System Sensor PDRP-1001 - Manual (Page 19)

Initiating Device Circuits 2. Installation
PDRP-1001 Instruction Manual PN 50734:D0 04/06/01
19
Four-Wire Smoke Detector Connections
A maximum of 200mA is available from the 24VDC Resettable Power circuit on TB1 (+24VR terminals).
Any power that is drawn from the 24VDC Nonresettable Power on TB2 (+24VNR terminal) must be
subtracted from available resettable power. See "Specifications" on page 12 and "Powering External
Devices" on page 22.
Note: Refer to the "Appendix B: Compatible Devices" on page 39 for suitable 4-wire smoke detectors.
Notes on Style D (Class A) and Style B (Class B) field wiring:
1. The Power Supervision Relay coil leads must be connected to the last detector base 24V screw
terminals.
2. Calculation of the maximum allowable resistance in the 24VDC resettable power wiring:
Where:
Rmax = maximum resistance of the 24 VDC wires
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
Figure 8 Typical Connection for Four-Wire Smoke Detectors
Rmax =
(20.6 - Vom)
(N x Is) + (Na x Ia) + (Ir)
–
–
+
+
–
–
+
+
TB1 TB4
IN #1
B+ A+ A– B–
IN
B+ A+
MS
44
-4
wir
esd
.cd
r
24 VDC Four-wire
Smoke Detectors
4.7K, 1/2-Watt ELR
PN 71252 (UL listed)
Power
Supervision
Relay
(A77-716B)
Style B
Initiating Device Circuit
Control Panel
Power Circuit