5
ELECTRICAL RATINGS*
24 VDC Power
You may connect multiple PS-5N7s to the
same 24V power supply as long as the total
line loss is within specified limits. Follow the
information given below to calculate the
allowable line losses.
CAUTION
Failure to follow these guidelines
may result in excessive voltage
drops that cause improper or no
operation of the system.
To determine the total line loss, and there-
fore, the maximum cable length permitted,
use the following values and limits.
V
max
—The maximum allowable voltage
loss due to wire resistance. V
max
must
not be more than 4V. (See Table 2.)
I
max
—The total alarm current drawn by
all PS-5N7 modules connected to the 24
VDC supply. If a PIM-1 is used in the
system, include its current. (See the I
max
values for the approved power supplies
at the bottom of this column. See Table
1 also.)
R
max
—The value of wire resistance
that results in a 4 volt drop due to Imax.
To calculate the total line loss, use the fol-
lowing equation:
R
max
= V
max
÷
I
max
(Where V
max
= 4V in all cases)
The Rmax result obtained with this equation
is the total of all wire resistance in ohms in
the 24 VDC supply lines.
The following power supplies are compat-
ible with the PS-5N7. They are listed with
their maximum output current (I
max
):
MMB
1 amp
PSR-1
2 amps
PLM-35
1.5 amps
ALARMSAF
4 amps
PAD-3
3 amps
The maximum module current is shown in
Table 1 below.
Table 1
Maximum Module Current
Model
Imax
PS-5N7
300mA
PIM-1
20mA
Once the wire resistance is calculated, use
Table 2 below to determine the maximum
allowable cable length. (See Figure 5.)
Table 2
Wire Resistance
AWG
Ohms/1000
Feet
10
1
12
1.6
14
2.6
16
4.1
18
6.5
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