SFC-102 Installation & Operator’s Manual
15
To calculate the wire run distance for any gauge wire and any maximum current value, use the following
formula:
Secur-bus Capacitance
Maximum wire capacitance for proper operation of the Secur-bus is 90 nF (nanofarad). Typical wire
capacitance for 22 awg quad cable is 20 nF per 1,000 feet. Thus, for 22 awg quad cable, the maximum wire
run distance is ((90/20)× 1,000) =
4,500 feet
. Other types of wire have different capacitance values. Consult
the wire manufacturer’s data sheets for typical capacitance values.
The following devices may be connected to the Secur-bus. All devices are supervised. See section for adding
and deleting devices on the Secur-bus.
Remix =
1.25
ohms
Immix
Amps
Distance =
Remix × 1,000
feet
2(wire resistance in ohms per 1,000
feet)
Note:
Shielded wire has a much higher capacitance value and distances are severely reduced.
Devices
Description
MR-2605-T
External to control panel.
Up to 4 of each device may be connected.
MR-2605-AT
MR-2806
Mounted inside control panel. See diagram in “3.3
Mounting the SFC-102” on page 9.
1. Do not run the Secur-bus adjacent to sources of high transient noise such as AC wiring, tele-
phone cable bundles or computer wiring.
2. If the Secure-bus must go through a high transient area, use shielded cable.
3. If shielded cable is used, the distances in the chart above are cut in half.
