GE Security EST3 User Manual

System calculations
EST3 Installation and Service Manual B.15
Calculating cable length
To calculate the maximum NAC cable length:
1. Calculate the total current (Itot) as the sum of the maximum
operating currents for all the appliances.
Itot = ΣIa
Where:
Ia = appliance maximum current
See the appliance installation sheets for Ia. Remember to use
the maximum operating current specified for DC power.
2. Calculate the minimum voltage (Vm).
Vm = Vr − (Itot × K)
Where:
Vr = rated voltage
Itot = total current (from above)
K = load factor
For the power supply, Vr is 20.4 V and K is 0.37 V/A.
3. Calculate the allowable voltage drop (Vd) between the
power supply and the appliances.
Vd = Vm − Va
Where:
Vm = minimum voltage (from above)
Va = appliance minimum voltage
For regulated notification appliances, Va is 16 V. For
unregulated notification appliances, Va is the lowest
operating voltage specified on the appliance installation
sheet.
4. Calculate the maximum resistance (Rmax) the wire can
have.
Rmax = Vd / Itot
Where:
Vd = voltage drop
Itot = total current
5. Calculate the maximum length of the cable (Lc), based on
the maximum resistance allowed, the resistance of the wire,
and the number of wires in the cable (two).
Lc = (Rmax / Rw) / 2
Where:
Rmax = maximum resistance
Rw = wire resistance factor

GE Security EST3 Specifications

General

Brand	GE Security
Model	EST3
Category	Security Sensors
Language	English