Emerson Bristol 2808 Series - High Power Conductors and Signal Wiring; Lightning Arresters & Surge Protectors; Use of Proper Wire Size

S1400T-2808B Page 5-4 Section 5 - Wiring Techniques
5.2.7 High Power Conductors and Signal Wiring
When routing wires, keep high power conductors away from signal conductors. Space wires
appropriately to vent high voltage inductance. Refer to the National Electrical Code
Handbook for regulatory and technical requirements.
5.2.8 Use of Proper Wire Size
Series 2808 Transmitters utilize screw terminals that accommodate up to AWG 14 gauge
wire. Allow some slack in the wires when making terminal connections. Slack makes the
connections more manageable and minimizes mechanical strain on the PCB connectors.
Provide external strain relief (utilizing Tie Wrap, etc.) to prevent the loose of slack at the
2808 Transmitter.
Be careful to use wire that is appropriately sized for the load. Refer to equipment
manufacturer’s Specs. and the National Electrical Code Handbook for information on wire
size and wire resistance. After installing the field wiring, test each load to determine if the
correct voltage or current is present at the load. If you know the resistance of the field wires
(Circular Mills x Length) you should be able to calculate the load voltage. Conversely, if you
know the minimum load voltage and current, you should be able to derive the maximum
voltage loss that is allowable due to line resistance and then the correct wire size.
Referring to Figure 5-2, a relay that is picked by 100 mA, with a loop supply voltage of 24V
and a total line resistance of 20 ohms, the load voltage (voltage across the relay) should be:
V
L
= V
S
- (V
C
+ V
C
) where V
C
+ V
C
= (R
C
+ R
C
) I
22 = 24 - 2 where 2V = (20 Ω) x 0.1 A
Figure 5-2 - Calculating Load Voltage due to Line Resistance
5.2.9 Lightning Arresters & Surge Protectors
Use lightning arresters in association with any radio or modem equipped unit. BBI 9600
bps modems are equipped with surge protection circuitry. Lightning arresters or Antenna
Discharge Units should be placed on the base of the antenna and at the point where the
antenna lead (typically coax) enters the site equipment building. When a modem is used, a
lightning arrester should be placed at the point where the phone line enters the site
equipment building. If you use a modem (manufactured by other than BBI) it is
recommended that you also install a surge suppressors or lightning arrester on the phone