Appendix A: Power Considerations; A.1: Supplying Power To 24 Vdc Detectors And Nacs; A.1.1: Resistance And Size - Honeywell SLC Installation Manual

Appendix A: Power Considerations

A.1 Supplying Power to 24 VDC Detectors and NACs
A.1.1 Resistance and Size
To determine the minimum resistance that can be tolerated in supplying power to 24 VDC 4-wire
devices and NACs, use the calculation below. Use this resistance to select the proper gauge wire for
the power run from the manufacturers specifications for the desired wire.
For Four-Wire Detectors:
For NACs:
Where:
Rmax = maximum resistance of the 24 VDC wires
Vms = minimum supply voltage
Vom = minimum operating voltage of the detector or end-of-line relay, whichever is greater, in volts
N = total number of detectors on the 24 VDC supply circuit
Is = detector current in standby
Na = number of detectors on the 24 VDC power circuit which must function at the same time in alarm
Ia = detector current in alarm
Ir = end-of-line relay current
Nb = number of Notification Appliance Devices
Ib = Notification Appliance current when activated
NOTE: This simplified equation assumes that the devices are at the end of a long wire run.
The minimum supply voltages produced by Fire•Lite power supplies are listed below:
68
Rmax =
Rmax =
FACP
MS-9200
MS-9600
MS-9200UD/MS-9200UDLS 19.05
MS-9050UD
Table A.1 Minimum Supply Voltage
(Vms - Vom)
(N)(Is) + (Na)(Ia) + (Ir)
(Vms - Vom)
(Nb)(Ib)
Vms Power Supply
16.0 FCPS-24F
16.0 FCPS-24FS6/FCPS-24FS8
18.75
FireLite SLC Wiring Manual — P/N 51309:P4 9/17/2014
Vms
19.1
19.1