is too high, they will heat up and suffer reduced life­span. The PSM continually monitors this voltage and will report a low or h igh failure. If the h igh
or low condition in output voltage is short lived, it will be ignored. A good example of this is a
momentary drop in voltage caused by a large load being switched in. The out of range voltage
condition must be maintained for 30 seconds for the PSM to report it.

Once the high or low condition is maintained for 30 seconds, the PSM will report it in latching
fashion. A "high" or "low" yellow LED will illuminate on the PS M enclosure cover, the Sonalert
will emit a pulsing output and SPDT "trouble" contacts will switch for remote signaling. This
signal will be maintained even if the out of range voltage condition has corrected itself. The
power supply should still be examined. To reset the unit, voltage should be adjusted to the
correct level and then the reset toggle on the enclosure cover should be momentarily depressed.

Power supply adjustment should be done as follows. With the PSM connected to the power
supply as explained in Section 5, identify the voltage adjustment potentiometer on the power
supply. Slowly turn the pot so as to increase the voltage until the green "power normal" L ED
just turns off. Then slowly turn the pot in the opposite direction (the green LED will immediately
come back on) until the green LED turns off because of low voltage. Center the pot between
these two points of movement. If you have a voltmeter to confirm your result, voltage should
be at roughly 13.65V for a 12 volt unit and 27.3V for a 24 volt unit.

© Copyright, 2011, all rights reserved PN# 500-16200
Page 1 Rev. D, 08/11

3.2 BATTERY TEST

The only way to reliably test a battery pack is to disconnect it from its trickle charge circuit,
apply a load to it and measure the performance of the battery pack. A perfect test would
duplicate the actual load and conduct the test for the amount of time that the pack could be
expected to operate the load. Such a complete test would not only verify that the battery pack
was prepared to operate the load for some time, but would verify the full rated capacity of the
pack.

In a working installation, such a test is obviously impossible. It would not only ta ke too long but
would risk leaving the batteries in a discharged state at the moment that a real power failure
occurs. It is important therefore to understand what Securitron's PSM battery test signifies. The
battery pack is automatically disconnected and a heavy test load of two Amps is applied. The
test duration is three minutes every eight hours and during this time, the battery voltage is
monitored. If it does not fall below 11.5V (for a 12 volt pack) or 23V (for a 24 volt pack), the
test is considered passed and no alarm signal is sent. Such a test indicate s that the batteries
are properly connected and charging and that they have no major defect such as an internal
shorted or open cell. The end user is assured that in an actual power failure the batteries wi ll
operate the working load for some time, but it is possible that they may not deliver their full
rated capacity. Battery performance varies with temperature and degrades over time.
Batteries must be replaced every five years minimum. It is vital that the presence of the

Power Supply Monitor not lead to a false sense that as long as the Monitor does not
signal an alarm, the batteries are in perfect condition.

Another concern in automatic battery testing is that during the test, the batteries are
disconnected from the trickle charge voltage source. It is possible that an actual power failure
could occur during the test and, if so, the test must be immediately terminated so that the
batteries can return to their primary function of backing up the working load. In Securitron's
model PSM, this is automatically accomplished by detecting an actual DC output power failure
and terminating any concurrent battery test as well as preventing any test from beginning
during the period of power failure.

Battery test reporting is as follows. A yellow LED o n the enclosure cover illuminates during th e
test duration (three minutes every eight hours). If the test fails, it terminates at the failure
point and a red "loading failed" LED comes on. The Sonalert sounds a continuous tone and the
"trouble" relay contacts switch. Note that this auto matic test will not be conducted if the PSM is
in alarm from another condition such as voltage out of range. To reset the unit, the reset togg le
on the enclosure cover should be momentarily depressed. Be sure to replace the battery

pack upon any battery test failure.

It is possible to trigger a battery test manually at any time the PSM is in normal condtion.
Simply press the momentary "load test" toggle on the enclosure cover.

4. "ON BATTERY" REPORTING AND SYSTEM DISCONNECT

The PSM also reports any power failure when the batteries have switched in and are operating
the load. A yellow "on battery" LED will illuminate showing that the batteries are a ctive and the
"on battery" SPDT remote contacts will switch. The Sonalert will not sound from this effect as
this is not a test failure condition, but after 30 seconds, a low DC failure will also be detected so
the Sonalert will begin to pulse and the "trouble" contacts will switch. Note that the term "power
failure" does not only refer to a line voltage failure. The power supply could have an internal
failure which has either terminated or lowered its D C output. Any of these conditio ns will lea d to
the batteries taking over the load and the PSM will report that fact regardless of the cause.

Once the batteries have been switched in, they will only be able to operate the load for a defined
period of time depending on their capacity and on the current being drawn by the load. The
PSM's signal that the batteries have been switched in, can therefore be considered a type of
advance warning. If DC power is not restored, the installation will go down. The end user
should have an idea of how much reaction time he has by knowing the installation load current
and the battery pack size.

Under battery operation, the load will receive nearly the correct voltage until the batteries are
close to the end of their capacity. At that point, battery voltage will begin to fal l off rapidly. Th e
PSM will detect the point at which battery voltage has dropped to 88% nominal (10.5V or 21V)

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and automatically take the batteries off the load. At that point the "on battery" contacts will

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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 (LE D,
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 so mewhat 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 opera tin g voltage drops belo w 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 magne tic
locks and control devices for the locks such as timers or pow ered 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 batte ry
pack in system disconnect will continu e to be drained at roughly 50 mA. While quite small, thi s
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

PSM

C

NC NC NOC

C

ON B ATTERY
SPDT

OUTPUT

NO

TROUBLE
SPDT
OUTP UT

BATTERY
PACK

B+

B+

R1

F1 F2

F1

NC

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 ma nual. Be sure
that the voltage of the PSM (12 or 24) matches the voltage of the power supply.

NO

SYSTEM
DISCONNEC
SPDT
OUTP UT
(NORMALLY
ENERGIZED)

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