Specifications

Diagrams are for reference only.

Consult the appropriate installation sheet for wiring details.

3-SAC DATA BUS & 3-SAC POWER3-SAC DATA BUS & 3-SAC POWER

3-SAC DATA BUS & 3-SAC POWER

REFERENCE SECTION

3-SAC Data Bus

SAC bus wiring riquirements

Type: unshielded, twisted pair, > 6 twists per foot

Maximum bus length: 4,000 ft (1,220 m) @ 25 pF/ft

Maximum total circuit capacitance: 0.1 µF

Maximum total circuit resistance: 52 Ohms

3-SAC Power

This topic provides information to help you determine whether:

• A power supply must be added to the SAC bus

• Adequate voltage will be available to CRCs and KPDISPs on the SAC bus

• The standby battery in each CRC is properly sized

Determining the need for a remote power supply

The need for additional power is dictated by the current drawn by the devices on the

SAC bus. Each 3-PPS/M can supply a total of 7 A through two 3.5 A outputs. Each

SAC line can therefore draw a maximum of 3.5 A. This consists of the current drawn by

the CRCs and KPDISPs plus any readers, strikes, or maglocks.

If the load on the 3-PPS/M supply is greater than 3.5 A, you’ll need to split the devices

over two SAC buses, or add a remote power supply.

To determine the total load on the 3-PPS/M:

1. Complete Form A (below) to calculate the system alarm and standby load current.

2. Total the columns to determine the Total Alarm Load and Total Amp Hours. These

two totals will be used in later calculations.

3. If the Total Alarm Load is greater than 3.5 A, the devices must be divided between

two SAC buses, each with a separate supply — OR — a remote power supply

must be installed.

4. If a remote power supply is used a ground wire must be between the 3-SAC and

the remote power supply.