5.4 Connecting Multiple Units
Two or more HPFF8 and/or HPFF12 units can be connected to each other to provide additional NAC
extenders for a system; see wiring in Figures 5.5–5.10 and in the HPFF8 manual PN 53499.
Maintain separation of power-limited and non-power limited wiring as discussed in Section 2.5,
"Power-Limited Wiring Requirements".
NOTE: Multiple units should not be connected in a "daisy chain" fashion. DO NOT connect a
NAC output of one unit to the initiating device signal input of the next unit. The synchronization
signal will not pass unimpeded through multiple units with this wiring method.
NOTES for Figures 5.5–5.10:
The FACP's NAC output must be regulated (not Full Wave Rectified [FWR]) if the HPFF is programmed for
The number of possible units that can be interconnected depends on the current capability of the FACP
output. Each HPFF8 input draws 12.26 mA at 24 VDC.
The total line impedance for interconnected units cannot be such that it creates a voltage drop > 2 VDC.
Zline total =2V/(1 Unit + 1 ELR)
Example: Zline total = 2V/(12.26 mA + (24-2)/4.7K) =118.1 ohms
Figure 5.5 Typical System Connections
Figure 5.6 System Sync Connections
HPFF12 NAC Expander — P/N 53576:B 11/24/2010
Connecting Multiple Units