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A.1 Supplying Power to 24 VDC Detectors and NACs
Resistance and Size
To determine the maximum allowable resistance that can be tolerated in supplying power to 24 VDC four-wire devices and NACs, use
the calculations below. These simplified equations assume that the devices are at the end of a long wire run. With the computed resis-
tance and using the manufacturers specifications for the desired wire, select the proper gauge wire for the power run.
For Four-Wire Detectors:
For NACs:
Where:
R
= maximum resistance of the 24 VDC wires
max
V
= minimum supply voltage (see Table A.1 below)
ms
V
= minimum operating voltage of the detector or end-of-line relay, whichever is greater, in volts
om
N = total number of detectors on the 24 VDC supply circuit
I
= detector current in standby
s
N
= number of detectors on the 24 VDC power circuit which must function at the same time in alarm
a
I
= detector current in alarm
a
I
= end-of-line relay current
r
N
= number of Notification Appliance Devices
b
I
= Notification Appliance current when activated
b
NOTE: This simplified equation assumes that the devices are at the end of a long wire run.
The minimum supply voltages produced by Notifier power supplies are listed below:
AFP-100
AFP-200
NFS-640
CPS-24 on NFS2-640, NFS-320, or NFS-320SYS
A.2 Supervising 24 VDC Power
There are options for supervising 24 VDC power, as discussed below, according to Class A or Class B of NFPA 72-2013.
•
Using FlashScan Type Codes with Built-In Power Supervision (Appendix A.2.1)
•
Power Supervision Relay (Appendix A.2.2) (two-wire, Class B only)
•
Using the FCM-1 module without relay (Appendix A.2.3)
A.2.1 Using Type Codes with Built-In Power Supervision on N16, NFS2-3030, NFS-3030,
NFS2-640, NFS-320 and NFS-320SYS
Certain FlashScan type codes have external power supervision built into the software. For details, refer to "Devices Requiring External
Power Supervision" in the appropriate installation manual.
A.2.2 Power Supervision Relay
Power used to supply 24 VDC detectors, notification appliances (using the FCM-1) and two wire detectors (using the FZM-1) can be
supervised with a power supervision relay. This relay, energized by the 24 VDC power itself, is installed at the end of each respective
power run and wired in line with the supervised circuit of any intelligent module. This satisfies Class B supervision requirements under
UL 864 10th edition.
When power is removed from the relay, the normally closed contacts open the supervised circuit, generating a trouble condition. There-
fore, the relay needs to be installed at the end of the supervised circuit, so it does not disrupt the operating capability of all the devices on
66
Appendix A: Power Considerations
(V
R
=
max
(N)(I
(V
R
=
max
(N
FACP
Table A.1 Minimum Supply Voltage
- V
)
ms
om
) + (N
)(I
) + (I
)
s
a
a
r
- V
)
ms
om
)(I
)
b
b
Vms
18.1
MPS-24B
19.4
FCPS-24
19.15
MPS-24A
19.48
FCPS-24S6/FCPS-24S8
MPS-400
ACPS-2406
AMPS-24
ACPS-610
APS2-6R
PMB-AUX
Notifier SLC Wiring Manual — P/N 51253:U9 12/3/2021
Power Supply
Vms
20.1
19.1
19.6
19.1
19.23
19.8
20.14
19.57
20.0
20.03
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