Determining Wire Length And Size For Input Power - Teledyne Meridian User Manual

4.1.6 Determining Wire Length and Size for Input Power

Determine the proper wire length and size required to provide the proper voltage to the device(s). If the proper
voltage does not reach the device, it will not function properly. This is referred to as voltage loss and must be
planned for when installing. The formula for calculating the maximum wire length is:
Where:
Dir = Maximum wire length in feet based on the wire's loop voltage
VPowerSupply = Power supply output voltage
VMin = Minimum current voltage of device
IMax = Maximum current in amperes
RWire = Resistance of wire in Ohms/foot
To determine the maximum wiring distance, calculate the wiring's maximum allowable voltage drop by subtracting
the device's minimum operating voltage from the power supply's output voltage. Then, use
Cable Data for Input Power Length Considerations
Table 4-6: Typical Cable Data for Input Power Length Considerations
Cable Size
Cable Size
(Awg)
22
20
18
16
14
12
10
Note: Maximum allowable voltage drop can be calculated based on power supply output voltage and the device minimum voltage and maximum
current requirements. For 3 or 4-wire= 10VDC* Min. input, for 2-wire= 18VDC* Min. input.
*These values are subject to change.
WARNING: INSTALL ACCORDING TO APPLICABLE INTRINSICALLY SAFE WIRE PRACTICE
OR STANDARDS (i.e. IEC/ECN 60079-14). SEE
Length Considerations. FAILURE TO DO SO COULD RESULT IN INJURY OR DEATH.
Information contained herein is classified as EAR99 under the U.S. Export Administration Regulations. Export, reexport or diversion contrary to U.S. law is
Dir = VPowerSupply - VMin
IMax x RWire x 2
to determine the maximum wiring distance.
Conductor Cross
2
(Mm ) Section Area (Mm
0.50 0.33
0.60 0.50
0.90 0.82
1.5 1.50
2.5 2.00
4.0 3.30
6.0 5.26
USE AND DISCLOSURE OF DATA
prohibited.
UNIVERSAL GAS DETECTOR
Resistance
2
(Ohms/foot)
)
0.0158
0.01 12
0.0077
0.0039
0.0026
0.0016
0.0010
Table 4-6: Typical Cable Data for Input Power
MERIDIAN
INSTALLATION
Table 4-6: Typical
Resistance
(Ohms/meter)
0.0518
0.0367
0.0253
0.0127
0.0085
0.0054
0.0034
4-9