MT5 Multi-Tracer Operating Manual
page 14
Use a shielded-pair wire with a voltage rating greater than Voc of the PV module for the
voltage sense lead. Connect the shield of this cable to the GND pin of the Multi-Tracer
module connector or other suitable ground point. Connect the shield at one end only.
Keep the power leads as short as possible and use #10 AWG wire. This is the largest
wire that can be used with the Multi-Tracer connectors.
Wire Size and Voltage Drop
The MT Multi-Tracer loads operate in the first quadrant. This means that they only
dissipate power and only operate where the voltage is positive and the current is flowing
from the PV module into the Multi-Tracer. While the 4-wire module connection, with
separate voltage sense, eliminates any measurement error due to voltage drop along
the power wires, this voltage drop still exists.
Table 1 shows the approximate wire resistance for several gauges of wire. Note: The
largest wire the MT5 module connectors accommodate is #10 AWG. This is highlighted
in the wire table. The total wire length is the combined (or round-trip) distance of the
positive and negative module power leads.
As an example, the voltage drop at 10 A is shown. The significance of this voltage drop
is that it limits how close to a true short-circuit the PV module can operate.
For most applications, these voltages drops are insignificant as far as any discrepancy
between true short-circuit current and the minimum or near short-circuit current
measured by the Multi-Tracer.
Table 1. Module Wiring Resistance Chart.
Wire
Gauge
(AWG)
Res.
(mOhms/
Ft)
Resistance for
50 ft
(100 ft round trip)
(Ohms)
Voltage
Drop
@ 10 A
Res.
(mOhms/m)
Resistance for
15 m
(30 m round trip)
(Ohms)
Voltage
Drop
@ 10 A
#14
2.61
0.261
2.61
8.56
0.257
2.57
#12
1.64
0.164
1.64
5.38
0.161
1.61
#10
1.03
0.103
1.03
3.38
0.101
1.01
#8
0.65
0.065
0.65
2.13
0.064
0.64
#6
0.41
0.041
0.41
1.35
0.041
0.41
#4
0.26
0.026
0.26
0.85
0.026
0.26