MR-2900 Installation Manual
19
Style Z (Class A) Bell Circuit
This is a 4-wire Style Z (Class A) power-limited and
supervised signalling (notification appliance) circuit.
Devices are connected as illustrated in Figure 22.
Maximum wire lengths are shown in Table 4. This is
for the total length of wire, from the panel to furthest
device and back to the panel. Use only approved
devices. Return wiring must be in a separate conduit.
Table 4: Maximum Wire Lengths for Bell Circuits
Relay Connections
Unused relays are left unconnected. General Purpose Relays and System
Relays operate identically and are wired the same (see Figure 23).
All relay wiring is unsupervised. The general purpose relays (Function
Relays 1-4) have a power factor of .35, power-limited at .6A @ 30VAC/2.0A
@ 30VDC. The Alarm, Supervisory, and Trouble relays have a power factor
of .35, power-limited at .5A @ 30VAC/1.0A @ 24VDC.
Auxiliary Power Circuits
The auxiliary power circuits provide 24 VDC for external
devices. The polarity of the circuits is shown in Figure 24.
The Control Unit does not interrupt this circuit. For the wiring
to be power-limited and supervised an end-of-line relay (Part
number PAM-3) must be used. The relay is a 24VDC coil
with 3A contacts.
Note:
The inrush current of some devices may cause the current to exceed the 1.5A current limit
momentarily.
250 mA
500 mA
750 mA
1.0 A
1.25 A
1.50 A
12 AWG
1220m (4000 ft) 610m (2000 ft)
407m (1300 ft)
305m (1000 ft)
244m (800ft)
203m (667ft)
14 AWG
732m (2400 ft)
366m (1200 ft)
244m (800 ft)
183m (600 ft)
146m (480ft)
122m (400ft)
16 AWG
457m (1500 ft)
229m (750 ft)
152m (500 ft)
114m (375 ft)
91m (300ft)
76m (250ft)
Regulated 24 FWR
MR-2937
“Class A”
Converter
Figure 22: Style Z (Class A) Bell Circuit
Wiring
Figure 23: Relay
Figure 24 Auxiliary Power Connections
