EST EST3X - Introduction; Notification Appliance Signaling Line Circuit Calculations; What You will Need

Appendix A: System calculations
242 EST3X Technical Reference Manual
Notification appliance signaling line circuit
calculations
Introduction
This topic shows you how to determine the maximum cable length of a
notification appliance circuit for a given number of appliances.
Two methods are presented: worksheet and equation. The worksheet method is
simpler, but your installation must meet the criteria listed on the worksheet. If
your installation does not meet these criteria, you need to use the equation
method.
The methods given here determine cable lengths that work under all operating
conditions. The calculations ensure that the required operating voltage and
current will be supplied to all notification appliances. To do this, we assume these
two worst-case conditions:
• The voltage at the NAC terminals is the minimum provided by the power
supply
• The notification appliances are clustered at the end of the NAC cable
Other, more detailed methods that distribute the appliance load along the NAC
cable may indicate that longer cable runs are possible.
What you will need
Appliance and cable values
Whether you use the worksheet method or the equation method, you will need to
know the following:
• The minimum operating voltage required for the appliances
• The maximum operating current drawn by each appliance
• The resistance per unit length of the wire used (Ω/ft)
This information can be found on the appliance installation sheets and on the
cable specification sheet.
NAC source values
For either method, you will need some fixed or calculated operating values for
your specific NAC circuit source. An EST3X control panel has three possible
sources. These are listed in Table 76 along with their fixed values.